Black-and-White Tips and Techniques for Darkroom Enthusiasts

BLACK-AND-WHITE FILM PROCESSING

KODAK DEVELOPERS FOR PROCESSING BLACK-AND-WHITE FILMS

USING REPLENISHED BLACK-AND-WHITE FILM DEVELOPERS

The following information gives suggestions that will help you achieve better process control with three popular Kodak developers commonly used in replenished processing systems.

KODAK T-MAX RS DEVELOPER AND REPLENISHER

This is a moderately active two-part liquid developer and replenisher that offers enhanced shadow detail in normally processed and push-processed films. Here are tips for getting the best performance from this developer in replenished systems:

What is a "Fresh" Developer vs. a "Seasoned" Developer?
A freshly mixed tank of KODAK T-MAX RS Developer and Replenisher contains none of the development byproducts that start to accumulate with the first roll of film processed. As you process more film, the concentration of these byproducts (bromide, oxidized developer, etc.) builds and reduces the activity of the developer. The buildup would quickly lead to exhaustion of the developer if you didn't add replenisher as each roll of film is processed.

The replenisher plays two important roles:

• It replaces important chemicals consumed during development.
• It dilutes the byproducts formed by development.

As the tank becomes "fully seasoned," dilution by the replenisher compensates exactly for new byproducts released by development. At this point, the concentration of bromide and related chemicals reaches a "steady state." Barring accidents, you can operate the tank for a very long time with virtually no further change in the "steady state" concentration of development byproducts.

How Long Does It Take for a Fresh Mix to Reach a Seasoned Condition?
It depends primarily on the size of the tank, the replenishment rate (mL of replenisher added per square foot of film processed), and the number of rolls processed per day. It will take from several days to several weeks to reach a fully seasoned state.

What Happens When the Tank Changes from a Fresh to a Seasoned State?
Two key changes occur. If the development time remains constant during this seasoning-in process, small losses in real film speed and film contrast will occur. A speed loss of about 1/2 stop and a contrast loss of 10 to 20 percent are typical for a well-maintained process.

You can detect both effects if you monitor with process control strips, such as KODAK Black-and-White Film Process Control Strips (CAT 180 2990) and plot your readings. As you use a freshly mixed tank of T-MAX RS Developer and Replenisher, film speed and contrast drop for a while and then level off at their "seasoned-in" values. These downward trends on control charts that occur as a new mix seasons are of no real consequence. However, some careful workers will want to avoid them, as described below.

How Can I Avoid a "Seasoning-In" Period?
You can pre-season a fresh tank mix. When you prepare the new tank solution, you can add key development byproducts to achieve a level close to that of a normally seasoned tank.

The following two prescriptions will accomplish this. Remember, these procedures are optional. If you are not bothered by a small speed and contrast shift as natural seasoning occurs, you can ignore these procedures.

Instant Seasoning of a Fresh Tank, Method 1. Prepare T-MAX RS Developer and Replenisher as you normally do, and fill the tank to about 98 percent of its volume. Make note of the volume you put into the tank. Then add 1.7 mL of KODAK DURAFLO RT Developer Starter for every litre of solution in the tank (or 6.5 mL of starter per gallon). Mix the solution well. It will be seasoned to a near-steady-state concentration of important development byproducts.

Instant Seasoning of a Fresh Tank, Method 2. Use the same technique as in Method 1, above, but use KODAK First Developer Starter, Process E-6, instead of DURAFLO RT Developer Starter. The appropriate amount of First Developer Starter is 3.4 mL per litre or 13 mL per gallon of tank solution.

Note: Whichever method you choose, modify only the contents of the fresh tank. Do not modify your replenisher solution.

What About Replenishment Rates?
We recommend adding T-MAX RS Developer and Replenisher at a rate of 45 mL of solution for each 135-36 or 120 roll or 8 x 10-inch sheet (or equivalent) of film processed. This is an average figure. The best value to use will depend on tank size and utilization.

If you are setting up this developer for the first time, we suggest that you use one of the pre-seasoning procedures described in How Can I Avoid a "Seasoning-In" Period? and initially set the replenishment rate at 70 mL per roll rather than 45 mL per roll. Plot the process, and when it has been stable for two weeks, decrease the replenishment rate to 60 mL per roll. If the control charts continue flat for two weeks, decrease the rate to 50 mL per roll.

Keep decreasing in increments of 10 mL per roll until you notice contrast and speed beginning to trend down, signaling underreplenishment. Then readjust the rate to its previous level and stay with that rate. Generally, the rate will be about 40 to 50 mL per roll, but you may find your process requires somewhat higher or lower replenishment, again depending on tank size, utilization, and other factors.

Can I Modify T-MAX RS Developer and Replenisher to Provide Longer Development Times?
You can use KODAK T-MAX RS Developer and Replenisher over a wide range of temperatures. It does not give significantly better results at one temperature than it does at another. The most important consideration in selecting a temperature is the ability to maintain it easily year-round.

In warmer climates, a relatively high temperature can be easier to maintain. However, if development times fall below five minutes, the risk of nonuniformity increases. To lengthen development times while continuing to operate at a higher temperature, you can decrease the developer activity by adding acetic acid to the developer. The acid lowers the pH of the developer, which calls for an increase in development time.

There are practical limits to how much you can lower the pH without causing other effects. Method 1 and Method 2, below, offer two acceptable options for lengthening development times.

Decreasing Developer pH, Method 1. To each gallon of both tank solution and replenisher, add 15 mL (0.5 fluidounce) of KODAK 28% Acetic Acid. Generally, this will extend development times by about 25 percent over the unmodified developer and replenisher.

Decreasing Developer pH, Method 2. Add 30 mL (1.0 fluidounce) of 28% acetic acid to each gallon of tank solution and replenisher. This will increase development times by about 50 percent over the unmodified developer.

KODAK XTOL DEVELOPER

This is a new two-part powder developer for processing Kodak and other manufacturers' normally exposed, pushed, or pulled black-and-white films. It offers full emulsion speed and easy mixing. Use it as both a developer and a replenisher.

Do I Need to Season a New Tank Solution? How Would I Do It?
If you choose not to season a new tank solution of XTOL Developer, your initial development times should be about 10 percent shorter than the published starting-point recommendations. As the tank approaches a steady state, the appropriate times will become closer to those recommendations. (For detailed time/temperature tables, see KODAK Publication No. J-109, KODAK XTOL Developer.)

If you choose to season a fresh working tank solution, mix the developer according to the instructions. Fill the tank with developer. Then add 6.5 mL of KODAK Developer Starting Solution (CAT 146 6382) per litre of tank volume. Or you can use 1 mL of KODAK EKTACHROME R-3 First Developer and Color Developer Starter (CAT 102 0072) per litre of developer. Stir or recirculate the solution until it is uniform.

How Can I Convert to XTOL Developer from Another Developer?
Before changing to XTOL Developer, run several KODAK Black-and-White Film Process Control Strips (CAT 180 2990) through your current process at each of your standard development times. Measure and note the contrast index  (CI) of these strips. Drain and clean the developer tank of the processor.

To make a fresh tank solution, follow the mixing instructions (and season the solution as described above, if desired). Run several more control strips, adjusting the developer time or temperature (or both) until you identify a condition that matches each of your previous CI results.

If you process a broad film mix that requires a wide variety of development times, you may want to establish a few standard batch cycles, such as 5, 6, 7, 10, and 12 minutes. Then assign each film to the nearest of the batch conditions, based on the standard times.

Replenishment. Use the developer solution as a replenisher at a starting-point rate of 70 mL per 135-36 or 120 roll (or 80 square inches [516 sq cm]) of film processed. Monitor the process with control strips, and adjust the replenishment rate down in 10 mL increments to keep the process on aim. Use the lowest rate that will maintain process control.

KODAK DEVELOPER D-76 AND REPLENISHER D-76R

The following paragraphs provide tips for modifying Developer D-76 for maximum speed.

How Can I Get Maximum Film Speed with Replenished KODAK Developer D-76?
Replenished developers for use with black-and-white films typically provide less real film speed than do fresh or one-shot versions of the same developers. You will see this decrease in effective film speed as a slight loss in shadow detail with film exposed at the rated ISO speed.

The following procedure is an optional method of replenishing KODAK Developer D-76 to minimize this speed loss and maintain shadow detail similar to that obtained with fresh or one-shot developers.

This method involves a replenisher solution and replenishment rates different from those normally used. It is not intended as a replacement for the traditional process. It is an alternative to provide greater effective speed with Developer D-76 in a replenished mode.

Mixing the Optional Replenisher. Prepare solutions of KODAK Developer D-76 and KODAK Replenisher D-76R according to the instructions. Then combine 5 parts of the developer with 1 part of the replenisher. For example, you might combine the mixes from a 10-gallon developer package and a 2-gallon replenisher package. Mix the solution until it's uniform.

How Do I Use the New Developer and Replenisher System?
The next table lists development times for a typical rack-and-tank processor operated at 68° F (20° C). These are starting-point recommendations. You may need to customize them for your situation (processor, agitation, water supply, etc.).

The "optimum development time" in the table is the exact time your processor requires for ideal development. "Batched development time" reflects an effort to sort all the films into one of a smaller number of time slots. Although batched times will not always be exact, they permit improved production efficiency.

Replenishment Rates. The starting-point recommendation is 70 mL of the modified replenisher solution per roll of film (80 square inches, one 135-36 roll, or one 120 roll).

Keeping Properties of the New Replenisher. Use the modified replenisher within one month of mixing. Also, replace the working tank solution with fresh chemicals after one month's use or after using a volume of replenisher equal to twice the tank volume, whichever occurs first.

Notice: Observe precautionary information on product labels and on Material Safety Data Sheets.

ALL ABOUT PUSH PROCESSING BLACK-AND-WHITE FILMS

If you've never pushed a black-and-white film to the limit, you've missed out on some real fun--and some wonderful visual effects. Here are a few guidelines and ideas for experimenting with some amazingly versatile products.

WHAT EXACTLY IS "PUSH PROCESSING"?

Suppose you want to take some photographs at a late-night soccer game. You have a 300 mm f/2.8 lens and KODAK T-MAX 400 Professional Film. You must handhold the camera, so you need to shoot at 1/250 second or faster. Meter readings around the field before the action starts indicate that to work at these camera settings, you need a 1600-speed film. The only film you have is 400-speed. What can you do?

Enter push processing: Load the T-MAX 400 Film and use 1/250 second at f/2.8, as if you had a 1600-speed film.

Back at the lab, you develop the film for a longer-than-normal time ("push" the process). The negatives print similarly to film that is exposed and processed normally. However, the prints are grainier than usual and they lack some shadow detail. But it sure beats going home with no images.

IS PUSH PROCESSING BASICALLY A TECHNIQUE TO USE WHEN THE AVAILABLE LIGHT IS INADEQUATE?

Correct. Push processing has long been a popular technique, especially with photojournalists who shoot night or indoor sports where the action is fast and the lighting is poor. It's also useful for candid photography when you don't want to call attention to the camera by using flash.

Faster films, like KODAK T-MAX P3200 Professional Film, have reduced the need for some push processing; you can expose this film at its normal speed in these situations. However, it didn't take long for photographers to push this film to speeds of 6400 or 12,500 (or beyond) to take their cameras into places they'd never been before.

ARE THERE OTHER USES FOR PUSH PROCESSING?

Yes. Oddly enough, pushing can offer an advantage in a number of well-lit situations. For example, consider an outdoor tennis match at midday. You can easily shoot a 400-speed film at 1/500 second to stop action or us f/16 for good depth of field. But you might prefer to use a 100-speed film, pretend it is 400, and then push-process.

Push processing increases film graininess, but a 100-speed film pushed to 400 is not as grainy as a true 400-speed film exposed and processed normally. This technique sacrifices some shadow detail, but in many sports situations, such as tennis, golf, swimming, etc., shadow detail is not terribly important to the image. In situations like this, you can end up with better overall image quality by underexposing and push-processing a slower film than by making the more natural choice of a faster film.

HOW SERIOUS ARE LOSS OF SHADOW DETAIL AND INCREASED GRAIN?

It all depends on your requirements for image quality. Many purists would not even consider these techniques because of the associated grain and shadow degradation. Yet to say "never" to push processing is to deny yourself many photo opportunities.

The more you underexpose, the harder you must push the process, and the more grain and shadow detail suffer. How far is too far? You'll need to experiment with various degrees of underexposure and pushing to learn your aesthetic limits, realizing these change with the situation. Few people would pass up a once-in-a-lifetime photo opportunity because it requires push processing and some degree of image degradation.

BUT CAN YOU QUANTIFY THE PENALTIES?

Roughly, think of it this way: A one-stop push--exposing a 100-speed film at 200, or a 400-speed film at 800--will be difficult for most people to detect if it is done well. A two-stop push, such as 400-speed film exposed at 1600, is clearly detectable, in both lost shadow detail and increased graininess of the print. Three stops is generally the upper limit.

Many sports photographers have used a three-stop push for years. They rate KODAK TRI-X Pan Film at 3200 and push-process. The grain is genuinely gritty and the loss of shadow detail is substantial, but again, it beats having no newspaper coverage of an important event.

WHAT IS THE WORLD RECORD FOR PUSHING?

The most extreme situation we know about is using KODAK T-MAX P3200 Professional Film rated at 100,000. This was a certifiably special case related to a criminal investigation. Authorities needed a late-night aerial photograph that would establish the relative position of two groups of people. The print was not a prizewinner by our standards, but it provided the information to secure a conviction. By that definition, it was a successful photograph.

DOES ALL THIS MEAN THAT BLACK-AND-WHITE FILM HAS NO FIRM SPEED VALUE?

Absolutely not. Any film has one, and only one, ISO speed. This value is determined with a particular developer under very rigid conditions. However, this developer and the special conditions are not available to the average photographer.

The speed of a film in the real world is a function of many choices made in processing the film: the developer, the developer dilution, development time, developer temperature, and agitation.

Kodak lists Exposure Index (EI) values for its films, and these values are different for different developers. For example, T-MAX 400 Professional Film has an EI value of 400 when developed in fresh KODAK Developer D-76, but it has an EI value of 200 when developed in full-strength KODAK MICRODOL-X Developer. (These EI values are based on normal development for negatives intended to print on grade 2 paper in a diffusion enlarger.)

With longer development times, such as those used in push processing, EI values actually do increase, but only slightly. Underexpose a film by two stops and give it a two-stop push, and the real film speed will typically increase by perhaps a half stop. This means that the film is really underexposed by only 1 1/2 stops, not two stops. But it is underexposed.

The intrinsic speed of a film is largely set at the time of manufacture. You can trade much of this speed for other features (like finer grain with MICRODOL-X Developer) or simply lose it in a poorly maintained developer. However, increasing speed significantly is extremely difficult.

ARE SOME FILM/DEVELOPER COMBINATIONS BETTER THAN OTHERS FOR PUSH PROCESSING?

Yes. We've already mentioned the option of intentionally choosing a slower film, and the fact that many people push even turbo-charged materials like T-MAX P3200 Professional Film. In practice, though, the films most often pushed are 400-speed films. The choice of which 400-speed film is an important consideration.

A few years ago, Kodak did an interesting survey. We purchased black-and-white 400-speed films manufactured by Kodak, Agfa, Ilford, and Fuji. All the films received very precise sensitometric step-tablet exposures. We then mailed them to 119 pro labs all around the world for processing. When the films came back, we determined the exact exposure needed to produce a density of 0.10 above base plus fog, the ISO speed point.

For any one of the films, we saw a variety of speed numbers that reflected the processes of the various labs. But the film that most consistently provided the best speeds was T-MAX 400 Professional Film. The advantage ranged from modest to substantial, depending on the comparison, but in a world where fractions of a stop matter, this film offered a clear advantage.

A variety of so-called "push developers" is available. These developers are specially formulated to extract the maximum photographic speed from black-and-white films. A distinguishing characteristic of such developers is that they tend to produce very grainy results. KODAK T-MAX Developer and T-MAX RS Developer and Replenisher are exceptions. They are the "push" variety, but they don't exact a significant penalty in film graininess. Both offer maximum film speed, but with grain that is just slightly more noticeable than that produced by KODAK Developer D-76.

WHAT ABOUT DEVELOPMENT TIME AND TEMPERATURE?

Temperature is a matter of convenience. Pick a value that you can keep consistent, and stay with it.

Development time? The big caution is do not overdo it. When you underexpose film and develop it normally, all scene elements develop to lower densities. The negative is thin with little density range, and needs a higher-contrast printing paper. The objective of push processing is to expand that negative back to a normal density range so that it will print on a normal paper grade. Pushing beyond this buys no additional shadow detail; it only makes the negatives difficult to print.

If you underexpose film by one stop, you may choose not to push the process at all. The negatives will be a little thin and may require a paper one-half to one grade higher than you ordinarily use. With film underexposed by two stops, try extending the normal development time by about 25 percent, and extend the time by 50 percent for film underexposed by three stops. (Use less of an increase to produce negatives that will print normally with a condenser enlarger.) These guidelines are specifically for T-MAX Professional Films. You may need more of a push for other films.

Experiment with some non-critical film. Your goal is to find a development time that permits printing with a paper grade and printing exposure times similar to what you normally use for normally exposed and processed films.

ANY OTHER SPECIAL CONSIDERATIONS?

A couple of things are worth exploring. Consider diluting the developer more than usual. For example, consider using T-MAX Developer at 1:7 or 1:9 instead of the usual 1:4. Also consider using less frequent agitation--maybe once a minute (or even less) rather than every 30 seconds. These tactics require lengthening development times even further, because they both slow down development. However, the extra time buys a little bit more shadow detail (real film speed) without sacrificing the highlights. It also produces a slight sharpness improvement. The disadvantage is that film graininess also increases a bit more.

ANY PITFALLS?

Yes, two. You may tend to push too hard and overdevelop the film. This only makes printing needlessly difficult.

The second pitfall concerns film developed in replenished developers. Any replenished system contains development byproducts, and these byproducts reduce real film speed. A film that is an honest 400-speed film in a fresh one-shot developer is more likely to be a true 250- or 320-speed film if that same developer is reused and replenished.

Replenished systems may not be very well maintained (i.e., they are underreplenished) and the speed losses can be more significant. That 400-speed film may be only 200 or even lower. If you need to use a commercial lab that operates a replenished line, the film you think is two stops underexposed may be far more underexposed relative to that process.

Finding a lab that is running KODAK T-MAX RS Developer and Replenisher can be a help. The process will have some speed loss as the developer seasons, but contrast will remain the same. A seasoned process will give consistent results, so you can run tests to determine the best combination of exposure and processing for your application.

WHAT ABOUT PRINTING PUSH-PROCESSED NEGATIVES?

If the push was appropriate, printing times and paper grades will be very similar to those that you use for ordinary negatives. The problems will be lost shadow detail and increased grain, and--especially if the push was overdone--burned-out highlights.

KODAK POLYMAX II RC Paper is particularly well suited to printing pushed negatives. Its unique curve shape offers real help. The contrast at the shadow end of the scale is purposely inflated. This tends to separate the weakest shadow detail and render it more distinctly in the print. At the same time, the paper reproduces highlights with slightly lower contrast. This accomplishes two things:

• It tends to tame highlights that are too hot, reducing the need for burning in.
• It helps to control graininess. Grain in a black-and-white print is most noticeable at densities slightly less than an 18-percent gray card. Grain at any density is also directly proportional to paper contrast at that density. Because POLYMAX II RC Paper has slightly less contrast throughout the highlights and lighter tones, it tends to subdue the graininess you would otherwise see at these critical densities.

Only one: Have fun with it! You may well have photo opportunities or assignments that require push processing to get the job done. But beyond these, watch for--or create--opportunities. Pushing can lend a special aura to an otherwise ordinary image.

ANY LAST THOUGHTS ON PUSH PROCESSING?

One good way to explore such opportunities is to load your camera with T-MAX P3200 Professional Film, set the film speed at 6400 (or even higher), and do some candid late-night street photography. This film lets you capture images with a handheld camera without a flash that you never could obtain otherwise. The extra push in processing will yield substantial grain, especially in big enlargements. This is "good grain." It's sometimes described as "grain that looks like you could catch your fingernail on it" compared to the oatmeal-like grain older films produced.

Also explore offbeat printing techniques. One frequently successful technique involves printing grainy negatives on KODAK P-MAX Art RC Paper. This paper has a very "toothy" surface that adds to the image's gritty look, and it is very receptive to hand-coloring. An underexposed and pushed image made with this very fast film, enlarged onto P-MAX Art Paper, and spot-colored to highlight portions of the scene can be a very powerful and satisfying image.

FILM-HANDLING TIPS

FILM KINK MARKS

Physical deformation, buckling, or kinking can produce localized differences in film density. These usually appear as crescent-shaped marks that are lighter or darker than the surrounding area. Kink marks show up in prints as patterns of the opposite density--light marks (minus density) in the negative will be dark (plus density) in the print.

How Do Kink Marks Affect Different Film Types?
The specific appearance of kink marks depends on the type of film, when the kinking occurs (before or after exposure), the exposure level of the film where kinking occurs, and similar factors. Also, in color films, the color of the mark may vary with the product, the severity of kinking, etc.

What Causes Them?
Bending film during handling can exert pressure on the silver halide grains and affect sensitization of the emulsion. Pressure before exposure may desensitize the silver grains. This desensitization later produces minus-density marks in exposed areas of the processed film or plus-density marks in unexposed areas. Pressure after exposure may sensitize the silver grains.

Usually kinking or bending occurs during handling. For example, film may be bent sharply during loading of film holders and processing equipment, or it may be kinked by pressure from fingernails. Mechanical problems in mechanized processing equipment may also kink film.

Lower-than-normal temperatures may make film stiffer and more susceptible to kink marks.

What Can I Do to Avoid Kink Marks?
The best prevention is to handle film with care, especially under cold conditions.

After processing, you can't correct kink marks. However, you can use negative- and print-retouching techniques to correct less severe marks.

How Can I Tell If Kinking Is Really the Problem?
Light leaks, x-ray exposure, and other types of fog may produce similar patterns. If you notice random plus-density marks--especially crescent-shaped marks--consider film kinking as a potential cause.

LIP FOG

Lip fog is a patterned exposure sometimes found on 35 mm films. It usually appears as streaks running completely across the film, starting near frame No. 1 and repeating at decreasing intervals.

Black-and-white negatives will show dark streaks.
Color negatives will show dark-colored streaks.
Color reversal films will show white, yellow, orange, or light-colored streaks.
Black-and-white infrared films will show dark streaks.
Color infrared film will usually exhibit reddish streaks, but the color may vary.

Note: Infrared films are especially vulnerable because they are sensitive to light over a wider range of the spectrum.

What Causes Lip Fog?
Lip fog forms when film is exposed through the lips of the 35 mm magazine, where the leader protrudes. Exposure can take place when you load a magazine into a camera or leave unprotected magazines in direct sunlight. Infrared film may be fogged even when loaded into a camera in very dim light.

The following conditions contribute to lip fog:

• loading film in overused reloadable magazines with wider-than-normal lips
• bright light angled toward the lips of the magazine
• for infrared films, radiation high in the infrared region of the spectrum or loading in darkrooms with safelights

Also, if film is incompletely rewound into a magazine after exposure, light can leak into the magazine and fog the film.

How Do You Prevent Lip Fog?
Although lip-fog streaks are developable and form a permanent part of the image, you can take a number of steps to avoid them:

• Replace reloadable magazines regularly with new ones.
• Examine magazines frequently. (Comparing them to a factory-loaded magazine is a good check.)
• Keep magazines out of bright light. Keep film in lighttight plastic containers whenever possible.
• If you use infrared film, don't subject unprotected magazines to any light at all.

Do Any Other Conditions Look Like Lip Fog?
It's possible to confuse lip fog with--

• fog caused by light leaks from a camera back or camera body latch
• fog caused by light leaks in the darkroom
• safelight fog that occurs during loading film onto reels for processing

WHITE-LIGHT FOG

Fog caused by exposure to white light usually appears as an area of maximum density on negative films and minimum density on reversal films. When fogging is complete, no image or edgeprint will be visible on the film. When the film is partially protected or the light leaks are small, the fog can appear in a wide variety of patterns and densities.

Black-and-white negatives will show plus-density or maximum-density areas, which produce white or light areas on prints.
Color negatives will show neutral to blue plus-density areas, which produce white, yellow, or orange areas on prints.
Color reversal films will show neutral minus-density or minimum-density areas, usually with yellow or orange patches.

What Causes White-Light Fog?
As the name indicates, the cause is unwanted exposure of the film to light. The fog may produce overall exposure or various patterns and densities, depending on the intensity and duration of the exposing light, the presence of objects between the film and the light source, and the way in which the film was fogged. For example:

• A frame-by-frame repeat pattern on the film indicates a camera problem such as a slightly open camera back. The frames are formed in the camera and the fog repeats when the film is advanced.
• Usually fog confined to the image area indicates a light leak in the front of the camera. Only the area that is exposed by the shutter is affected by the fog.

How Do I Know When Fogging Occurred?
Shadow patterns of equipment may indicate how the fog occurred. Images of camera parts on the film indicate a camera problem. The images may be highly distorted, depending on the direction of the light and the shadows cast by the camera parts. Shadows of dust and dirt on the film may indicate the direction of the light.

If shadow patterns appear on the film where film clips held the film during processing, fogging probably occurred during darkroom handling.

Light leaks in the camera may come from--

• worn locks or seals
• dirt in camera locks or seals
• missing screws, broken or cracked parts, loose lens mounts, improperly seated lenses, or improperly seated interchangeable camera backs
• film-transport failure that requires opening the camera back
• accidental opening of the camera back

Fogging that occurs in the lab or darkroom may come from--

• light leaks in the darkroom or processing equipment (White-light leaks produce yellow marks or areas on color print paper.)
• processor breakdowns or accidents that require using a light in the darkroom
• opening a darkroom door that's not equipped with a light trap
• safelights that are poorly sealed or cracked

Do Any Other Conditions Look Like White-Light Fog?
Exposing film to high temperatures and relative humidity may produce an increased fog level. This type of fog is usually uniform and isn't so severe as white-light fog.

Chemical fogging during processing may increase the fog level. Chemical fogging looks more like heat damage because it produces less severe fogging than white-light fog.

X-RAY FOG

Until recently, x-ray inspection units used for airport security have been relatively safe for films. However, as airports step up their security measures, some have introduced a new type of inspection unit that has a greater potential to fog film. To date, these units are not widespread, but we expect them to become increasingly common.

This new equipment is intended for checked luggage, although it is possible that boarding-gate security checkpoints will use it in the future. Because your checked luggage may be subjected to these new units, we suggest that you hand-carry your film and request visual inspection.

Historically, fog caused by x-ray radiation has appeared as lines or patterns across the width of roll film. The patterns are usually widely spaced lines followed by many more closely spaced lines. This happens because the image of the plastic core at the center of the roll and the individual laps of the film are projected onto the other laps of film in the roll. Undulating or wavy patterns may also occur throughout the length of the roll; this happens when the film is x-rayed at an angle and the shadow from the end of the film spool and magazine alters the exposure. Shadow images from other objects may also be evident. For example, film x-rayed inside a camera may show images of camera mechanisms.

The fog caused by the new airport inspection units is usually more pronounced. It typically appears as soft-edged bands 1/4 to 3/8 inch (1 to 1.5 cm) wide. Because the new equipment uses a higher and more focused x-ray beam, the banding will be very dark on negative films and very light on reversal films. Depending on the orientation of the film to the x-ray beam, the banding may be linear or wavy, and can run lengthwise or crosswise on the film. It can also undulate, depending on the combination of the angle of exposure and the multiple laps of film on the roll. However, the fog will usually lack the more subtle patterns produced by traditional types of x-ray equipment.

Black-and-white films will show a plus-density area with patterns as described above.
Color negative films will show a plus-density area with neutral or brown patterns.
Color reversal films will show a minus-density area with patterns as described above.

How Does X-Ray Fog Occur?
X-ray fog can result from exposure to x-rays from medical equipment, airport inspection equipment, industrial x-ray sources, and other sources of x-rays, as well as from gamma rays from radioactive materials.

Airport x-ray inspection equipment is the most common source encountered by most photographers. Except for the new types of inspection units described earlier, most inspection units in use today are relatively safe for films with an ISO speed or Exposure Index (EI) of 400 or lower. However, multiple exposures without reorientation of the film, cumulative doses of more than five exposures, and malfunctioning inspection units can cause fog. Films with an ISO speed or EI higher than 400 require added precautions because they are much more sensitive to x-ray exposure. Even with "film-safe" x-ray units, you should limit exposure to one inspection. For films with a speed of 1000 or higher, request visual inspection if allowed by local regulations or law.

Other factors can affect the severity of x-ray exposures on photographic films. Film that is--or will be--underexposed and film that you intend to push-process may be particularly vulnerable to x-ray exposure.

Underexposure. X-ray fog occurs in the lower exposure range of the film. Film that is underexposed has more of the image recorded in this range. Therefore, the effects of x-ray exposure may further reduce the quality of underexposed images.

Push Processing. Push processing involves overdevelopment of film to increase the effective speed and increase the density of underexposed images. Just as overdevelopment increases image density, it will also increase the density of any fog, including x-ray fog.

Limiting x-ray exposure is increasingly important for film that may be subject to underexposure or push processing.

At airport inspection stations, be sure to look for posted advisories on potential effects on film. Requesting visual inspection of photographic materials is still the best preventive measure, when it's allowed. For easy inspection, carry the film in a clear plastic bag.

What Precautions Can You Take?
If you choose to place your film in luggage that you will check, ask if the luggage will be x-rayed. Be aware that security procedures in some locations may prohibit informing passengers whether or not their checked luggage will be x-rayed. Because of random x-ray examination of checked luggage and differences in procedures worldwide, we suggest that you not carry film in checked luggage. By hand-carrying your film, you will know if it is subjected to x-ray inspection.

If possible, you may want to have your exposed film processed locally before passing through airport security. X-ray exposure has no effect on processed film.

Any Other Conditions that Look Like X-Ray Problems?

• As noted earlier, exposure to the new airport security equipment produces a pronounced band of plus density or minus density that lacks the subtle patterns associated with x-ray exposure by other equipment. The fog pattern can resemble typical white- light fogging that occurs in a defined path--for example, from pinhole light leaks in equipment. The most defining characteristics of fog caused by the new equipment are the well-defined width of the bands and a fairly uniform density within the band. The banding will typically run through the whole roll (continuously or broken by patterns from the laps of film in the roll).
• On 135-size film, reverse-wind streaks are often mistaken for x-ray fog. However, these streaks are more evenly spaced and prominent, and tend to bow outward from the film perforations.
• Certain keeping conditions can produce effects that are confused with x-ray fog. However, you can usually distinguish x-ray fog by its distinct patterns.
• With focal-plane shutters, using shutter speeds higher than 1/60 second under fluorescent lights or higher than 1/125 second under high-intensity discharge lamps can produce crossbanding that may be mistaken for x-ray fog. However, these crossbanding patterns are usually widely spaced and diffuse.

STATIC MARKS

Especially during the winter, static can become a problem as you handle your equipment and films. Most photographic materials are susceptible to exposure by static electricity. Several different kinds of static marks have names such as branch marks, blotch static, bar static, starfish, and distorted starfish.

What Causes Static on Film and Cameras?
When you subject a camera or film to friction, it can become positively or negatively charged with static electricity. The film or camera then tries to return to a neutral state by transferring electrons to or from other objects.

Sometimes this transfer occurs slowly, without any adverse effects. But sometimes the charge builds up faster than it can safely dissipate. Then a sudden discharge produces heat, light, and ultraviolet radiation. The ultraviolet radiation forms a latent image on the film in the shape of the static discharge. You'll notice these images on processed negatives and transparencies.

Although friction is the chief culprit in causing static charges, the separation of film surfaces during rapid unwinding of roll film can also cause static.

As a rule, static is most troublesome when the relative humidity is low. Using 35 mm camera motor drives in very dry air can cause static marks.

How Does Static Affect Different Types of Materials?

Black-and-white negatives will show dark areas, which produce light areas on prints.
Color negatives will show yellow areas, which produce blue areas on prints.
Color reversal films will show blue areas.

The yellow/blue coloration of static marks on color films rarely varies unless exposure occurs through the back of the film. This is because the light from a static spark is predominantly blue or ultraviolet. When the light strikes the film, it first affects the blue-sensitive (top) layer. A yellow filter layer under the blue-sensitive layer prevents the blue light from reaching the other layers. Static exposure through the back of the film will appear as cyan areas on color negatives (red in prints) and red areas on color reversal films.

What Do Static Marks Look Like?
Positive polarities of charge produce spots. Lines, bars, and blotches usually consist of many closely spaced--or even overlapping--spots. Negative polarities produce branches. The branches may look like trees, rivers, lighting bolts, or starfish.

The branch-like markings you see occasionally on sheet-film negatives are the typical result of a negative charge that is discharged to a small point or object.

Diffuse spots with dark centers can occur when a charge builds up on the camera and then discharges to the film. A similar marking, called bar static, looks like a row of spots (often surrounded by fogged areas) that extend across the width of roll films. This type of marking can occur when you unwind a roll of film that has been tightly wound.

Unrolling the backing paper from roll film and passing the film rapidly between your fingers can produce a line of closely spaced bead-like spots down the center of the roll.

Surprisingly, high relative humidity can also cause static. It softens the emulsion of a film, so layers of tightly wound film make better contact with each other. You may cause an irregular blotchy pattern if you unwind a roll of slightly damp or tacky film. This blotchy pattern is typical of moisture static or "tacky static."

What Can You Do to Prevent Static Marks?
During manufacturing and packaging, Kodak takes every possible precaution to avoid the buildup of static charges on sensitized products. Taking the following precautions will help you avoid problems caused by static:

• Avoid handling film with sudden movements that might cause friction.
• If possible, keep the relative humidity at 40 to 60 percent in areas where you load and unload film.
• Don't advance or rewind roll films rapidly; don't wind rolls too tightly.
• Move plastic dark slides in sheet-film holders slowly. Don't withdraw or replace the slides quickly. When you remove the slide, don't place it under your arm and then withdraw it quickly to reinsert it into the film holder. This can cause a static charge on the slide that may discharge to the film.
• Remove the backing paper from roll film carefully. Don't pass the film between your fingers to unroll it.

FILM-PROCESSING TIPS

AIR BELLS

When air bells or bubbles of air form on film surfaces during processing, they produce circular spots on the film. These spots may have distinct edges or relatively diffuse edges. They may be higher or lower in density than the surrounding areas. Patterns vary from isolated spots to clusters where a heavy concentration of air bells or foam formed.

How Do Air Bells Affect Photographic Materials?
Air bubbles adhering to film surfaces prevent processing solutions from penetrating the emulsion. If this occurs in the developer, the result will be a circular spot that shows lack of development. Air bells in other solutions may produce spots of overdevelopment where the developer continued to act on the emulsion, or spots may form where incomplete bleaching, fixing, or washing has occurred.

With color materials, the color of the marks depends on the process and at what step in the process the air bells formed.

Why Do Air Bells Form?
Air bubbles may simply cling to film surfaces when you first immerse the film in a processing solution. That's why initial agitation to dislodge bubbles is so important.

Also, any condition that causes bubbles or foam in a processing solution can help to form air bells. All of the following factors can contribute to air-bell problems:

• overagitation
• equipment that draws air into solutions
• use of solutions too soon after mixing
• temperature changes in solutions
• insufficient filling of closed processing tanks
• incorrect filling of rotary-tube processors
• improper distribution or leaks in gaseous-burst agitation systems
• freeing up of dissolved air when cold incoming water warms to room temperature or is heated to provide hot water

How Do You Prevent Air Bells?
The most important factor is proper initial agitation. In batch systems, rap the reels or racks against the side of the tank to dislodge air bells carried in on the film. Agitating too vigorously causes bubbles to form. Agitating for too long a time can produce mottling.

In automatic processing systems, properly maintain the agitation system. In closed tanks and rotary-tube processors, be sure to observe proper filling procedures.

Treat dissolved air in a water supply by installing an aerator on the faucet. An aerator produces large bubbles, which rise to the surface and don't adhere to the film. Allow cold tempered water to stand before using it; this will allow dissolved air to dissipate.

When the water supply is cold, you can minimize air bells by connecting 100 feet of coiled hose between the water supply and the chemical-mixing area or processor. The water will warm up gradually and the freed air will collect at the top of the coils, producing larger bubbles that won't present air-bell problems.

Allow freshly mixed chemicals or chemicals diluted before use to stand for a time so that dissolved air can dissipate.

What About Films Already Affected?
Air bells that are present in the developer produce spots that are a permanent part of the image.

When spots have formed in other solutions or washes, you can reduce or sometimes eliminate them by reprocessing, starting with the solution in which the spots formed.

Air Bells? Or Something Else?
Sometimes chemical splashes can make spots that look like spots from air bells. Air bells are usually round, so irregularities in the shapes of the spots indicate splatter may be the source.

Air bells may be more irregular when they are caused by heavy foam concentrations. However, you can usually see a foam pattern.

Effects of differential drying can also resemble air-bell patterns. Differential-drying spots occur when small drops of water cause areas of film to dry at different rates. This produces a physical deformation of the surface. In this case, wash films immediately to help reduce the effect.

DIFFERENTIAL DRYING MARKS

Differential drying marks appear as a deformation in the gelatin surface; they range from highly irregular and elongated marks to pits, craters, or rows of small circular spots.

Most drying concerns occur when the weather changes--from fall to winter, when humidity gets quite low, and in the spring or summer, when humidity starts to rise.

How Does Differential Drying Affect Film?
Differential drying marks on film will print as plus-density marks. When you examine the film closely, the surface will appear deformed. The deformations may also appear as slight minus-density areas when you view them by transmitted light.

These marks are caused by differences in the rate of drying in localized areas on the film surface. The more slowly the gelatin dries, the more it will contract. If water is unevenly dispersed on the film surface during drying, the areas underneath the surface solution will dry more slowly, forming a crater, pit, or other deformation in the emulsion surface.

What Conditions Cause Differential Drying?
Quite a variety of conditions can cause differential drying:

• drying differences caused by changes in drying temperature or humidity
• excess solution on the film surface because of poor squeegeeing
• solution splatters striking the film after drying has begun
• dirt particles on the film (These can hold droplets of water and cause a drying problem. Be sure that the drying area is clean and that processing solutions do not contain particles that can stick to the film.)
• poorly aligned rollers in roller-transport processors that allow too much water to be carried into the dryer
• excessive hardener or stabilizer carryover that causes dirt in film dryers

Can You Correct the Problem?
To remove differential drying marks, rewet and redry the film. In most cases, the sooner you do this, the more success you are likely to have. You can repeat the treatment twice. When gelatin swelling occurs in an alkaline solution, completely reprocessing the film may be more effective. Be sure to wash the film adequately before reprocessing so that you won't contaminate the developer.

What Can You Do to Prevent It?
Any change in drying conditions can either cause or eliminate differential drying problems.

Check the following:

• Dryer temperature--Lowering the temperature to slow drying (particularly in the initial stages) usually will help. This allows time for uniform drying. In some cases, increasing the temperature during the later stages of drying may also help.
• Solution splashes--Check for solution splashing into the dryer area.
• Squeegees--In continuous processors, check the condition and operation of squeegees.
• Solution carryover--In rack-and-tank processors, solution carried over in film clips can splash on the film.
• Delay in drying--In rotary-tube and sink-line processing, problems may occur if there is a delay between removing the film from the last solution and hanging it in the dryer. Splattering may also occur when you hang other rolls in the dryer.
• Roller alignment--In roller-transport processors, check the alignment of the rollers. These rollers provide the only squeegeeing. If roller clearance is too great, too much solution will carry over into the dryer.

Bathing the film in KODAK PHOTO-FLO Solution promotes better drying. It contains a wetting agent to promote water shedding from the film surface. Be sure to dilute the solution with water in the correct proportions.

Do Any Other Conditions Look Like Differential Drying?

• Foam or air bells on the film surface during development can limit the initial swelling of the emulsion and produce an effect similar to differential drying.
• Uneven roller surfaces in roller-transport processors can emboss a texture into the film surface that resembles differential drying.
• Films with backing paper are subject to a texturing condition known as "orange peel." This texturing can occur when heat or high relative humidity softens the film surface so that the texture of the backing paper is embossed onto the film. (This effect may not show in prints.)

WATER SPOTS

These spots are usually round, but can occur in a variety of shapes.

What Causes Them?
They are formed from water droplets or "bubbles" on film surfaces that dry more slowly than the rest of the film, or by chemical deposits in the water. They may also result from air bells on film during washing. Water spots can occur on film during manual or machine processing.

Differential drying of the water drop and the area surrounding it causes the edges to dry first while the thicker center of the drop is still liquid. This slightly alters the thickness or hardness of the gelatin, causing a printable image of a crater. If the water contains residual processing chemicals or other chemicals, the residue left after drying will magnify the problem.

How Can You Prevent Them?
Very rapid drying, lack of a wetting agent, splashed water or chemicals in manual or machine processing, low relative humidity, and hard water can all contribute to this condition.

The following may help prevent water spots:

• Filter the wash water.
• Dry films at 20-percent relative humidity.
• Eliminate splashing through techniques such as fabricating baffles for machine processors.
• Use an adequate dryer temperature-neither too high nor too low.
• Avoid air bubbles.
• Check cleanliness.
• Use a water softener in extreme cases.

In less severe cases, you can minimize spots by washing and redrying the film several times. Be sure to watch out for bubbles and air bells. Use KODAK PHOTO-FLO 200 Solution after the final wash.

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O-3  • October, 1999