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Masking 101

by Barry Sherman
( Barry was killed in an ultra-light airplane crash on Saturday, April 20, 2002)

There are lots of different techniques. Mine are derived from a section in a book by a gentleman named Krause titled "Complete Guide to Cibachrome Printing", from a book and video tape by Bob Pace (custom Ilfochrome and dye transfer printer), from a workshop on Ciba masking offered by Charley Cramer and from the Ilford booklet on the subject. Kind of a mish-mash of  techniques. So everything I say here reflects my own ways of working and is strictly IMHO.

* Bob Pace's book and video may be obtained from:
Bob Pace
2823 Amaryllis Ct.
Green Valley NV 89014
(702) 896-2515

It costs around $100 and has lots of good information, although I've come to think that he over-tests and that his strongly sensitometric-based technique yields results little better than more seat-of-the-pants ways.

* Charley Cramer's phone number is: (408) 243-0390. His workshop lasts two or three days (not sure in its current incarnation) and is excellent, offering both lecture and hands-on experience making masks. Unfortunately, he only offers it once a year and always on the West Coast, currently in the Santa Clara Valley (Silicon Valley) south of San Francisco. If you do call him, tell him that I said hi!

* The Ilford book can be obtained by calling them at (201) 265-6000.

NB: What I'm about to describe will probably sound very complicated. In actual practice it isn't. Making a contrast reduction mask typically takes me maybe 20 minutes, including setting up the trays and cleaning up. Making the print typically takes 6-30 hours depending on degree of  difficulty, how important it is to me and how many copies of the final print I want to make and how obsessively perfectionistic I happen to be feeling at the time. So making the mask is a pretty small part of the entire process.

Ciba Papers

I don't find the various contrast grades within Ilfochrome papers terribly useful. They don't seem to me to span enough of a range. I have far better control using masks and can print a far higher contrast original than I can using Ilfo low contrast paper. Others, however, have different experience. I prefer a print which has contrast similar to that of a C print only with the Ilfo saturated colors. Others like a little more contrast. All of our milages always vary.

I recently learned a discouraging fact about my preferred paper: Ilfochrome classic RC Pearl finish. I noticed some unpleasant "mottling" in a smoothly toned area. Lots of investigation led me to a local Ilford rep who was really honest. He told me that this is a known defect in some batches of RC Pearl paper and they're working on eliminating it. I tried making the same print with other emulsion batches and the problem didn't happen. But it's difficult to feel comfortable buying large quantities of large Ilfochrome Pearl paper now that I don't know whether it'll be defective. The rep said that he's never heard of the problem with the glossy finish RC, nor with the super-glossy polyester paper, nor could I replicate the problem on those emulsions.

[ NOTE: Since I wrote this, several years ago, Ilfochrome has dropped the contrast on the Pearl finish to where some of my images won't print even unmasked.

So I've switched to the high contrast polyester super-glossy material, CPS.1K. I also investigated Fujichrome type 35 super-glossy as I've concluded that in most respects the new R3 materials are superior to Ilfochrome. All respects, that is, except for longevity and color saturation, and Fujichrome is supposed to be at about 70% the longevity of Ilfochrome. As a result I now use both Ilfochrome and Fujichrome, depending on which works best for a given print. Fujichrome is somewhat lower in contrast than Ilfochrome super-glossy but does still require masking at times.]

What is a contrast reduction mask ?

Put very simply, a contrast reduction mask is a b/w negative which is produced from an original and is sandwiched with the original to alter contrast. Being a negative it will be dark where the original is light and light where the original is dark, thus lowering contrast.

Masking can get quite sophisticated, however. You can take a negative contrast reduction mask, contact print it onto another sheet of film, getting a positive, and use this as a contrast-increasing mask. You can use either type of mask with b/w and color negatives as well as with color transparencies.

I have also done contrast masking with both color and b/w negatives. Why mask with b/w negs when we have different contrast grades, variable contrast papers and different contrast developers available to us? With a little care it is possible to produce masks which are clear except for certain areas, where they'll affect contrast. Localized contrast control. This, along with flashing and bleaching, helps to bring to graded papers the level of contrast control available to those who use variable contrast papers.

You can vary the overall density of the contrast reduction mask so that it reaches down to the mid-tones or even to the shadows, thereby varying where contrast will be altered.

In addition, you may at times make a mask which is used in making the final mask. Several generations can be involved. More on this later.

Masking equipment

Equipment can be simple or fancy. Basically, the equipment, if any, is used for registering the original and the mask.

* Light box and loupe. After producing the mask you lay the original and the mask on a light box and use a loupe to line them up, taping them together when they're right. Mylar tape, available in better photo shops works well for this. This can just about drive a person crazy, especially in 35mm where not only do you have to worry about getting them lined up perfectly, you also need to worry about removing every last speck of dust. (Dust is less critical in large format as it's enlarged less.)

A friend who works in 4x5 opines that this technique works just fine for him, while it drove him nuts when he worked in 35mm. The larger images are easier to register. Personally, I'm lazy and am delighted to have Condit pin registration equipment.

* Condit Pin registration equipment. This is a set of equipment comprising a punch, contact print frame and negative carrier. The punch punches little 1/16" holes in the edges of 4x5 or larger film. These holes are used to align the original and the masking film in the contact print frame and in the negative carrier. Models are made for most of the standard large format (4x5 and larger) enlargers: Beseler, Omega, Durst, Saunders, DeVere ...

Quite expensive. A typical setup costs about $1000 purchased new. I got mine for $400 from a Shutterbug ad. It is without doubt the most useful darkroom accessory that I've ever had. You can take the color analyzer, Jobo, print washer, compensating developing timer, you name it. I can improvise around these losses. Just leave me my Condit Pin Registration setup.

Also, it's not necessary to order all the equipment at once. The largest expense is for the registration negative carrier. This is a fancy device which will actually allow one to remove the negative carrier, change masks, re-insert the carrier and make a second (or third or fourth) exposureon the same sheet of paper without losing any sharpness. But if one just wants to use contrast reduction masks then it'll work just fine to only buy the punch and contact print frame. After drying the mask, it can be put back on the pins of the contact print frame along with the original and the two can be taped together. The punch and contact print frame will run around $350, I believe.

Condit Mfg: U.S. (203) 426-4119

* Wess Plastics makes some equipment (a duper and a registration punch/slide mount system) that some people have used with some success for working with 35mm. Others report that precision is insufficient for serious use.

The duper uses the rectangular sprocket holes of the film to register it with the masking film. The mask is exposed as it would be with any masking equipment, making a contact print under the enlarger light source. After processing the masking film, Wess registration slide mounts are used to carry the registered mask and original. These mounts also use the sprocket holes and precisely sized rectangular projections to register the two.

I believe that the duper costs less than $100. Wess Plastics advertises in most of the photo mags.


* Film.

Kodak Pan Masking Film used to be the standard. But it's been discontinued.

So I now use Tmax 100. It requires different handling to produce the unsharp masks, but I think that it works just fine. Only problem is the amount of effort required to remove the purple stain, which is pretty tedious. Why Tmax 100 ? Because I have it lieing around so it's handy.

Roll films such as Tmax 100 are easiest to use if one is working with roll film originals and using the Wess equipment to aid in registration.

Roll film can be used for masking 35mm or medium format. Tmax 100 is certainly an option here. FP4, both in sheets and rolls, is popular as well.

Kodalith. Kodalith high contrast film is used for highlight protection masks. More on this later. Very useful stuff to have around. Very cheap. Something like $40 for 100 sheets of 4x5. One technique made easy using large format and registration equipment is "dye dodging" in b/w printing. You register a blank piece of film with a b/w negative and use spotting colors to paint over areas on the blank piece of film where you want the print to be a little lighter. Kind of like dodging using impossibly small dodging tools. I like Kodalith for this because the anti-halation backing rinses off much more easily than with more conventional films like Tmax 100. Just pop an unexposed sheet in some fixer for a few minutes and it's clean and clear. But I digress ... :-)

Freestyle in L.A. sells a really dirt-cheap litho film which they claim is the same as Kodalith. Sells for $15.00 per 100 sheets, far cheaper than the Kodak stuff. I have some at home which I haven't tried yet and so cannot comment on its usability.

Kodak LPD4. This is a litho type positive film. Dunno how it works but developed in any standard developer it yields a high contrast *positive* image. Yup. Positive. Useful in making highlight bump masks. More on that later. This can be difficult to get hold of. Apparently it's classed as a graphic arts item and most photo shops won't know what you're talking about.

I ordered mine through the 
Aperture Film Center
127 Main St.
Los Altos CA 94022
(415) 941-1500

I believe that they do mail order. The smallest size of LPD4 available is 8x10 in 100 sheet boxes. I paid $100 for mine and figure that what with the 400 sheets of 4x5 that it'll be cut up into, it's dirt cheap and that's enough for most of the rest of my life.

Both Kodalith and LPD4 can be used with a red safelight. Nice convenience. I use one of the little "painted light bulbs" for this.

* Developers. 

For developing contrast reduction masks using Tmax 100 I use HC110 diluted 1:11 from stock, not syrup. I've also used Agfa Rodinal diluted with 11ml of stock in 11 ounces of water. Yeah, I mix-and-match my measuring units. :-)

For developing Kodalith, used in highlight protection masks (discussed below), I use either HC110 diluted 1:11 if I want relatively low contrast, D11 undiluted for most work and occasionally Kodalith RT (two part litho) for very high contrast.

I use tupperware type sandwich containers for developing masks. Just use them as trays. They're convenient as I can keep the fixer and stop bath in them permanently, what with the self-sealing lids that they come with.

* Bleach

Often a highlight protection or other type of mask will have density in unwanted areas. The answer is to bleach with Potassium Ferricyanide. I just pour some in a 35mm film cannister, add water and apply with a cotton swab. Several applications, alternating between applying the ferricyanide and dunking in fixer to remove the bleached silver will completely remove all silver from the areas being bleached, leaving clear film there. You want a strong solution. A saturated solution is fine. Be sure not to omit the "dunk in fixer" step. The ferricyanide converts silver to a fixable (dissolvable) form but leaves it. The fixer bath is what actually removes the silver (and the density).

* Diffusion material.

This is used either above the original or between the original and the masking film when exposing the mask and increases the unsharpness of the mask. I use some stuff called Duralene, which I believe to be used for drafting purposes. It's like a sheet of plastic frosted on both sides. I get mine at a local art store. I've tried tablets of "frosted acetate" but found them abominable. One side was glossy and they attracted dust like nothing I've ever seen. The Duralene doesn't. Duralene costs around $1.50 per 16x20 or so sheet but I've been using the same 4x5 piece for several months now. (If you live in the Santa Clara Valley, CA, you can get Duralene at University Art.)

Condit Mfg also sells "Herculene" which I gather is similar but possibly more expensive.

Making a mask

* Exposing the material.

Exposure is done as a contact print. I use one of two different "sandwiches".

Layers from top to bottom, top being closest to the light source:

diffusion material
transparency, emulsion up
masking film, emulsion up


transparency, emulsion up
diffusion material
1 sheet of clear, fixed-out film (acts as a spacer)
masking film, emulsion up

I used to use the former sandwich when using Pan Masking Film with its inherent unsharpness and now use the latter when using Tmax 100. 

* Determining exposure and development.

Exposure is easy. Just experiment. With time you'll develop the ability to guess exposure based on the appearance of the transparency. Don't forget that these contrast reduction masks are developed to a low contrast. This means that variations in exposure don't have a huge effect on density. 

Bob Pace teaches a technique based on equating development time and exposure: less development means more exposure and vice versa. I haven't found this to be necessary. He also adjusts exposure based on the average density of the original. I find that three exposure times usually suffice: one for a thinner mask, one for an average mask and one for a heavy mask. The thinner mask will have density only in the highlight areas. The average one will have a little density in the mid-tone areas. A heavy mask will have density going down to the lowest of the mid-tone areas.

Naturally, exposure time will also vary with overall density of the transparency. Thus I might use my "heavy" exposure time for either of these two cases:

* Dense transparency with dense highlights but I want to mask highlights only.

* Thinner transparency overall but I want the mask to extend well into the mid-tones.

For my enlarger and working conditions and with enlarger light intensity set as described below, my exposure times are:

  With Tmax 100 With Pan Masking film
Thin 2 seconds 8 seconds
Average 4 seconds 16 seconds
Heavy 8 seconds 32 seconds

 You need to set light intensity to be similar to mine in order for these times to work for you. Put a sheet of white paper on the easel - a sheet of b/w paper works nicely. Set a reflective light exposure meter such as a spotmeter or an auto-metering camera for ISO 80. Now adjust the light intensity until the meter, reading the sheet of paper, indicates an exposure of 4 sec. @ f/2.8. This is *NOT* the exposure for you to use, but rather gets your light intensity roughly the same as mine, so that these exposure times will be good starting points for you. Probably you'll have to adjust them but this should get you in the ballpark.

I always set the enlarger head at the same height and I first focus the lens for that height and then de-focus it slightly, to reduce dust marks from any dust that may be on the negative carrier glass.

Your exposure will vary, probably greatly. This is offered as a sample only. I get the mask right on the first try about 50-75% of the time. The other times I get to some point in the printing process and decide that contrast is not quite right and go back and make a new mask. Naturally, I prefer to decide this after making only one teststrip. :-)

Development, since it controls contrast in the mask and, therefore, in the final print, can be more complicated. The basic term used is "gamma" where gamma is defined as:

density_range_of_transparency - exposure_scale_of_printing_paper

The calculated gamma will typically fall between 0.0 and .6 or so. The rule of thumb taught to me by Charley Cramer is that:

transparency contrast gamma  developing time in HC110 1:11 from stock
low contrast .1 1 minute
average .2 2 minutes
average .3 3 minutes
higher .4 4.5 minutes
high .5 5.5 minutes
really high .6 7 minutes

 NOTE: I've also found that Rodinal diluted 1:30 provides similar results when used with Tmax 100.

Exposure scale of the paper is defined as the density range of an original which will print with slightly less than total black (Dmax) and slightly less than total white (Dmin). Two ways to determine the exposure scale of the paper. The first technique starts with printing a step tablet. Find the steps which are just lighter and darker than Dmax and Dmin. The difference in density between the corresponding steps in the original tablet is the exposure scale of the paper.

Or you can just accept that Ilfochrome high contrast material has an average exposure scale of ~1.75 when developed in P3 chemistry. Somewhat higher, more like 2.00, if developed in P30P. P30P is formulated to give lower contrast.

With a given transparency you can:

1) Learn to judge the gamma required in the mask and to develop accordingly.
This is Charley's usual technique. He does stunning prints.

2) Measure the lightest and darkest areas using a densitometer or a baseboard light meter, calculate the gamma required and develop accordingly. I used to use this approach, using my color analyzer as a baseboard densitometer. But I found that 'in-the-enlarger-bellows' flare affected the readings from the color analyzer, causing inaccuracies. Being the cheap person that I am and not wanting to spend the money to buy a real densitometer, I bought a Booster II set for my Minolta Autometer IV (camera light meter). This setup permits taking readings off a view camera ground glass. I find that it gives me far more accurate density readings of the transparencies, also. I put the transparency on the light box and use the Booster probe to get EV readings on the light and dark areas that I'm interested in and then multiply the difference in EV's by .3 to get log density units.

And I've gone one step further. Having determined the density range of the slide, I look at the print of the step tablet and decide which step represents how I'd like the highlights to look and which step represents how I'd like the shadows to look. Then I use the difference in density between these steps in the original step tablet as the exposure scale of the paper when I calculate gamma. This has significantly increased the number of masks that are right on the first try.

* Developing the mask

I just use 4x5'ish tupperware trays and agitate constantly. Stop bath and fix as normal. I give a quick rinse (often just dropping the mask in the Jobo water bath for a minute or two), dip in distilled water with wetting agent added and dry in a closet with an electrical space heater running. I've tried blow-drying masks but they seemed to shrink somehow as they never registered quite right when dried this way.

Printing with masks

Very simple. Just register the mask with the original and print. The mask goes on top of the original, closest to the light source. Expect exposure times to go up significantly. Probably around 1-2 f-stops.

Sometimes I try a print without a mask or I decide to change the mask. If I've already determined a "ballpark" exposure time it's irritating to have to go back to find a new exposure time with the new mask. So what I do is to use my color analyzer to meter a highlight with the old mask (or no mask, as the case may be. Then when I put the new mask on, the meter tells me what the new exposure should be for the altered highlight density. Or maybe I'll use the aperture ring to adjust exposure time to be the same as it was before. The inexpensive EM10 baseboard exposure meter (~$30 or so) works well for this technique. And I've seen the Beseler Analight 400 baseboard exposure meter, which would work fine for either technique, for around $40- $50.

Developing the print

Certainly this is a topic removed from masking. But I've developed strong feelings on the subject. I very much prefer to use Cibachrome P3 chemistry to the "amateur" P30 or P30P versions. The P30 variants cost considerably more on a per-unit basis than does P3. Enough so that the only way that I can see to use them affordably is to use the Ilford "partial re-use" scheme in which you save 1/2 of the chemistry each time and mix it 50-50 with fresh.

My experience was that print quality was not consistent using the partial re-use technique. Color and density varied slightly but noticibly from print to print.

So I started using P3 chemistry one-shot in my Jobo after first checking with the Jobo people to verify that it's safe for the equipment. P3 costs less but Ilford recommends using double the volume that one would were one processing with P30. Thus, where they recommend 75ml for an 8x10 processed in P30, they recommend 150ml for an 8x10 processed in P30.

I tested, decreasing chemistry volume below the 150ml level until I could see a change in print appearance. Based on that test I find that I get the same results using 110ml per 8x10 as I do using 150ml per 8x10. So I use 110ml per 8x10. This reduces the cost of using P3 down to where it's only slightly, if at all, more expensive than partially re-using P30.

In addition to greater consistency from using P3 one-shot, others have noted, and I concur, that there is decreased cross-over, particularly the commonly seen cyan-red crossover which produces ugly cyan highlights. P3 produces noticibly greater contrast than does P30. Since I'm masking anyway, I consider this a plus as that contrast increase is noticible in the highlights, a problem area in most slide printing.

In fact, I was pushed over the edge into using P3 when I was printing an image of a very foggy beach. In the original transparency you could just barely see the line of demarcation between the sand and the fog, off in the distance. In my P30-processed print that line just disappeared. When I tried P3, that "horizon" was just as apparent as it was in the slide.

Since then the only time that I've used P30 was when I was trying to use a CAP40 processor and the P30 chemistry was one of the reasons that I abandoned that project.

Ilford does strongly recommend against using P3 at home. But I've never been able to get them to tell me why. The only indication that I've heard from them is that the sulfuric acid used in the bleach is sufficiently concentrated to be dangerous in the liquid concentrates that you buy. My own personal decision is that I'm a big boy who knows how to wear eye protection and rubber gloves and to exercise care when mixing the working solutions. I've deliberately put a few drops of the concentrated acid on my skin and, over the course of 10-15 seconds, incurred no damage. I'd prefer not to splash it in my eyes, however, and do wear eye protection when working with it. The working solutions appear to be safe enough. They claim that if one neutralizes the bleach with baking soda first then one can pour the chemistry down the drain without harming the environment.

Of course your milage may, and probably will, vary.

[NOTE: since I wrote this I've switched to using the super-glossy polyester base material instead of using the pearl finish RC. I found that I had trouble with color shifts when switching from one size print/Jobo-tube to another and that these color shifts were minimized by increasing the amount of P3 chemistry used up to the amount recommended by Jobo. Try it both ways and make your own decisions.]

Additional masking

Highlight protection masks:

Ilfochrome has a fairly pronounced toe to its characteristic curve. I.e. not a lot of contrast in the highlights. And transparency films have the same. So highlight contrast, or lack thereof, can be a problem even without masking.

This can be exacerbated when a mask is introduced which decreases contrast in the highlights. Also, sometimes a sense of "sparkle" is lost when specular highlights are increased in density in the print by a contrast reduction mask. One answer to either of these problems is to make a "highlight protection mask".

The highlight protection mask is made using Kodalith film. It's made sharp.
I.e. Emulsion to emulsion with the original in the contact printer. It's exposed so that only the brightest highlights in the original show any density in the highlight protection mask. Sometimes ferricyanide bleach is used to remove unwanted density from it.

This mask is then laid on top of the original when exposing the contrast reduction mask. I.e. it goes between the original and the light source. It "increases density" in the highlights so that they result in less density in the contrast reduction mask and print brighter in the final print.

I know one person (Charley Cramer) who has gone so far as to make a pre-highlight-protection mask which was used when exposing the highlight protection mask. The effect was to darken a small area in a highlight in the final print. I haven't gotten quite this far into it yet.

Highlight Bump Masks:

An alternative is to use Kodak LPD4 positive litho film to make a "highlight bump mask". This mask is exposed such that it's all black except for little clear "holes" where the brightest highlights are. This film can show significant chemical fog so it may be helpful to lightly bleach the entire mask in dilute ferricyanide to clear the highlight areas. Don't forget to either mix a little fixer in with the ferricyanide or to dunk the film in fixer after dunking in ferricyanide. The fixer is required to dissolve silver which was converted to a fixable form by the ferricyanide.

After exposing the print with the contrast reduction mask, the negative carrier is removed from the negative stage and the highlight bump mask is laid on top of the original and an additional burn or "bump" exposure is made to brighten the highlights. Obviously this type of technique can only be used if one has a full pin registration setup. (You'll have to pry mine from my cold, dead fingers - to take a page from the NRA. :-)

Once the registration equipment is available and some experience has been gained there are lots of other possibilities. Contrast increasing masks. Area masks - evenly toned masks which "dodge" an entire area of the print. Kodalith area masks which are all black or all clear and allow printing different parts of the print completely separately from the others. Lots of new worlds to explore!

Area Masks:

Sometimes you want to lower the value of the brighter areas of an image without lowering contrast within them, as will happen if you simply expose a sheet of b/w film to the image. Often, lowering the contrast within bright areas leaves them looking too flat (contrast-wise) in the print.

My technique doesn't always work, and will only work for larger sized transparencies, but sometimes it does work. I register a sheet of clear film with the original and, using Kodak Opaque black, carefully paint on the clear film everywhere that I'll want to have mask density in the final mask. Sometimes I just paint outlines and then cover the areas inbetween with Scotch Black Photographic tape. After this dries, I contact print it onto a sheet of Kodalith, developed in Kodalith RT super-high-contrast developer.

At times you can use litho film to separate out the areas as well.

Now I have a b/w negative that has no density in the areas of the original that need to be held back. This is now used to produce an unsharp mask of the appropriate density, as described above. I call this an "area mask". It will hold back the bright areas without reducing contrast within them, helping them to retain their sense of brilliance.

I make the contact print of the "clear film with Opaque Black" onto Kodalith because the Opaque black often doesn't dry completely and if I've used black tape to fill in areas the whole assemblage is somewhat bulky and damp.

Color Area Masks:

Recently I was printing a picture taken under extreme lighting conditions (a slot canyon in Arizona). One area, which in the 16x20 final print measured about 1"x2", was grossly overexposed. There was some detail running through it, but mostly it was just clear film. Looked awful. Dodging it back during exposure just made it look gray, which looked wrong when surrounded by the brilliant yellow/orange/red rocks of the canyon.

So I registered a sheet of clear film with the original, broke out my set of Ilfochrome retouching dyes and mixed up a color which matched the rocks near the blown-out area. I painted this onto the clear film over the areas which lacked tonality. The cure was perfect. In the final print you'd never know that there are totally overexposured areas at all.

It was just a little more complicated: it's difficult to paint on film like that and get it sufficiently even to be unnoticible. It was important that this "color area mask" was laid on top of the contrast reduction mask because this left the painted portion separated from the transparency emulsion (and the plane of focus) by three thicknesses of film and made it sufficiently out of focus for any unevenness to be unnoticible. Had I not been using a contrast reduction mask, I'd have used a clear sheet of film as a spacer between the colored area mask and the transparency.

In addition, I found that I'd painted the area mask a little too dark and so wound up giving about 80% of the exposure with the area mask in place and then removing the negative carrier, removing the area mask, replacing the negative carrier and giving the remaining 20% of the exposure. Being able to do this is one of the biggest advantages of using a factory made pin registration system. In addition, sometimes when the contrast reduction mask turns out to be a little too strong, you can do the same thing - give a partial exposure with the mask and then remove it for the remainder of the exposure. But first you have to invest in the registration equipment. 

You can take the color analyzer, take the Jobo, take the Zone VI compensating developing timer, no problem. But you'll get my Condit pin registration setup when you pry it from my cold dead hands!

Hope this helps get you started!


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