Caught in the Web Pt 2
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An Occaisional Series of Interesting Items found caught in the threads of the World Wide Web.
But I digress ...
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.
Both Kodalith and LPD4 are available in the UK in 35mm wide rolls as well as sheet sizes and can be used with a red
safelight. Nice convenience. I use one of the little "painted light bulbs" for this.
* Devlopers.
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 plastic 35mm film canister, 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. Condit Mfg also sells "Herculene" which I gather is similar but possibly more expensive.
The Kodak UK catalogue lists "Diffusion Sheets" which are matt acetate designed to produce diffuse illumination
rom point light sources, but they come in packets of 12 (11 x 14 or 20 x 24) - expensive.
You might also try the type of material sold for rear projection screens.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
or
transparency, emulsion up diffusion material 1 sheet of clear, fixed-out film (acts as a spacer) masking film, emulsion up
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 fairly close. 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 test strip. 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-------------------------------------------------------------------------------
density_range_of_transparency
The calculated gamma will typically fall between 0.1 and 0.6 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 colour analyzer as a baseboard densitometer.
But I found that 'in-the-enlarger-bellows' flare affected the readings from the colour 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 0.3 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 cupboard 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 an "approximate" 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 colour 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 works well for this technique.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. Colour and density varied
slightly but noticably 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 you may have different experiences.
[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 colour shifts when switching from one size print/Jobo-tube to another and
that these colour 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.Continued next time