Multicontrast filters for 8x10 printing

[ic-racer]

I did some tests with a double-layer of the Rosco blue, in an attempt to get number 5 contrast.

I think I have reached the point of diminishing returns and the double blue is just ever so slightly higher contrast than the single blue. This may be as much contrast as the paper will give. If it comes out to the correct ISO grade, I can't really tell because I'm not an 'authorized ISO testing facility'

It is interesting to note that when Ilford tested the W45 bulb they concluded:

"With the Aristo W45 lamp,... It can be seen that a full contrast range can
be achieved, [with Ilford VC filters] ..."

from: http://www.ilfordphoto.com/Webfiles/...0201152306.pdf

[Nick_3536]

Using two of the same filters should be no different then one filter.

The first filter will pass some light frequency.

The second filter will pass the exact same light.

[ic-racer]

Using two of the same filters should be no different then one filter.

The first filter will pass some light frequency.

The second filter will pass the exact same light.

Thank you, that's right, I'm just making neutral density. That's why I'm posting this as I go, so I can be double-checked.

I checked my Rosco Primary Blue diagram and it has a little hump in the cyan/green area, that's what I need to get rid of. Looks like the CC90 will be better. I'll check with my local store to see if they have that CC90B.

After buying too many of these Rosco filters, I might be better off just to get the Ilford 00 and 5 filters at $20 a piece, but what's the fun in having it all figured out already

[ic-racer]

So, the main problem with the Rosco Primary green is that it is very very slow. I would gladly give up some softness in contrast in exchange for more speed. ie a little blue in the filter.

Here is the Primary Green (#91) and two others I might try. The Chroma Green looks like it will be very fast (tall peak) but has a little cyan in it. I guess the only way to know for sure is to test it.

[ic-racer]

A swatch book would be great for testing; turns out the Rosco site has a page to fill out for a free one. I may hold off more testing until the swatch book arrives.

[Jrewt]

20$ a piece is a little steep for 2 filters! I have a set of 6x6 ilford filters, but the lowest contrast filter is 1/2. Don't know why 0 or 00 isn't included! I don't think I'll spend 20$ on ONE filter =)

[ic-racer]

20$ a piece is a little steep for 2 filters! I have a set of 6x6 ilford filters, but the lowest contrast filter is 1/2. Don't know why 0 or 00 isn't included! I don't think I'll spend 20$ on ONE filter =)

I was looking at prices on the B&H web site and the description of those 6x6 Ilford filters is that they can also be used UNDER THE LENS. This is news to me. If that is the case, the stalk on my lens board can easily hold two filter holders that can be flipped in and out. Or just stick a Roscoe yellow up in the filter drawer and use the set of filters in the standard manner under the lens.

I measured the image circle at the level of my under the lens filter holder and it is 3.5", so I don't think those 3" Ilford filters with the holder will work.

Anyway, here is the list of all the other options I could find:

FOR FILTER DRAWER:

Roscoe 20x24" = $6 per filter

Ilford 12x12" = $20 per filter

Kodak acetate 12x14" filters = $80 per filter.

UNDER THE LENS FILTERS:

6x6" glass filter = $320 to $400 per filter

Round 86mm screw in filter for the Rodenstock 300mm/5.6 = $124 to $150 per filter

Kodak Wratten filter 4x4" = $50 to $100 per filter

Optiflex 4x4" = $35 per filter

Lee filter 4x4" = $20 per filter

Ilford 6x6" (Can really be used under the lens??) = $45 (whole set only?)

[ic-racer]

Well, I splurged on another $6 filter and got the Rosco 389 Chroma Green. Based on the transmission spectrum I was expecting more speed with perhaps some loss of range.

Just because I am not using 'standardized conditions' and all these tests are 'relative' I re-tested all filters on the same test strip. This also gave me relative speed info. So, the numbers may not all be the same as yesterday's tests.

#91 = Rosco Primary Green
#80 = Rosco Primary Blue
#389 = Rosco Chroma Green


Log values:
#91 = 2.10
#389 = 1.95
#80 = 0.60
Bare = 0.90


Relative speed to 'middle gray' (the step in the middle, between the black and white; not some standard gray value)

Bare = +1 stop
#80 = 0 by my definition
#389 = -1.5 stop
#91 = -3.5 stop

So, I knew #91 is really slow, but now I have a number for it.

The conclusion is that for less than $15USD a nice balanced set could be made from a singe #389 and a double #80. Again, doubling it just for extra density (the $6 gets you get enough material to make 2 filters).

[ic-racer]

Why do you need a balanced pair? I didn't think it was that important, like 'so what' if the green is 80 seconds and the blue is 1.5 seconds, my electronic timer can handle it.

The problems came when I went to change the aperture without changing overall exposure. Doubling 80 and doubling 1.5 were not the same. The slow time IS reproducable, however, because of afterglow or whatever else, 3 seconds was not the real double. If both times had been close to 80 sec. or close to 1.5 sec, changes in aperture would have been more predictable.

Up until now I have been avoiding chaniging the aperture in the middle of the test print sequence.

Tonight I will try the #80 as single and double, along with the #389.


You might ask why I would want to mess with the aperture, and it is only because the 300mm Rodenstock is new to me and I am curious to see how it responds to different settings on the aperture scale. Some of my shorter lenses are really useful only over a small range (f8 or f11). Under the magnifier this 300mm lens seemed to not have any change in edge sharpness or detectable diffraction over a large aperture range. Curious to see if this holds up during printing.

[ic-racer]

1) A very quick and inexpensive way to do MC or VC printing is to use Rosco filters
2) A combination of #389 Chroma Green and a double layer of #80 blue will make a good combination for 'split grade' printing. The contrast range is about the same as a dichric head that was tested. About 00 to 4
3) I could not detect a speed or contrast advantage to blue vs magenta or yellow vs green and I suspect there are many other Rosco filters that will give excellent results.



What's next?

This temporary solution with the Rosco filters worked so well last night that it could easily function as a permanent solution. Altough the split grade printing concept seems to be favored by many, I need more control over middle gray values (though the prints I made last night were some pretty fantastic; my first good 8x10 projection print enlargements to 11x14).

I imagine that if I were to stick with the two filter technique I will make up a chart of color ratios (contrast grades) and exposure factors for each color. This way I can work in a manner more suitable to my style. That is to say (a) set the grays and the overall intensity of the image with exposure first then (b) adjust the contrast, pivoting on the grays (ie blacks blacker at the same time that whites get whiter).

So what the chart would do would let me go from a ratio of say 3:1 (Grade X) to 2:1 (Grade Y) and keep the middle grays constant. It really will be easier than calibrating a color head. I just need to choose some ratios and do step-wedge prints at the same TOTAL exposure. Then just line up the middle grays, counting the number of steps the deviate from each other, realizing that each step on my wedge is 1/2 stop. So my chart will show 1:1 as defined as 0 for the factor. Then 3:1 may have -1/2 stop for the factor and 2:1 may have -1 stop for the factor. So to go from 3:1 to 2:1 I will just calculate the resultant factor (1 - 1/2 = 1/2) and apply that to get my new TOTAL exposure. With this number I apply the new ratio (2:1 in this case) to get my individual exposures.