filter color for hightest contrast with VC paper

[David Lyga]

The other day I tried exposing VC paper using a circular blue camera filter (the one for exposing color film under tungsten), instead of the standard VC filter, and found out that using the highest grade magenta filter (intended for VC printing) gave slightly more contrast. I thought that 'blue' was the color needed for the highest contrast. Comments? - David Lyga

 

[cliveh]

No, it's Magenta.

 

[Neal]

Hello David,

A long time ago I found the same thing when using a blue dichroic filter. After looking more closely at the transmission curves I came to the conclusion that the magenta (Polymax #5) filter I had blocked more of the green than the blue filter. Then I bought a color head and only bring out the #5 on grand occasions.<g>

Neal Wydra

 

[DREW WILEY]

The high-contrast layer is blue sensitive, so the correct answer is blue. What magenta does is filter
out the complement low-contrast color (green), so that only the blue gets to the blue component of white light. Some red light gets thru too, but the VC emulsion is blind to this. This is just basic color theory, i.e., additive versus subtractive. But given the fact that primary blue filters are quite dense,
it is generally easier in practice to work with subtractive magenta. I use both methods, and identical
results can be achieved. But if you do additive split printing, you need a blue tricolor like a 47,
not just a light blue tungsten-balancing filter, which will still allow a considerable amt of geen thru.

 

[David Lyga]

Ah, so that is the answer. Thank you Drew. The green gets by with the blue filter and needs to be stopped. That gives me my answer because, at least theoretically, and as Drew re-stated, the highest contrast demands blue. - David Lyga

 

[Andrew4x5]

According to Ilford, blue light will give you maximum contrast (as described in the link).

However, the filter you are using won't completely block out green light because it is, after all, a color correcting filter. Presumably, a blue tri-color filter would give maximum contrast.

http://www.ilfordphoto.com/Webfiles/2006130201152306.pdf.

Cheers, Andrew

 

[DREW WILEY]

What you do to see how the paper sees, is to take some bright green object and view it thru your
chosen filter material. A blue tricolor will block all green - hence the green object will appear completely black. But papers are typically a little more complex than this in real use, and with some
you might not be able to achieve DMax (maximum density) without at least some token exposure
of the green layer too. Hence you might get maxiumum contrast, but it still won't look "contrasty"
because you won't achieve a deep black. Not all VC papers are the same in this respect.

 

[cliveh]

Ah, so that is the answer. Thank you Drew. The green gets by with the blue filter and needs to be stopped. That gives me my answer because, at least theoretically, and as Drew re-stated, the highest contrast demands blue. - David Lyga

So when you want to print the highest contrast, are you going to use a Blue or Magenta filter?

 

[DREW WILEY]

Time is the critical factor for me, so I'll load up different enlargers ahead of time with different size
negs I plan to work with. My high-tech color enlargers are generally dedicated to color work, but I
do have a traditional Omega D with a colorhead, which is handy for 4x5, MF, and 35mm VC printing
using the subtractive variable YM route. My 8x10 unit, however, is fitted with a blue-green cold light,
so is ideally controlled using tricolor red and green filtration (split printing). My negs are developed
with enough consistency to where I often just use unmodified light, or just slightly tweak it with
green to put more detail in the highlights, or some blue punch for more contrast in the shadows. With
the Omega colorhead, I often might want a bit more simple contrast using magenta when higher degrees of magnification are needed. The problem with strong blue filters in particular is that you need a very strong light source. Not all enlargers will handle these. But unlike color printing, the needs of VC paper are not nitpicky, and you can get optimized, even identical, results with either additive or subtractive filtration.

 

[DREW WILEY]

Sorry ... I noticed a typo ... my cold light system is accommodated to green and blue tricolor. Didn't
mean to say red. (I had just responded to an additive COLOR printing question on a completely different forum, where red is also relevant).

 

[ic-racer]

The other day I tried exposing VC paper using a circular blue camera filter (the one for exposing color film under tungsten), instead of the standard VC filter, and found out that using the highest grade magenta filter (intended for VC printing) gave slightly more contrast. I thought that 'blue' was the color needed for the highest contrast. Comments? - David Lyga

The 'blue' filter you used passes too much yellow to achieve the maximum contrast available from the paper. What is wrong with using the #5 VC filter?

 

[David Lyga]

cliveh: the magenta is best for highest contrast because, as others have re-iterated, it stops most of the green. The green (and yellow) LOWERS contrast. The lighter blues let it through. - David Lyga

 

[Steve Smith]

It's worth a look at Ilford's data sheet for variable contrast papers. They state that all of the emulsions are sensitive to blue and the varying contrast layers have varying amounts of green sensitising dye added.

When the paper is exposed to blue light, all parts of the emulsion react and contribute equally to the final image. This image is of high contrast because of the additive effect produced by three emulsions with the same speed and contrast.

When the paper is exposed to green light, only the parts of the emulsion with the larger amounts of green sensitising dye react initially. This is because the three emulsions have very different sensitivities to green light. This image is of low contrast because of the additive effect produced by three emulsions with different speeds to green light but with the same inherent contrast.

http://www.ilfordphoto.com/Webfiles/2010628932591755.pdf

So a bit more complex than one emulsion sensitive to blue and another sensitive to green.


Steve.

 

[RalphLambrecht]

drew is spot on, butdon't forget one other variable, and that is light intensity. regardless of color. more light willgive more xposure. even a narrow-band red diode will expose the paper over time and make a poor safelightgiven enough time.

 

[ic-racer]

IC- the blue filter passes too much green, not yellow.

Of course, thank you.

Anyway, getting back to the topic on hand I would predict a speed advantage using the Ilford #5 filter. I'm surprised I did not test for speed when comparing the #5 to all my magenta dichroic filters. But if you just look at the #5 you see it is not just a magenta filter. I suspect the #5 has some some unique spectral parameters, but Ilford does not give the specs. I have subsequently given away my Ilford filters so can't test it now.

 

[DREW WILEY]

Even among papers offered by Harman the different VC papers have different nuances, which one
just has to learn by experience. But if one is going to jump into the pool in the first place, it's easiest
to teach simple Blue versus Green tricolor, or basic Magenta versus Yellow variable filtration. Once
these basics are understood, then the more complex interactions of the actual paper engineering can
be fine-tuned, like adjusting the water temperature after you dive in. It's a lot easier to demonstate
on test strips than it is to explain. No need to make a religion out of any single method.

 

[bill@lapetelabs.com]

Variable contrast paper is essentially two emulsions coated on one paper base. The low contrast emulsion is green sensitive and the high contrast emulsion is blue sensitive (positive filtration). Magenta and yellow are negative filtration. With a VCL aristo head the two tubes are blue and green, green at 100% out put and blue a various percentage of out put controlled by a rheostat to create various contrast grades.

 

[cliveh]

So guys a lot of confusing responses here, but lets give a straight answer, is it blue or magenta for highest contrast when using multigrade paper?

 

[MattKing]

So guys a lot of confusing responses here, but lets give a straight answer, is it blue or magenta for highest contrast when using multigrade paper?

Blue, if you have a source of light with no inherent green (e.g. a later version Ilford 500 head).

Magenta, if your light source is more typical.

Magenta with more typical light source is easy to work with.

 

[cliveh]

Blue, if you have a source of light with no inherent green (e.g. a later version Ilford 500 head).

Magenta, if your light source is more typical.

Magenta with more typical light source is easy to work with.

Matt, not quite sure what you mean by typical (mudying the water here)? Have you done a practical test of blue v magenta?

 

[MattKing]

Typical = halogen or incandescent or cold light? bulb.

Non-typical = blue LED with narrow spectrum filter to remove green - harder to make work.

The challenge isn't with the paper itself, it is with the systems used to control the light hitting it.

It is far easier to control green light with a magenta filter then it is to produce blue light that isn't contaminated with green.

And the excess red light that a magenta filter "transmits" improves visibility, without affecting the print.

 

[DREW WILEY]

It would be pretty damn difficult to design any automated system of exposure to predict all the variables. You'd have to settle on a single product, and then just about the time you think you have it
figured out, they'd probably tweak something in the emulsion. Even with Ilford, you've got different VC
products with different personalities, plus Kentmere VC products offered by the same corp. It would be
like trying to write a Zone System computer program for multiple film, developer, and lighting situations. You could spend years fiddling with something that only takes minutes with a simple test
strip.

 

[DREW WILEY]

Matt - it's super simple to pass blue without green. You just need a blue tricolor separation filter like
a 47 or 47B. Zero green gets through. Or you could hypothetically use the blue output on an additive
colorhead, though not many of us own those kind of rigs. The only logistical problem with a deep blue
separation filter would be due to having a hard time seeing the projected image when doing complex
dodging and burning under the blue light. I don't personally have this problem because even my cold
light is quite powerful. I have a 14x14 V54 Aristo which uses a single tube of blue-green, so works
wonderfully for split printing. Without any filtration, it lands VC paper around grade 3.

 

[ic-racer]

The other day I tried exposing VC paper using a circular blue camera filter (the one for exposing color film under tungsten), instead of the standard VC filter, and found out that using the highest grade magenta filter (intended for VC printing) gave slightly more contrast. I thought that 'blue' was the color needed for the highest contrast. Comments? - David Lyga

You shoot color, right? I'm surprised you ask this. If the 80A did not let any green pass through, your color pictures would look strange (all the green would be black).



Based on the transmission profile I'd guess the 80A prints around #3. Is that what you got?

 

[nworth]

You need to expose with more blue light to get more contrast with modern VC papers. The magenta filters pass both blue and red light. The paper is not sensitive to the red, but your eyes are, so the magenta filter makes the image easier to see. In a like manner, you need to expose with less blue light to reduce contrast. The yellow filters block some of the blue light and passes red and green. The green sensitive emulsion in the paper receives proportionally more exposure. The yellow filter allows you to see the image better.

For maximum contrast you can use a sharp cutting blue filter like Wrattan #47. You will have a very hard time seeing the image through this filter, but it usually gives a bit more contrast than the Multigrade #5. Blue filters designed for color work, like the 80B or the 82 series, pass all wavelengths. While they do increase contrast with VC papers, they are mot as effective as the Multigrade or Polycontrast filters.