Pyrocat HD, VC papers, light source and contrast

[john_s]

.......................Another issue that has to be taken into cosideration is whether or not one is using a UV filter in the enlarger. The stain of most staining developers is highly actinic and greatly impedes the passage of UV light, and most photographic, both graded and VC, are very sensitive to UV light.

Sandy King

I have had some experience with PMK negs with a 2-tube VC head which I have not fully understood. The contrast reduction in the highlights did not seem to occur to the degree reported by others. I put it down to the fact that my negatives were deliberately not very dense (due to generous exposure and developed to not very high contrast), which would result in not great levels of stain in the highlights. But another explanation was that my VC head was producing more UV than most setups. I was under the impression that most lenses don't pass much UV, but maybe it's a matter of degree. I can easily imagine a 2-tube VC head producing more UV than a colour head, though.

 

[gainer]

It is often stated that yellow proportional stain reduces contrast in highlights. If that were possible, the print of a bleached, stained negative would not be possible. The highlights would have to be printed as negative. I assure you, such prints can be made on both graded and VC papers. The total contrast may be lower when measured by a densitometer, but the contrast of the silver image is also lower than it would be for a good print of only the silver image on eithe graded or VC paper.

Ctein found focusing errors when using blue light, but IMHO he did not find the correct reason for it. He thought the paper manufacturers were making paper with significant UV sensitivity, and the projection lenses were not achromatized for UV. If some of that is present, nevertheless, the focus of the eye changes quite a bit even over the range of graded papers. This focus shift of the eye is easily demonstrated, and has been known to astronomers for many years. There are two effects of the eye's chromatic aberation: The focus shift is quite easily seen on a single trial. The other effect is due to loss of sensitivity of the eye away from its natural bandwith, which causes more scatter in those readings and a consequent bias of the average in the direction one would expect from chromatic abberation of the eye.
The best way to test is to use movements of the enlarger head to focus rather than movements of the lensboard. Considerably more movement of the head than of the lensboard with respect to the head is required to correct a given focus error. This is easier to do on enlargers with a geared track and crank to move the head.

 

[dancqu]

The contrast reduction in the highlights did not
seem to occur to the degree reported by others.

You've two explanations; thinner negatives and
possible high violet and UV output from the light
source. I'd think another might be the spectral
response of the papers. Dan

 

[dancqu]

The best way to test is to use movements of the
enlarger head to focus rather than movements of
the lensboard.

That is exactly what Ctein did when he tested.
He altered the distance twixt the baseboard and
the film plain. He did so by shimming; the measure
of which was the adjustment. Dan

 

[john_s]

You've two explanations; thinner negatives and
possible high violet and UV output from the light
source. I'd think another might be the spectral
response of the papers. Dan

The two papers were Agfa MCC and Ilford Multigrade IV, both pretty much standard VC papers. I'm sure the spectral response of the papers is part of the explanation, in fact it has to be if the papers are variable contrast: it just surprised me (it was a pleasant surprise) that I didn't see unwanted contrast reduction. I think that I did see contrast reduction in a couple of photos that were taken inside churches: the overexposed windows were easy to burn in. But that degree of density was, obviously, fairly extreme.

 

[sanking]

It is often stated that yellow proportional stain reduces contrast in highlights. If that were possible, the print of a bleached, stained negative would not be possible. The highlights would have to be printed as negative. I assure you, such prints can be made on both graded and VC papers. The total contrast may be lower when measured by a densitometer, but the contrast of the silver image is also lower than it would be for a good print of only the silver image on eithe graded or VC paper.

I think you are looking at this the wrong way.

In a previous message I wrote: "However, the stain (read here yellow or brown) does not impede the passage of green green light so it (the stain) has very little effect on the green sensitive part of the VC emulsion. The net effect is that as shoulder density increases less blue (high contrast) light can affect the VC emulsion (*because of the brown stain which impedes blue light), while the green sensitive layer remains unaffected. This results in highlight compensation, which can be a good thing when shooting in high contrast situations.

It is not that the yellow stain reduces contrast "per se", but that the yellow or brown stain impedes passage of light to the blue sensitive (high contrast) part of the emulsion, while allowing without restriction passage of light to the green sensitve (and low contrast) parts of the emulsion.

Sandy

 

[Tom Stanworth]

Leon,

I had this problem and posted it a number of times. I found that I was having to develop for FAR longer then supposedly required to get good printing on VC paper with either of my colour enlargers. My solution?

Use 2:2:100 Only. Forget 1:1:100 with my colour heads. You will find a decent time (forget what everyone else says works for them).
Bin HP5+ and use TriX instead - far punchier.
Standardise on G3 (I still found myself printing mainly at g3.5-4).
with the substntially increased development required you can afford to increase film speed a touch.

I have been using non-staining devs moresince being overseas so I am totally happy with a number of alterntives. I will go back to Pyrocat when I rtn home but will probably use it mainly when photographing scenes where I need to be concerned with retaining highlight detail, such as fog, water, snow, sand, bright skies etc. For normal stuff I am going to predominantly use a normal dev, such as Xtol, ID11. The other disadvantage ith Pyrocat is the speed which I just have not found to be as good as standard devs and half that of the likes of DDX/Xtol. Still, for tripod work and slow films, it injects and acutance otherwise missing. I might start playing around with making FX-37 other non staining acutance devs too and comparing them.

 

[john_s]

.............Use 2:2:100 Only. Forget 1:1:100 with my colour heads. You will find a decent time (forget what everyone else says works for them).
Bin HP5+ and use TriX instead - far punchier.
Standardise on G3 (I still found myself printing mainly at g3.5-4).
with the substntially increased development required you can afford to increase film speed a touch.................

Tom, is there a grain penalty in doing this? Compared with using a VC head or filter system that gives the desired contrast with less development, HP5+, etc?

 

[sanking]

I have had some experience with PMK negs with a 2-tube VC head which I have not fully understood. The contrast reduction in the highlights did not seem to occur to the degree reported by others. I put it down to the fact that my negatives were deliberately not very dense (due to generous exposure and developed to not very high contrast), which would result in not great levels of stain in the highlights. But another explanation was that my VC head was producing more UV than most setups. I was under the impression that most lenses don't pass much UV, but maybe it's a matter of degree. I can easily imagine a 2-tube VC head producing more UV than a colour head, though.

It is true that most enlarger lenses block a high percentage of UV light, but they don't block all of it.

My own comments about the importance of UV were made within the context of contact printing with graded silver papers, including AZO, where no lens was used. In those circustumances I found that the use of a UV filter blocked light below 400 nm resulted in a lot of printing speed of well over two stops. That suggests to me that most silver papers have a lot of sensitivity to UV light.

Sandy King

 

[sanking]

The two papers were Agfa MCC and Ilford Multigrade IV, both pretty much standard VC papers. I'm sure the spectral response of the papers is part of the explanation, in fact it has to be if the papers are variable contrast: it just surprised me (it was a pleasant surprise) that I didn't see unwanted contrast reduction. I think that I did see contrast reduction in a couple of photos that were taken inside churches: the overexposed windows were easy to burn in. But that degree of density was, obviously, fairly extreme.

Perhaps the contrast reduction that you expectected did not take place because of the VC filter (or CYM combination) you used. If you used a filter of 3 1/2 or more, or a CMY combination very high in magenta, you are blocking green light, which is the source of the contrast reduction.

In some of the curves I have plotted comparing staining and non-staining developers it is fairly obvious that if the filter used is high in magenta both negatives print the same. As I indicated earlier, with VC papers the use of filters high in magenta eliminates or greatly reduces highlight compensation with stained negatives. The way to take advantage of this fact to get compensation is to develop the negatives longer to increase printing CI, and then use a filter of 3 1/2 or less. Or a CMY combination not very high in M.

Sandy

 

[gainer]

I think you are looking at this the wrong way.

In a previous message I wrote: "However, the stain (read here yellow or brown) does not impede the passage of green green light so it (the stain) has very little effect on the green sensitive part of the VC emulsion. The net effect is that as shoulder density increases less blue (high contrast) light can affect the VC emulsion (*because of the brown stain which impedes blue light), while the green sensitive layer remains unaffected. This results in highlight compensation, which can be a good thing when shooting in high contrast situations.

It is not that the yellow stain reduces contrast "per se", but that the yellow or brown stain impedes passage of light to the blue sensitive (high contrast) part of the emulsion, while allowing without restriction passage of light to the green sensitve (and low contrast) parts of the emulsion.

Sandy

I agree. But I was reporting what others have said, and disagreeing with them. Certainly, the fact that one can make a print from the stain image alone illustrates the truth of what you say, and the falsity of the idea that the yellow part of the stain acts mainly as a softening filter on VC paper.

 

[Tom Stanworth]

Tom, is there a grain penalty in doing this? Compared with using a VC head or filter system that gives the desired contrast with less development, HP5+, etc?

To be honest I have not done the comparisons to say. Certainly with the finer grained films I have used it just is not an issue that I have seen at MF and LF sizes. In some respects what confused me was thinking about what everyone else claimed to be doing...normal 1:1:00 times, VC paper...yeah right! When I actually removed the blindfold I found out i was not alone so just did what I needed to do to get good prints regardless of what everyone else claimed. I found, right or wrong, that 2:2:200 gave me the basic 10 min times (roughly, been away from notes for 1.5 years so cannot really remember) and decent negs. The prints looked fine, just economy was twice as bad. Lets put it this way, I found I got effectively grainless (not if you really screwed your eyeballs looking) 10x8s from 645 TriX negs developed to give a normal print on g3 when the conditions were flat overcast. That will do OK for anyone surely? The prints had a nice tonal range and were very crisp. I used TriX which just printed better than Hp5 plus when dealing with overcast scenes even if the negs looked of simialr contrast to the eye.

With my colour head I have to develop everything more than the conventional norm of 50% or so more exposure and 25% less development (even with normal non staining devs). Do this and I am in G5 territory. I often expose at 1/2 to 2/3 box speed with D76 or the like and develop between -15% and +15%. I just found that Pyrocat tipped things oevr the edge and without extended devlopment left me with no wiggle room at the harder end.

 

[dancqu]

... the falsity of the idea that the yellow part of the
stain acts mainly as a softening filter on VC paper.

Mainly? THE softening filter for VC IS yellow. Stain density
is in some proportion related to image silver density. If a
stain only VC print were made the shadows would be of
higher contrast and the highlights of lower contrast.

I just wonder if there is a point of diminishing returns.
That is, will at some point in image silver density a point
be reached where stain density will cause a lowering of
contrast in the print. I see some are using more time
and higher concentrations. Dan

 

[Donald Miller]

Mainly? THE softening filter for VC IS yellow. Stain density
is in some proportion related to image silver density. If a
stain only VC print were made the shadows would be of
higher contrast and the highlights of lower contrast.

I just wonder if there is a point of diminishing returns.
That is, will at some point in image silver density a point
be reached where stain density will cause a lowering of
contrast in the print. I see some are using more time
and higher concentrations. Dan

If one attempts to develop film past the point of the maximum density then there will be a diminishment of effective density range. This can also be hindered by overexposing film. That usually occurs when the film is unilaterally downrated or if the exposure is placed too high. A case in point would be if one automatically bases exposures on a Zone IV shadow placement.

 

[gainer]

Mainly? THE softening filter for VC IS yellow. Stain density
is in some proportion related to image silver density. If a
stain only VC print were made the shadows would be of
higher contrast and the highlights of lower contrast.

I just wonder if there is a point of diminishing returns.
That is, will at some point in image silver density a point
be reached where stain density will cause a lowering of
contrast in the print. I see some are using more time
and higher concentrations. Dan

It appears you have not tried to make a VC print from a yellow-only negative. I did it once for publication in the article "More Pyrotechniiques" in Photo Techniques, I think while it still had the old title. I don't remember which issue.
In your theory, would a point be reached where the yellow density is so high as to cause no contrast? You could test the effect of different ratios of silver to stain by bleaching without fixing and redeveloping the negative partially with a non-staining developer.