PMK or Pyrocat HD for enlarging 4x5 negs?

[scott_6029]

Brian, based on your comment regarding printing, I would offer the following....You said it didn't print all that bad...stained vs. regular developed negatives can be misleading until you print. So, my advice is expose, develop and print, then make judgements....

Also, for me, I prefer less stain (shorter print times and is working great for me on azo), so I use pyro mc (tray develop) (or HD - I can't tell a whole lot of difference honestly between mc and hd, except for a little less stain with mc) - slightly longer development times - since I shuffle 6 or 8 negs at a time it would be considered minimal agitation.

I have found that overexposure is really a bad thing with pyro. I rate my films at box speed or higher....you may want to test your film speed rating. If you overexpose, it looks a lot like fog and contrast is lost. You may hear folks say, cut your box speed in half or more....well with pyro, this isn't always a good thing.....

Try rating at box speed or more, meter shadows for zone 3 and develop accordingly...to get the highlights you are envisioning.

Scott

[brian steinberger]

Thanks everyone!

Chilihead,

I'm using the standard dilution for rollo pyro (1:2:100). I would prefer to not mess with dilution until I get more experience.

Sandy,

Why, Pyrocat MC over HD? And why would you prefer less stain?

Thanks!

[sanking]

Thanks everyone!

Chilihead,

I'm using the standard dilution for rollo pyro (1:2:100). I would prefer to not mess with dilution until I get more experience.

Sandy,

Why, Pyrocat MC over HD? And why would you prefer less stain?

Thanks!

Pyrocat-MC gives slighly more acutance with rotary processing than either Pyrocat-HD or Rollo Pyro. This is the main reason I introduced the -MC variation. Rotary processing with -MC gives an edgy look, compared to a creamy look with -HD. The difference is not great.

As for stain, we don't want less proportional stain, but B+F or general stain is undesirable so that is what I want to see less of. When developing for alternative printing you need very long development times to reach the needed CI. With rotary processing, these long times tend to produce more general stain. You will get less general stain in this type of condition with -MC than -HD. Again, the difference is not great.

Sandy King

[Jay DeFehr]

I think you need to be more specific. Of course they can produce the same effect but the filtration would be different, therefore the color of the stain results in a different behavior for the paper. If, as you say, the color of the stain had no effect, then the filtration would be the same for both types of stain. This is an important distinction, specially if you are heading down the road of developer manufacturing, testing and experiment design.

Which reminds me, where do you get the light bands or strips they use for the sensitometers? As you know, they come with blue/green, or just blue or green. I would like to put one that is white (preferably 5500 ºK). Is this what you did with your sensitometer and where did you buy the band?

Hi Jorge.

When we measure the stain with the blue channel of our densitometers, we're measuring the yellowness of the stain, because yellow-minus blue. So it doesn't matter whether the stain was formed by catechol or pyrogallol, it only matters how yellow it is. In other words, a catechol stained neg that measures log 1.0 by Blue channel densitometry will produce the same print density with VC paper as a pyrogallol stained negative that measures 1.0 by blue channel densitometry, and both negatives will require the same amount of magenta filtration to neutralize. Please overlook any typos, I just returned from the optometrist, where I had my pupils dilated, and so I'm typing blind. My point is that the two agents differ only in degree. Pyro developers generally produce more stain than catechol developers do, but this is not universal.

My sensitometer uses a very bright white LED as its light source, and a Stouffer 21 step transmission scale.

Regarding stain:

Image stain is good, general stain is bad. There is no advantage to limiting image stain, except as a means of reducing general stain. Overexposure is the enemy of stained negatives, as others have rightly stated. and is proportionally more detrimental when using developers that produce significant general stain.

For those printing stained negs with VC papers, it is critical that the YFE is neutralized before assessing film development. Keep in mind that the exposing light is formed below the negative, so adding magenta filtration to neutralize the YFE doesn't contract the paper's Exposure Scale, but approximates a no-filter condition. If you don't neutralize the YFE you are essentially printing at grade 1-0, and you'll see the highlight compresion so often associated with stained negs and VC papers.

Jay

[sanking]

My take on this is that the color of the stain matters, but that the use of filtration can balance it.

I explain it this way. Start by understanding that the emulsion of VC papers consists of two different parts or coatings: a blue sensitive high contrast part or coating, and a green sensitive or low contrast part or coating. As you introduce more and more magenta into the filtration package, either by the use of higher number VC filters or by dialing in more magenta on color heads, you progressively block more and more green light. Eventually you will block almost all green light, and at that point only the high contrast blue sensitive part of the emulsion is exposed, and the VC paper will print almost exactly as a graded paper. At this point highlight compression, which results from the impact of the yellow/brown/green stain on the green sensitive part of the emulsion, is entirely eliminated. This happens with all staining developers, regardless of the exact color, but the color of the stain does determine how much magenta filtration is needed to balance the effect. If you are using a VC or MC filter set, the filter number at which most light to the green layer is blocked is about #3.5, though this will vary by filter set. Another complication is that VC papers are not all the same, i.e. their point of optimum sensitivity to both blue and green light varies.

This issue is of such fundamental importance to understanding highlight compression when printing with VC papers with stained negatives that I am almost stunned that it has not been sufficiently explained to this point in the literature. But of course, you could only fully see how this work if you test these premises with good sensitometry.

Sandy

[Eric Biggerstaff]

Hey everyone,

Thanks for a great (and civil) discussion on staining developers. I have learned a lot from this thread and I appreciate that it has maintained a polite tone despite the difference of opinion.

Please keep it up.

[Jay DeFehr]

Hi Sandy.

I've been investigating these effects using a color analyzer and a color densitometer, and you're on the right track, but still a little off. The object is to neutralize the light below the negative, so it's neither blue, nor green. Most light sources require balancing even without a negative in the carrier. Once the light source is balanced, or neutralized, placing a stained negative in the carrier introduces the Yellow Filter Effect (YFE). If that stained negative happens to be a step scale, one can place the probe of the color analyzer beneath any step of the scale and determine how much magenta filtration is required to neutralize that particular step. The only color in the negative that has any effect on the VC paper is Yellow, which is minus-blue (remember we're talking about subtractive filtration), and which creates the YFE that expands the Exposure Scale of the VC paper. Yellow+Magenta= Neutral Density, so adding magenta filtration neutralizes the YFE at the point of measurement by the analyzer probe. If the probe is placed beneath the densest step of the scale, the highlight compression is totally eliminated, and the shadow contrast is increased because the proportional image stain is practically absent in the thinnest parts of the negative, and the magenta filtration neutralized by the YFE in the highlights remains magenta in the shadows. The highlight and shadow contrasts are balanced by the placement of the neutralization point on the scale. This allows for very fine control when used intelligently. As I stated in an earlier post, and again here, the only color of stain that mattters is yellow, the color measured by Blue channel densitometry, so .1 densty from a catechol neg = .1 density from a pyro neg, both will produce the same print density with VC paper, and both will require the same amount of magenta filtration to neutralize. There is absolutely no advantage to one agent or the other regarding stain color for printing on VC papers, and I hope that particular myth will die a timely death.

Jay

[Jorge Gasteazoro]

a catechol stained neg that measures log 1.0 by Blue channel densitometry will produce the same print density with VC paper as a pyrogallol stained negative that measures 1.0 by blue channel densitometry, and both negatives will require the same amount of magenta filtration to neutralize.

I disagree with this statement because while what you say is true, it matters in what step that 1.0 density it was reached. For example you might read a 1.0 in step 11 for a green stain and you might read the same 1.0 in step 9 for a yellow stain. If we agree that paper "sees" green and blue then where it "sees" the green and blue matters.

For example you might be able to correct for the difference in the stain with filtration but that difference could mean that my enlarger might or might not have enough blue light to make up for the difference in the yellow stain.

[sanking]

The object is to neutralize the light below the negative, so it's neither blue, nor green. Most light sources require balancing even without a negative in the carrier.

Jay

Jay,

At what wavelength in nm should the light source be balanced? And why that wavelength?

Sandy King

[sanking]

If we agree that paper "sees" green and blue then where it "sees" the green and blue matters.

And it is important to remember that VC papers don't "see" equally all the way from a specific wavelength in the blue to a specific wavelength in the green. Rather, there is a specific peak in the blue, and another in the green , with a fairly large bandwith in between the two where VC papers have no sensitivity.

Sandy King