Push Processing

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Ian-Barber

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When pushing film ( under-exposing) and then increasing the development to give more tonal separation, does the type of developer have much play in the outcome and if so, how does PyrocatHD perform in the above scenario.
 
I push processed some HP5 in Pyrocat HD to 1600/3200 EI, I was very pleased with the results in terms of grain and how both shadow and highlight details were retained. It was evening light dropping fast and the sun had partially dropped behind a football stadium. I was photographing Tornado on the SVR and what should have been 1/100 f16 @ 400 EI ended up being 1/25 f5.5 at approx 1600/3200 EI. The engine/train was over 45mins late, 1/25 is too slow for a moving loco and the f5.5 aperture on a 360mm telephoto gave shallow DOF.

The top of the loco and coaches were in sunlight the rest in shadow but the negative was easy to print, I put that down to the developer and particularly the staining, controlling the highlights, from memory I processed for 45 or 50 minutes 1+1 to 100 @ 20°C normal inversion agitation.

Ian
 
With that long dev time Ian, am I right in saying this was a semi stand development, or please elaborate your method
 
Normal inversion agitation in a Jobo 2000 tank, these tanks predate the later rotary tanks. However after agitating every minute for perhaps the first 5 minutes so so I think it was more like every 2 or 3 minutes, I wasn't really expecting much as the light level had dropped so low it was dusk that's the reason for the long development time. I wasn't sure of the actual light level my last meter reading was for 1/25 f5.5 @ 1600 EI and the light was dropping by the second as Tornado approached.

1771

Ian
 
So the extra, long, time with reduced inversion was to achieve more contrast in the negative because of the under exposure, is that correct?
 
On my screen, it looks like a good rescue of underexposure. A seriously picky eye might want a little more detail in the shadows under the carriages, but it's not pictorially significant. Railway enthusiasts might prefer to see every rivet, everywhere.
The main difficulty must have been controlling the very bright reflections on the locomotive. Normal pushing could have made them unprintable.
It sounds as though you estimated the development time by experience and inspiration.
 
martin henson said:
So the extra, long, time with reduced inversion was to achieve more contrast in the negative because of the under exposure, is that correct?
Click to expand...

In theory the under exposure and greatly increased development should increase contrast, however Pyro developers work differently because they have a tanning effect as well as the staining. So with longer development the highlight areas start to harden slowing development and increase in stain whereas then shadows in particular continue developing faster, the reduced agitation has less of an effect.

Old style Pyro developer were much more concentrated in use with short development times and used constant agitation tanning effects were stronger and happened faster but had the effect of preventing excessive contrast build up.

Ian
 
So, it's the tanning effect that's significant?
 
So, the staining increases density and the tanning, by reducing the penetration of the developer, reduces silver density in the highlight regions. Presumably this reduces local contrast in the highlights. I'm guessing that further control might be possible be bleaching away the stain, although I don't know what would be a suitable bleach. Prolonged fixing, perhaps?
 
The Pyrocat staining is quite stable and I've not found a way of reducing/bleaching it after processing. Over fixing will bleach the Silver image.

The staining and tanning is advantageous as it helps stop the highlights blocking up, and also because it's slightly more diffuse than the Silver component reducing apparent Graininess. I've not noticed a drop in local contrast in the Highlights rather that areas that would typically need quite a bit of burning in with a non staining developer print more easily and need only a little burning.

Ian
 
My reasoning was thus:
Staining will increase the negative density and increase film base plus fog. We'd expect any increase in density to record as an increase in overall contrast. The reduced penetration of developer in the tanned areas will reduce the silver density.
So we have an increase in FB+F and a decrease in silver density in the highlight areas. That should reduce micro-contrast in the highlight areas, making them easier to print with significant detail.
I haven't touched on the overall contrast of the negative with Pyro, but I assume that it's well controlled by the process.
I'm trying to understand the process here, not to dispute its benefits.
 
You need to think of how chromogenic films work, that's modern colour films and XP1/2, the dye couplers in processed film have far less physical density than a conventional B&W film but because of the coupler colour have a greater effect than the comparable density of a silver negative. With XP1/2 the coupler(s) give a reddish brown colour and of course that's similar to a safelight.

So when you add the staining to a slightly lower density silver component with a Pyro staining developer you're effectively extending the highlight end of the films characteristic curve, this actually helps give better highlight detail, and less compression of highlight contrast.

I don't notice any increase in base fog with Pyrocat HD, my negative print for pretty much the same times and grades as when I used Rodinal and Xtol, they are easy negatives to print even in quite difficult lighting conditions.

Ian
 
Interesting. I had quite a different idea of how it worked. Thank you.
 
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