Rating Acros at 25 ASA

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For my next pinhole outing, I want to have longer exposure times using Acros. At box speed, I get 1-2 seconds, which is a bit marginal for keeping things stable when operating the shutter in my pinhole camera (a bit of thin wood that slides in and out of a slot). A bit of shake or mishandling could be a fair proportion of the overall exposure time. At 4-8 seconds, the proportion of time that might have shake reduces quite a lot. I'd also like to introduce some subject motion blur if the opportunity presents itself.

I'm interested in rating the film at 25asa, with the aim of getting negs that will scan okay in my Epson V700. I'd appreciate thoughts on whether my plan for developing is likely to work.

The film is 120 format, so 600ml of solution, and the developer is HC-110. I'm thinking of using this quite dilute to get a reasonable development time - in dilution B at 100asa, Acros is developed for 5.5 minutes with inversions at 1 minute intervals. On the other hand, a dilution of 1+99 means 6ml of concentrate which is about the limit for the developer not becoming exhausted. Adjusted for 1+99, the time for 100asa becomes about 17 minutes.

To pull to 25asa, about all I have to go on is some times from the Massive Dev Chart for 100asa and 50asa. For Acros in Rodinal: 13.5 mins at 100asa, and 11 mins at 50asa, and Ilford Delta 100 in HC-110: 6 mins at 100asa, 5 mins at 50asa. In other words, a ballpark guide to pull one stop is to develop for about 80-85% of the time.

I have two questions...

To pull another stop, do I reduce the development time by the same percentage a second time? In other words (rounding for easy minutes), 80% of 80% (=64%) of 17 minutes gives 11 minutes.

If that's about right, would normal agitation be okay, or should I consider less agitation to hold the highlights? Every 2 minutes? 3 minutes?
 
Pulling the development will reduce the contrast. If you use the information you quote above, you are likely to end up with a very low contrast negative. If you develop at box speed, you will end up with a very dense negative. Personally, I would split the difference and go for 11 mins in Rodinol. I certainly would not reduce agitation as you will just add further issues to your negatives.
 
Cheers, Peter. I had done some searching a week or so ago and found that thread, and then forgot about that when I posted the above. I think the two most notable things are that there's not much talk of hacking about with agitation, and somebody mentions that subject contrast could be a factor. Also, the reductions in time seem to be a bit less than what I'm considering - they seem to be angling on 20-30%, while my initial guess is more like 36%.

Noted on contrast, John. However, the developer will be HC-110, because that's what I've got.

So, I'm thinking of trying 12 minutes (30% less) in HC-110 at 1+99 with normal agitation.
 
I'd probably develop normally the in the first instance, this will give you a comparison with 100 iso negatives so you can decide if it needs much adjustment. If it does I'd start with a 10-15% reduction and work from there, normal agitation unless you have cause to reduce it.
 
Just developed a test roll (shot in the ETRS) in HC110 at 1+99 for 13 minutes. My feeling is that it's a little bit thin in the skies, but the shadows look okay. I'll see how it looks when it's dried and scanned.
 
Seems like a bit of a faff for a longer exposure time.
If that's all I wanted I'd figure out a way of using an ND, shoot box speed and dev normally.
I mean, if that's what you like to do, push/pull dev calcs and all that, fair play to you...:)
 
It's less of a faff than fitting an ND filter to the front of my pinhole camera in a manner that doesn't involve gaffer tape or superglue (ie, removable without making a mess). Aside from that, the adjustment to the process does interest me in any case.

I changed the dilution to 1+74 (8ml of HC-110 instead of 6). A quick peek at the end of the roll after fixing looks a bit better for density. That said, the test roll seems to scan pretty well, so I think it'll be fine.
 
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