How can I estimate development times for unknown A125 black-and-white film, especially in T-Max RS?
Asked 7/6/2019
7 views
2 answers
0
I bought several rolls of an unfamiliar black-and-white film labeled “A125” in Russia. It appears to be bulk-loaded into reused canisters, and I was given conflicting development times for D-76 1+1: 12 minutes in one store and 14 minutes in another. My usual lab uses T-Max RS rather than D-76, and I can’t currently process the film myself.
What’s the best way to handle an unknown film like this? Is there a reasonable way to estimate a T-Max RS time from known D-76 times, or should I approach it differently? Any reliable development information for this film would also help.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
2
First of all development times for B/W are just not that critical: you can get decent negs with fairly widely-varying times. Obviously if you want optimal & very repeatable negs you need to be significantly more careful. But you're not going to get that anyway if you buy random film, and actually some variation can be interesting sometimes.
That being said: look up a bunch of films in the massive dev chart and find their processing times with D-76 1+1. Especially look for ones with dev times around 10-15 minutes. Look up the same films' times for TMax-RS. Compute the ratios between the times: are they all approximately the same? If they're not, are the ones with D-76 times in the right ballpark approximately the same ratio? If they are use that factor, if not, look for films which have the same speed, and times between 10 & 15 minutes & repeat. Finally if there really is no common factor just guess something reasonable: chances are it will be fine.
Originally by user82065. Source · Licensed CC BY-SA 4.0
user82065
7y ago
0
Generated from our catalog & community — verify before relying on it.
For unknown black-and-white film, the safest approach is testing rather than chasing an exact published time. B&W development is somewhat forgiving, so a 12–14 minute D-76 1+1 recommendation at 20°C is not wildly inconsistent.
From the answers provided, reported times for this film are:
- D-76 1+1: 12 min at 20°C, normal agitation, about ISO 140 (lower contrast)
- D-76 1+1: 15 min at 20°C, normal agitation, about ISO 150
- HC-110 dilution B: 3 min 10 sec, rated at ISO 400
If your lab uses T-Max RS, the practical option is to sacrifice one roll and ask for clip tests at different development times to find a good density. That will be more reliable than guessing.
If clip testing isn’t possible, you can estimate by comparing several films in a development chart: find films with similar D-76 1+1 times, compare their T-Max RS times, and use the approximate ratio as a starting point. But this is only an estimate, since unknown emulsions may not track cleanly across developers.
Recommended products
UniqueBot
AI7y ago
Your Answer
Related Questions
Can Kodak T-Max film developer be used for black-and-white photo paper?
How should I develop Kodak T-Max 100 if it was overexposed by about 1.5–2 stops?
Why am I getting uneven development when tray-developing 4x5 black-and-white negatives?
Why do some black-and-white negatives look flat while others on the same roll look normal?
How can I get harsher contrast and darker blacks from Kodak T-Max 400 while scanning?