Hitting ASA Triangle Does Not Mean You Got Full Film Speed
I'm consistently getting EI 250 from TMY-2. Have been for two years. The curves look great. The negatives look great (except for scratches that I complain bitterly about).
All along I thought I was getting full rated speed of 400 because I hit the ASA triangle. I made 400 my benchmark.
(Real quick: ASA triangle is 0.8 rise over 1.3 run from 0.1 over base plus fog).
I didn't question my benchmark until a roll of Panatomic-X rated extremely fast.
Reference post 146 of this thread...
I know tray processing in stacks of six sheets gives less agitation than small tanks with plenty of developer circulating around the film. But I thought hitting the triangle made up for it.
In that thread at least two estimates discredited my 400 benchmark. Now I believe my benchmark is close to 250 (may move again if new trends emerge).
Ironically, I felt clever using half box speed from the beginning. And even more ironic... after a while I felt like bumping it up to 250 because of consistently "more than enough" shadow density.
So even though I thought I was getting 400, and thought I was overexposing... I was actually using the right speed all along. That is just too scary. I could just as easily have used 400 and botched a lot of film.
I know I have insufficient agitation to meet ASA specification. I may continue to develop the way I do because the negatives meet my quality standards. I currently have no "need for speed".
But at least now there is little risk that I will overrate my film. It also emphasizes the need for photographers to determine their own effective EI. From now on, I'll be using 250 for TMY-2 and it's not just because it's "half box speed"...