The toe data had a transcription error: I corrected the numbers to agree with what I used for graphing and replaced the original file on web server.
9/9/2011 TMY-2, 6 min, B+F 0.03 *Corrected toe*
I have not verified the calibrated step tablet. Can't remove it from glass to clean without possibly destroying it. (First on list of things to replace). It is a 21 step tablet, and I extend its range to 25 steps by using a gelatin 0.6 ND filter. (Steps 22-25 are not really calibrated). I put two or three step wedge exposures on a sheet of film, and average the readings.
My ASA triangle typically is 13 minutes. (Jerevan, it's just a nickname I gave the ASA/ISO standard that defines two sides of a right triangle). I use D-76 1:1 and process in trays with 6 sheets at a time, tightly stacked.
I used to "gently" and "loosely" stack the film which gives these curves upswept high values. That is not a film characteristic, it is a common development anomaly in all my curves. I ignore it.
I assume upswept curves happen because edges with more access to fresh developer - develop more - and that is where the high steps are positioned, near the film sheet edges. Lately I have been "jogging" the sheets. This reduces the upswept curves... At the same time restricts the entire sheet's access to fresh chemistry.
Last edited by Bill Burk; 07-22-2012 at 04:40 PM. Click to view previous post history.
Reason: Data error again