My testing has revealed an odd phenomenon with both XTOL and D316: Large areas that are heavily exposed can develop to a greater density, and nearby thinner areas will develop to a lower density, causing an overall increase in contrast. Here's an example showing a small amount of this:
Notice that the slope increases slightly after X=1.5. That's where the top row of denser Stouffer wedges starts. This slope-change is not due to uneven lighting because other graphs are straight through there. Here's a more severe example with XTOL:
This is two Stouffer graphs concatenated together at X=3.0, where the second got much more exposure. The D316 graphs match nicely, but XTOL's graphs have a big jump where density was higher. This density-boost only seems to occur where large areas have much exposure, so maybe nobody cares about it. But I'd like to avoid it in my testing. I'm thinking of shooting a roll where each frame has only a small area of a given exposure. That would eliminate this "overexposed neighbor effect" as I'll call it, and would give me 37 wedges instead of 21.
Any idea why this occurs? Is this a well known phenomenon?
Last edited by albada; 12-19-2012 at 03:09 PM. Click to view previous post history.