Quote Originally Posted by pellicle View Post
... I was surprised to find that even that didn't have the densest area being as dense as the element of a light bulb I photographed and developed normally. I'm sure that there is some substantial difference between the snow and the filament brightness. ... I wish I could compare numbers with people as I find that easier to reconcile with.
Some random thoughts:

I'm not sure I'd use the image of a light bulb filament as an absolute standard for evaluating negatives. I presume you processed that too.

Similarly, I'm not sure a snowy scene is the best for getting the hang of a "normal" developing time, etc. A scene composed of really dark and really bright elements and probably a rather extreme contrast may lead you astray. A set up with a full range of mid tones as well as a modest representation at the extremes would be the easiest starter.

I think that comparing numbers with someone else is less useful than what you are doing now; doing prints and finding out where you can improve. The numbers are good for a lab, but won't do the important work of creating a proceedure based upon your results.

Quote Originally Posted by pellicle View Post
... I developed sheets in 3min 6 min and 12 min (where N = 6 min for the temperature I was using) ...
Great start - the idea of geometic jumps in developing times as a test series is exactly the way to do it. When you are more zeroed in on a time, you can do jumps at a smaller increment of time. Use the FStop series as a basis. Half stop or third stop series and you will find you can fine tune film development. I keep a set of those numbers handy for all sorts of uses. I calculated them wayyy out into the thousands for just such tasks as yours.

Given that you needed grade 4 to get a good print, maybe you need to push your film developing time further to build enough contrast so it works better on grade 2 or 3.