First time poster, short time reader :-)(posted 8467 days ago)I've recently got into large format photography, and have embarked on a testing binge over the last week or so.
I don't have a densitometer (who does?), and don't have the time to alter my Minolta Spot into one, so I purchased a gray scale card from the local camera store (named, strangely enough, 'The Camera Store' :-) ).
I mounted the gray scale (and the color scale, just for fun) on a gray card, and metered (at 400 ISO) on the gray card. I took a single picture.
I then took an unexposed negative, and developed it at roughly 73F for about 9 minutes (standard dev time is 68F/9.5m). I also developed one oother negative for the same amount of time, at the same temperature.
I took the negative of the gray card, and focused the enlarger such that the exposed image would match the gray scale card so I could do comparisons. I then placed the blank negative into a carrier, and determined that dMax is about 13 seconds at f/11 at the set height of 60. I then took the first exposed sheet of film, exposed it the same way, and developed the print. After the print dried, I compared it to the gray scale card, and found that I was off three graduations, which from reading the card is 0.3 in density, or 1 full stop.
I then took two more shots with a full stop more exposure (200 ISO), and proceeded to develop one of the negative the same as above, and the other with about 30% development. The first negative with 1 stop more eexposure didn't show much difference. The second negative, with about 30% more development, was 1/3 stop closer to the gray scale.
After making the print (and not changing anything), I only gained 1/3 stop more exposure.
Now I'm a bit stumped. I would have thought that 1 stop more exposure should have pretty much nailed the gray scale card, and the second + developed negative would have shown some signs of expansion, but no such luck.
After thinking about this for a while last night, I remembered that the film developer (IFOSOL-S) is probably getting a bit old, and the airspace in the original container was getting pretty big. Am I looking at aging of the developer? Would that cause what I've seen?
I'm heading to the store at lunch today to buy a fresh batch of developer, and I'm going to try again. If anyone has any other suggestions other than getting new film, I'd love to hear them.
Thanks!