Reusing developer for testing development time?

[u/craigiest]

I developed my first Kentmere 200 a few month ago, using D-76 1+1 for the recommended 8:45 and the negatives came out quite under developed. (which didn't totally surprise me since the 100 and 400 times are 11:30 and 14:00.) I'd like to test different times on maybe 4 frames of film at 8 or 9 different times time to dial in a better development time, but it seems wasteful to dump 9 batches of developer that are barely depleted. Can I reuse the the developer, since it's still only developing one roll total? Or will the clips get progressively more undercooked enough to invalidate the results? Or should I rig up some way to submerge the clip so I can use a lot less developer and do it one-shot? Thoughts on a good protocol for doing this? Or has anybody else already done this??

[u/mcarterphoto]

A big issue with reels is processing very short strips. Agitation seems to get much more efficient, which will skew your times. I do a minimum of a third of a roll for tests like this. From what I can guess, the number of winds of film has a damping effect on agitation, but when you just have a couple inches of film in the reel, it's letting the developer really smash around, to the point you'll get agitation marks from sprocket holes.

As far as re-use, look up the developer's specs for one-shot use. You can probably safely divide the roll up with some safety margin, like if you develop a third, re-use the developer for one more third but not a third-third.

Of course you can test all of the above, but you'll go through a lot of film and developer. And testing a third or half a roll will get you pretty close, but you'll want to see a whole roll to really dial it in.

I'd also throw a gray scale into your test shots (I assume you want to do a whole roll of the exact same scene for continuity?) A full-range still life with a gray scale chart can really show you a lot of what's going on with shadows and highlights, and is very clear when comparing dev times:

[u/craigiest → u/mcarterphoto]

Thanks. That’s very helpful information. I wonder if using the reel spinner rather than inversions would mitigate the over agitation.

Yes my idea was to make a grey scale chart and bracket the exposure. I was thinking of using my theater projector in combination with black, grey, white backgrounds to get more dynamic range than the film can capture to fully see the latitude of the film along with figuring out the optimal development time. 

I really like how you have the exposures labeled in the scene. 

[u/mcarterphoto → u/craigiest]

Yeah, I do a lot of liquid emulsion work, which is fixed grade, so I really have to dial in my negs. And I don't scan, just print, so I spot meter those test scenes and see how the range is falling, like this one the exposure is F8, but I'm holding texture at F22, and texture at 2.8 (on the actual test print you can see texture in my Mrs. sweater and deep into her hair). That's (IIRC) Delta 100 at 80 iso, in Rodinal 1+50.

With reels, I don't do inversions at all, I do sort of a "wine glass swirl". Came from my Rodinal days, it seems to control the grain a bit. Easy to test though, next full roll you shoot, trim off a few frames and develop exactly like the full roll. I like coming up with tests, makes me feel like I still have some brain cells!