Test procedure for even development?

[Bill Burk]

I was going to say that is awful - makes using an enlarger for sensitometer look like a bad idea.

Until I realized. I keep the enlarger locked at the height to make an 11x14 print from 4x5 neg. So I am only using the sweet spot near the middle.

I placed the film squarely under the lens, but positioned the test strip on the left-hand side - so maybe I fortunately avoided the hot-spot at dead center.

And I am using a grid light source, not condenser.

What is your light source (does the lens really have a hot spot in the middle or do condensers play into it)?

[Michael R 1974]

Any light source is subject to falloff off-axis.

I raise the enlarger head (diffusion) way up for a giant print size. The little 4x5 negative is in the middle of a comparatively huge imge circle and within that 4x5 area I don't have variations of even 1/10 stop. That's good enough for me. But if someone prefers to use a softbox 30 feet from film taped to a wall that's probably good too.

Anyhow best of luck to OP. I would be curious to hear about your results with the Mod54.

[Bob Carnie]

Michael is right, he is not using the edges. I have used enlargers for this test as well as lighting on a copy board.
I prefer the copy board method as I am tethered and can read the numbers for eveness.

Any light source is subject to falloff off-axis.

I raise the enlarger head (diffusion) way up for a giant print size. The little 4x5 negative is in the middle of a comparatively huge imge circle and within that 4x5 area I don't have variations of even 1/10 stop. That's good enough for me. But if someone prefers to use a softbox 30 feet from film taped to a wall that's probably good too.

Anyhow best of luck to OP. I would be curious to hear about your results with the Mod54.

[Jeff Bannow]

Thanks everyone for the advice.

[Bill Burk]

I would suggest using a zone 7 density rather than zone 5 because in my experience uneveness problems will show up more.
Back in my days of shooting products on a blank light grey it was a real headache getting it even.
Also because it is useful to have your zone 7 processing time down.

If using your enlarger make sure it is way out of focus from the light source.

Dennis

That graphs under Stouffer scale step 11 which is 1.56 density.

So if you expose film that much less than the full 5 seconds at EV0, you will possibly get 1.0 density when developed.

1.56 divided by 0.3 is 5.2 stops...

So somewhere about a 1/4 or 1/8 second should do the trick...

[DREW WILEY]

Glad to see that others have pointed out the potential errors in using an enlarger if you don't select
the even part of the field. If you don't have a good transmission densitometer, then contact print
onto a hard grade paper to exaggerate any issues with the film itself. Try to expose the film somewhere around an even middle gray or gray card value. There are any number of ways to dev
film very evenly - tray, drum, brush dev, nitrogen burst, whatever - the most important thing is practice, consistency, then learning the finer points of each technique.

[Jeff Bannow]

That graphs under Stouffer scale step 11 which is 1.56 density.

So if you expose film that much less than the full 5 seconds at EV0, you will possibly get 1.0 density when developed.

1.56 divided by 0.3 is 5.2 stops...

So somewhere about a 1/4 or 1/8 second should do the trick...

How could I get that short of an exposure under the enlarger though? I don't think my timer is that accurate.

[Bill Burk]

How could I get that short of an exposure under the enlarger though? I don't think my timer is that accurate.

I'd put a camera body under the lens with the back removed.

Or, once you find EV0 close down the aperture on the enlarging lens as far as you can, and then cut the time to one or two seconds, for this test - close is good enough.

[Bob Carnie]

ND filters will help

How could I get that short of an exposure under the enlarger though? I don't think my timer is that accurate.

[laser]

Keep it simple.


A lens formed image like one produced by an enlarger or camera will have Cosine to the 4th falloff.

An easy technique that is free of the optics problems is to use low wattage incandescent lamp i.e. 7.5 watt, four or more feet from the film. A dimer is useful to lower the output. Control the time with an electric timer.

A density of 1 to 1.2 will make it easy to see the differences.




Expose to a mid-scale density.