How do you determine the exposure for contact printing a step wedge to film?

[Jac@stafford.net]

I don't want to spend god knows how many sheets of film (at ~$2/sheet) and who knows how many hours babysitting development, to arrive at the correct exposure. There's clearly some math applicable to this situation, it's just a matter of finding someone who knows the math and can explain it to me.

Well, you got some very good solutions, but the cost of film is probably insignificant compared to the other gadgets you purchased to get around it. A step-wedge transparency makes it easy. Besides, you will have to come to a development standard anyway.

[Drew Wiley]

Gosh. Talk about doing things the hard way!

[ic-racer]

Now that I finally have a densitometer that works, I want to contact print my Stouffer step wedge to a sheet of film to check on my developing. My plan is to have my Gralab 450 timer flip an LED light bulb on and off rapidly to provide the exposure. At this point, I'm more interested in just getting all the steps recorded so I can look at the characteristic curve of the film than I am about knowing precisely to the photon how much light I gave it (in order to determine speed point).

How do I determine the correct exposure before making the first test?

Thanks as usual.

Use trial and error, just like making a test print. You want to record the toe and as much of the rest of the curve. You may not be able to fit it all on. Let it fall off the shoulder.

For example, when using a 21 step wedge, your resulting negative might have two clear steps before measurable density. So, plot that out and if you still are missing all of the straight line then up the exposure for your next test one-half stop at a time, but at least try to keep the lightest film density above 0.1 log D.

To see that you are in the 'ballpark,' I use diffusion enlargers with multicoated lenses. I most frequently print on Ilford Multigrade. My best prints are from negatives that were processed to a gamma or contrast index around 0.65 to 0.75.

[Luis-F-S]

I would do a test strip of the clear edge base increasing the exposure until the paper doesn't get any "blacker". Picker's proper proof, then expose the step wedge for that exposure. L