Hardness of light source and contact print contrast

Jarin Blaschke · May 24, 2017

Common sense would seem to indicate that the type of light (hard light vs. soft light) would not impact the contrast of a contact print, but I thought I might ask anyway:

Has anyone experienced a contrast difference in using a bare bulb for contact printing versus a diffuser or heck, even bouncing the light off the ceiling? I wonder if this might be a tool to control contrast on graded paper, almost like a condenser enlarger vs. a diffusion enlarger.

Thanks!
Jarin

Leigh B · May 24, 2017

The light source characteristics have no impact on contact prints on graded papers.

The negative emulsion is (should be) in intimate contact with the paper emulsion.
Therefor, no separation exists within which an intensity gradation can occur over an edge.

- Leigh

ic-racer · May 24, 2017

If you are not in perfect contact with the negative, the loss of sharpness will be more evident with a diffuse light source.

tedr1 · May 25, 2017

When contact printing I usually have the paper on a very flat baseboard, the neg on top of the paper and then a piece of high quality heavy glass plate on the top which keeps the neg pressed against the paper. I agree the light source quality point source/diffused makes no difference. I use the enlarger as the light source because it is a convenient way to get the necessary variable contrast filtration into the light.

MattKing · May 25, 2017

I can think of a couple of reasons why it might matter a little, but I'm not sure how noticeable the difference would be.
I would point out that a film negative is not strictly two dimensional. It has depth, both within the emulsion, and within the substrate. There is room within that depth for flare/internal reflection.
So the combination of a diffused light source and a slightly three dimensional negative may cast slightly different shadows on the printing paper than a combination of a point or collimated light source and a slightly three dimensional negative.

Leigh B · May 25, 2017

MattKing said:
I would point out that a film negative is not strictly two dimensional.

Hi Matt,

I seldom disagree with you, but...

While your observation is technically correct, the thickness of an emulsion is measured in millionths of an inch.

That is certainly orders of magnitude larger than the wavelength of light, but scant room for substantial reflections.

- Leigh

MattKing · May 25, 2017

I mostly agree Leigh.
But would point out that the substrate is much, much thicker.

pdeeh · May 25, 2017

The big advantage of a hard-light system is that it allows one's hologrammatic coworkers physical interactions with the world, of course.

Leigh B · May 25, 2017

MattKing said:
I mostly agree Leigh.
But would point out that the substrate is much, much thicker.

Absolutely true.

But the substrate is above the emulsion, not in the image-forming light path.

- Leigh

Jarin Blaschke · May 25, 2017

Well, I might do tests to see if there's any subtle micro contrast difference anyway and report back. Still at least a month before I can make prints in my space...

I wonder if diffusing the light helps with averting newton rings, however? I would still want to do it above the contact print frame (I got mine from formulary), so I can still see the image and dodge and burn.

J

Hardness of light source and contact print contrast

Jarin Blaschke

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Hardness of light source and contact print contrast

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