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  #1  
Old 6th May 2016, 07:50 AM
Adrian Adrian is offline
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Default Contact Sheet Contrast vs Enlargement

I made some contact sheets at grade 1.5 (using Ilford under-lens filters) and found a Neg. I wanted to print which had good contrast in the contact sheet. The contact sheet was exposed at f/4, 4 seconds.

So I set the enlarger up for a 10" x 10" print. I set the enlarger for G1.5, f/8 16 seconds. But the resulting print was not only much lower contrast but also darker by I reckon at least 1/2 stop. I know contact prints can be higher contrast so I raised the contrast to G2.0. Still not much better. I then wasted a lot of time and paper trying to get the contrast how I wanted it with split grade printing, dodging and burning and just ended up with an over-printed mess. I gave up.

Normally I print contact sheets at G0 or G1 - G1.5 and the enlargement exposure is not that far off and it's not an issue with easy to print negatives. I always thought negative enlargement is a bit like inflating a balloon with black writing on it. Before the balloon is inflated (i.e. enlarged) the writing is dense (black). As the balloon is inflated the writing becomes less dense i.e. grey as the separation between the printing dots (grain) increases. Is this what is happening with enlarging a negative?

So I can account for the contrast being lower, but why was the exposure off with the enlargement?

Your thoughts and suggestions please.
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Old 6th May 2016, 09:15 AM
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B&W Neil B&W Neil is offline
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Have you checked for light leaks from your enlarger, an un safe safelight or any other light entering your darkroom? These are the obvious things to check first, a 10x10 print should have really decent blacks if everything is right.

Chemical exhaustion, or aged stock, is also another consideration.

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Old 6th May 2016, 10:36 AM
alexmuir alexmuir is offline
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I don't tend to base a new exposure with a change in aperture on a calculation. I think it's better to make a test strip. Others may have a different view. The calculated exposure for the enlargement should get you close to the optimum time, from which you can better target the test strip intervals. By changing the aperture, and the time, you are adjusting two variables that could affect the outcome. I assume enlarger head height remained constant from contact to enlargement.
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Old 6th May 2016, 11:27 AM
paulc paulc is offline
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Quote:
Originally Posted by Adrian View Post
Normally I print contact sheets at G0 or G1 - G1.5 and the enlargement exposure is not that far off and it's not an issue with easy to print negatives.
When I do contact sheets, I normally use G2 and aim to use the same grade for the print. If I find the neg needs a softer grade, I have room to adjust in that direction.
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Old 7th May 2016, 08:37 AM
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RH Designs RH Designs is offline
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Reciprocity and Callier effects will influence the result, and the eye tends to see more contrast in a smaller print. I never found contact sheets much use for judging enlargements, personally.
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Old 7th May 2016, 04:00 PM
Jerry Bodine Jerry Bodine is offline
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Quote:
Originally Posted by RH Designs View Post
Reciprocity and Callier effects will influence the result, and the eye tends to see more contrast in a smaller print. I never found contact sheets much use for judging enlargements, personally.
I totally agree. I make a low contrast contact 8x10 print of the negative full-frame so I can mark it with the cropping choice used in the fine print, just to have a record of the cropping for future prints. It also provides some clues for needed dodge/burn. But tests strips are still needed to make the fine print. After modifying my 5x7 Omega enlarger's light source to LEDs, I made a number of tests with Stouffer step wedge to check how it performed with Ilford under-lens filters (which proved to be just right). But I was always wondering about a difference in contrast between a contact and an enlargement, that I'd read about; so while doing these tests I first projected the step wedge for a Gr2 print (masking the wedge as much as possible in the carrier to minimize flare), then made a contact print of the wedge with same Gr2 filter and unchanged enlarger height). Checking the two results with a reflection densitometer showed a definite contrast difference - results of the two prints are shown in the attachment. But I suppose the inherent flare from the enlarger lens/bellows in the projection print could explain the difference - I may never know for sure. BTW, the two curves have been adjusted to intersect at a .09 density in order to show the difference in slopes more easily.
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Old 7th May 2016, 05:03 PM
Jerry Bodine Jerry Bodine is offline
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If it helps in reading my attachment, notice that it shows at REL 1.7, for example, the difference in the blacks is substantial (density of 1.45 represents Zone III + 1/3) - even though the highlights are unchanged. Also, these measurements were done on DRY prints, so the effects of dry down are included.

Last edited by Jerry Bodine; 7th May 2016 at 05:27 PM.
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Old 7th May 2016, 05:38 PM
JOReynolds JOReynolds is offline
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Bravo, Jerry. This is the first time I have read a proper evaluation of the contrast difference between contact and projected prints - with numbers! Proper science.
This will have ULF practitioners crowing.
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Old 7th May 2016, 06:27 PM
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Quote:
Originally Posted by Adrian View Post
I made some contact sheets at grade 1.5 (using Ilford under-lens filters) and found a Neg. I wanted to print which had good contrast in the contact sheet. The contact sheet was exposed at f/4, 4 seconds.

So I set the enlarger up for a 10" x 10" print. I set the enlarger for G1.5, f/8 16 seconds. But the resulting print was not only much lower contrast but also darker by I reckon at least 1/2 stop. I know contact prints can be higher contrast so I raised the contrast to G2.0. Still not much better. I then wasted a lot of time and paper trying to get the contrast how I wanted it with split grade printing, dodging and burning and just ended up with an over-printed mess. I gave up.

Normally I print contact sheets at G0 or G1 - G1.5 and the enlargement exposure is not that far off and it's not an issue with easy to print negatives. I always thought negative enlargement is a bit like inflating a balloon with black writing on it. Before the balloon is inflated (i.e. enlarged) the writing is dense (black). As the balloon is inflated the writing becomes less dense i.e. grey as the separation between the printing dots (grain) increases. Is this what is happening with enlarging a negative?

So I can account for the contrast being lower, but why was the exposure off with the enlargement?

Your thoughts and suggestions please.
You are complicating the entire process and suggest you make contact prints with no filtration/contrast values.
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Old 8th May 2016, 09:35 AM
John King John King is offline
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Quote:
Originally Posted by RH Designs View Post
Reciprocity and Callier effects will influence the result, and the eye tends to see more contrast in a smaller print. I never found contact sheets much use for judging enlargements, personally.
I will go along with this reasoning. I only use contact sheets as a reference what the subject is recorded on the negatives and when I come to print I don't shortcut and use test strip(s) every time.

If you use Ilfords dual filtration range, then between G1 and 4 there should be no exposure change. So estimating extra/or less exposure for split grade printing will be simplified. The grades for duel filtration are included with every box/packet of paper. The only downside is this increases the exposure times.
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