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> Difference between a test-strip and the print |
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#11
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I have noticed there is a slight difference between my test strips and the final exposure.
I do my test strips in 1/12 stop increments and then do my print for the chosen amount in one go. Yes, there is a very small difference between the two - but that difference pales in to insignificant compared to the woes of dry-down. I have a RH Stop-Clock and a colour DeVere 504. I assume that the difference is from the response of the halogen bulb - it takes a very short time to get going, it then over-achieves light output as it warms up and finally it settles back down to a steady-state light level as it achieves a steady operating temperature. I think the effect starts to become noticeable after about 12 steps in the test trip. I never expect to get my exposure right from the test strips even on a wet print - but use the test strip as way of getting in to the ball park for the print as a whole. The test strip can also be used as a guide for dodging and burning - but again it is a guide. If you really are hung up on trying to get your test strip to be exactly as the final print and you own a Stop-Clock - you can always cut lots of test strips and expose each one for incrementally greater times. Martin |
#12
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'Hurrah!' and 'Dooohhh!!' I said in equal measures over the weekend, during a printing session, for I think I may have discovered why some test prints, as well as multiple prints of the same negative, have varied in density to each other recently.
After putting the problem out there, numerous ideas were put forward. First of all, I checked all the sockets with a socket tester, having found a loose wire with this, when first moving into the darkroom. I also bought and tried a voltage tester, which proved everything to be normal. It was an intermittent problem, and when it happened during a printing session, I would give up for the day, living in hope it would go away on the next session, which it mostly did, allowing me to proceed normally. Well at the weekend, I think I may have resolved the problem... hopefully! And this is going to sound so stupid, but I'm sure others would have exclaimed the same phrases as myself. Now I don't know when, but it's become a recent-ish habit of mine, to check the focus of the negative with a Paterson Focus Finder, after I have put an Ilford graded filter into the holder just below the lens and double checked the position of the easel, just before pushing the exposure button on my R H Design's unit. During the weekend session, I exposed and printed a test strip and all was fine. I adjusted the exposure on the R H Design's unit and printed a print and again all was fine. I then made a second print, doing exactly as the first, but when pulled out of the fixer, it was noticeably darker than the first. I stood muttering for a minute, annoyed how it was happening again, after a short break of it not happening. And then I noticed. I'm presuming that the following happened when I did the final focus check, but some how the lens had opened up by about half an f-stop! It really was a 'Eureka!' moment and I can only presume that somehow, my head brushed against the filter holder, which is screwed tight against the lens, which made it turn just a little bit, but enough to change the aperture by about the half f-stop, which in turn increased the exposure. I now add checking the aperture ring at the last moment to my list of things to do when making a print. I really do hope that this simple answer is what has been happening, otherwise I will return to going slightly mad again. I just hope that this is of help if something similar happens to anyone else. Terry S Last edited by Terry S; 30th June 2022 at 01:20 PM. |
#13
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I periodically forget to close the lens aperture after checking the focus between test strip and print. I usually notice immediately, say something to myself (**!!**) and bin the paper before developing.
Mike |
#14
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I haven't made a test strip for printing for many years, I find using the Analyser/pro both faster and more accurate, it does a better job than I can do, but I do make test strips when setting up the analyser/pro for a new paper setting, such as when MG5 came out, I follow the analyser/pro's automatic test strip generater if and and when making a test strip, but with a long exposure ( I aim for at least 25-30 seconds) a small deviation from the time makes no difference
to the finished print, but if you aim for say ten to fifteen seconds then the faster time does make a huge difference to the finished print, the tighter the time the more accurate you have to be, both in dodging and burning and for the initial exposure Richard
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#15
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Quote:
You are really unlucky that you can sometimes manage to flick the aperture half a stop - enough to make a significant difference to your print density but not enough to be really noticeable to the eye. My aperture control problem is usually forgetting to stop down at all after a focus check - which is very noticeable (and annoying). Martin |
#16
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Quote:
For some reasons concerning warmups and cooldowns my 8x10" Homrich enlarger has a simple shutter. Second he has a relais which gives a little delay to the exposure: Lights on>> warmup>> opening the shutter/starting the clock. The same of course to my extremely professional Holux Elektron 12x16" enlarger with his 8000Watts Xenon bulbs and resulting short times. First a warmup, then the shutter. "" Thinking more about it, it has made me wonder if it was to do with agitation being slightly different between the test-strip and the final print?"" To this question my way always is printing both times at the same place of the easel, and then developing both stripes together. If there are any differences it must be the light. Or the paper |
#17
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Probably this could help:
The aperture blades movements work fine in one direction, but opening and closing the aperture instead will result in different values. It's good praxis to close the aperture lets say to f11, but going back to f5,6 for ending in f8. But i wouldn't expect a difference of half a stop from an old and slouchy aperture gear. On the other side I wouldn't expect half a stop just " VERY slightly darker" :-) |
#18
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Quote:
I use F-Stop print timing and 1/12th stop steps are small but significant. I cannot technically explain why print density response if different to negative density. Try it for yourself the next time you are in the darkroom - you might surprise yourself. Martin |
#19
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Something must be wrong with my post before - I am totally with you, Martin.
Half a stop is something but not no little accident. What I wanted to say is that Terry's description "very slightly darker" couldn't mean " hald stop difference", but probably I wasn't able to translate Terry's post in a correct way. ""I cannot technically explain why print density response if different to negative density. Try it for yourself the next time you are in the darkroom - you might surprise yourself."" Speaking in Zone System parameters, Film captures more zones than paper. Paper is more contrasty than film. But closing the aperture one stop hopefully will give the same densities either to the negative or to the paper furthermore. |
#20
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You could try reducing the wet print exposure by about ten percent and see if that helps the dry print look more satisfying.
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