Reciprocity Failure of Darkroom Paper?
I had some strange behavior in the darkroom last night. My first test print had hot contrast and it was dark, so I put in a grade #1 filter, and left the exposure alone. Contrast looked better, but the print was still a little on the dark side, so I reduced the exposure from 15 seconds to 10 seconds. The print was not too dark or light, but it now had gone soft. I pulled the filter and went for a 3 second exposure. The print came out looking almost exactly the same as the #1 with 10 seconds of exposure. It was also soft. What the heck? I know that a 3 second exposure is a little too short for darkrooom printing. I have read somewhere that reciprocity failure for prints occurs under 10s exposures. Does this make prints go soft? I know RF of film makes contrastier negatives for film. Is it the opposite for print paper?
I had the iris of my enlarger lens stopped all the way down, and I was still getting these crazy short times. I have a rheostat for the lamphouse, but I am afraid of changing the paper grade because the incandescent bulb would be giving off a more yellow light as a result of it burning cooler. Do I need a neutral density filter in the filter box? I am using a Besseler 4x5m. I am not a total newbie, but I have never ran into this problem before.
After careful examination of your problem I can confidently say that something is wrong. Oh, you knew that already?
Seriously there might be several things to be checked but there is no reciprocity failure at either of these exposures. A 3 sec exposure with no filter will be closer to a 10 sec exposure at filter grade 1 but there should still be a difference. No filter assuming VC paper is the equivalent to a grade 2 so there is a grade difference which should be noticeable.
The print hadn't gone any softer with the same filter but if it lightened as it will have done at 5 secs less then the softness will be more apparent as you can presumably see more details assuming the 15 secs exposure made the print far too dark.
I take it that you know the paper to be in good condition and the developer isn't exhausted?
There are a few threads here on APUG that make reference to paper and reciprocity characteristics, but I don't think this is what you are experiencing.
A completely stopped down lens aperture might be giving you some diffraction problems, but generally that effect is small, when it is visible.
Try the rheostat - the cooler bulb doesn't really give you more yellow, just less blue .
What paper are you using.
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Why is 10 seconds too short of an exposure? I routinely print 5-10 second exposures on printing paper. How old is the paper? What temp was the developer? Lose the rheastat and get a couple of neutral density filters. BTW, sounds like a thin negative, either underexposed or under developed, or both.
How big was the print? I am not familiar with the light output of the Beselar 45M , but a lot of the big 4x5 units were meant for some degree of production printing, so they could pump out a lot of light if needed to produce short exposure times.
No filter usually gives a # 2 contrast grade; the multigrade filter sets all incorporate neutral density.
I routinely print 5x7 test exposures from 4x5 negatives in an Omega D with a Chromega dichroic head with exposures in the 6.3-30 second range with an aperutre openning of f/16 to f/11 depending on the density of the original negative.
I have never been concerned about short exposure times (longer than 2 seconds, other than the light output of the lamp is not equal to the light output for the time between 6 and 8 seconds, since we are dealing with lamp warm up delays with such short exposures.
I have encountered recipricity faliure in colour paper for longer than 30 second exposures in terms of colur shifts. I have never encountered the same issues in b&w.
I do strive to standardize development of 1' for RC, and 2" for FB paper in a developer at 20C. Pulling a dark overexposed print early will change the contrrast of the resulting print.
I hope this gives you food for thought.
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Ok, it sounds like reciprocity was not the issue. This enlarger does crank out the light. The negative is not thin at all. If anything it is slightly over developed for the contrast of the scene. Hence the #1 filter. I am wondering if it was the developer. I had filled my big 16x20 trays the night before. Normally, I don't have issues with printing in developer that was left out for up to three days. However, that being said it was in the garage because by big trays don't fit in the DR. They might have been a tad on the cold side -- maybe the low 60s. However, why would the first print come out ok, and a few minutes later the start coming out soft. It does look like the developer was pooping out, but the solution in the tray is usually a lot darker before it starts to go south.
I am using Arista.EDU MG FB paper for testing. I use my Gossen lab attachment to keep the light constant when I raise the lens to give me 16x20. This works really well for me I need to adjust slightly to compensate between the speed of the two papers. However, the contrast is identical. Last night I never even made it to the 16x20" stage of my print session. I don't like to waste those big sheets for test prints. I like to get set up with a smaller paper size. It worked perfectly the night before last.
I will mix up some fresh Dektol tonight and give it a whorl in an 8x10 pan. I will check the temperature too. I have no ND filters for my Beseler, so I can't eliminate the time variable until I pick up one. Hope it is as simple as that.
Last edited by kq6up; 12-01-2011 at 03:09 PM. Click to view previous post history.
Pentaxuser, I will rule out the developer tonight. If I am still having issues, it could be reciprocity failure. Another user here suggest that reciprocity does not effect the contrast down to two seconds. I am not sure about this conflicting information since I have heard that reciprocity kicks in for paper on the short side of 10 seconds.
Originally Posted by pentaxuser
Well the verdict's in. The developer had gone south from either being too cold or experiencing some other form of sudden death. I had a successful printing session last night.
The same thing has happened to me. It was my experience with exhausted developer that the key test for it is to print the same neg at a grade or grade and a half apart. If there appears to be no change in the print then it is almost certainly the developer which seemed to be the case when you said that there was no change between a grade 1 print and an unfiltered( grade 2 ) print.
Originally Posted by kq6up
Glad you achieved success and that it was nothing more serious than exhausted developer.