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#11
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#13
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In article ,
(Stefan Kahlert) wrote: (kpphoto) wrote in message om... up from a 6.45 neg, I have areas that go out of focus almost like a "areas" that are sometimes but not always blurred... sounds like you are using a glassless carrier. doubling of the image over the original. If the neg pops (forth or back) between basic and additional exposure the image will be blurred the way you describe it. Yep As stated; 120 film on longer exposures is suseptable to negative popping and that would cause the problem described. I've never seen it happen because 99% of my negatives print around 15 seconds at mid range on the apeture scale. -- LF Website @ http://members.verizon.net/~gregoryblank "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 |
#14
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On Thursday 04 November 2004 14:42, kpphoto wrote:
I am having a problem with sharpness when I am burning in an area of a print. I am using a D5 with a dicro head. On larger prints, 14x14 and up from a 6.45 neg, I have areas that go out of focus almost like a doubling of the image over the original. The enlarger is stable & so is the easel. It does not happen all the time. It is sharp on a straight print. What varieing factor am I overlooking. The lens is stopped down 4 stops. I use my hands halfway between the lens and paper with a large opening than smaller. Is it a form of diffraction that is causing the image to do this? Has any one had this happen? If the change in the image is "large" as you say, this sounds like negative pop due most likely to heat from the dichroic head. You say this doesn't happen all the time. Does it happen mostly with longer rather than shorter burn times? If yes, then it's probably negative popping. Check that your light head has the heat absorbing glass in place. The only way to be sure this no longer occurs is to use a glass carrier, but that of course introduces a whole other set of problems. Are you changing the f-stop of the enlarger lens between the primary exposure and the burn exposure? If yes, you may be experiencing lens focus shift. This is usually more of a problem with Tessar (4 element) or Trinar (3 element) lenses than with Plasmats (6 element) ones. In any case, always do the final focus with a grain focuser at the printing aperture, and to be on the safe side, don't change the f-stop when burning. Is your enlarger REALLY stable? Do this test: Put a glass of water on top of the enlarger head, and have someone walk/stomp around your apartment or home. Do little vibration rings form in the water? Does a large vehicle going by outside do the same thing? Rap firmly with a couple of fingers on the side of the dichroic head. How long does it take for the water rings to decay? If in any of these tests, it takes longer than about 20% of your normal print exposure time, you should consider bracing your enlarger and/or the column. I have a Beseler 45M which is mounted on a custom-built, free standing bench on a concrete floor, and it only takes about 2 to 3 seconds for the water to calm. My base exposure is around 20 seconds. -- Stefan Patric |
#15
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On Thursday 04 November 2004 14:42, kpphoto wrote:
I am having a problem with sharpness when I am burning in an area of a print. I am using a D5 with a dicro head. On larger prints, 14x14 and up from a 6.45 neg, I have areas that go out of focus almost like a doubling of the image over the original. The enlarger is stable & so is the easel. It does not happen all the time. It is sharp on a straight print. What varieing factor am I overlooking. The lens is stopped down 4 stops. I use my hands halfway between the lens and paper with a large opening than smaller. Is it a form of diffraction that is causing the image to do this? Has any one had this happen? If the change in the image is "large" as you say, this sounds like negative pop due most likely to heat from the dichroic head. You say this doesn't happen all the time. Does it happen mostly with longer rather than shorter burn times? If yes, then it's probably negative popping. Check that your light head has the heat absorbing glass in place. The only way to be sure this no longer occurs is to use a glass carrier, but that of course introduces a whole other set of problems. Are you changing the f-stop of the enlarger lens between the primary exposure and the burn exposure? If yes, you may be experiencing lens focus shift. This is usually more of a problem with Tessar (4 element) or Trinar (3 element) lenses than with Plasmats (6 element) ones. In any case, always do the final focus with a grain focuser at the printing aperture, and to be on the safe side, don't change the f-stop when burning. Is your enlarger REALLY stable? Do this test: Put a glass of water on top of the enlarger head, and have someone walk/stomp around your apartment or home. Do little vibration rings form in the water? Does a large vehicle going by outside do the same thing? Rap firmly with a couple of fingers on the side of the dichroic head. How long does it take for the water rings to decay? If in any of these tests, it takes longer than about 20% of your normal print exposure time, you should consider bracing your enlarger and/or the column. I have a Beseler 45M which is mounted on a custom-built, free standing bench on a concrete floor, and it only takes about 2 to 3 seconds for the water to calm. My base exposure is around 20 seconds. -- Stefan Patric |
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