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#11
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Road ruts with Jobo
"Brian Kosoff" wrote
Every photographer I knew in NYC, either bracketed in 1/4 stop intervals or push/pulled in 1/4 stop intervals ... We must move in very different circles. Most photographers I know bracket in 4-stop intervals. Or is it true that most people can not discern differences smaller than 1/3 stop? For normal processing, with normal contrast material, I claim a 1/3 of a stop won't be noticed. With high contrast material, grade V paper as an example, a 1/3 stop difference is significant and shadows or highlights drop in and out - at least I can see a difference; my neighbor, that's a different story. We can jaw on this subject till everyone in the group is pushing up daisies. The only way to find out is to experiment. Let me explain what I mean by noticing a 1/3 stop difference: o Day 1: make two prints, one 1/3 stop under or over and one at 'ideal' exposure. Put them away. o Day 2: At random, look at one print. Don't look at the other. Look at the print as you would in a gallery, from a civilized distance. o Day 3: Look at the other print. Again, never look at both at the same time. o Day 4: Can you tell which was which? Do you think anyone else can. Do you think a gallery viewer would care? For grins, take your favorite original print by another photographer. Visit someone who also has a print. Compare the two. When I tried it there was quite a difference between the two. Even better compare an original with a duotone reproduction - they are almost different photographs - yet the viewer, seeing each separately, likes them both. The eye is very good at detecting local, abrupt, changes in tone - that's a fundamental principle of vision. If two 18% grey tones, normal paper, normal processing, but differing by 1/3 of a stop are placed side by side (a test strip made with no negative makes a good test vehicle) the demarcation between the two exposures is plainly visible. To an experienced eye it is even possible to make out the demarcation at 1/10th of a stop. I don't think small stop differences are noticeable in most prints, and certainly aren't worth chasing. As an experiment cut out the two squares from the above test strip, place one in each room. My result is that an observer walking between the rooms can't tell the difference. A 'road rut' of 1/10th of a stop difference is another matter, though, and I believe an eye looking for the rut will find it. -- Nicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics. |
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