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Road ruts with Jobo



 
 
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Old January 26th 04, 04:22 PM
Nicholas O. Lindan
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Default 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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