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false_Aesthetic
5-Feb-2009, 20:26
Hi,

(Mods, feel free to move this if necessary)

Been gone for a long time. Grad school finished. Then I found myself working for a print house... suddenly helping clients realize their photos became more important than realizing my own photos . . . . this is where the following question comes from.

I'm trying to figure out the bestist, most-"neutral" way to duplicate the 51-STEP-Gray (image attached) image in the darkroom.

The 51Step goes from 255/255/255 to 0/0/0 in roughly steps of 5/5/5. Theoretically when printed digitally all the steps should be even (making a real pretty and straight L curve). I'd like to duplicate that as best as possible on silver paper so that I can harvest that data (LAB)

Now, I realize that dev. combos and toning and all that jazz will make the image 51-Step come out differently. I'm ok with that. What I'm hoping to avoid is the changes in density that would occur by using filters.

I've come up with 2 solutions:

1) Have a neg made from the .tif, print it with no filter in the enlarger and develop it as I normally would.

2) Eff the neg... Using a set fstop figure out how long it takes me to get to photo black. Divide that time by 50 and then essentially make a 51-Step Test Strip.

Can ya'll see where I'm going with this? Am I making sense?

Thanks
T

D. Bryant
5-Feb-2009, 22:09
Hi,

(Mods, feel free to move this if necessary)

Been gone for a long time. Grad school finished. Then I found myself working for a print house... suddenly helping clients realize their photos became more important than realizing my own photos . . . . this is where the following question comes from.

I'm trying to figure out the bestist, most-"neutral" way to duplicate the 51-STEP-Gray (image attached) image in the darkroom.

The 51Step goes from 255/255/255 to 0/0/0 in roughly steps of 5/5/5. Theoretically when printed digitally all the steps should be even (making a real pretty and straight L curve). I'd like to duplicate that as best as possible on silver paper so that I can harvest that data (LAB)

Now, I realize that dev. combos and toning and all that jazz will make the image 51-Step come out differently. I'm ok with that. What I'm hoping to avoid is the changes in density that would occur by using filters.

I've come up with 2 solutions:

1) Have a neg made from the .tif, print it with no filter in the enlarger and develop it as I normally would.

2) Eff the neg... Using a set fstop figure out how long it takes me to get to photo black. Divide that time by 50 and then essentially make a 51-Step Test Strip.

Can ya'll see where I'm going with this? Am I making sense?

Thanks
T
Use option 2, don't waste time with the other.

Don Bryant

nolindan
6-Feb-2009, 09:51
To best answer your question, could you please post what are you trying to do - what is the end goal of the excercise?

The Gretab 51 grey scale is in linear 2% reflectance steps - but nothing in photography is linear. Dividing the max black time by 51 will not get you a result you would want:

1/50th of max black is 5.6 stops down from black exposure, this will result in white if you use VC paper with a #1.5 filter, and so the print will span the range of black to white if you use 50 linear steps.
However paper response is logarithmic, so if you want a 50 step grey scale you would need to make a strip at 1/10th stop intervals, this will give you somewhat linear OD steps in the middle of the scale, over a 5 stop range (grade #2) in 50 steps.
Furtherever the paper has toe and shoulder regions that will compress the ends of the grey scale, so these regions will show very little variation step-to-step.

If you want to make a 2% linear reflectance scale in the darkroom, using photographic paper, you have quite a job ahead of you.

Darkroom Automation, my firm, provides rather detailed exposure to density information for common photographic papers. You may want to start there and use a spread sheet to calculate the exposures you will need. Look in the support files section of the web site http://www.darkroomautomation.com/da-main.htm

Bruce Watson
6-Feb-2009, 10:08
I seem to recall a story about Fred Picker. Early on he worked with several expert printers, a variety of workflows. One challenged him to see how many uniquely distinguishable shades of gray he could make with a given paper and developer. He thought he'd get lots. IIRC he struggled to get 50 or so. There are people participating here who actually worked with Mr. Picker who can perhaps fill in the details of this story. Assuming it's more than a myth.

I'm just saying that you might have a lot of difficulty printing a 51 step wedge in the darkroom. You're going to fight toe and shoulder compression, the limited dynamic range available from photo paper, and highlight dry-down. At the very least. All of which will have a significant effect.

nolindan
6-Feb-2009, 10:25
I seem to recall a story about Fred Picker. Early on he worked with several expert printers, a variety of workflows. One challenged him to see how many uniquely distinguishable shades of gray he could make with a given paper and developer. He thought he'd get lots. IIRC he struggled to get 50 or so.

It's very easy with an f-stop timer. Well to get 50 shades of grey at a reasonably even-tempered scale.

No 50 steps with a linear scale is a bit of a bitch at the light grey end, though laughably coarse at the black end. To get any accuracy exposure will need to be timed to 1/50th of a second or so. With a 4 second exposure for white, the light greys are going to be 0.15 seconds apart in exposure.