Confusion about how to determine the Standard Printing Time

[donbga]

Well I've finally found time to begin the calibration process using the method outlined in the PDN manual.

Last night I printed and processed quite a few step tablets on grade 2 AZO developed in Ansco 130 using a 31 step step tablet lapped with clear Pictorico OHP.

Today I have a large pile of test strips to analyze and I have some basic questions about how to correctly analyze these to determine the SPT.

Reading Mark's procedure, viewing and measuring the strips has lead me no where close to concluding what my Standard Printing time should be.

First my DMAX value read from exposed paper that wasn't covered by the step tablet is 2.1. Visual inspection of one particular strip (actually several) shows no difference in density between step 1 and the uncovered paper. However taking a reading with my densitometer shows that step 1 of the OHP side of the test strip has a log density value of 2.08. I would say that this should pass for matching DMAX of the exposed uncovered paper. Visual inspection of steps 2 and 3 appear to match step one although my densitometer indicates that they are slightly less dense; step 2=2.07, step 3=2.04, and step 4=2.01. Step 4 is the first step that is significantly visually lighter that the 1,2,and 3.

My question is how to properly interpret the step differences. Using Mark's exposure calculator and intepreting his outline for correcting the baseline exposure indicates that I need to reduce exposure by 2 steps. Since my original exposure for this strip was 20 secs the exposure calculator indicates the Standard Printing Time should be 12.6 seconds.

However as I mentioned, I made several test strips beginning at 15 seconds. The 15 second strip visually shows a slight difference between step 1 and 2, with a log difference of .05. Step 3 of the 15 second strip shows a .1 log difference. Using Marks exposure calculator computes a 1 step change (making step 3 density step 2 density) would result in a Standard Printing Time of 11.91 seconds.

So going by the information that I've shared above, does it seem reasonable that my Standard printing time would be 12 or 13 seconds?

Am I splitting hairs to thinly here and making this difficult?

Should my log density difference between step 1 and step 2 (on the substrate side of the lapped exposure) be .1 log density (assuming that step 1 log density = the DMAX reading)?

Sorry about the long drawn out post, hopefully I've made myself somewhat clear. Counting the number of steps between DMAX and DMIN (black to white) indicates 21 discernable steps for a log density range of 2.1 which would seem to support the validity of my densitometer readings.

Thanks,

Don

[Joe Lipka]

Be warned, my suggestion is from my experience. I have not purchased the book, read the book or made precision digital negatives from deskjet printers. (I have been using film negatives made from my photoshop files for the past three years.)

With that caveat in mind, what do the mid tones look like? In testing, I am likely to look for the maximum black, then see how the midtones look. If I can back off the exposure a little bit to get the 50% patch right and still have a good black, then I know that is the minimum test time. Adjustments to the highlights and shadows are then done by adjusting the curve.

That being said, it's always pretty much a crapshoot at the extreme ends of the curve. For us alt process types, coating skill becomes an issue as well as the quality of the printing frame used to hold the negative to the printing paper.

Is your denistometer capable of reflective as well as transmission readings? In this particular testing, a reflection densitometer capable of reading percentage dot gain is a huge asset.

[sanking]

Well I've finally found time to begin the calibration process using the method outlined in the PDN manual.

Reading Mark's procedure, viewing and measuring the strips has lead me no where close to concluding what my Standard Printing time should be.

My question is how to properly interpret the step differences. Using Mark's exposure calculator and interpreting his outline for correcting the baseline exposure indicates that I need to reduce exposure by 2 steps. Since my original exposure for this strip was 20 secs the exposure calculator indicates the Standard Printing Time should be 12.6 seconds.

Thanks,

Don

I personally determine Standard Printing Time by making sure that Step One is maximum density, or very close to it, rather than matching two steps and then doing the calculation. If you have three densities in a row that read 2.08, 2.07 and 2.06, and a fourth that reads 1.95, the correct one to choose for maximum density would be 2.06 since you will not see any visual separation between 2.06, 2.07 and 2.08, but there will be a lot between 2.06 and 1.95. In other words, I derive Standard Printing Time directly by the first step that has maximum black and shows separation from a previous step. I find this more accurate than merging two steps and then subtracting time according to Mark's calculations.

Whichever way you do it my experience is that in actual practice your printing times will turn out to be slightly different than what is suggested by the Standard Printing Time, though not by a lot. This is due to the fact that real subjects should be printed interpretatively to render the most pleasing image, which may mean clipping one end of the scale to accentuate the other.

Sandy

[donbga]

Be warned, my suggestion is from my experience. I have not purchased the book, read the book or made precision digital negatives from deskjet printers. (I have been using film negatives made from my photoshop files for the past three years.)

With that caveat in mind, what do the mid tones look like? In testing, I am likely to look for the maximum black, then see how the midtones look. If I can back off the exposure a little bit to get the 50% patch right and still have a good black, then I know that is the minimum test time. Adjustments to the highlights and shadows are then done by adjusting the curve.

That being said, it's always pretty much a crapshoot at the extreme ends of the curve. For us alt process types, coating skill becomes an issue as well as the quality of the printing frame used to hold the negative to the printing paper.

Is your denistometer capable of reflective as well as transmission readings? In this particular testing, a reflection densitometer capable of reading percentage dot gain is a huge asset.

Joe,

Thanks for the warning! Using Mark's PDN method the minimum exposure time for DMAX is the first step in the calibration process. Howver your method of keying off the midtones isn't an unusual approach. Mark does have sections in his book covering negatives made from imagesetters which you might find helpful or at the very least interesting. It would probably be best to contact Mark if you are really interested in his imagesetter method.

My densitometer is a reflection/transmission densitometer. Since I'm reading patches exposed on silver gelatin paper I'm not sure I need an instrument that can read percentage dot gain. Is that what you are using? A graphic arts densitometer. I assume this may be for film and not for the print.

Thanks for chiming in,

Don

[donbga]

I personally determine Standard Printing Time by making sure that Step One is maximum density, or very close to it, rather than matching two steps and then doing the calculation. If you have three densities in a row that read 2.08, 2.07 and 2.06, and a fourth that reads 1.95, the correct one to choose for maximum density would be 2.06 since you will not see any visual separation between 2.06, 2.07 and 2.08, but there will be a lot between 2.06 and 1.95. In other words, I derive Standard Printing Time directly by the first step that has maximum black and shows separation from a previous step. I find this more accurate than merging two steps and then subtracting time according to Mark's calculations.

Whichever way you do it my experience is that in actual practice your printing times will turn out to be slightly different than what is suggested by the Standard Printing Time, though not by a lot. This is due to the fact that real subjects should be printed interpretatively to render the most pleasing image, which may mean clipping one end of the scale to accentuate the other.

Sandy

Sandy,

Thanks for your input. What you describe makes sense. I'll try that approach.

Don

[Joe Lipka]

My densitometer is a reflection densitometer commonly used in the printing world. My step wedges are from Dan Burkholder's book. They are constructed to display photoshop percentages in 2% increments. So, my step wedge print has 50 little squares, not 21 rectangles.

Measuring dot gain on the print gives me a percentage reading, which I compare against the PS percentage on the computer screen. Then I adjust the curve from there.

There are many ways to get to the right answer.

[sanking]

My densitometer is a reflection densitometer commonly used in the printing world. My step wedges are from Dan Burkholder's book. They are constructed to display photoshop percentages in 2% increments. So, my step wedge print has 50 little squares, not 21 rectangles.

Measuring dot gain on the print gives me a percentage reading, which I compare against the PS percentage on the computer screen. Then I adjust the curve from there.

There are many ways to get to the right answer.

That is very interesting. I did not realize that a dot gain reading corresponded to a percentage reading. But would you explain how you adjust the curve in PS using the dot gain readings?


Sandy

[philsweeney]

Am I splitting hairs too thinly here and making this difficult?
Don

Hi Don,

Remember once the curve is constructed, small time changes have the greatest effect on the highlight densities. Occasionally I'll print at a time greater than my standard, to gray down highlights (or as Sandy said "This is due to the fact that real subjects should be printed interpretatively").

There is room to move at max black. I like to think of the standard print time as the anchor for the curve. I'd use whole numbers for my time.

phil

[donbga]

Remember once the curve is constructed, small time changes have the greatest effect on the highlight densities.
phil

This seems to be what one would expect most of the time, however if one has a standard printing time of 12 or 15 secs even a 1 second change could affect the highlights strongly. Perhaps I'll reduce my light output by a stop to get a longer time. My exposure lamp is voltage regulated.

Occasionally I'll print at a time greater than my standard, to gray down highlights (or as Sandy said "This is due to the fact that real subjects should be printed interpretatively").
phil

Here is where I have a conceptual problem, sort of; if I'm composing on the screen I should hopefully know what I want my print to look like to begin with, deviating from that after printing a negative seems to be counter productive unless of course one is speaking of a small tweak which I can understand.

There is room to move at max black. I like to think of the standard print time as the anchor for the curve. I'd use whole numbers for my time.
phil

I'm not sure I follow ..."there is room to move at max black."

Possibly the best thing to do is to use a light integrator to time exposures

Thanks,

Don

[philsweeney]

I'm not sure I follow ..."there is room to move at max black."



Thanks,

Don

Hi Don,
My point was small time differences effect the shadows slightly.
best,
phil