Testing for Relative ISO Range Numbers

[Chuck_P]

A sharper scan of the paper curve I uploaded previously in post #24.

 

[Chuck_P]

The width is measured by subtracting the Log Exposure Minimum (Emin) for reaching the highlight density limit from the Log Exposure Maximum (Emax) for reaching the shadow density limit.

I was re-reading this earlier post and found that I made an error.

It's correct to say the width of the Exposure Scale Value is found by subtracting the Log Exposure Maximum (Emax) needed for reaching the shadow density limit from the Log Exposure Minimum (Emin) needed for reaching the highlight density limit. This is clearly seen in the attachment but I wanted to make clear my wording.

RN = (Emin - Emax) x 100

 

[ic-racer]

Just a clarification of my first post above that my comments were only intended to be directed at the misuse of the term ISO(R) in the OP and the title of the thread. Kind of like reading a thread with respondents mentioning their personal ISO film speeds (rather than the more correct term of personal exposure index).

Also implying that it is incorrect to say the ESV you determine from that test is the PAPER'S ESV. You are measuring a SYSTEM ESV that contains flare. Which is fine. (Just make sure the flare of the step wedge projection conditions matches that with which you normally print, as Steve mentions above).

 

[Chuck_P]

Just a clarification of my first post above that my comments were only intended to be directed at the misuse of the term ISO(R) in the OP and the title of the thread.

I guess I should have used quotation marks around the title of the thread: "Testing For Relative ISO Range Numbers" because that is straight out of the text I used to guide me through the test, Chapter 3, "Calibrating Variable Contrast Papers" --- The Variable Contrast Printing Manual by Steve Anchell. I titled it that because that is the test I carried out. Not sure how it is perceived as being a misuse of the term ISO. I'm sure that it is "Relative" because the ISO produced is relative to the filter or filtration setting used to expose the step wedge.

But I am sure that I have referred to the test being relevant to my "printing system" to include the light source, the paper, the filtration setting, the developer choice, and toning.

Perhaps I misunderstand your post.

 

[ic-racer]

In spite of any nomenclature issue (which may be nit-picking on my part), I was curious about how much contrast is lost in your step wedge projection test due to flare. I did check it in my own system a while back and made a bunch of masks because the flare was extensive (using a 10x10 glass carrier for smaller formats).

I did not have any numbers so I just re-did the test. So, some RC paper strips fresh off the test-print dryer:

Max Magenta, Contact: Range = 67.5
Max Magenta, Projection (no masking of stray light): Range = 97.5

Projection was kind of 'worst case' conditions. A full 10x10 mixing box with full coverage modern Multicoated Rodagon 300mm lens at f8 projecting a little step wedge with no masking of the light around the step wedge.

What is the lesson? Make sure no stray light gets around the step wedge when projecting it and ditto for your negatives when printing. The flare can really be quite significant even with a modern multicoated enlarging lens. If your projection tests are corrupted by too much flare, it shoots down the whole rest of the system if you are going to try and match the negatives to the paper.

 

[ic-racer]

Also, what I did not show is what happens when the step wedge is masked tightly. In prior testes the range measured on the paper was very close to that obtained with contact printing when things were optimized for the projection , like using a smaller aperture to minimize lens flare.

 

[Ken Nadvornick]

I was curious about how much contrast is lost in your step wedge projection test due to flare.

This is indeed a valid concern. And the reasoning behind the variable masking attachment included standard by Omega with their D6 enlarger. (Optional with the D5.)

But my results performing the same test and using a contact-printed step wedge show results reasonably in accord with CPorter's results. Others have reported similar results, all presumably using different batches of paper.

So while flare may indeed have made a contribution, it also may not be the whole story here.

Ken

 

[ic-racer]

But my results performing the same test and using a contact-printed step wedge show results reasonably in accord with CPorter's results.

Yes, good. A contact printed wedge will point more directly to potential paper/developer problems.

 

[Chuck_P]

Also, what I did not show is what happens when the step wedge is masked tightly. In prior testes the range measured on the paper was very close to that obtained with contact printing when things were optimized for the projection , like using a smaller aperture to minimize lens flare.

I understand the concern for flare, but I have no means right now to control it (when projecting) outside of the capability of the enlarger and lens itself; I use a 150mm Componon-S.

I wander if the VCCE (Variable Contrast Constant Exposure) nature of my LPL reduces flare. The light is filtered above the enlarging lens and negative stage. I can dial in a filtration change at any point and not have to figure any exposure difference. Going from a #2 setting to #3, for example, introduces the necessary ND to maintain a constant exposure. I typically will print at f/8 to f/11.

 

[Stephen Benskin]

As with most things, it's usually a combination of factors. I suggest carefully working through all the possible variables.

I would like to add that in projection printing flare not only comes from unmasked areas surrounding the negative but from the thinner areas within the negative itself. The question comes down to how much flare should you introduce into the testing in order to produce results that will reflect (no pun intended) normal printing conditions. The only other way is to make the tests under zero flare conditions (contact) and to mathematically factor in the affects of normal flare.

 

[Stephen Benskin]

I'm sure that it is "Relative" because the ISO produced is relative to the filter or filtration setting used to expose the step wedge.

Chuck,

The "ISO" prefix can only be use when there is strict adherence to the specifications of the standard. For example, if Anchell didn't use a non-intermittent sensitometer (which also means contacting), or if the tests weren't done in complete darkness, he couldn't use the term ISO. "Relative ISO" is saying that the results are similar to but the testing methods don't conform to those specified in the standard.

When TMX and TMY first came out, the ISO developer used at that time didn't produce results with the films that reflected real world use, so Kodak tested the film according to the ISO standard except they processed the film in D-76. Even though everything else was done to the standard, they couldn't use the ISO prefix. For awhile they used EI.

 

[Ken Nadvornick]

I understand the concern for flare, but I have no means right now to control it (when projecting) outside of the capability of the enlarger and lens itself...

Just curious. Did you get that chance to check for and hopefully eliminate safelight fogging as a variable?

Ken

 

[Chuck_P]

"Relative ISO" is saying that the results are similar to but the testing methods don't conform to those specified in the standard.

I see. Thanks.

 

[Chuck_P]

Just curious. Did you get that chance to check for and hopefully eliminate safelight fogging as a variable?

Ken

Not able to as I had a later work day than I planned the last couple of days, but I'm looking forward to getting that done before the end of the week if possible.

 

[ic-racer]

I understand the concern for flare, but I have no means right now to control it (when projecting) outside of the capability of the enlarger and lens itself; I use a 150mm Componon-S.

I wander if the VCCE (Variable Contrast Constant Exposure) nature of my LPL reduces flare. The light is filtered above the enlarging lens and negative stage. I can dial in a filtration change at any point and not have to figure any exposure difference. Going from a #2 setting to #3, for example, introduces the necessary ND to maintain a constant exposure. I typically will print at f/8 to f/11.

Maybe you answered earlier, but when projecting the step wedge did stray light come around the step wedge? If so, you ARE in control of that. When you print your negatives you have to have the same flare conditions as the paper test, otherwise you won't be able to match negative to paper the way you want.

So, yes you can't eliminate flare, but make sure the flare conditions are the same when doing the test as when printing a negative.

 

[Chuck_P]

Just curious. Did you get that chance to check for and hopefully eliminate safelight fogging as a variable?

Just reporting back that my paper did not show any safelight fogging.

 

[Chuck_P]

Maybe you answered earlier, but when projecting the step wedge did stray light come around the step wedge? If so, you ARE in control of that. When you print your negatives you have to have the same flare conditions as the paper test, otherwise you won't be able to match negative to paper the way you want.

So, yes you can't eliminate flare, but make sure the flare conditions are the same when doing the test as when printing a negative.

I did not detect any stray light coming from around the wedge; the flare conditions are the same with the test as when printing. Thanks.

 

[Ken Nadvornick]

Just reporting back that my paper did not show any safelight fogging.

I didn't think it would.

I didn't mention this earlier, but after seeing such low contrast in my tests I opened my originally sealed box of Oriental VC FB and removed a sheet from the middle of the stack while in total darkness. Then I performed an identical wedge exposure and processed the sample also in total darkness. No safelight illumination ever touched the sample. The results were the same.

So I'm not sure what's up with this paper. Maybe it got x-rayed somewhere along the line? If someone elsewhere has managed to coax a grade 4 or grade 5 out of this paper using an Aristo VCL light source, I really be interested in hearing about it.

Thanks for the follow-up info.

Ken

 

[Mahler_one]

Hi Ken: Interesting....a few months back I threw out an entire pack of Oriental VC RC paper because of low contrast. I thought that the paper had become fogged some how. Reading of your experience makes me wonder what the "story" really is!