Enlarging - printing f stop chart?

pentaxuser · Jul 20, 2019

jay moussy said:
Highly informative, all a bit overwhelming to this beginner..!

Yes things can get quickly overwhelming unfortunately but the key to why you should use f stop timing lies in the consistency of the steps. As you will no doubt have worked a test strip with steps of 2 secs will in 5 steps get you to 10 secs but each step represents less of a change each time so 10 secs is not 5 times as exposed as 2 secs in terms of the print it produces. The percentage method used by Doremus Scudder is already explained here and that combined with spijker's chart gets you very close to the correct fstop times without a calculator

Have a look at Ralph Lambrecht's chapter on f stop printing. He explains the concept very well and shows the difference from the same time interval strips. In the past Ralph has very kindly provided a wealth of information from his book but The WayBeyondMonochrome link I have is now defunct but maybe others here can help with a link to the article. I have his book so losing a link isn't a disaster for me

pentaxuser

RalphLambrecht · Jul 20, 2019

jay moussy said:
Highly informative, all a bit overwhelming to this beginner..!

actually,starting with f/stop timing will shorten your learning curve in the long run.

RalphLambrecht · Jul 20, 2019

MattKing said:
Courtesy of Ralph Lambrecht and Chris Woodhouse' "Way Beyond Monochrome" - a truly valuable resource.
I only share it here because Ralph has generously done so before here on APUG/Photrio.

no problem;sharing is what photrio is all about.

logan2z · Jul 20, 2019

OK, so I understand the concept of f-stop printing, I get the math, I understand that photographic emulsions are logarithmic in nature, and I own an f-stop timer (RH Designs Analyzer) so I don't have to commit the sequences to memory. The one thing that isn't immediately obvious to me (and I'm possibly being dense here so bear with me) is how simply following an f-stop sequence using a standard timer will produce paper densities in precisely equal steps. Doesn't this depend on the characteristic curve of a specific paper? Or are we just talking about approximately equal steps that could vary based on the characteristic curve? Better than simply following a linear sequence but not exactly equal steps? The RH Designs Analyzer needs to be calibrated to the characteristic curve of the paper so that it can accurately predict the tone on the paper given a particular exposure, it doesn't simply provide an easy way to generate an f-stop sequence.

Am I missing something fundamental here?

MattKing · Jul 20, 2019

An f-stop sequence provides you with steps that are visually close to equal when working within the mostly straight part of the characteristic curve with most normal photographic paper.
A fully calibrated RH Designs system will be more precise, but in many situations it will be hard to see the difference.

logan2z · Jul 20, 2019

MattKing said:
An f-stop sequence provides you with steps that are visually close to equal when working within the mostly straight part of the characteristic curve with most normal photographic paper.
A fully calibrated RH Designs system will be more precise, but in many situations it will be hard to see the difference.

Thanks Matt, that's what I thought but just wanted to confirm that I was understanding things correctly.

RalphLambrecht · Jul 21, 2019

logan2z said:
OK, so I understand the concept of f-stop printing, I get the math, I understand that photographic emulsions are logarithmic in nature, and I own an f-stop timer (RH Designs Analyzer) so I don't have to commit the sequences to memory. The one thing that isn't immediately obvious to me (and I'm possibly being dense here so bear with me) is how simply following an f-stop sequence using a standard timer will produce paper densities in precisely equal steps. Doesn't this depend on the characteristic curve of a specific paper? Or are we just talking about approximately equal steps that could vary based on the characteristic curve? Better than simply following a linear sequence but not exactly equal steps? The RH Designs Analyzer needs to be calibrated to the characteristic curve of the paper so that it can accurately predict the tone on the paper given a particular exposure, it doesn't simply provide an easy way to generate an f-stop sequence.

Am I missing something fundamental here?

if you understand the math of a loarithmic sequence then,you'll see that tthe steps increment in equal %amounts where in a linear aequence,they don't.

Bill Burk · Jul 21, 2019

I think we should work printing exposures in “Delta-E” terms. But I haven’t sketched out a System for that.

Roughly what I mean is... the least noticeable difference would be 1 Delta-E

In terms of percentage or time, it would vary per grade. Contrasty papers need less time difference to look different. Lower paper grades can have greater time differences to have a similar change in print results.

But I also take Doremus’s point that we’re all wasting time... you don’t need to over think this, just listen to suggestions and try them out to see what works for you.

RalphLambrecht · Jul 21, 2019

Bill Burk said:
I think we should work printing exposures in “Delta-E” terms. But I haven’t sketched out a System for that.

Roughly what I mean is... the least noticeable difference would be 1 Delta-E

In terms of percentage or time, it would vary per grade. Contrasty papers need less time difference to look different. Lower paper grades can have greater time differences to have a similar change in print results.

But I also take Doremus’s point that we’re all wasting time... you don’t need to over think this, just listen to suggestions and try them out to see what works for you.

+1

Enlarging - printing f stop chart?

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