How to build a curve for QTR using a Noritsu 810 densitometer?

Take2 · Jun 16, 2014

Hey folks,

I'm working with Ron Reeder's Quadtone RIP method to produce digital negatives for contact printing. I'd like to try using a densitometer to evaluate (printed) step tablets, calculate curves, and so forth.

Can someone help with the math involved?

Thanks so much!

RalphLambrecht · Jun 16, 2014

Take2 said:
Hey folks,

I'm working with Ron Reeder's Quadtone RIP method to produce digital negatives for contact printing. I'd like to try using a densitometer to evaluate (printed) step tablets, calculate curves, and so forth.

Can someone help with the math involved?

Thanks so much!

piece of cake.start with the attached and after that ,I can send you a spreadsheet to do it automatically

Take2 · Jun 16, 2014

ralphlambrecht said:
piece of cake.start with the attached and after that ,I can send you a spreadsheet to do it automatically

Thanks, that's pretty much what I was looking for. I take it a "transfer function" is a fancy way of saying "adjustment curve" ?
Never understood why some authors love to state things in a needlessly complicated way.

Yes, I'd very much like the spreadsheet.

pschwart · Jun 16, 2014

In Photoshop, transfer curves are applied at print time, while adjustment curves are applied to the image while you are editing. The curves are interchangeable, they are just applied at different times in the workflow so the distinction is valid.

RalphLambrecht · Jun 17, 2014

I'm afraid that would needlesly complicate things at this point

RalphLambrecht · Jun 17, 2014

a curve is a curve and a function is a function.you asked for the mathematicsnot a canned curve.so,I'm afraid ending you the spreadsheet would needlesly complicate things at this point.

Take2 · Jun 18, 2014

ralphlambrecht said:
I'm afraid that would needlessly complicate things at this point

Nevermind then.

edit: apologies. I didn't realize you authored that book! (just noticed your signature) I stand by what I said, but the tactlessness was unintentional.

Take2 · Jun 18, 2014

pschwart said:
In Photoshop, transfer curves are applied at print time, while adjustment curves are applied to the image while you are editing. The curves are interchangeable, they are just applied at different times in the workflow so the distinction is valid.

Did you mean "in QTR.." ? Never came across "transfer curves" anywhere in Photoshop.

pschwart · Jun 18, 2014

Take2 said:
Did you mean "in QTR.." ? Never came across "transfer curves" anywhere in Photoshop.

Photoshop: File->Print->Output->Transfer
Note that you can load a acv in the transfer curve dialog, and in the acv dialog you can load a transfer curve (atf).

RalphLambrecht · Jun 18, 2014

Take2 said:
Nevermind then.

edit: apologies. I didn't realize you authored that book! (just noticed your signature) I stand by what I said, but the tactlessness was unintentional.

no problem.I've got s thick skin and I'm still happy to help you. I'm currently working on a digital version of the book andlove some feedbackbut I need an email request(address below)because the spreadsheet is on a different computer and I can't send it from this one.You'll be amazed how well this simple custom luminance calibration works.

pschwart · Jun 18, 2014

Here you go: Dead Link Removed
I think the Noritsu 810 is a rebranded X-Rite 810, so you can use the X-Rite toolcrib driver to capture the densitometer readings directly in the spreadsheet. There are various schemes for automating curve creation, but it's easy to get in the ballpark with 1 or 2 iterations, and I always end up hand tweaking the curve anyway.

Take2 · Jun 18, 2014

pschwart said:
Photoshop: File->Print->Output->Transfer
Note that you can load a acv in the transfer curve dialog, and in the acv dialog you can load a transfer curve (atf).

I was referring to an acv used in part to generate an ink distribution curve in Quadtone RIP.

Take2 · Jun 18, 2014

pschwart said:
There are various schemes for automating curve creation, but it's easy to get in the ballpark with 1 or 2 iterations, and I always end up hand tweaking the curve anyway.

Thanks. I'll read through it.

I tweaked my QTR profile to where it can produce digital negatives [that produce prints] that visually match what I see on screen (subjectively speaking) without applying *any* acv. I'm quickly starting to see how subjective the dn process really is.

-- Attached: source digital file & scan of a fiber print

pschwart · Jun 19, 2014

You can create the curve in Photoshop and reference it in your QTR profile.

RalphLambrecht · Jun 24, 2014

TAKE2,THIS IS A GREAT IMAGEand well worth your efforts.congrats!

Take2 · Jun 27, 2014

ralphlambrecht said:
TAKE2,THIS IS A GREAT IMAGEand well worth your efforts.congrats!

Thanks for your remarks about the image. In fairness I should say its not my photograph; this is Creative Commons Domain. I simply used for its tonal qualities in testing my process.

I've been meaning to respond to your earlier post but haven't had the time. I'm happy to provide (constructive) feedback if you feel such would be helpful to you, especially since you mentioned a new edition of WBM. My expressed frustration was directed at photography books that are a "hard read". Ansel's triology being at the very top of the list; I've owned it for about a decade-and-half and barely got through a portion of the first volume. Its not that its incomprehensible; the material is technical enough as it is -- more so then average "photographers" would care to endure. I think the language of the book should make the material "mentally accessible" to a broader audience. Hopefully that makes more sense then my earlier one-line rant

RalphLambrecht · Jul 6, 2014

Dear Take2,
one of the hardest parts of writing for enthusiastic photographers is the fact thatall of them seem to think that they are about average or that whatever they do must be what most of them do or like;nothing could be farther from the truth.we are all different,vry different in our approach and likes;what's to hard and complex for oneis too simple and unchallenging for the next.In WBM,I simply presentedwhat Chris and Ifound to be interesting and not obvious to us.I oftrn use the book as a reference myself.in a way ,it is my photographic diary.if it isn't in there,I've never used itand most likely never will.I'm currently working on the digital version of WBM, called 'Digital Monochrome" and hope to have it done for its scheduled publication date of Oct 2014. again ,itt's my diary,collecting my experience of moving from analog to digital and recording what I thought was worthwhile remembering.so far ,so good.
all the best.

How to build a curve for QTR using a Noritsu 810 densitometer?

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