Long question - start with funadamentals go to QTR

[seans]

Hi all,

I apologize for the basic portions of this question - but I still "don't get it"

1. Density Range to Exposure Scale - I understand the need to match - lose tones. What I have not seen explicitly in all the books or online - do you actually measure the density range of your neg with a UV densitometer to determine it's range? Or is it a measurement in PS?

2. I have seen all the scales in Na2 tables and so forth that for from S1 to S7 or S1 to S13 if using A-B. But how do you determine which one to use? Trial and error - or does the answer to Question 1 answer this question?

3. I have been working with everything from PDN to BW only now to QTR. With PDN I was able to generate very linear output as read by densitometer. But I do not feel that system works for me as it is very prescriptive - and for good reasons. It works - it is just not for me. I really like the notion of having the printer driver do the work and the image remains unchanged. So that is why I have moved to QTR.
But I am not having as much luck getting the critical endpoints established - not even into the curve yet.
I read some of the other posts that state to keep reducing ink density until you get a differences between 0 and 5%. I now have that - but that has caused 85 - 100 to merge. I always print with a 31 step to check my exposure time and it continues to demonstrate good time - difference between step 1 and 2 under film, step 1 and 2 merged with out film.
So - as I understand it - using QTR the first step (just like PDN) is to set the density range. I am unclear how to get the range set unless it is ok that the darker steps are merged and we take care of this with the curve.

I have all my results in a spreadsheet should anyone dare to ask to look.
I started with the 2200 curve that Ron has on his site. I have tried ink levels of 50, 40 and 30. 30 finally go a difference between 0 and 5 - the others basically merged from 0 - 25.

Here are some of the details -
Pure Pd
No Na2
Exposure time 9' 30" using UV box
Fab Aristico paper acidified for 15 minutes in 4% oxalalic acid

Any help would be appreciated. I do have the QTR manual - have read it multiple times - love it - but still need some help.

Thank you
Sean

Here is a screen grab of graph of data

 

[seans]

Hi all,



Here is a screen grab of graph of data

Updated screen grabs

The density readings now show my latest attempt - using boost to try and get some difference between 0 and 5
I have now included graph of the values as read by eyedropper in ps

Thanks again for any help
Sean

 

[sanking]

Hi all,

I apologize for the basic portions of this question - but I still "don't get it"

1. Density Range to Exposure Scale - I understand the need to match - lose tones. What I have not seen explicitly in all the books or online - do you actually measure the density range of your neg with a UV densitometer to determine it's range? Or is it a measurement in PS?

If you have a densitometer capable of reading UV densities you can measure the maximum and minimum densities and determine the DR for any specific ink distribution you try. Then you just match this DR to the ES indicated by a specific emulsion mix. Or you could go back to QTR and adjust the ink distribution to give lower or higher maximum density.

In my own case I simply identify a target ES for my process and either choose a color (in PDN), or adjust ink density with Piezography to produce the necessary DR on the digital negative. Then I just create a correction curve and apply it as in PDN.

Sandy King

 

[mkochsch]

Hi all,

I apologize for the basic portions of this question - but I still "don't get it"

1. Density Range to Exposure Scale - I understand the need to match - lose tones. What I have not seen explicitly in all the books or online - do you actually measure the density range of your neg with a UV densitometer to determine it's range? Or is it a measurement in PS?

You can if you want but you don't have to. Personally I don't see the need. You have to keep in mind that it's the result that counts -- not how you get there. I think UV densitometers were more neccessary prior to digital negatives coming into play. Back when we had to test our materials to set development times to longer or shorter depending on the paper/emulsion's ES. If you're using one of the "pick-the-first-white-step" methods it doesn't matter because the density becomes a relative number in PS. Think of it like this ... standard exposure time sets your black point and negative colour sets your white point (dMax) then the curve just has to fix up a discrepancies in the middle. There you're done.

2. I have seen all the scales in Na2 tables and so forth that for from S1 to S7 or S1 to S13 if using A-B. But how do you determine which one to use? Trial and error - or does the answer to Question 1 answer this question?

Simple. Pick one. Use it until you think you can do better and then use a different one. Or try using no contrast agents at all. There is more to the topic I'm sure but getting back to what I said in the first point... Using contrast agents use to be a necessity because it was a big deal to remake the negative. People would shoot for silver and then want to use the same negative for pt/pd. Well they found out pretty quick that didn't work because the highlights and shadows get blown so they started dinking with the chemistry lowering it with contrast chemical so they could use silver negs. Unfortunately sometimes contrast agents degrade the image quality. The only reason I would use contrast agents with digital negatives is to help out inkjet inks with low yielding UV numbers. Something is better than nothing.

3. I have been working with everything from PDN to BW only now to QTR. With PDN I was able to generate very linear output as read by densitometer. But I do not feel that system works for me as it is very prescriptive - and for good reasons. It works - it is just not for me. I really like the notion of having the printer driver do the work and the image remains unchanged. So that is why I have moved to QTR.
But I am not having as much luck getting the critical endpoints established - not even into the curve yet.

If you're going down the QTR road then hold on to the UV densitometer I guess. You're still going to have to throw a curve in there at some point. I would only use a RIP if you are also using Quad-tone or blended black inks like Wiz does otherwise what is the advantage? And if you're going to all the trouble than why not consider investing in a real printer profiling system and generate an ICC profile that avoids all of the above hassles?

~m

 

[seans]

. I think UV densitometers were more neccessary prior to digital negatives coming into play. Back when we had to test our materials to set development times to longer or shorter depending on the paper/emulsion's ES.
~m

M - thank you for this response. It helps to understand that some of the instruction comes from the legacy of the darkroom - which is something I do not have the benefit of - so I am happy to learn this from others

.
If you're going down the QTR road then hold on to the UV densitometer I guess. You're still going to have to throw a curve in there at some point. I would only use a RIP if you are also using Quad-tone or blended black inks like Wiz does otherwise what is the advantage? And if you're going to all the trouble than why not consider investing in a real printer profiling system and generate an ICC profile that avoids all of the above hassles?

~m

Not sure I understand this last comment. I do calibrate my monitor and use ICC profiles for my printer - what I am missing here is the use of a printer profile to avoid creation of curves for creating digital negatives. Would you please explain.
Thank you
Sean

 

[seans]

In my own case I simply identify a target ES for my process and either choose a color (in PDN), or adjust ink density with Piezography to produce the necessary DR on the digital negative. Then I just create a correction curve and apply it as in PDN.

Sandy King

Sandy - thank you for the response. I take it from this that you do not use QTR but use correction curves from within PS?
Also - it appears that using Piezography requires a few test prints as you are adjusting the ink density for each image. Is this correct? Then you have to calibrate for each image to create a curve?
Thank you
Sean

 

[mkochsch]

To clarify my last point Sean. I you could get an automated system like a Greytag Macbeth iO printer profiler it automatically creates a printer profile that you can use each time you print, once calibrated. All the curve and ink density information is built into the icc file. So all you have to do is edit your photo and click print letting Photoshop manage the colours with the profile for your process. The only drawback is the cost of the system. $2,000. Not in my hobbyist's budget.
~m

 

[sanking]

Sandy - thank you for the response. I take it from this that you do not use QTR but use correction curves from within PS?
Also - it appears that using Piezography requires a few test prints as you are adjusting the ink density for each image. Is this correct? Then you have to calibrate for each image to create a curve?
Thank you
Sean

Sean,

I am using QTR to run the Piezography ink set, and I use QTR to regulate ink density so that I get the right UV blocking density. Then I create a correction curve similar to what one does in PDN. I have not yet used QTR to linearize output for my process.

Yes, using Piezography requires a few tests prints. In fact, every method you might imagine will require a few test prints, and using QTR to control ink distribution also requires a densitometer. Or at least a densitometer makes this control much faster and easier. PDN is a much simpler system and has the advantage that everything can be evaluated visually without the use of a densitometer, but it is not necessarily the best method for every printer.

Sandy King

 

[Katharine Thayer]

You can [use a densitometer] if you want but you don't have to. Personally I don't see the need. You have to keep in mind that it's the result that counts -- not how you get there. I think UV densitometers were more neccessary prior to digital negatives coming into play. Back when we had to test our materials to set development times to longer or shorter depending on the paper/emulsion's ES. If you're using one of the "pick-the-first-white-step" methods it doesn't matter because the density becomes a relative number in PS. Think of it like this ... standard exposure time sets your black point and negative colour sets your white point (dMax) then the curve just has to fix up a discrepancies in the middle. There you're done.

Thank you Michael, this is eminently helpful, and I think answers the questions I was struggling to articulate in another thread, when I was trying to find a relationship between the numbers (DR and ES) and the print. The numbers are just window dressing; knowing the numbers or not knowing the numbers has no bearing on the print, as long as one is aproaching it this way. "It's the result that counts, not how you get there." Amen, and thanks.
Katharine