Creating digineg using blacks only - what gives?

[seans]

Hi all,
I have been inspired to try making a digital negative for pd using b&w only.

I recently acquired a UV densitometer to go along with my 810 reflective densitometer - hoping to get readings on the neg and then see how that calibrates to the reflective readings.

So - here is where I am at - and I could use some help:

1. after a few trials I have come to a curve that gives me a UV range of .11 to 2.67. This is using a 21 step wedge in photoshop, pk ink in 2200 on pictorico ohp.

2. using this neg I got a baseline expsoure time of 4 minutes using equal amounts of pd and fe - no na2 at this time.
My density ranges from .05 to 1.38 - very close to what I was doing with PDN.

Now here are the curves themselves -
Note the UVCurves - series 5 is the curve I am talking about.
Note on Reflection Curves series 4 is the corresponding reflection curve.

So - my question -

Note on the UV curve there is a dip - it is not linear and seems to be too thin in the midtones.
Yet in the reflection curve it is also not linear - it is too light in the midtones - that seems to be the opposite of what I would expect if the UV is too thin.

So.... others have experience with this non linear response in pd to uv density?

I would appreciate any insights.
Thank you
Sean

 

[mkochsch]

Is the Series 5 the "final" curve or the first. Show us the first curve you made to get to the 2.67 logD. How are you controlling the overall density -- using a RIP with curves or selecting a percentage of black as a fill? Or just curving it out with the ACV? Maybe all this means is your negative needs to apply even less density at the area in question to straighten out the reflected output. Could you give a little more details on how you did the measurements

~m

 

[seans]

Is the Series 5 the "final" curve or the first. Show us the first curve you made to get to the 2.67 logD. How are you controlling the overall density -- using a RIP with curves or selecting a percentage of black as a fill? Or just curving it out with the ACV? Maybe all this means is your negative needs to apply even less density at the area in question to straighten out the reflected output. Could you give a little more details on how you did the measurements

~m

Series Five is the last curve

I started with the 21 step digital table that comes with PDN. I then applied a curve in PS. The previous series are other attempts - including the highest curve on the graph - which was linear but way too light a print.

So I adjusted the curve - over a few attempts to get to series 5.

I measured using an xrite 361 calibrated uv densitometer.

I printed using +5% ink as I read in a few posts in this forum.

The net of my question is - I am not sure I want linear in the uv as it does not give linear in the reflection reading - which was done using a calibrated xrite 810.

So I am asking if others see a linear uv gives a linear reflection - or not.

Thank you.

 

[mkochsch]

I'm not familiar with the (sic) "SYSTEM" you're using but, in short, no you don't want linear in the UV curve. You want linear in the output. You want/need more bend in the UV curve to straighten your output. Using a 21-Step for the initial calibration seems like underkill to me. I use at least a 101 Step on the first round and have been contemplating creating a variable scale for "tough" curves that starts out at 256 steps and then backs off in steps once you're a couple of stops away from the dense area and into the later mid-tones.

- You're adding +5% to get to your target dMax in the negative for your process, correct?

- Personally I would stop using the UV densitometer for a moment and just go with correcting the output from an initial step wedge using the reflection densitometer. I think Sandy has pointed out that other wavelengths of light may also be passing through the negative material and may be adding to the exposure of the emulsion, so measuring the UV opacity of the negative can be misleading or give outright bad results. The proof is in the print as they say. Go with your gut.

- Posting a screen grab of your ACV curve may shed some light too.

~m

 

[seans]

OK - got it

I'm not familiar with the (sic) "SYSTEM" you're using but, in short, no you don't want linear in the UV curve. You want linear in the output. You want/need more bend in the UV curve to straighten your output. Using a 21-Step for the initial calibration seems like underkill to me. I use at least a 101 Step on the first round and have been contemplating creating a variable scale for "tough" curves that starts out at 256 steps and then backs off in steps once you're a couple of stops away from the dense area and into the later mid-tones.

- You're adding +5% to get to your target dMax in the negative for your process, correct?

- Personally I would stop using the UV densitometer for a moment and just go with correcting the output from an initial step wedge using the reflection densitometer. I think Sandy has pointed out that other wavelengths of light may also be passing through the negative material and may be adding to the exposure of the emulsion, so measuring the UV opacity of the negative can be misleading or give outright bad results. The proof is in the print as they say. Go with your gut.

- Posting a screen grab of your ACV curve may shed some light too.

~m

I think I got it. I will go back to the basics of the 101 step like I used to do in PDN. But I will keep using B&W only and no NA2 - which is the only "system" I was after - after I was clued into not needing the complexity of the different curves for every na2, paper, ink combination. I thought I would go straight B&W.
Thanks for the advice on not starting with the UV as well - that was another tip I was using from someone else
thanks