digital negative chararistic curves

[nmp]

With Relative Colorimetric (in fact with all the rendering intents), BPC is grayed out. You only get to check BPC if Photoshop manages color, and I have been letting the Printer manage color. So should I let Photoshop manage color? The document profile is Adobe RGB and the printer profile is "SC-400 Series Photo Paper Glossy," which I have been using to print transparencies. I'm ready to print, but I'll wait to hear from you. Here are the proposed settings:

https://photos.app.goo.gl/EXWaJjSEJaiZaqiG9

Yeah, that looks good. Let it RIP! (pun intended.)

Didn't realize Printer Managed didn't allow BPC. One more reason to use Photoshop Managed (which is what I always do.)

So looks like we have the same printer.

:Niranjan.

 

[nmp]

Yeah, that looks good. Let it RIP! (pun intended.)

Didn't realize Printer Managed didn't allow BPC. One more reason to use Photoshop Managed (which is what I always do.)

So looks like we have the same printer.

:Niranjan.

Oh, I just realized, your printer profile should be Premium Glossy not Photo Paper Glossy....

 

[jisner]

looks like we have the same printer.

I have two P400's. I use one for printing digital negatives with PiezoDN. The other one (the one I'm doing these experiments on) is a normal color P400. The color P400 never gives me any trouble. The PiezoDN printer with refillable cartridges has been a pain in the neck. I have spent more money on ink for head cleanings than ink for prints.

I just realized, your printer profile should be Premium Glossy not Photo Paper Glossy

Got it!

 

[jisner]

if you like to see if you can have a normal curve for the B=0 case, change the rendering intent to Rel Col with BPC checked and see if there is a difference. I guess you only need to do a few points in 90-100% zone to verify if it is a factor.

I'm sorry to say that there was no improvement. But I will continue to use your recommended print settings.

https://photos.app.goo.gl/wPU8o6ENwDUWRtGX6

 

[nmp]

I'm sorry to say that there was no improvement. But I will continue to use your recommended print settings.

https://photos.app.goo.gl/wPU8o6ENwDUWRtGX6

Oh, well....there is theory and then there is real life. I wouldn't say there was no difference, though. Hard to see exactly without the 2 curves side-by-side, but it looks like in the new curve, the approach to Dmax is gentler and the roll-over happens at slightly higher K and the solarization is not as dramatic. Slight improvement, but no cigar...

The profiles in this range are notoriously inaccurate - I have at times added a correction curve to deal with blocked deep shadows when making digital B&W prints even with BPC activated. More recently, I have tried to make a B&W-specific profile with i1Studio but the jury is still out if I got any big improvement.

I have had a refurbished/unused 1430 for some time and was thinking may be this year I might do something with it. Piezography inks seem to be very expensive just for playing around. I am tending towards Paul Roark's self-compounded Eboni inks. This could be one more rabbit-hole to pursue, but at least the raw materials will be cheap enough.

:Niranjan.

 

[jisner]

but it looks like in the new curve, the approach to Dmax is gentler and the roll-over happens at slightly higher K and the solarization is not as dramatic.

Actually both "go bad" at 94%. With your print settings, the curve flattens. With my old print settings, they max out and then drop off -- admittedly worse! The differences could be meaningful, or just random variation, but I will stick with your print settings from now on.

When I get the negative curve integrated into my software simulation I'll post again. Working on it now....

 

[nerologic]

John, any updates on this?

 

[jisner]

John, any updates on this?

Hi nerologic. Yes, I made some progress. I created a custom negative characteristic curve for my printer. It is specific to my printer (Epson P400), ink (Ultrachrome), printer settings (suggested by Naranjan), and transparency material (Pictorico Ultra). How I did it: Using Photoshop, I printed a 101-step grayscale step table on Pictorico Ultra. I measured the UV transmission density of each step with an XRite 361T. Plotting transmission density vs K% gives the digital negative characteristic curve. It is analogous to an analog film curve, with K% (gray image tone) playing the role of exposure (logH). From a single master curve I can derive a family of curves having density ranges lower than the master curve.

As I mentioned earlier in this thread, I am using this curve in simulations of the tone reproduction cycle. A simulation requires two inputs
(1) the characteristic curve of the process that you wish to study. Get this by printing a target with a Stouffer step wedge and measuring Lab L* values for each of 21 or 31 steps. The plot of L* vs logH is the characteristic curve of the process. But since logH is the inverse of transmission density, you can also look at the curve as a plot of L* vs. transmission density, which is how it is used in the simulation.
(2) the characteristic curve of the digital negative. Get this as described above.

With (1) and (2) you have the ability to map L* to K%, from which you can derive an image adjustment curve.

The above simulation is for a negative whose density range is perfectly matched to the process exposure scale. I can simulate the effect of negative density range errors (negative too dense or too thin) and exposure errors (overexposure, underexposure). It's interesting to observe how these errors affect the image adjustment curve.

The first question anyone is likely to ask is: Do your simulations produce usable adjustment curves? The simulator can generate a LUT which can be used as a Photoshop image adjustment curve, but I have purposely avoided darkroom testing until I'm confident that the simulation is mathematically sound. Once I start testing, I'll be glad if the results are even somewhat encouraging. After all, my goal was to develop an educational tool, not a tool for automating digital negative calibration.