Creating custom camera profiles for digital camera "scanning" of slides using an IT8 target: anyone tried this?

[GLS]

So what does that mean regarding using a Kaiser panel and the Sony A7RIV camera to read Kelvins? what does that mean vis a vis :scanning film?

I'm sure the A7RIV does a pretty good job at reading the colour temperature of the panel. However, this is a measure of the colour of the light itself. Its CRI (or another related standard) is a measure of how the colours of objects appear when illuminated by the light.

As grat pointed out, I probably used the incorrect technical term before when referring to "discontinuities" in emission spectra. There won't be a literal blank space in the spectrum, but LEDs typically feature a dip in intensity in the cyan-blue range (the "cyan gap"), and also of red wavelengths. This produces shifted hues in objects illuminated with the light, compared with how they appear in daylight.

More info here:

What is CRI? The ultimate guide to the Color Rendering Index | Waveform Lighting

Confused about CRI? Our easy-to-understand guide helps to break down the color rendering index and what it means for your lighting.

www.waveformlighting.com

What is the difference between CRI and Ra? | Waveform Lighting

You may hear CRI and Ra used interchangeably to refer to LED color quality. But they can mean different things, depending on who you ask.

www.waveformlighting.com

 

[Adrian Bacon]

Hello Adrian Bacon, would you agree with, that color correction like you described, is the basis correction from
raws ? If your way to digitize is then the same, you may
save this settings. From time to time you have to improve
your basic settings because from time to time there is a change in the workflow (the scanning workflow).
If you work with 2 scanning units you need two basic settings a.s.o.

2..) with lightroom or other products you come to the first flor of color correction (same procedure as in the darkroom)
but with digital filters.

but before this can be done you have to do

1.) your Monitor ( or TV sceen ) need its own calibration.
If you have color bars it would be fine in other cases you produce your own color test-chart.

If you have all this done correct you have neutral colors!!!

If that is fine for you then you have finished.

But with this saved data in true (uncompressed) raw format you may play your own (let us say ) game!

now you can change your colors how you feel fine with.
(that is the difference to darkroom color corection for me)

AND THIS SETTING CAN BE SAVED (Your personal Look/LUT) and with a little luck you can save a lot of time.
If your workflow is pretty correct your correction steps can be applied to full groups of shots.

Yes, the correction is from raws. Yes, you should be working with a calibrated monitor, though using the histograms should also at least get you in the ballpark. And yes, in Lightroom, once you get to a base setting you like, it's a simple copy/paste of the settings to all the other images for that roll in the develop module, thus saving a large amount of time.

 

[Beverly Hills]

Yes, the correction is from raws. Yes, you should be working with a calibrated monitor, though using the histograms should also at least get you in the ballpark. And yes, in Lightroom, once you get to a base setting you like, it's a simple copy/paste of the settings to all the other images for that roll in the develop module, thus saving a large amount of time.

Thanks for your response Adrian

 

[DCS]

So an update on this.

I decided to splurge some more and do this thing properly. Bought the Negative Supply Scanning Light Source Pro 5x7" 99 CRI. Overpriced, but extremely well made and ideal for my existing setup; I discovered by happy chance that my custom-made 4x5" film scanning holder sits perfectly astride the built in plastic mask that the NS Light Source Pro comes with, blocking out all extraneous light.

With the light source sorted, I'd already ordered a 4x5" LaserSoft Provia IT8 hand measured target as I mentioned previously. I established an ideal RAW exposure for this target in the rig, converted the ARW to DNG using Adobe's free tool, and then used that to create a custom profile in Lumariver Profile Designer Pro, on a freshly calibrated monitor.

I've now made test repros of sheets of Provia, Velvia and Ektachrome E100 with the new light and profile. Frankly I'm blown away. A *huge* improvement over what I was getting before. The Provia repro is 99% of the way to how it appears on a lightbox. The Velvia and Ektachrome repros are maybe a hair less faithful, as one would expect, but still 98% I'd say and absolutely good enough as a starting point.

@L Gebhardt you were correct to some degree about the light panel. The base result from the 99 CRI light is a notable improvement over that from the Kaiser, but the custom camera profile is ultimately where the biggest difference was made.

Being about 5 stops brighter than the Kaiser, the NS light also has the added benefit of allowing higher shutter speeds during capture. This appears to have essentially eliminated the edge artifacts that can result at 100% in pixel-shifted captures from the A7RIV due to micro vibrations at lower shutter speeds.

Overall I'm one damn happy camper right now, despite the lighter wallet

GLS, Thank you for such encouraging posts. My outfit for scanning color slides is a Sony A7RII on a modified Honeywell Repronar (with electronic flash removed). I have used an LED movie light for a light source for thousands of slides. I have been unhappy with the results for the same reasons you described. My digital copies do not have the beautiful colors that I see looking at the slides as I am photographing them.

Before I came upon your post I built a prototype light source with an incandescent enlarging bulb. Comparing digital copies of an IT8 from Wolf Faust visually with Lightroom 6 on a uncalibrated MacBook Pro the incandescent source is significantly superior. But the copies are still disappointing. Up to this point I consider my digital copies as just an index to my collection. I also have a Nikon Coolscan when I want a high quality result. The Nikon takes so long for each scan that it is rarely used.

From your posts I see that I need to use a camera profile using the IT8 and Lightroom. Did you use the Lumariver Profile Designer? Standard edition? From its documentation I know it will work with the XRite ColorChecker. But does it work with the IT8 and the measured data from Wolf Faust?

Do you know of a description of making the profile and the workflow using the camera profile and LR6?

Sounds like you have walked out ahead of me on this adventure. Any advice would be welcome!!

 

[GLS]

From your posts I see that I need to use a camera profile using the IT8 and Lightroom. Did you use the Lumariver Profile Designer? Standard edition? From its documentation I know it will work with the XRite ColorChecker. But does it work with the IT8 and the measured data from Wolf Faust?

Do you know of a description of making the profile and the workflow using the camera profile and LR6?

Sounds like you have walked out ahead of me on this adventure. Any advice would be welcome!!

Yes, I used Lumariver Profile Designer (the Pro version). It does work with an IT8, although the grid preset name refers to a reflective (rather than transmissive) IT 8.7 target. However all this preset does is determine where the patches are for sampling, so works equally well with a slide. The IT8 I used was from LaserSoft, but as far as I know the ones from Wolf Faust have the same layout so should also work fine.

For workflow I suggest you read the manual thoroughly. It's all pretty well explained:

Lumariver Profile Designer

I didn't do anything hugely involved in creating the profile (like messing with the "look adjustments"); mainly just tweaked a custom tone curve and chose sub-settings in the Tone Reproduction Operator I thought looked best and made the most sense. Obviously it's important to be working on a properly calibrated, colour-accurate monitor when creating the profile. When you have the custom DCP file, it just needs to go in the correct "CameraProfiles" sub-folder:

On Windows this is: C:\Users\UserName\AppData\Roaming\Adobe\CameraRaw\CameraProfiles
On Mac: ~/Library/Application Support/Adobe/CameraRaw/CameraProfiles

The next time you start Lightroom it should then show up in the profiles drop-down in the develop module. You can check the results here on real slides, then go back to Lumariver and tweak the profile settings further if needed.

If you try it and get stuck I can send you some screenshots of my settings within Lumariver.

 

[DCS]

GLS, thank you so much! I think I am on my way to success. I will post here either way.
Best regards,
DCS

 

[shijan]

I made a small FAQ and package based on Argyll_V2.3.1 with examples to create so called "Well Behaved" Matrix Input Profile for camera/scanner that is specially useful for negatives invert and processing. "Well Behaved" input profile with D50 white point behave and respond in same way as normal working profile, so you can pick film base, invert and pick WB directly inside original unmodified data in linear gamma.

Dropbox links not allowed here so you can find package here in original thread https://liftgammagain.com/forum/ind...per-cineon-inversion.13714/page-6#post-167174

Based on these articles:
https://ninedegreesbelow.com/photography/well-behaved-camera-profile.html
https://argyllcms.com/doc/scanin.html
https://argyllcms.com/doc/colprof.html

Some background info:

ArgyllCMS folder form ZIP archive should be placed on Desktop
Files and folders names should have no spaces
Don't use TIFF compression. Argyll can't read compressed TIFFs

Test_Chart.tif is a scanned IT8.7 chart image.
Reference_File.txt (or .cie) is a reference file for IT8.7 chart with measurements provided by chart manufacturer.
it8.cht is a grid guide file for patches autodetection. It is provided by Argyll for all supported color charts. You can find it in Argyll_VX.X.X/ref folder downloaded from here https://argyllcms.com/. I use it8.cht file which was extracted from RoughProfiler because its grid better optimized and modified for IT8.7 chart that i use.
diag.tif is a file generated for visual inspection only. It helps to check if all patches where autodetected in correct places.
Test_Chart.ti3 is a file generated by scanin that contains measured data. It is used by colprof to generate ICC profile.

-v Verbose mode
-p Compensate for perspective distortion
-dipnoa different options to adjust the look of diag.tif
-G1.0 Gamma of Test Chart. It helps to improve patches autodetection
-D"" Internal Profile Name
-Zp Profile default intent Perceptual
-qh Profile quality High
-am Profile type Matrix only
-u Auto adjusts Exposure of Test Chart, so white patch became 100% white

-----------------

Prepare your Test Chart
Based on this tutorial https://ninedegreesbelow.com/photog...ra-profile.html#raw-process-set-white-balance
Open your Reference_File.txt in text editor and search for the most neutral LAB_A LAB_B gray patch that have LAB_L value at least 50.00. In most cases it is somewhere between GS1 to GS8 patches.
In Raw editor pick White Balance based on this patch and export Test_Chart.tif in Linear gamma with disabled color management.

Step 1
Generate .ti3 data file and diag.tif file. Type this code in Terminal:

~/Desktop/ArgyllCMS/scanin -v -dipnoa -G1.0 ~/Desktop/ArgyllCMS/Test_Chart.tif ~/Desktop/ArgyllCMS/it8.cht ~/Desktop/ArgyllCMS/Reference_File.txt ~/Desktop/ArgyllCMS/diag.tif

Step 2
Based on this tutorial https://ninedegreesbelow.com/photog...rofile.html#add-D50-white-black-color-patches
Open Test_Chart.ti3 in text editor and add additional lines with perfect synthetic D50 white and black color patches. Also NUMBER_OF_SETS should be changed from 288 to 290. So it should look like this:

NUMBER_OF_SETS 290
BEGIN_DATA
00W 96.4200 100.000 82.4910 100.000 100.000 100.000 0.000000 0.000000 0.000000
00B 0.000000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.000000 0.000000

For matrix profiles ArgyllCMS automatically pick WB from whitest and darkest patches in the chart, but in most cases whitest patch is very far from perfect white and also have huge tint compare to other darker patches. So this "hack" helps to bypass White Balance shift of IT8.7 target. Guess it should be used only for simplest matix-based profiles that don't allow to fine tune every WB patch separately. Also perfect D50 white point makes input profile behave and respond in same way as normal working profile, so you can pick film base, invert and pick WB directly inside original unmodified data in linear gamma.
Note that simple matrix-based profile produce decent calibration results only with high CRI light sources. If your light source have low CRI or use RGB LEDs with non uniform peaks, it usually needs way more complex correction than simple matrix input. Guess in this situation it is somehow possible to create additional secondary correction LUT that will adjust colors in complex way.

Step 3
Create Input Matrix ICC profile. Type this code in Terminal:

~/Desktop/ArgyllCMS/colprof -v -D"Profile Name" -Zp -qh -am -u ~/Desktop/ArgyllCMS/Test_Chart

 

[GLS]

Excellent info @shijan thanks.

Quite a bit to digest in that guide and linked thread. Is Argyll alone limited to ICC profile output? I don't think Lightroom supports ICC camera RAW profiles, only DCP.

 

[shijan]

ICC profile will not work with Lightroom and Argyll can't create other profile type. To work with custom made ICC profile you need somehow convert raw to tiff with fully disabled color management. PhotoLine or Iridient Developer can do this. I posted some tips about specific Iridient Developer earlier in same thread on LGG.

 

[jejes]

You could use with capture one

ICC profile will not work with Lightroom and Argyll can't create other profile type. To work with custom made ICC profile you need somehow convert raw to tiff with fully disabled color management. PhotoLine or Iridient Developer can do this. I posted some tips about specific Iridient Developer earlier in same thread on LGG.

You could use with capture one, I’ve been profiling my cameras since 15 years ago.