Profiling Phase one P65+

[autumns_child]

Hi!

I'm shooting fine art (paintings of different techniques) and faced the fact that color of P65+ even with such profiling solutions as Colorchecker Passport some hues are extremely inaccurate. Firstly it seems that some parasite green presents in each color. And what is more annoying is when there is some ochre in the painting, it's never comes right - usually it's dark brown instead of earthy yellow. So for the moment I stuck with manual color correction, but it takes lots of time and some technical solution is necessary. 

I've tried Pictocolor Incamera as well, but it delivers something completely strange - for my skill it's difficult to describe.

So, maybe some of you have an experience with P65+? I think any advice from you can be helpful.
Thanx, Alex

[rasworth]

What is the lighting?

Richard Southworth

[autumns_child]

What is the lighting?

Richard Southworth

I'm using two fluorescent panels, 4200K.

[rasworth]

This doesn't go directly to your original question, but IMO with general flourescent lighting you will always have difficulty copying artwork.  Even though it's rated at 4200K it likely has spectrum peaks, often in the green, giving the effects you described, i.e. a tendency toward green tints and dirty reds/browns.

There are newer flourescent lights that purport to be more suitable for photographic work, but the nature of the technology is it always is going to have spectral "bumps", unlike incandescent lighting which behaves very much like sunlight, only at a lower color temperature.  There are halogen bulbs at 4500-5000K, but I don't know of their suitability for copying use, i.e. do they put out enough light and they are very hot.

Richard Southworth

[autumns_child]

Hi, Richard!

I had some doubts about this light, but there is also another case when it works pretty well. My main camera is Betterlight scan back and the results with these fluorescent panels are quite good (at least no such problems as was described above). However I'm awaiting new hid based lighting system - so, let's see if there will be any difference.

Anyway, can you advice some camera profiling system? For me it is the most difficult quest. Thank you.

Alex

[rasworth]

I'm no expert at camera profiling, but you might want to try the Adobe DNG Profile Editor, using a color checker chart for the target.  It may have an advantage over the Passport in that it uses a LUT (look up table) approach.  I believe the Passport only generates a matrix profile, and therefore may not have as much flexibility to correct for extreme lighting conditions.

In any event it's worth a try, and it's free, http://labs.adobe.com/wiki/index.php/DNG_Profiles

Don't be turned off by its beta status, it's stable.

Richard Southworth

[autumns_child]

Hello Richard!

Thank you for that advice. Surprisingly DNG Profile Editor from Adobe is delivering pretty good results! I'd say much better than Color Checker Passport (have no idea why) and the workflow is more easy.

Alex

[digitaldog]

Surprisingly DNG Profile Editor from Adobe is delivering pretty good results! I'd say much better than Color Checker Passport (have no idea why) and the workflow is more easy.

You can still edit DNG profiles built with Passport with the Adobe editor. Whether the initial custom DNG profiles are better in that product or Passport is the next question (I’ve always preferred the Passport generated profiles).

There IS a difference in building a DNG Passport profile in Lightroom versus the standalone in that the former can’t build dual illuminant DNG profiles and the later can. With your light setup, I don’t see how a dual illuminant would be of use.

[rasworth]

Not sure which is better, but the standalone Adobe Profile Editor builds (for me) a 28kb profile, whereas the Passport generated profiles are around 3kb.  I believe the Adobe Profile Editor starts with a base profile, and then uses the measured 18 color patches of the color checker image to build a hue/saturation LUT on top of the base profile.  Apparently the passport version is much simpler, probably a straight matrix/gamma curve type.

My assumption is the Adobe Profile Editor method may handle spiky illumination better because of the LUT approach, and it seems to be true for a sample of one.  And the Adobe Profile Editor can construct a dual illuminant profile, although it's more limited in that the illuminants have to be closer to two fixed values, i.e. 2850K and 6500K.

Richard Southworth

[digitaldog]

Not sure which is better, but the standalone Adobe Profile Editor builds (for me) a 28kb profile, whereas the Passport generated profiles are around 3kb.

Its odd that I too have varying sizes, from 4K to as large as 57K from Passport. I haven’t seen size/quality correlation however.