Home · Register · Join Upload & Sell

Moderated by: Fred Miranda
Username  

  New fredmiranda.com Mobile Site
  New Feature: SMS Notification alert
  New Feature: Buy & Sell Watchlist
  

FM Forums | Post-processing & Printing | Join Upload & Sell

  

Archive 2014 · Spectral adjustment in post?

  
 
Access
Offline
• • •
Upload & Sell: Off
p.1 #1 · p.1 #1 · Spectral adjustment in post?


I'm not sure whether to post this in lighting or post, but I figure this group makes more sense.

I honestly don't do a great deal of photoshop anymore, not in the last several years at least. But in photoshop, or outside of it (preferably outside of it), is there a common filter to reverse modern light sources? I'm using an upgraded version of a beleuchtungschalttafel-3000L and the CL-840-P215 panel, the spectral response is something like:

http://www.intematix.com/uploads/files/chromalit_datasheet.pdf

page 6, second graph, red line.

Lightroom has some basic color adjustment but is not very usable for anything this dramatic since it is a hard cutoff at each color. I'd like to be able to enter about 6 points on the adjustment graph and than have it approximate the rest of the graph using splines or something similar. The main problem is the valley around 480nm, I obviously cannot use gels as that would cut the efficiency way down (it needs to stay bright and portable).



Jan 13, 2014 at 02:42 PM
colinm
Offline
• • • •
Upload & Sell: Off
p.1 #2 · p.1 #2 · Spectral adjustment in post?


If you're shooting raw and using Adobe tools (which the mention of Lightroom suggests you are), this is pretty much exactly the kind of problem the X-Rite ColorChecker Passport solves.

Light the test chart, shoot the test chart, software magic attempts to compensate for the eccentricities of your light source.

It certainly won't be perfect, as that's a pretty heinous spectral output curve, but it'll probably be better (and will certainly be lower-effort) than attempts to do it by hand.



Jan 13, 2014 at 02:48 PM
Access
Offline
• • •
Upload & Sell: Off
p.1 #3 · p.1 #3 · Spectral adjustment in post?


Cool that sounds like exactly what I need, thanks.


Jan 13, 2014 at 03:56 PM
skibum5
Offline
• • • • • •
Upload & Sell: Off
p.1 #4 · p.1 #4 · Spectral adjustment in post?


Access wrote:
Cool that sounds like exactly what I need, thanks.


Yeah I tried that. Either that or write some custom software to your image in spectral response terms and then apply an inverse function based on data you plug in from that graph.

I'm not aware of any generally available commercial software that does color management or control using spectrums, they all seem to use the classic simple three primary color management. COlor researchers and probably some scientific or industrial labs have fancier software, custom written, using spectral based color management, and that sutff would probably let you apply such transforms. Not sure where, how you'd get a hold of it.




Jan 13, 2014 at 05:41 PM





FM Forums | Post-processing & Printing | Join Upload & Sell

    
 

You are not logged in. Login or Register

Username       Or Reset password



This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.