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Author Topic: X-Rite Passport: Dual or Single Illuminant?  (Read 1962 times)
walter.sk
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« on: May 22, 2013, 04:34:09 PM »
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I've been playing with the X-Rite Color Checker Passport and DNG profiles for my camera in LR4.4.  So far, the results appear to give me more vivid purples as a starting point for processing, and I like the results.

X-Rite indicates that I could make a profile for  given lighting situations (e.g., daylight, shade, overcast, etc), or choose two of the lighting situations and make a "Dual Illuminant" profile.  I have two questions:

1)  Would the Dual Illuminant profile actually be a compromise between the two lighting situations, and therefor less accurate than using the single-lighting profiles for those images shot in that particular light?

2)  I can easily be sucked into making profiles for many lighting situations (e.g., daylight early, noon, late; spring, summer, fall, winter, etc)  Would that be total over-kill for landscapes, where I don't have to get "precise" color values, anyway?  (I do understand that in very specific lighting situations where I want consistency among a group of pictures it would be good to profile that situation for those pictures.)
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Schewe
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« Reply #1 on: May 22, 2013, 04:57:37 PM »
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1) Not less accurate, more accurate. ACR/LR tween the white balance between Standard Illuminate A (about 2800ºK) and D65 (about 6500ºK). If you have build a dual illuminate profile under those (or similar color temps) you'll get more accurate profiles between those ranges and at either end of the range. A single illuminate is really only gonna be accurate for the condition it was made for.

2) You need a profile for tungsten and one for daylight (or a dual illuminate) but no, you don't need to spawn off profiles for other lighting conditions relating to continuous spectrum light sources like the sun. So, cloudy, shade, overcast is all taken care of with a dual illuminate profile. Were other profiles can come in handy is where the light sources are not continuous and have spikey spectrums like fluorescent or LED lighting...I think X-Rite has oversold the concept of special profiles for every lighting condition under the sun (literally).
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walter.sk
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« Reply #2 on: May 22, 2013, 06:57:28 PM »
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Thanks for the info.  I hadn't thought of continuous vs spikey light sources.  I will happily settle for a 2-illuminant profile of the 2800K-6500K variety, and use single illuminant profiles for more quirky lighting.  The obsessive part of me can go back to its cage Cheesy
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Schewe
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« Reply #3 on: May 22, 2013, 09:04:33 PM »
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Yeah, the real reason for dual illuminate profiles is that camera sensors can have  illuminant metameric failure because a sensor is tuned to a certain illuminate (using daylight such as D50 or D55, but could be D65–depends on the sensor). The tricolor separation filters for the Bayer array may not perform the same way under daylight as they do under tungsten (in fact it's highly unlikely that they would).

So, the dual illuminate should take care of that. Aside from the spikey light sources, there's another reason one might want to create special DNG profiles and that is to modify the sensor response to certain specific colors like John Deer green, or Budweiser red or Kodak yellow (ok, less important these days :~(

However, the X-Rite solution does offer DNG profile editing...for that you would need the free DNG Profile Editor available on Adobe Labs. You can build an X-Rite profile in the Passport software then edit that profile in DPE to tune colors. It's really not hard...(only a little geeky) but the documentation is very well done (by our own Eric Chan–MadManChan).
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digitaldog
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« Reply #4 on: May 23, 2013, 09:13:10 AM »
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1. Give the dual illuminant a try!
2. Don't feel that you have to use the target and build a profile in every case. Sure, if you're doing a studio setup, have a client around, have the time for one capture, go ahead and shoot the target in the scene. But the idea you have to always do this and always make a custom DNG profile for each scene isn't necessary. If you enter a really odd lighting situation, grab a capture and maybe try a new custom profile. Otherwise you'll only need a couple profiles.
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Andrew Rodney
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Stas Wilf
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« Reply #5 on: June 16, 2013, 10:15:39 PM »
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2)  I can easily be sucked into making profiles for many lighting situations (e.g., daylight early, noon, late; spring, summer, fall, winter, etc)  Would that be total over-kill for landscapes, where I don't have to get "precise" color values, anyway?  (I do understand that in very specific lighting situations where I want consistency among a group of pictures it would be good to profile that situation for those pictures.)

Besides the above-mentioned difference between continuous-spectrum light sources and spiked-spectrum ones, you may wish to create separate profile for deep twilight, when CT is high. White balance alone, as demonstrated here, is not enough:



Crescent-shaped pictogram shows the result of shooting in twilight, compared to daylight (background). Color temperature in this case was about 13500K.
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Vladimirovich
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« Reply #6 on: June 16, 2013, 10:59:25 PM »
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I've been playing with the X-Rite Color Checker Passport and DNG profiles for my camera in LR4.4.  So far, the results appear to give me more vivid purples as a starting point for processing, and I like the results.

you don't need to shoot a target - just modify the OEM profile(s) /LUTs inside/ using one of dcp profile editors (Adobe DNG converter /free/ or from QPCard /$/) to your taste.

PS: ask Schewe if his C1 w/ single illuminant OEM icc/icm profiles renders colors "worse" then his LR/ACR with dual illuminant OEM dcp profiles  Wink

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walter.sk
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« Reply #7 on: June 17, 2013, 09:38:40 AM »
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Besides the above-mentioned difference between continuous-spectrum light sources and spiked-spectrum ones, you may wish to create separate profile for deep twilight, when CT is high. White balance alone, as demonstrated here, is not enough... Color temperature in this case was about 13500K.

Well, since it is so easy to shoot the Passport Color Checker and make a profile, it certainly seems worth it in extreme situations.
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Schewe
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« Reply #8 on: June 17, 2013, 11:18:03 AM »
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PS: ask Schewe if his C1 w/ single illuminant OEM icc/icm profiles renders colors "worse" then his LR/ACR with dual illuminant OEM dcp profiles  Wink

In some cases, yes...C1's tungsten rendering and correction isn't as good as ACR/LR with a dual illuminate DNG profile for my P65+ back. The IQ 180 back it's about 50/50.
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