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For your modeling lights you are probably shooting in controlled conditions so I would follow Tutorial 5 and just make a single illuminant profile. The color temp of your lights doesn't matter in this case. PE will optimize the profile for that specific lighting condition.
If you were to take the chart image in evenly lit open shade would that still be accurate enough to generate both illuminate profiles?
I understand that for a single illuminant profile, color temp isn't highly critical. I'm asking about generating a dual illuminant profile.
Jim, are you asking if I shoot one image in open shade, and the other under controlled tungsten lighting? Or something else?
If I understood tutorial 5, it says that you can take the image under one illuminate and set PE to create both color tables an once so I was asking if evenly lit open shade was good enough to use for the chart image.
Well, the whole point behind a dual illuminant profile is that the sensor responds differently under different light sources. Tutorial 5 is a single illuminant example. I'm specifically looking at Tutorial 6, not Tutorial 5.
ETA - the point being, to get the best "all purpose" profile, you can create a dual illuminant profile that matches your camera and covers a wide variety of lighting situations. It allows ACR/LR to vary the profile based on the white balance of the image (and therefore, in theory, to the spectral response of your camera at that white balance).
Nothing is perfect, obviously, but...
I understood that you were looking to do D65 and tungsten images, I was just curious to know if open shade was sufficient for generating both color tables.
My understanding is that it would only be sufficient for the D65 image, not the tungsten (because the sensor will respond differently under tungsten lighting).
To answer your question, if you want to do Tutorial 6, then on the D65 end it's not super-critical to get that close to 6500 K. On the 2850 K side you want to be as close as you can.
It boils down to how you want to use the profile. If you're trying to get one profile that does it all, then try tutorial 6, with the understanding that the better you do capturing the data, the more accurate the profile will be. If you're shooting in a specific condition often then use tutorial 5.
Trying to do a dual illuminant profile for a Canon 40D I'm facing some problem hitting the target values 2850 K and 6500 K.
In the Tungsten end I tried different brands of bulbs, they all come in at 2650 to 2750 K ( Including a light cabinet with Tungsten setting for matching color samples at work).
Sales material for some brands indicates 2700 K and Ra value between 90 to 100.
Is the 2750 K close enough ??
On the 6500 end I guess i will hit it when mother nature is in the mode, so far I reached around 6200 K.
2750 K __may__ be close enough but it does depend on the spectral characteristics of the bulb.
Ok, Eric, but is there any way to verify a supposed bulb spectral distribution at 2750K? What is the "official" light source used to generate the original 2850K profile used by ACR beta profiles?
Thanks for the answer!
Massimo, the light source in the CR beta profiles for the 2850 K end is the Standard Illuminant A as defined by the CIE. You can get data here if you're interested:
In general, to verify that a given bulb that you have is close (or not) to a reference like Standard Illuminant A requires the use of instrument like a spectrophotometer which can actually measure the spectrum of that bulb.
There are many spectra that can map to a given pair of temperature & tint values, so having those 2 numbers alone is insufficient.