Re: Target for camera profiling?
Re: Target for camera profiling?
- Subject: Re: Target for camera profiling?
- From: David Iannarelli <email@hidden>
- Date: Tue, 20 Jan 2004 05:37:06 -0500
Hi Bertho,
It sounds like I should play and practice with some of the 5" x 7" targets that
I have while waiting for Gretag's update since I already spent too much money on
the Gretag software that I bought.
I know what you mean. I thought for $4,00.00 I was getting the camera
profiling option as well. Oh no, $700.00 more for that little ad on. I
was told to buy the ColorEyes product because it was better at camera
profiling. There was a $250.00 version of ColorEyes that used the
regular Gretag color checker. I tried that version first. It built an
okay profile but not good enough for a professional to use. You got
color shifts in some areas of the image like saturated colors and skin
tones. So, I bought the upgrade and have been happy with the profiles I
have made. The regular color checker just does not have enough colors
on the target for the profiling softwares to map out an accurate
characteristic of every possible color the camera can capture then build
that perfect profile from the data. I have not experimented much with
the scanner targets for making a camera profile.
One thought: Is it possible and practical to buy the just the target from
ColorEyes and use it with the GM ProfileMaker Pro?
I do not believe they sell the target separately. I have spoke with
the guys at integrated color and from their comments about the program
there is some customized calculations going on when using their target
and software together. No target has a black as black as the camera can
record and many targets do not have enough saturated and skin color
patches for building that perfect profile. The software has to help.
Each software developer has their own philosophy on the best way to
handle all the variables.
I came up with a neat trick for digital cameras when setting up the lights for
even target illumination:
I use the studio strobes in two soft boxes at 45 degree angle and replace the
target with a uniformly white sheet and I set the camera to show "flashing high
lights". It is very fast and easy to see the uniformity, or lack thereof, of
the lighting. The same can be done in tethered mode with the new curves display
in NC-4. Then if tethered, a final eye dropper check and it will be perfect.
Bertho
Is the color values the same in all the corners? If one of your lights
has a slightly different color temperature it can effect how the profile
is made. Say the patches on the left 1/4 of the target has a few points
more red and blue light on them. The profile software thinks the camera
is the reason for this. The profile will be made to compensate for the
colors only from the effected area.
There is a chance that the camera may be less accurate in the outer
edges of the sensor. Try not to fill the entire frame with the target to
be on the safe side.
... the DC seems to have some
metamerism problems in some of the patches
Did you find that out through some CIE Metamerism Index determination?
The eastern regional sales manager confirmed the rumor when I asked him about it.
I like Bertho's idea of photographing one patch at a time. Then building the target back in Photoshop. Not much of a chance for unevenness with this approach. Not sure if the profile would be any better for all that work though. I have also herd photographers building custom camera profiles using paint swatches. If you were photographing paintings for artists that would be a very useful profile.
I guess there are differences in philosophy regarding the color temperature
issue, or I'm missing something. If there is a big effect on the profile from
the difference in strobe color temperature, is a profile made from
illumination with a single strobe more useful than a profile made from an exposure
averaging 2, 3, or 4 strobes, if that's what you typically use?
Try all the options. It makes sense if you have a lighting setup that you use enough to make a profile for that lighting. A general profile for every day work would be best made from one light. As Jack said the key is proper white balance. The custom profile will map the colors accurately in the areas of the image that match the white balance.
This ICC profiling technology has only just begun. The more we experiment and share our ideas the more we will all benefit.
Regards,
David Iannarelli
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