Using the x-rite Colorchecker Digital SG card.

Mack

Mu-43 All-Pro
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Jan 14, 2018
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This I've learned shooting the x-rite Colorchecker Digital SG card.

I followed what this website guy did by putting his SG card into a three-sided box covered with black Tee-shirts: Making color profiles with Colorchecker cards. Seems the glare off the semi-gloss colors of the Colorchecker Digital SG card can be problematic if one does not take care in minimizing reflections and glare. Seems more problematic than the Colorchecker Passport which has a matte color set of patches.

So I came up with a three-fold display board (36"x48") from the local Office Depot for $7.99 which is plain cardboard with a black finish on one side. I folded it in half and cut halfway up on the folds so the lower folded part would become the bottom. I also found a small black wooden artist easel for $12 at Micheal's Art Supply to hold the Colorchecker Digital SG card parallel to the sensor.

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Luckily, I cut the cellophane that the SG card comes packed in on the side with the slot that opens into the envelope holding the card. The cellophane, left on the carton, can act as a mirror so you can look at it through the camera's viewfinder and see if you can minimize any reflections behind you or from the sides that might influence to SG card. Some use a plain mirror, but the cellophane wrapper worked for me.

I had to put up a black curtain as I could see a bright reflection on the cellophane wrapper from the bright building behind me. Some old black fabric I hung over a lightstand and horizontal pole. I could shoot through the middle of the fabric, but I found I could put the cameras slightly over the top of the curtain and the cellophane remained dark with no reflections. The guy in the above link put his jacket on the tripod legs to block the light behind him - or so I think.

I had five cameras to check. Same 12-100mm Pro f/4 lens on the Olympus. All set at f/16 in sunlight and default ISO of either 100 or 200 depending on Nikon or Olympus respectively. I ran manual exposures from 1/30 up to 1/400 by 1/3 stop speeds. I set the WB Kelvin at 5,200K on all cameras as I read 5,201.1 Kelvin on the Argyll PRO Color Meter app on my Samsung S10+ phone attached to an i1 PhotoPro 2 spectrometer head plugged into the phone. Phone has enough power to run the spectrometer via the USB-C port in the phone. App works really well for color too! The Argyll app told me at ~11:30AM the sun was at 5,201.1 Kelvin (Screenshot below circled in green.) so I ran all the cameras at that time with all set manually to CWB=5,200K (Yeah, I was 1.1 Kelvin degrees off. Bummer! Maybe 5 minutes earlier.).

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Once shot, I culled the five cameras RAW exposure shots using FastRAW Viewer looking for where the histogram bottoms out around the +3 EV axis which is the best/optimum exposure. Doubled checked on the white square for a RGB of ~243 with Olympus Workspace and its pointer.


Now for the setup's results:
Best part was once I checked the white square in the four corners of the SG card, they are all a perfect RGB=243 in each corner and not one point off with the E1 Mark II and the 12-100mm Pro lens set on f/16 at ~40mm. The Pen-F came in at exactly RGB=241 in each corner reading too reading it in Olympus Workspace. Not bad at all, and zero glare or reflection on the SG card given the above setup. Oddly, the E-M1X was +/-3 points off from the E-M1 Mark II which was spot on. Don't know why the E-M1X differed slightly (e.g. RGB=239, 240, 237) verses the E-M1 Mark II and Pen-F, but I can live with that small difference. Surprised to see the white RGB to be that good, and maybe due to the (expensive) Digital SG card having tighter tolerances than the Colorchecker Passport? Dunno.

Now another day to finalize the DCP profiles with Lumariver Profile Designer Repro edition. I'll make two profiles for the Olympus camera trio I have: One for a shadow boost (i.e. Black point compensation off.) so the Olympus blacks don't get crushed, and a second for the stock OEM setup (i.e. Black point compensation on.) since the Lumariver software allows for that sort of color profile tuning.
 
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