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Archive 2011 · Colorchecker Passport and gelled flash
  
 
Zenon Char
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p.1 #1 · Colorchecker Passport and gelled flash


I normally use DPP for my converter and then PS for final PP. I'm hoping to speed up my workflow for event photography so I just picked up a ColorChecker Passport and I'll be using it with CS5. I don't do enough of this so I won't be getting LR. So far I found the Colorchecker is one smooth and easy operation. DPP's workflow is not that bad with the recipes, etc but I'd like to get closer to the colors from the start.

I have this scenario. When shooting in a tungsten environment I gel my flash and set my colour temp to 3300 and fine tune during PP. I have yet to do a CWB in real world applications with flash but my guess it is no different than without flash. I am thinking the correct procedure is to CWB with gelled flash using the WB tab on the colorchecker, take a shot of the Colorchecker pallet and them I'm off to the races?

Reason I am asking his I did a few tests last night with a gelled flash and tungsten lighting. CWB first then Colochecker. I thought the Colorchecker profile looked like it had a yellow tint to it. Both Abobe Standard and DPP faithful (imported into ACR) looked closer to the original scene. I may have been doing something I did wrong. I'm trying to wrap my head around CWB and flash - particularly a gelled flash.

I watched a one on one Adorama video and the presenter was using the WB tab on the Colorchecker with studio strobes so it appears that is the correct to do. Obviously they were not gelled.



Nov 28, 2011 at 09:57 PM
Zenon Char
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p.1 #2 · Colorchecker Passport and gelled flash


Note: When I open the image of the Colorchecker in ACR and select the profile I set up for that shot the blue patch on the pallet becomes deep blue just like all the examples I have seen. So it appears to be working correctly.


Nov 28, 2011 at 10:04 PM
cgardner
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p.1 #3 · Colorchecker Passport and gelled flash


What I do when mixing flash and tungsten is gel the flash with 1/2 CTO then set Custom WB off the gelled flash with my 8x10 Kodak gray card. Then as a reference I shoot my other gray card with color targets, including the color checker, on it.







Here's the rationale. 1) Perceptually we expect faces to look "normal" (i.e. free of extreme color casts) because in person our brains adapt color perception based on things like white shirts and other assumed to be neutral content. 2) Stuff in the foreground of photos is more usually more important than the stuff in the background. 3) Setting WB off the gelled flash using the gray card makes all the content in the foreground "technically" R=G=B neutral at capture making the faces in the foreground more "normal" looking.

1/2 CTO isn't always a perfect match to the background lighting but slightly warmer than neutral usually looks more normal perceptually because that's what is perceived in person. Depending on the situation and crop I'll adjust the foreground from the neutral capture baseline. The tighter the crop and less background seen the more "technically correct" R=G=B WB seems "normal".

The shots below were from a teen talent show at my church. The stage lighting was pretty flat and uninteresting so I put my gelled OCF on stage out of frame to the left as rim light with the gelled flash on the bracket doing the frontal lighting addition to the stage lighting:












Same stage different problem. Here the key and accent lights are the stage spotlights. The problem was the stage fill was magenta creating an unnatural color cast in the shadows of skin and suit. So I added gelled fill from a single flash on bracket to overpower the stage fill and eliminate the magenta color cast....










Nov 29, 2011 at 02:48 PM
Zenon Char
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p.1 #4 · Colorchecker Passport and gelled flash


Thanks Chuck. That is what I was looking for regarding flash gelling and WB. I have seen those first two images before.

What I am finding with with the colorchecker pro is it sure pushes the blues. I did some tests and my wife's shirt was teal and it came up blue in images. Adobe standard and DPP were much closer. Skin tones look pretty good on all three.



Nov 29, 2011 at 03:24 PM
cgardner
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p.1 #5 · Colorchecker Passport and gelled flash


White balance is measured in neutral tones. Changes in colors relative to each other in the Color Checker are more accurately termed "Selective Color" changes.

For example. This is what the color checker should look like if reproduced exactly, per the RGB values in the documentation...







Here's what it looks like when shot with R=G=B neutral White Balance with different "styles" applied...






Note how the gray tones are the same? All four maintain the neutral WB but change in their selective rendering of the colors.

Photography is an engineered process based on human vision. The nominal result of the camera design is a "normal" looking image with the default camera settings when two conditions are met by the user:

1) Exposure / Lighting is controlled to record a full range of tone in highlights and shadows SIMULTANEOUSLY:

Outdoor lighting is problematical because scene ranges usually exceed sensor making it impossible to meet the basic requirement of recording detail everywhere. But recording a full range is trivial with studio lighting. Start with a dark room, add fill until shadow detail is recorded then overlap the key light until the highlights are exposed correctly just under clipping ON 3D OBJECTS. Flat charts are not ideal for setting exposure because there are no shadows. What you need for setting exposure is a 3D target like black and white terry cloth. That allows visually seeing when there is detail in the SHADOWS on a black object, and the subtle difference between a clipping highlight that obliterates detail and one 1/3 stop below clipping which retains the see by eye detail.

2) Gray Balance: Gray balance keeps neutrals neutral, no more no less. But it is a very important part of the perception process because we gauge and calibrate our vision to neutrals for tonal range and color. Our eyes adjust to any light not by seeing the teal blue blouse, but by seeing any objects expected to be neutral.

The reason you want to have a portrait subject hold a target for a test shot after setting Custom WB off a gray card of known neutrality is so when looking at the image on the monitor your brain will be able to calibrate to that neutral baseline to more objectively judge the skin tone. Without the target your color perception of the image will be biased by that bright blue clothing.







Capturing with a neutral baseline, and viewing from a neutral baseline are just process control steps necessary to overcome the fallibility of our adaptive color vision. So you open the file with the test target, adjust it with the baseline target in view until the skin tones look "right" then copy the adjustments to the other RAW files without the target.

If you make the adjustments with "styles" it will shift the colors around but retain the neutrals. That's where the Color Checker is valuable. It is easier to objectively see the changes on the chart than in the photo content...







Landscape is a good choice for portraits. Portrait style is actually even worse tending to over saturated the reds. But look at the target. Despite the over the top shift in the colors the perceptually important neutrals on chart and in the clothing have remained neutral. That's how profile based color management works.

Open an image in ACR, then click on the camera icon tab to access the style menu. Abobe, when adding a camera to ACR, creates profile which duplicate the camera styles. Try all with a test image like the one above as see which is the best "fit" for that subject. If one of the pre-sets isn't perfect you can tweek it with the sliders and save it. That selection also then becomes the default for all the other RAW files you open until you change it to something else.

By changing the color via the Styles menu you will be moving the colors around without affecting the overall gray balance as you would by moving the "Temperature" (blue/yellow) and "Tint" (green/magenta) sliders in ACR. Within Photoshop functions like Hue/Saturation and Color Balance will shift color without changing gray balance, but functions like Photo Filters, Color MIxer or adjusting channels separately with Levels and Curves.

There are times when you will want to move everything, including neutrals, warmer or cooler to change the mood of the photo, or adjust Tint to get rid of a green color cast when shooting under trees.

It's important to understand the difference between shifting WB and selective color editing and the MacBeth Color Checker is a tool designed to allow you to see the difference when adjusting color in your images. The goal is making the results look "normal" or not. The chart allows you to quantify the differences visually from knowing what the target usually looks like, and numerically with RGB eyedropper readings.



Nov 29, 2011 at 04:25 PM
Zenon Char
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p.1 #6 · Colorchecker Passport and gelled flash


I typically shoot faithful and portrait does over saturate reds. Today in not the first fay I have heard about using landscape for portraits. Also I'm using a full CTS so I guess that does bot help. Perhaps a 1/2 CTS would be better.


Nov 29, 2011 at 05:29 PM
hugowolf
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p.1 #7 · Colorchecker Passport and gelled flash


Zenon Char wrote:
What I am finding with with the colorchecker pro is it sure pushes the blues. I did some tests and my wife's shirt was teal and it came up blue in images. Adobe standard and DPP were much closer. Skin tones look pretty good on all three.

There is variation amongst color checker cards, although not usually so much in the grays. But it is still possible that you don't have a very good card.
Color Checker Variation



Nov 29, 2011 at 05:56 PM
 

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Zenon Char
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p.1 #8 · Colorchecker Passport and gelled flash


Here are my results. Actually I made a mistake. I do shoot with CTS but I had a CTO on for these.

Shot under tungsten light, gelled flash and CWB set using the Colorchecker WB card.

Look that the sleeve in the upper left had corner. My wife and I both agreed that DPP's version was the actual colour of her shirt.

Canon DPP faithful - converted to a tiff using DPP







ACR - custom profile using passport







ACR - Adobe Standard.








Nov 29, 2011 at 06:02 PM
Zenon Char
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p.1 #9 · Colorchecker Passport and gelled flash


Where can I get the actual numbers/codes (not sure what to call it) to purchase gels. Last time I went to our local theatre supply store I just told them 1/2 CTO and it took a while to figure it out.


Nov 29, 2011 at 06:07 PM
BruceF99
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p.1 #10 · Colorchecker Passport and gelled flash


Zenon Char wrote:
Where can I get the actual numbers/codes (not sure what to call it) to purchase gels. Last time I went to our local theatre supply store I just told them 1/2 CTO and it took a while to figure it out.


http://rosco.com/us/filters/roscolux.cfm#colors



Nov 29, 2011 at 06:21 PM
cgardner
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p.1 #11 · Colorchecker Passport and gelled flash


Do you ever order from B&H? If so put one of this $2 samplers into your shopping card which has everything Rosco sells with the specs on the divider sheets....








Nov 29, 2011 at 07:30 PM
Zenon Char
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p.1 #12 · Colorchecker Passport and gelled flash


Thanks Bruce and Chuck. Any ideas on my colorcheck tests? What is are your toughest on the blues?


Nov 29, 2011 at 07:45 PM
cgardner
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p.1 #13 · Colorchecker Passport and gelled flash


Zenon Char wrote:
Thanks Bruce and Chuck. Any ideas on my colorcheck tests? What is are your toughest on the blues?

All of them look OK.

Beyond keeping neutrals equal in RGB color is a subjective judgement of what looks best for a given subject. If the camera isn't recording the blue dress accurately, or if it is accurate and you just want it to "pop" more then either pick a style that boosts saturation in blues in ACR or DPP, or alternately in Photoshop add a Hue/Saturation adjustment layer select "Blues" and adjust saturation that way.

The adjustment layer method has the advantage of masking. Below I alter the color of her sleeve selectively starting with this image...





I adjusted Saturation and Brightness selectively in Cyans..





Note the change in the circled areas and lack of change in other colors. To isolate the change to just the sleeve I did a magic wand selection on it, inverted the selection, clicked on the mask in the adjustment layer to select it, then filled with black creating a window mask that only applies the adjustment to the sleeve...






Chuck








Nov 29, 2011 at 08:19 PM
Zenon Char
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p.1 #14 · Colorchecker Passport and gelled flash


Thanks for your help Chuck. It appears Canon is doing a fine job. I have always used DPP as my converter as I find the skin tones are nice and easy to adjust later.


Nov 29, 2011 at 08:39 PM





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