X-Rite ColorChecker SG review
Review: ColorChecker SG card
Advanced colour reference card for profiling cameras
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The ColorChecker SG card has been around a few years, but until recently wasn’t supported by X-Rite’s ColorChecker Camera calibration software. The software is a free download – from X-Rite.
Keith has been looking at use of the SG card for our photography.
There are also links to related articles explaining different uses of the card (and its basic version) in more detail, including scanner profiling.
X-Rite ColorChecker SG
I use ColorChecker cards regularly in my commercial photography, whether to adjust for mixed lighting (such as in a factory) or to improve colour rendition for product photography.
The card I’ll typically use is the smaller Colorchecker Passport, with it’s hard plastic case and grey card.
The bottom half of the passport shows the ‘classic’ 24 patch target. This is actually ‘inside’ the larger target, seen from the info on the back of the SG card pack.
The SG card is also rather more expensive, so when not in use is kept in a plastic bag, inside of the card holder, in a desk. The Passport lives in my camera bag…
About the SG card
The first card I tested was for an article here in 2006, where I looked at creating camera ICC profiles using the GretagMacbeth card and Eye One Match software. [Camera profiling with the SG]. The problem was that I had very few applications that could make use of the profiles, that and they are very much suited to particular types of work and workflow.
The key features listed by X-Rite:
- Array of 140 colors: 24 patches from original ColorChecker, 17 step gray scale and 14 unique skin tone colors.
- Each square reflects light the same way as its real-life counterpart in all parts of the visible spectrum, under any illumination, and with any color reproduction process.
- Create a white balance with your digital camera to guarantee precise, uniform, neutral white under any lighting condition.
- Pair with i1Profiler scanner profiling software to create a custom ICC profile of your scanner.
Image processing software supporting profiles has become more common (Phocus, Capture One and PhotoLab for example), but for Lightroom and Photoshop, I’d use camera DNG profiles.
With V2 of X-Rite’s camera calibration software introduced ICC profiling with the SG [Notes] and V2.1 expands this to creating DNG profiles too
New in release 2.1.0
- Added support for the Digital ColorChecker SG in the DNG workflow
- Improved the color profile from targets that are not evenly illuminated
- Improved the quality of the shadow and dark color reproduction
Capturing the SG card
The SG (semi-gloss) has a distinctly different surface finish to the patches than the normal ColorChecker.
Even at an oblique angle, the colours are clear. They are not well enough illuminated for calibration purposes though.
The SG card has those black/grey/white patches around the edge to make it easier for the software to check for even illumination. They are relatively glossy too and quickly show up extraneous reflections.
The reflection is easy to see, with a slight rotation of the card.
Outdoor use needs particular care. If I needed this regularly I’m probably make some form of tent to go over the card. A white polythene bag might be neutral enough, but would need testing.
Remember that the better exposed the source image, the better quality you can expect from any profile you make, whether ICC or DNG.
If you look at this view, you can see the lights well off to the side and the camera high above the card.
You don’t need to fill the frame, since the software can handle smaller targets in images, and it keeps the card in the better quality area of lens coverage.
The RAW file was captured with the camera tethered. I’d note that critical focus isn’t essential. The lens is set to f/13 to minimise any vignetting.
Creating the profiles
Unless your camera uses DNG format, the camera’s RAW file needs converting to DNG format to use. This is easy to do using Adobe’s free DNG converter software. For a normal single light source, just one image is needed.
I can just drop the DNG file on the application to make a profile.
The software will attempt to find the target in the image.
It’s usually pretty good, but sometimes slightly misses things. You can set the grid manually though.
You can make dual illuminant profiles that allow for light variation as well. These need two source images.
Using the profiles
The profiles are used when initially processing RAW camera files. Two reminders though: your editing application may need to be restarted to notice the new profiles, and secondly, remember to give them a meaningful name.
A photo using compact fluorescent lights (CFL) and a profile handles strong artificial colours such as the toy cars very well. An animated GIF file switching between the camera default look and my custom profile shows the difference.
Remember though, that the image you’re seeing here are sRGB ones optimised for web display.
Strong natural colours can benefit too from the refinement of a custom profile. The problem is that natural light varies widely in colour temperature, so a dual illuminant profile may be more useful.
Camera makers also go to a lot of trouble to produce good looking images. Keep all this stuff in perspective and always note that accurate colour and pleasing colour are two different concepts.
One area where the profile did help was the strong colours of this cactus.
The profile helped me capture the right tinge of orange and deep reds in this other cactus. I’ve written an article about how you print a strongly coloured photo like this which looks deeper into colour management and editing/printing.
Which card do you need?
X-Rite have a range of cards aimed at helping capture better colour. The SG sits at the upper end and is probably of much more use to studio photographers, where accurate reproduction is a vital part of product photography.
The SG (and basic card) can be used for scanner profiling with i1Profiler
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