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White Balance - Color Correction - Gray Cards - LAB Mode
When I shoot film, I often stick a gray card in one of the early frames and inform the lab that there is a gray card in frame #X. That helps them with color correction and color balance. Essentially, I do the same thing when shooting digital. I'll put a gray card in one of the frames for a particular lighting setup. I shoot RAW and usually just set the camera for auto white balance. I edit all my shots in Photoshop in LAB mode. I use the frame with the gray card to set my neutrals in the A and B channels and then adjust the non-neutral colors from there. It's pretty simple once one grasps the concept of exactly what LAB mode is all about. Jul 13 05 05:30 am Link question.. why not get a 3 color card to use to set up your white balance and color balance.. i went to a show a few months ago..has true white, black and a grey in the middle.. when you take a white balance shot, you look at your scale and look for even spikes in the history.. if they are skewed to one side or another.. adjust your f stop, etc.. it has worked quite well for me since.. i am always setting a custom white balance for all shooting.. kevin Jul 13 05 11:04 pm Link In camera, that can all be done with a normal grey card. Any shade of true grey can be used to set WB, although dark grey can become problematic. Just use an 18% grey card. Histogram should spike right in the middle for proper exposure and use the same frame to set custom WB. Those 3 level cards are really meant for something like Photoshop for setting levels for white, middle grey, and black. I have found that these are sometime too glossy and the black on the card is not black-enough for setting black-point levels. Otherwise they are nice to have. Jul 13 05 11:29 pm Link Posted by Belair: It's simple, but it's also unnecessary in most cases. Correction in the semi-native RGB format is usually more than sufficient for any situation where the original color balance isn't off by thousands of Kelvin or has discontinuous spikes (Sodium vapor lights, anyone?). Additionally, most mixed lighting situations are harder to correct in LAB than in RGB or CMYK. Jul 14 05 03:34 am Link Of course, editing in LAB can get a little quirky when certain areas of the frame are subtly different than that which has to be neutralized. However, I like LAB in that it provides greater contrast control without color shifts than does RGB. The same holds true of CMYK where tweaking the K curve can enhance contrast greatly with little or no color shift. Of course, working in CMYK can be a little unnerving for some because of the smaller gamut. Jul 14 05 05:23 am Link Kevin, I see the 3-card system as a tool for accomplishing 2 different things. The black and white cards are for setting the contrast range, while the gray card establishes a calibrated neutral. I prefer to establish the contrast range based on shadows and highlights present in the scene, and then bend the L curve to alter the contrast among scene elements to my liking. I'm sure the black and white cards will work just fine, it's just not a practice I employ. I find the gray cards to be a useful tool in color correction and color balance, as described in the opening post. Jul 14 05 05:31 am Link Posted by Belair: This can be handled by using Luminosity mode in RGB or CMYK. I often use 2 Curves layers on complex corrections/enhancements, one to optimize color using Color mode, and one to optimize overall tonality using Luminosity mode. (Sometimes I'll use 3; the above two plus one in Overlay mode to do additional contrast tweaking up or down.) Posted by Belair: ...just as RGB is unnerving to some pre-press folks who don't like not having the K channel available. Jul 14 05 01:44 pm Link |
