I've recently discovered the whole idea of UniWB for maximising the dynamic range of digital cameras that can take raw images. In principle it sounds like a great idea if you are already shooting raws. I'm lazy but I was curious anyway. To be honest it's a bit useless on my LX3 due to the amount of optical distortions I get, plus I'm too lazy to process the images. Anyway, as a result of messing around with UniWB I found setting the white balance of the images to be interesting. I was reading this site http://www.guillermoluijk.com/tutorial/uniwb/index_en.htm. So to make a UniWB you just take a dark frame (lens cap on) at say ISO100, f/22, 1/4000sec, note that these files are usually camera model specific. Take the resulting raw file and check it with dcraw by doing
dcraw -v -w FILENAME.RW2
The multipliers are all supposed to be as close to 1 as possible (say with in a 5% error, this is just a guess), if it is then great, if not try again. You then take this raw file and set it as your custom white balance and then take pictures as normal. The previews will all come out greenish, so you will need to post process the image and correct the white balance. The basic idea is that the custom white balance will cause the histograms on your camera to give you a more realistic view of what's happening, you could probably get 1 or so stops more out of your shots.
So I got these settings by using dcraw -v -w FILENAME.RW2 for my LX3
- Daylight
- 2.049430 1.000000 1.661597 1.000000
- Cloudy
- 2.281369 1.000000 1.539924 1.000000
- Shade
- 2.528517 1.000000 1.418251 1.000000
- Flash
- 2.326996 1.000000 1.517110 1.000000
- Halogen
- 1.361217 1.000000 2.319392 1.000000
Some sample images....
This is what the camera see's in terms of white balance based on the UniWB custom white balance
This is dcraw's auto white balance
This is applying the mulitplier's got from above
This one was balanced using my whibal keyring using ufraw cause I was too lazy to figure out the patch to use dcraw to calibrate the image
The auto white balance in dcraw was pretty similar in look to the whibal calibrated image. I'm not too sure if I and committed enough to use raws. I do like being able to maximise my exposures for HDR or panoramic stitches though. It's more useful on my DSLR than on the LX3, since the LX3 doesn't have an RGB histogram.
