White Balance/Histograms and Raw

[Will Milne 0]

Hi

 

Been playing around with using a UniWhite Balance in my D200- interesting concept.

 

Problem- The Histograms displayed on the LCD are an approximation of the RAW file info . There are adjustments made to the individual colour channels when the camera creates the embedded JPEG on which the camera's histogram is based. So any adjustments ( compensation/ETTR- expose to the right approach) made based on the dislayed histograms are based on the jpeg data not the Raw data.

 

White Balance is acheived in camera by multiplying the values of RGB( simple explanation) by a set amount for each channel. so that white/grey appear white /grey in a given lighting condition. This is a problem because a channel can display blown in the interpolated Jpeg histogram that is not in the Raw file.

 

Solution- Set a custom white balance that causes the camera to display histograms on the LCD that reflect the Raw data by feeding it multipliers of 1,1,1 for each channel. Now the Histogram is displaying more accuratlly the data in the Raw file instead of the interpolated Jpeg.

 

The white balance is corrected to normal in the Raw editor of choice in post.

 

 

I've been playing with this a fair bit and there are subtle but real differences in images shot/processed using a UniWB versus the same scene shot/processed with a standard in-camera Wb setting.

 

Anyone else playing with this???

 

There is a discussion here ( mostly Canon Based)-

 

http://photography-on-the.net/forum/showth...5349&page=2

 

 

 

 

 

 

Will

 

 

 

 

[Wulff 0]

Interesting ut all tha math gives me headaches. I deal with it enough at work

 

I think as long as you shoot raw your ok. The only real danger are images where according to your histo nothings been blown, but in your raw file there are blown pixels. If the histo says blown, iwhen n reality there arent any and you back off a tad as a result it should still be reocverable in raw.

 

I use the in camera histo as a guide, not gospel and am really only looking to ensure im a bit right but more importantly not blowing much (sometimes a little unavoidable) on either side

 

 

[WYKnot 0]

Will and Wulff,

 

I am enjoying your exchange on WB, do not have a lot to offer, but (as always) learning from your comments.

 

Russ

[Will Milne 0]

Hi

 

To be honest - I'm not sure how much I will invest in this - though it does seem to make a difference on high dynamic range images with respect to keeping highlights from blowing. The other thing that can be added to the mix is a custom curve that is linear and does not transfer gamma/contrast info to the embedded jpeg. Now the LCD is VERY dark but the histograms are an even more accurate reflection of the the Raw data. Sucks for checking composition though- lol.

 

Will