Digital BW, The Print

Paul D. DeRocco wrote:




> On the other hand, when people shoot raw, they typically don't even think
> about things like white balance that have no effect on the raw data. At
> least they don't if they understand what raw is.

I understand what raw is, and I pay very close attention to white 
balance when shooting raw - as do a great many photographers. One reason 
is that I rely upon the histogram to insure I am getting the levels I 
want in the photograph. The displayed histogram on every digital camera 
I've ever picked up is a histogram of the demosaiced image, with a white 
balance correction applied. So, if I did not set the correct white 
balance in the camera at the time of shooting, my histogram will be 
systematically in error when displayed in camera. That can lead to 
problems - clipping, if the systematic error reduces levels in a color 
channel of interest; or excessively lowered signal to noise ratio if the 
systematic error increases levels. This, in turn, certainly affects BW 
conversion and the ability to process for printing down the line. This 
is a major technical reason to set the white balance correctly in 
camera, when shooting raw.

There is also a reason involving convenience. As already mentioned, it 
is de rigeur to color-meter the light and set this in a digital camera 
directly. Alternately, you can shoot your gray card and set a white 
custom balance by selecting that image in-camera with the appropriate 
menu choices, the camera deriving the color temperature and tint terms 
necessary to balance images in that light. It is a great convenience, if 
you are doing either, to have your conversion software automatically 
respect this setting, rather than having to try to figure out what the 
setting was, or read it off redundant paper notes you took at the site 
and type it into your raw converter manually. Clicking on photos of gray 
cards in the converter works fine, but it is more labor intensive (in 
some converters, significantly more) than just having the converter read 
the raw metadata.

-- 
Jeff Medkeff
Eagle River, Alaska