Two White Balance questions (from a stills guy)

A

arch

New member
hi team,

just got my DVX100AE yesterday, first ever camcorder and enjoying it.

all looks pretty straightforward so far, but coming from a digital photography background, couple of quick questions re: White Balance.

- there are only two preset WB options to choose (Tungsten and Daylight) ... would it not be useful for the user to have the option to manually dial in a color temperature? no big deal, careful control of your custom A and Bs will get you by, but the ability to dial in a number in degrees K would be nice. (anyone know of any cheeky service menu hacks, or such ;) ?)

- i always thought the term white balance was a bit of misnomer, and for photography prefer to gray balance (ie use a light gray card and set a custom white balance off that).
even with careful exposure, "white" with all RGB channels getting perilously near fullscale, could maybe hide some unfortunate color casts if you were to WB against it, (of course you could use white card, stop down the exposure a bit, but you are effectively making a gray card there, so why not start off with one in the first place)

... what is the mood of the board on this one, do you WB off white or gray card ?


like i say, still brand new, but really enjoying playing about with the DVX, should be good.
 
You'd have to know the temp of the light to manually dial...too much trouble, and hardly anyone has a color-temp meter.

White balance is to tell the camera what white is, not to set exposure, so a grey card wouldn't work out too well. (Unless you were going for an effect...)
 
Since most gray cards also have a white side, just flip it over and now you have a great white reference for the camera. Flip it again and now you have a pretty decent exposure reference as well. If you have enough light (say hot enough to get a gray card to read about 80%) you could white balance off the gray side since it is spectrally neutral, but it seems just as easy to use the other side.

Enjoy your new DVX!
 
A point that arch was making wasn't really addressed in my first reply, namely what happens if you try to white balance with too much illumination level. Luckily, the DVX is smart enough to give you an over warning in that event, so you don't have to worry about falsely balancing the relative red/blue levels.
 
thanks for the replies,

even without a color-temp meter it is sometimes useful to be able to fine tune the color temperature, either for consistency, or just for creative effect

a gray card is manufactured so that the color or chrominance values are equal, and hence gray, and is therfore an excellent target for AutoWB systems to help eliminate any color casts in the light source.
(seperate product from the gray cards that are sometimes used for exposure metering, that you might be thinking off)

i'll have a play with the camera and see how it deals with being told to balance an extra hot white, see what happens.
... as we all know when digital hits fullscale, that's your lot .... so taking an 8bit example, if a white card is being lit and "wants" to be recorded as say 280, 240, 240 .... it'll show up as 255,240,240 ... if you were to WB that target, it would push you way off neutral color temp

maybe the firmware spots the fullscale channel as stops you .... but again maybe you have metered the scene and want the exposure at that particular level, so having to back off exposure, do a WB, and then open again seems awkward .... again a gray target means you can accurately balance even in hot lighting conditions.


hopefully i'm not missing anything obvious, but it's just one of the first differences that i've noticed between digital stills and digital video (well that and the fact that you guys talk about units of 3dBs for gain and ND, instead of stops like you should, hee-hee)

all the best,

arch
 
As I mentioned, the DVX is smart enough not to let you make a horrible white balance mistake (clipping one of the color channels) so you can effectively balance on any source that is spectrally neutral and illuminated within a normal exposure range. You can prove this to yourself by balancing the camera at a number of different illumination levels with the same reference and compare a color chip chart capture from each balance point. As long as they are within the middle to upper range of the CCDs you'll find that each has the same balance.

Actually a stop (2:1 or 1:2) is +/- 6.02 dB (20 * {log 2} or 20 * {log .5}) but hey, who is being picky (ha-ha).

I was a large format (4x5) still guy for a lot of years before I ever even thought about picking up a motion camera. You will find that much of what you learned in still photography will apply to shooting motion projects.

Have fun.
 
Arch, there really isn't as big a difference with digital stills and the dvx. If you want to dial in a specific color, you can do that as well, in the scene files setting under color temp. As far as white balancing, if you have enough light, yes you can whitebalance off of a grey card, but i find stopping down, and white balancing works just as fast and is easy to do.
 
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