2. With a diffusion screen, like the Expodisc, isn't the reading distorted by the subject? For example, imagine a portrait where the subject is wearing a red outfit, the subject then changes into a blue outfit but the lighting and composition remain exactly the same, wouldn't you get two dramatically different readings?
This is a thread Ive been thinking about for some time.
I think you are right about the expodisc - however it is quick to use - you cant always hand your subject a grey card - your subject may be a lion
Basically an expodisc will get you in the right ballpark very quickly if for instance you have floucenent source
THere seem to be two approaches to white balance
A ) shooting a product - you want the colour accurately reproduced even if for instance you are shooting the product under tungsten
B ) shooting a scene or an architecture pic at dawn - with a sunset you will want warm glows and and maybe very yellow light coming from internal tungesten rooms
In both cases using a card or expo would seem to be heavily affected by the scene (say you are shooting a an interior with orange walls - the reflected oragne will hit your greycard and throw the room blue once you click on the cardFor the b type approache probably you need to get a neutral setting for your camera maybe by photographing a grey card on a half cloudy day
Using that setting/parameter will make you tungstens yellow and sunsets gold
Another method that interests me is using a combination of a grey card (at the scene) and a colour temperature meter
So you click for grey and then dial in the appropriate coolness or warmth
Balancing the different cameras should work if you build a standard setting for each camera at the same time
A more complex method would be to shoot a gregtag card in a neutral light and build profiles for the cameras and then you have a standard setting
If you add light using flash or hot lights it then of course gets even harder - especially if thier temperature varies with power output
I think my prefered method would be to get a great gregtag image on a neutral day, get filters on my flashes until they match that and shoot away
I think there are so many variables that at the end of the day we always tweak the final image by eye anyway so over technicalisation probably aint worth the time
CUrrently I have a few profiles I have made basically grey day and elinchrom - I use those as a start point
I shot a (horses - dont hold grey cards and the steward enclosure was flouro) job the other day 20-35 with the SLRn 80 on the blad and 300/28 an the D200 - getting a consistent look amounted to trial and error - if only I could just have had velvia in all of them !
I am also not convinced that an expodic is any better than the lid off an ice cream box which is cheaper and comes with free ice cream
THe expo/ice cream box will at least give you a similar start point between the different cameras