white balance and exposure-barry please?

R

Rod Pike

Well-known member
Hi, when white balancing I always set the exposure to 100 IRE (using the WFM) on my white card. But I note that exposure isn't mentioned in the manual or Barry's book so does it make a difference to the calibration?
 
Rod Pike said:
Hi, when white balancing I always set the exposure to 100 IRE (using the WFM) on my white card. But I note that exposure isn't mentioned in the manual or Barry's book so does it make a difference to the calibration?
Click to expand...
Hi again guys, has anyone any thoughts on this? does correct exposure matter, and if so where are you setting it on the IRE scale?
 
Rod,
My short answer is: I don't know.
My long answer is: I would make sure it's at least 70 IRE, so the camera has enough light to get a good read. But I wonder if setting it all the way to 100 IRE might risk clipping one of the color channels, causing a flawed white balance for the parts of the scene below 100 IRE. (Again, I don't know.):huh:
 
Ken Hull said:
Rod,
My short answer is: I don't know.
My long answer is: I would make sure it's at least 70 IRE, so the camera has enough light to get a good read. But I wonder if setting it all the way to 100 IRE might risk clipping one of the color channels, causing a flawed white balance for the parts of the scene below 100 IRE. (Again, I don't know.):huh:
Click to expand...
Thanks Ken that's at least reassuring that I am not the only one HEHE!! So c 'mon guys what do you do? Can Ken and I be the only AF100 users that don't know what is the correct procedure?
 
I've always just made sure it wasn't overexposed and clipping. Figuring if there was adequate light to shoot the scene and I was exposed properly for that, the low end would take care of itself.

Just to note that Black Balancing is vital for getting good images out of an AF100. It really helps to quiet down the lower 20% of the signal.

A Black Balance should ideally be done after every single:

- ISO change
- frame rate change
- resolution change
- power On and Off
- battery change
 
I was bitten once or twice by bad WB reads due to clipped highlights... so I always go just shy of 95% (where my upper zebra are set)
 
tflak said:
I've always just made sure it wasn't overexposed and clipping. Figuring if there was adequate light to shoot the scene and I was exposed properly for that, the low end would take care of itself.

Just to note that Black Balancing is vital for getting good images out of an AF100. It really helps to quiet down the lower 20% of the signal.

A Black Balance should ideally be done after every single:

- ISO change
- frame rate change
- resolution change
- power On and Off
- battery change
Click to expand...
Yep I always black balance-madness not to on the AF100 it is so easy. I think that I will drop to MCBobs <95%. I may be a bit high at 100%
 
White cards are calibrated so that "proper" exposure would normally be at about 55 IRE. Rating them hotter is okay, but there's really no need for it. For checking proper white balance, 70% is plenty hot enough and would ensure no clipping of color channels. I definitely wouldn't try balancing to white at 100 IRE, because there's a good chance that at least one of the channels might be clipping at that point.
 
Thanks Barry that's great info. another step on the road to enlightenment with the AF100!! (although it sounds as though I had a bit too much enlightenment at IRE 100!) Ho Ho! have a great Christmas!
Cheers!
Rod
 
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