Ray,
I've no idea why that happened and getting several EX1s to match indicates it isn't a firmware error. However I just tried that on mine and the colour is fine (not green or any other deviation). First I thought you might have set white offset, but it isn't possible to confuse those. Obviously you set the white balance to "preset" (to use the PP set WB CT), so I'm at a loss to figure how you achieved that outcome.

Serena

Probably not related, but although the "kosher" way to set WB is to point at something white then press the button under the lens, I've found on occasions that just pressing the button anytime produces an acceptable result.

My theory is that whatever light source lit the card for the camera that was given a proper WB had a bit of green in it. Not an usual situation. So that camera set the gain on the green channel back a bit to compensate. The other cameras didn't as they were only set to match a theoretical light without the green.

Nothing broken, nothing unexpected once you understand how the EX cameras do a WB and they do take their time about it.

Bob.

It's a known fact that dialed-in CT values apply to all RGB channels in "preset" way, i.e. cannot make for magenta (or green for that matter) shifts/hues of a real scene. On the other hand, AWB does - so with multicamera shot it's extremely important to either use dialed-in preset for all cameras, or - better still - AWB all of them to the same white (grey) card.

Not sure that we've read the situation correctly. As I understand the original query, setting the cameras to 5100K resulted in a strong green bias; "totally green". Even if the lighting has somewhat excess green (e.g. commercial fluorescent) I wouldn't expect the result described. I agree that a WB from a card may compensate for the green while indicating 5100K, and the manual setting would not do so. But totally green?

Hoping someone here might know the answer to this one. Ran into a perplexing situation

I know you shoot mostly bands Ray. Were you in a club? What kind of lighting did they use?

John

These cameras are twice as sensitive to green as any other color. This doesn't surprise me in the least. Why do you think people use Greenscreen for video based chromakey?

Thanks for all the replies, just for clarification I've sloppily thrown together a little vid just so you can see what I was saying. I've also added it to my original post above.

This was shot in a studio with studio lighting.

Sony EX1 White Balance Issue Demo
password: sonyforums

- Ray
Underground Planet

So you got a green caste.

1) Page 73 of the EX1 manual:
Except when Preset white balance mode is selected, you cannot confirm the results of changing the Preset White settings on the screen.

2) Any filters on these cameras, specifically the Tiffen IR cut filter?

Bob.

Ah, "totally" was a bit misleading. Actually neither shot looked, to me, to be correctly WB. What lighting source? I did my little experiment under daylight and wasn't looking for lesser shifts.

No filters used. I believe they were 5100k lights.

The basic confusion for me is that 5100k should be 5100k regardless right? That is the point of it isn't it? So if the camera says it's set to 5100k whether by card or by dialing it in ...

- Ray
Underground Planet

From past experience, I believe this is just normal.

If you white balance under neon lights, you may get a reading of 3200K which will be different from a preset 3200K (for balanced tungsten lights).
That is why indoors, I would always do a white balance, unless I would be certain that it is 3200K studio lights.

I own an EX1, but haven't tested for this matter since this is the way I have been working for over 20 years, mind you that viewfinders where black & white and most of the time no color monitors!

Rob

"The basic confusion for me is that 5100k should be 5100k regardless right?"

Not at all: http://en.wikipedia.org/wiki/Color_temperature

"The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of comparable hue to that light source."

Modern light sources are not "ideal black-body radiators". When you do a full WB with the EX it adjusts the gain in the R,G,B channels to get white. There's a large range of combinations of R,G,B light all of which give a CT reading of 5100K.
So when you simply dial in 5100K the EX has to assume an ideal light source, it has no way of knowing it isn't ideal.
So what has happened is one camera has adjusted for whatever the light source truly is and the others haven't.

If you go back to the Wiki and look down the page at the CIE 1960 UCS chart and look along the isotherm for 5000K you'll see it covers a range of colors. In fact you can move the line into the green and you still get 5000K. As noted however for delta uv values greater than 0.5 the CT becomes a meaningless figure. The good news is the EX cameras can cope to.... some extent.


Regarding filters, all the EX cameras we rent out are fitted with B&W 486 IR cut filters. Unless you looked you wouldn't know. It wouldn't suprise me if other rental companies are now fitting the Tiffen T1 filters. If the cameras have the T1 filters fitted then they absolutely must be WB'ed off a card or you will get a green caste. Based on Serena's comment that even the one that was WB'ed properly doesn't look quite right makes me very suspicious that this is what has happened.

Bob.

Well that's a lotta info! Thanks Farss, and everyone else even though its not what I was hoping to hear.

And yea, totally understand Serena about the white balance not looking right, but the goal wasn't to get perfect wb but to try to figure out why the two were different if set to 5100k or perceived as 5100k. I still can't say I full understand the whys and wherefores but it seems the upshot is that you risk getting unwanted color casts when trying to dial in the temperature as opposed to using a white balance card. A shame, the hope was that once wb was achieved on the one camera it would be just as simple to go to the other cameras and change them based on the kelvin that that first camera perceived.

Great info all, thanks for looking into it and taking the time to post.

- Ray
Underground Planet