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View Full Version : White balance issue - seeing color shift between A/B switches and PRESET



eplamondon
09-22-2011, 10:53 PM
I'm encountering a strange white balance issue on my camera. Or perhaps operator error......

I like to use the PRESET function to fine tune white balance - using the Kelvin temperature dial.
What I typically do is use the A or B setting and white balance to see what the camera registers.... then I click the switch down to PRESET and then dial in that number as a starting point. And then I have the choice of fine tuning if I like to warm the picture up or cool it down a little.

So what I'm experiencing is this.... when I set white balance on the A or B settings, then dial in that EXACT white balance temperature reading in the PRESET switch, the picture appears to exhibit a greenish tint.
I would expect that the image would look exactly the same since I dialed in the exact same temperature.


I've turned my picture profiles off to be sure it wasn't a result of a setting in one of my profiles, but also get the same result.
I even went so far as to reset the camera to it's factory setting to see if I had changed something along the way - but I get the same result as well.


It's getting a little frustrating as I do this on my Z7 all the time with no problems. But on my FS100 I'm seeing a color shift between the A/B switches and my PRESET setting when set to the same color temperature.


Not sure if others have seen this or can recreate what I'm talking about.
Or perhaps know what I might be doing wrong.


I'm inclined to quickly videotape this and posting it to show exactly what I'm talking about....
But any help in the meantime would be tremendous.


Thanks!

speedracerlo
09-23-2011, 04:20 AM
I started a thread about this issue a few months ago and never figured out what the cause was, except that when you turn Picture Profile to OFF, there is no shift at all so I nailed it down the PP settings affecting custom white balance

I stopped using the Preset A and B and stick to custom settings

http://www.dvxuser.com/V6/showthread.php?254661-White-Balance-Preset-and-Memory-A-B-look-different-at-same-temperature&highlight=

Neex
09-23-2011, 05:08 AM
When you set the white balance using A or B, the camera's not just doing a blue-red shift, but also a green-magenta shift. When you're dialing in WB manually, you're only affecting the blue-red shift. That's where the difference arises.

You can affect the magenta-green shift in the picture profile if you want manual control.

morgan_moore
09-23-2011, 10:02 AM
What is annoying - or I dont understand how to do it is..

My preferered method is to take a WB

This would give a temp and a tint

I then want to adjust from this start point

But as descirbed - you see the temp value selected by the sample but not the tint value

S

Matthew Bennett
09-23-2011, 12:29 PM
I was getting strange magenta/green shifting within the span of a shot the other day. Pretty disturbing... Only one clip though.

MattDavis
09-24-2011, 06:25 AM
Sticking my head over the parapet here and quite expecting it to get shot off, but...

If you white balance using A or B, the camera will take all three primary colours into consideration.

If you use preset, you're not actually white balancing, just taking the camera's natural WB and shifting it warmer or cooler.

Therefore, if you WB in a room with a colour cast to it, or some nasty Fluorescents, the WB should be near-as-dammit neutral as the camera boosts towards magenta to take out a green cast, but reports a K of, let's say, 4200.

If you then dial in 4200 using the 'preset' position, the colour balance will be off between green and magenta, as you're using the base balance - the camera hasn't had a chance to examine a grey or white card and juggle things, just adapt what it's got to your settings.

OTOH, if doing run and gun in areas of rapidly changing light (e.g. daylit interiors with little pockets of tungsten and fluorescent), without chance to properly white set, I'd prefer to adjust on-the-fly with the preset and roller rather than use something (clothing, wall) that 'looks' white near the subject. Horses for courses, glad there's a choice.

moldcad
09-24-2011, 06:45 AM
I know I'll be called things after this, but the FS100's auto WB does an amazingly good job (compared to a more "pro" model like the EX series), so - in run&gun in drastically changing lighting conditions - I tend to use that...

Seems to adjust all 3 channels properly.

morgan_moore
09-24-2011, 06:52 AM
Sure it adjusts all channels properly what you cant to is ride a look over that adjustment

In stills I typically balance off a grey card getting both temp (Red->BLue) and tint (Mag->Green) correct and then put in a little warmth on the temp slider

So I take my technically correct image and warm it up to my aesthetic preference

It would be nice to similar in camera but the controls dot really seem to be there although the core technology is

S

MattDavis
09-24-2011, 06:56 AM
the controls dot really seem to be there although the core technology is

40630

"there be dragons" - if one dares.

PS: apologies, everyone - I missed Neex's reply that my post appears to merely duplicate. Sam, was replying to OP, rather than addressing your specific frustration, which I think can be addressed by somebody who has deep dived into WB menu. Alister C?


I know I'll be called things after this, but the FS100's auto WB does an amazingly good job.

It does, and yes we all use it now and again. My only deep rooted fear is the sudden voxpop, or longer developing shot, when the WB gets yanked during the shot, or leaving it on during an impromptu interview... I sometimes wish for a 'nag' mode in the viewfinder, where you only see the 'dangerous' tell-tales - something left in auto. :-)

morgan_moore
09-24-2011, 07:18 AM
In the menu profiles you can dial in temp and tint

What you cant do (AFAIK) is take a reading and modify the temp and tint using that reading as the start point

Thats what Id like

S

eplamondon
09-24-2011, 10:14 PM
Actually - I was playing with this tonight and still see the shift regardless of my picture profile setting - on or off....

eplamondon
09-24-2011, 10:29 PM
Thanks for all the replies so far. Interesting to get a deeper understanding.
Weird though as I don't ever recall seeing this in my Z7U - it always worked like a charm to set my balance on A or B, then dial that same reading into the Preset, then adjust from there if I wanted.

I recognize it's probably best to white balance using the A or B and just sticking with it - perhaps for more accuracy. but sometimes you want to warm it up a little. I do own some Warm Cards, so I also realize I could just aim my camera at one of the blue cards for a warmer look, but there are times where I simply don't have them handy and the only thing I have is someone's white shirt, a piece of paper lying around or a white table cloth... In those instances are where I truly like the notion of fine tuning things manually.

I was shooting in an industrial kitchen last month and took my white balance - I wanted it just a tad warmer, but when I dialed that same WB value in preset, the result was a bit glaring.
I ended up just going with my "A" white balance as it was the better of the two options.

I'm hearing that I can certainly dial out the shift using the green / magenta slider, but then isn't that constantly messing with the Picture Profile? many folks out there like Abel Cinetech are sharing picture profiles, and I have a few of them assigned to my PP values. I feel like I'd ultimatelyI'd be screwing those up. And picture profiles aside, I'm also seeing this happen with my Pic Profile is set to OFF.

I guess I"m hearing that's just the way it goes. Any further thoughts on the topic are appreciated, but I guess if it's just the way things are, I'll quit my belly-achin'

morgan_moore
09-25-2011, 12:52 AM
The Industrial Kitchen - Bingo - you have given an example wheras I have just been giving meaningless waffle about control options

That is exaclty where I want the facility I described before

Kitchens have the wierdest set of lights often based aournd Flouoro some very green some less green all muddled up

Taking a WB will adjust the tint correctly (and of course the temp)

Now this accurate white look often makes the kitchen look like a morgue - its just too white and cold

What I want to do is walk in, hit AWB, lock that, then use a 'nudge wheel' to add a little warmth

In other situations - like maybe a morgue - I would of course want to AWB and nudge the image a little cooler

I proably want to be able to save those setting to a (name - able!) profile so I can keep consistency if I return to that location later in the day.. or maybe years later

It seems like at the mo the kitchen shot you have two bad options..

1) AWB and warm in post

Bad becuase it degrades the file

2) Creaate a profile

Goto menu and do the temp and tint to your desired look in the profile facilities

Bad because it takes an age of diddling with sub menus and also you are reliant on judging colour on your set monitor

S

morgan_moore
09-25-2011, 01:11 AM
On card balancing you may want to consider an expodisc

Doubtless as an FS100 user you have a wallet full of ND - an expodisc can easily be added to that unlike an a4 grey card - that I always put down and lose

You can consider the 'portrait' exposdisc too which adds a little warmth

Or you could keep a selection of gels cut to the size of your expodisc to fool the camera into warming cooling, or doing whatever you want

http://www.expoimaging.com/product-overview.php?cat_id=1&keywords=ExpoDisc

S

Postmaster
09-25-2011, 02:12 AM
I noticed some shifting during a shot (actually I realized it not during shooting).

Im 99% sure it was not on auto WB.

Anyone else?

Frank

rejdmast
09-25-2011, 01:56 PM
"Im 99% sure it was not on auto WB."

You can check that in the metadata: Visual Index > Data Code