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Old June 25th, 2011, 06:55 AM   #1
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Problems White Balancing with Magic Lantern on T2i/550D

Hi

I've installed Magic Lantern 0.2 (and firmware 1.09) on my 550D. It's a great piece of software Magic Lantern and it's really really helpful. Except that when I hold up a grey card and use the ML auto white balance feature I get a different result every time even though the light hasn't changed.

To do the auto white balance I set my exposure with a grey card to 0EV
Then I go to the Expo menu in Magic Lantern
Then I I scroll down to the WhiteBalance option
Then I press Q to auto white balance

- however the results vary quite widely sometimes its really warm, sometimes about right, sometimes really bluish..

Is any one else having trouble with this feature? Am I doing something wrong?

I tried to adjust the white balance manually using the set and disp buttons to raise and lower the Kelvin setting. But I can't see the histogram while I do it, argh!

Anyone have any solutions? I really don't want to have to keep switching to photo mode and take a reference photo of the card then tell it to set that to manual white balance.

Thanks for your help!

Stuart
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Old June 25th, 2011, 05:50 PM   #2
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Re: Problems White Balancing with Magic Lantern on T2i/550D

Have you tried using the auto WB without pointing it at the card? That is, after all, how auto WB is designed to work - automatically, without needed any 'prompting' from a card. My guess is that by holding a card in front of it, it's confusing the camera and not letting it do whatever it is it does when it's on auto WB. Imagine using auto-exposure and holding a pure white piece of paper in front of the lens for it to meter. Would you expect the camera to expose the scene properly?

Also, you should be doing WB with a white card. Grey card for exposure, white for WB.
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Old June 26th, 2011, 03:01 AM   #3
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Re: Problems White Balancing with Magic Lantern on T2i/550D

Hi John, thanks for the reply

I followed what it says in the Magic Lantern manual:

--
WhiteBalance: 1500...12000
Kelvin white balance. Extended range (*) is only available in Movie mode and
LiveView. For still pictures, Kelvin WB will be clamped to the native range, i.e.
2500...10000.
In LiveView, press the Q button on this entry to set the WB temperature using the
center color as reference gray. The measurement area is 200x200 pixels, centered.
--

But it could be that these instructions are from an older version of Magic Lantern. I've already tried a white card with similarly variable results. But I'll try without a card at all and see if that works...

I thought grey or white cards worked for white balance?

Thanks for helping John
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Old June 28th, 2011, 10:48 AM   #4
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Re: Problems White Balancing with Magic Lantern on T2i/550D

Grey cards definitely don't work with a camera's white balance feature, since it's asking you for a neutral white as reference, and you're giving it grey- so you're basically saying "this grey = white." But you're right, the ML instructions are different, and my ML auto-balance doesn't work well- it basically ends up warmer than it should be, and then I just nudge it up to what looks good / the numerical value I know it should be near (5600 outside sunny, etc.) The most useful thing here is that you get actual numeric values, so if you have multiple cameras, you can dial in to the same value, etc. Think of the auto as a quick way to get close to what you want, since there's no "down" button, just "up", so if you're at 5000 and you want to get to 3200 it takes forever- much faster to hit the auto button and then correct it from there...

...at least, that's my experience...
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