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  #1  
Old June 7th, 2006, 01:52 PM
Tuan_Nguyen Tuan_Nguyen is offline
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Default 5D Flash WB too warm with dedicated flash, but OK with single contact flash.

Hi all,
My first post here. I'm hoping to bring what I think is a problem with the 5D in general to Chuck.
I started a thread in DP a few weeks back, but didn't really get much reponse from fellow members there.
http://forums.dpreview.com/forums/re...ssage=18465305

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The problem is that when using AWB with flash ( I tried both my 550EX and Metz 54), the images come out too warm. Since I shoot RAW, it's not difficult to correct in CS2, but the K temp reported in ACR is around 5000-5100K (where a more desirable temp should be around 4600-4800K).

I've also see this in the camera's JPG and DPP so it's not ACR.

The reason why I think it's a problem with the 5D (mine at least) is that both flashes work fine in term of AWB and exposure on my 1D2, and recently on my friend's 30D. Another interesting finding is that if I tape up all 4 flash contacts (leave the middle one open) on my 5D, then the WB temp drops down to what it should be with my Metz 54 (550EX won't work right with only 1 sync contact)

What I'm doing is just using the middle contact to fire my Metz flash, essentially creating a "dumb" flash. The flash and camera worked fine this way, and the only down side is that I have to set ISO,F-stop on the flash since it no longer communicate with the camera. I also verified with another "dumb" flash (Sunpak 383 - only sync contact), and the WB is also fine.

But if the 5D WB works fine with a single-contact flash, then its FW or algo is messed up when resulted WB is too warm when it KNOWS you are shooting with a dedicated flash.

Attached are some samples:
550EX AWB

This is what WB should be:

Metz 54 5 Pins AWB

Metz 54 1 Pin AWB

Sunpak 383 (1 pin) AWB
http://photos.imageevent.com/bayarea...pak383_AWB.jpg

So as you can see, in both cases where I'm only using 1 pin (dumb
flash, Metz54 and Sunpak 383), the AWB works much better (K temp
reported much lower in ACR). A few others have confirmed similar problems.

Since the camera WB system works fine without flash or with a
single contact flash, I think the problem is fixable via FW upgrade.

Anyone running into similar problem with the 5D.
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  #2  
Old June 8th, 2006, 04:57 AM
Michael Tapes Michael Tapes is offline
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A workaround is to use a WB reference to set WB. Especially helpful if you mix ambient light with flash.
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  #3  
Old June 8th, 2006, 07:47 AM
Tuan_Nguyen Tuan_Nguyen is offline
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Thanks for the suggestion Michael, but I already have a simple work around.

The point I was making is that the two other cameras (1D Mark 2, 30D) AWB worked fine with the flash (Met54), but it's too warm on my 5D. The WB using the same flash would also work fine on my 5D if I only use a single contact (taping up the other 4 dedicate, communication contacts).
It sounds to me that the 5D WB algo is making it warmer than it should be, something that I imagine can be fix in the FW.

Since you have the 5D, what's your experience?

Best,
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  #4  
Old June 9th, 2006, 05:55 AM
Michael Tapes Michael Tapes is offline
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Quote:
Originally Posted by Tuan_Nguyen
Since you have the 5D, what's your experience?

Best,
AWB is useful in mid day. Other than that it is too problamtaic to use, so I now keep the 5D on Daylight, unless I am in a specific lighting condition for an entire shoot.

Since I use WhiBal on each shoot, the 5D looks great, and is more subject to the bias of the RC and the camera profiles.

One cannot discuss the color bias of a camera without explaining how the image was developed. If in the camera than what settings. If in a raw converter, then what profile and what settings.
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