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Old Jan 10, 2005, 12:03 PM   #1
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I have two pictures that I took one after the other. One is dark the next is great. Here is the full exif from the dark one, Full auto mode. resized only. Any help is greatly appreciated.

File Name
IMG_1467.JPG
Camera Model Name
Canon EOS 10D
Shooting Date/Time
1/7/2005 10:56:35 AM
Shooting Mode
Auto
Tv( Shutter Speed )
1/60
Av( Aperture Value )
4.0
Metering Mode
Evaluative
Exposure Compensation
0
ISO Speed
100
Lens
15.0 - 30.0 mm
Focal Length
18.0 mm
Image Size
3072x2048
Image Quality
Fine
Flash
On
Flash Type
External E-TTL
Flash Exposure Compensation
0
Red-eye Reduction
On
Shutter curtain sync
1st-curtain sync
White Balance
Auto
AF Mode
AI Focus AF
Parameters
Contrast Normal
Sharpness Normal
Color saturation Normal
Color tone Normal
Color Space
sRGB
File Size
2121KB
Custom Function
C.Fn:01-0
C.Fn:02-0
C.Fn:03-0
C.Fn:04-0
C.Fn:05-0
C.Fn:06-0
C.Fn:07-0
C.Fn:08-0
C.Fn:09-0
C.Fn:10-0
C.Fn:11-0
C.Fn:12-0
C.Fn:13-0
C.Fn:14-0
C.Fn:15-0
C.Fn:16-0
C.Fn:17-0
Drive Mode
Single-frame shooting

Attached Images
 
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Old Jan 10, 2005, 12:07 PM   #2
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Here is the second one Full EXIF only resized.



File Name
IMG_1468.JPG
Camera Model Name
Canon EOS 10D
Shooting Date/Time
1/7/2005 10:57:45 AM
Shooting Mode
Manual
Tv( Shutter Speed )
1/60
Av( Aperture Value )
4.0
Metering Mode
Center-weighted averaging
ISO Speed
800
Lens
15.0 - 30.0 mm
Focal Length
18.0 mm
Image Size
3072x2048
Image Quality
Fine
Flash
On
Flash Type
External E-TTL
Flash Exposure Compensation
0
Red-eye Reduction
On
Shutter curtain sync
1st-curtain sync
White Balance
Auto
AF Mode
One-Shot AF
Parameters
Contrast Normal
Sharpness Normal
Color saturation Normal
Color tone Normal
Color Space
sRGB
File Size
2997KB
Custom Function
C.Fn:01-0
C.Fn:02-0
C.Fn:03-0
C.Fn:04-0
C.Fn:05-0
C.Fn:06-0
C.Fn:07-0
C.Fn:08-0
C.Fn:09-0
C.Fn:10-0
C.Fn:11-0
C.Fn:12-0
C.Fn:13-0
C.Fn:14-0
C.Fn:15-0
C.Fn:16-0
C.Fn:17-0
Drive Mode
Single-frame shooting
Owner's Name
Attached Images
 
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Old Jan 10, 2005, 12:14 PM   #3
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Easy - The difference are:
1. Auto
2. Evaluative
-> both of theses can throw you for a fit!

Notice the 2nd shot with 'Center-Weighted' (when you swith to manual) averaging vs the 'Evaluative' metering with the 1st picture where everything is key off on where a particular 'AF point' happened to fall upon...
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Old Jan 10, 2005, 12:20 PM   #4
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Hello NHL, I saw that Auto verses Manual, and Evaluative verses Center-weighted averaging. I was expecting better from using full auto mode on the camera and ETTL on the flash. It looks to me like the flash decreased the power output when using full auto. Also I am not sure I understand the difference between Evaluative verses Center-weighted averaging any chance you could enlighten me? Thank you, Pat
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Old Jan 10, 2005, 12:52 PM   #5
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In full Auto you lose control of both the aperture and the shutter speed -> In manual you can control the background with both the aperture and shutter(there's less leeway in controlling the shutter) while the flash can remain in full automatic E-TTL

The kicker is the 'evaluative' metering which mess the whole image up because the camera 'evaluate' the exposure around the AF point (the one that is lit up) selected by the camera and not neccessary the one you want the camera to use, which probably in your case somewhere up-front close to the race car body / front spoiler -> It put more emphasis on areas around this AF point which is brighter than the rest of the picture (ie illuminate by the flash and not the rear back wall).

In 'centerweight' the entire picture is average toward the middle of the viewfinder which is more 'correct'... This is a very well know issue with the Canon flash system -> You can also use the flash exposure lock (FEL), the AE button, for locking down the active AF point!
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Old Jan 10, 2005, 1:00 PM   #6
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Thank you for the enlightenment it makes lots of sense the way you put. So in the future I should be using one of the modes M, AV, TV for better control. I mostly use only a center focusing point and AV mode when I have taken other pictures. Is there one mode that would be better than another when using the Sigma flash? Again Thank you.
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Old Jan 10, 2005, 1:03 PM   #7
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Always use manual, and if possible in other mode (P, Av, Tv) lock it with the FEL * button! This has nothing to do with Sigma, the 420/550EX behave exactly the same, as it's how the Canon E-TTL metering in the body work...

FYI - http://www.stevesforums.com/forums/v...72&forum_id=37
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Old Jan 18, 2005, 12:30 PM   #8
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I have to believe the fact that your ISO was up to 800 in the brighter one was a factor too. Am I wrong?
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Old Jan 18, 2005, 2:17 PM   #9
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pcimaging wrote:
Quote:
I have to believe the fact that your ISO was up to 800 in the brighter one was a factor too. Am I wrong?
It's possible, but when in Auto the camera overide the user's ISO setting(800) to whatever the camera thinks is 'correct' (ie -> 100)
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Old Jan 18, 2005, 10:10 PM   #10
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Hello pcimaging, I did see that in the second picture that was shot in manual mode I did have the ISO set to 800 accourding to the EXIF. I am still trying to fully understand all that is going on when using the external flash.
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