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Old May 19, 2005, 2:59 PM   #1
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Yes I know, the 20D is supposed to underexpose slightly. However, I have had trouble with proper exposure when taking outdoor portraits in moderate to bright conditions with and without flash at ISO 100, in P mode, evaluative metering, with the 420EX flash. Exposures using flash are at 1/60 of a second and I let the camera set the aperture. Distance is from 4 to 10 feet. Some exposures are 2+ stops overexposed with flash and not correctable in photoshop. Shots in moderate to heavy shade appear correctly exposed. Indoor shots are usually well exposed. In tight close up portraits, I can see that the flash needs to be diffused, but not at 10-12 feet? Anybody have this problem or any idea of the best way to handle it? My D70 correctly exposes identical shots (I use the cameras side by side, best of both worlds?) in the same conditions at ISO 200. Thanks.
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Old May 20, 2005, 12:38 AM   #2
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use raw its a godsend if you exposure is close you can get it perfect in CS2 under auto modes most the time but sometimes to get the look a certian way you can adjust seting to your perferences.
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Old May 20, 2005, 3:56 PM   #3
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If you want to use flash as fill-flash for outdoor potrait shots, use the Av mode, set your aperture and let the camera/flash do its things. You might have to dial in some -ve flash compensation based on your subject. Also on my 10D, I have disabled the "auto reduction of fill flash" custom fn.

Can you post some shots with the exif settings?
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Old May 20, 2005, 6:24 PM   #4
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doc1064 wrote:
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Yes I know, the 20D is supposed to underexpose slightly. However, I have had trouble with proper exposure when taking outdoor portraits in moderate to bright conditions with and without flash at ISO 100, in P mode, evaluative metering, with the 420EX flash. Exposures using flash are at 1/60 of a second and I let the camera set the aperture. Distance is from 4 to 10 feet. Some exposures are 2+ stops overexposed with flash and not correctable in photoshop.
I don't even own the 20D. But, when you mention shutter speeds of 1/60 second in moderate to bright conditions outside, I can see where photos may be overexposed.

Outdoors, if light is at an EV of 15, you'd need to be stopped down all the way to f/22 for proper exposure at 1/60th second and ISO 100. If light was brighter than EV 15, you may need to stop down even further (for example, f/32 at ISO 100, 1/60 second with light atEV16).

Many lenses don't have available apertures any smaller than f/22. Does yours?

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Shots in moderate to heavy shade appear correctly exposed. Indoor shots are usually well exposed.
Again, this sounds like light is simply too bright for the shutter speed you're shooting at (depending on how far your lens can stop down) when the problem is only occuring in brighter light. Chances are, the camera is giving you some kind of warning about it when it occurs.

It sounds to me like you'll probably need a Neutral Density Filter if you plan on shootng at 1/60th second outdoors in bright light (to block some of the light)

Is there a reason you need to shootoutdoors in bright light at 1/60th second?

BTW, use of a larger aperture (smaller f/stop number) is generally the preferred technique for portraits (so that your subject stands out from distracting backgrounds).

Using shutter speeds this slow forces a very small aperture (higher f/stop numbers) outdoors. This gives you greater depth of field (more of the background in focus), and probably gives you softer photos than using an aperture "mid range" somewhere, too (from diffraction errors at smaller apertures). Most lenses are not as sharp on either extreme of the aperture range.
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Old May 21, 2005, 10:17 PM   #5
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you can also buy a grey card ($15 @ B&H photo), meter on the grey card, get your reading, and set the camera manually for aperture and shutter speed. This will give you the most accurate exposure, anyway. Also, make sure your flash is shooting at half power or less (I don't know exactly how the 420ex works). If it has flash exposure compensation (FEC) set it to -1, and you might need to go down to -2. The flash is just supposed to "fill" in the shadows so that the shadow areas aren't too dark, but you don't want the flash to be equivalent to the primary light source (the sun), that also could be overexposing the image. Try to shoot a subject at high noon, where the face becomes very shadowy. Experiment with different flash exposures. You just want the flash to brighten the shadow areas. I, personally, like to see the shadows, but not so that they are almost black (which would be the case at high noon with no flash). You want the picture to look like a flash didn't fire (to a layman who wouldn't realize that there is a catch light in the center of the pupil). Good luck, if you have any other questions feel free to PM me.
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Old May 28, 2005, 9:19 AM   #6
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I have the 20D and had the 10D as well.What you describe is true for both of them. I don't know what Canon is doing with these flash algorithms butoutdoor flashwon'twork well without compensation. I use 1 1/3 minus flash exposure compensation and 1/3 stop minus abmbient exposure compensation to get proper exposure.

I find I prefer 1/3 minus ambient even without flash. It's like what we used to do with slide film. Slight underexposure for more saturation.

For indoor flash I set flash and ambient to normal. i.e. no compensation. I think you'll find the overexposure is only a problem with outdoor flash.

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Old Jun 19, 2005, 12:26 AM   #7
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Jim C, Sorry, I meant to say 1/250 of a second - the max sync speed - but I still get overexposure.
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Old Jun 19, 2005, 12:33 AM   #8
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tonyM, Thanks for the feedback. At least I know someone else is experiencing the exact same problem. I tried ambient compensation and this did help some - I bracket shots more now. I'll have to check the 420EX manual to see if I can change flash compensation. I'll experiment a bit. Thanks for the setting info.
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Old Jun 19, 2005, 8:56 AM   #9
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In bright sun, you can always go back to the sunny 16 rule that we used with film cameras. Set your aperture to f/16 and your shutter speed to what ever ISO speed you have your camera set to. This will give you perfect exposure everytime.
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Old Jun 19, 2005, 4:29 PM   #10
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You don't have to worry aboutadjustments on the 420EX you can adjust flash exposure via the 20D.

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