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Old Feb 16, 2011, 8:02 AM   #1
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Default Bracketing - technical question

How does bracketting actually work? I took a lot of bracketted shots recently and while the ones in good light worked as I'd expect, I noticed in low light I was getting odd results where the light shot didn't really look any lighter than the middle shot.

This was with the FZ38 in P-Mode. I can't check the actual images at the moment but I think it's because the shutter speed was limited to 1/4s and it wanted longer. I *think* +1ev corresponds to doubling the expoure length so it wanted 1/8s for the dark shot, 1/4s for the middle shot and 1/2s for the light shot but being limited to 1/4, simply repeated the middle shot.

Does that sound right? I'd expected the exposure compensation to do something other than adjusting the shutter speed.
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Old Feb 16, 2011, 8:30 AM   #2
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Originally Posted by MartinSykes View Post
Does that sound right? I'd expected the exposure compensation to do something other than adjusting the shutter speed.
Nope. That's what it does (changes shutter speed or aperture to brighten or darken an exposure).

If you use a -EV setting (needle to the left of center) with Exposure Compensation while shooting in Aperture Priority mode, you'll have a darker exposure than the camera would have used. It gives you a darker exposure by using a faster shutter speed with the selected Aperture. If you use a +EV setting (needle to the right of center), you'll have a brighter exposure than the camera would have used. It gives you a brighter exposure by using a slower shutter speed with the selected Aperture.

If you go to Shutter Priority (where you select the Shutter Speed and the camera selects the Aperture needed), it does the same thing (brighter or darker exposure with Exposure Compensation) by varying the Aperture instead.

If you shoot in Programmed Auto, it may vary either one (or both) to change the exposure. But, if the Aperture is already wide open at lower ISO speeds and/or dimmer lighting, it's going to change Shutter Speed if you need a brighter exposure than metered.

If you're using manual exposure, there is no Exposure Compensation. You're controlling the variables by setting the Aperture and Shutter speed (using the meter as a guide, with the needle to the left of center giving you a darker exposure, and the needle to the right of center giving you a brighter exposure, as compared to the way the camera metered the scene).

Exposure compensation is just a tool that makes it easier to vary your exposure while still taking advantage of other auto type features, without the need to resort to setting both aperture and shutter speed manually in changing lighting.

As for the 1/4 second limitation, that could be what's going on from your description of the symptoms. But, I'm not very familiar with that model's features to know what it's behavior would be. So, perhaps others will chime in.
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Old Feb 16, 2011, 8:57 AM   #3
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from
http://www.cameralabs.com/reviews/Pa...8/design.shtml

"Note the FZ38 / FZ35 like other Panasonic compacts has a menu option to set the lowest shutter speed available in the automatic modes. By default this is set to 1/8, but you can reduce it to one second, or increase it to 1/250 if desired. If you’re shooting in low light at lower sensitivities in one of the auto or semi-auto modes, remember to set this to a lower value than the default 1/8 or your images could be underexposed; obviously you’ll need to be aware of potential camera shake though. "

from steve's review:
"Min. Shtr Speed - 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250"
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Old Feb 17, 2011, 12:57 AM   #4
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Thanks guys. I wish I'd figured it out at the time as I've got quite a few incomplete sets from the dark museums I visited.
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