GH1 Aperture Priority mode with manual lens

HDkilledFILM. said:
Off topic but is that a camera growing out of your pants? lol...
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Actually you are right, i have since fabricated another strap that attaches to the bottom of the removable tripod shaft and loops around my neck, very stable and adjustable. No more tucking into the pants. Great for run and gun.

Also have a little weight to put on the bottom and a quick attach handle ...bingo ...instant simple steadyCam device.
R
 
It was hard to tell whether anyone had clearly and completely answered the original question, so I wanted to offer an explanation.

The question I'm answering is, "What does the 'exposure compensation' do if a camera is set to a fixed aperture (i.e,. in aperture priority mode) and iso (i.e, not in auto-iso mode)?"

The answer is that it would adjust the shutter speed. A -1EV adjustment to exposure would underexpose by halving the exposure time. E.g., if the fixed aperture was correctly exposed (i.e, 0 EV) at 1/120s then a -1EV adjustment will result in exposure of 1/240s. Conversely, +1EV would overexpose and result in exposure time of 1/60s. -2EV and +2EV contribute another halving or doubling of exposure time, and -3EV and +3EV result in a third halving or doubling.

Historically exposure compensation in a fully automatic camera could adjust either aperture or shutter speed or both. But if you locked one then the exposure compensation would necessarily be limited to adjusting the other. ISO wasn't in the mix with film cameras because whatever film was being used had a fixed ISO, i.e., ISO was always locked.

Now many digital cameras have an auto-ISO setting that throws ISO into the mix with aperture and shutter as the three settings that can be adjusted to get a desired exposure (i.e desired EV). When ISO is locked or set manually then ISO can't be adjusted by camera to obtain desired exposure.

A CAVEAT: Although if shutter, aperture, and/or ISO are locked the camera should _in theory_ not be able to alter the locked settings to obtain the desired EV, on the Canon 5D at least this is not the whole story. The 5D has a setting called "Exposure Safety Shift" that I believe defaults to 'On' and which _will_ alter the shutter speed even if a fixed speed is set in shutter priority mode. This works to adjust shutter speed from the fixed value, but _only_ when the aperture has been moved to the end of its range (i.e, wide open or fully stopped down) and the desired EV can't be obtained. With "Exposure Safety Shift" set to 'Off' the camera would refuse to fire; with it 'On' the camera will adjust shutter speed despite the speed being fixed in shutter priority mode. I don't know whether the GH1 has any settings like this or not.

Wikipedia has a good piece on EV units, which are basis of exposure compensation:
http://en.wikipedia.org/wiki/Exposure_value
 
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hsitz...that makes sense to me. I would think it's the shutter that's adjusted in the background also.
 
Can the setting changes be checked in MJPEG mode since it also takes a still shot with EXIF info for each video? Just checked this, the only thing it doesn't show is the ISO setting.

Randy
 
GH1 has iexposure function and i have it enabled so i wonder if that is similar to the EXPOSURE SAFETY SHIFT on the 5D?
 
rambooc1 said:
GH1 has iexposure function and i have it enabled so i wonder if that is similar to the EXPOSURE SAFETY SHIFT on the 5D?
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It is different, apparently, a function that will in some cases slightly increase ISO to capture more shadow detail. Described about half way down the page here:
http://www.dpreview.com/reviews/panasonicdmcgh1/page18.asp

From link above sounds like the iexposure rarely makes changes even when it's switched on, and default setting is off.
 
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