I don\'t have the exact numbers here but yesterday I checked some of my USAF test chart series. I have no independent reliable way of checking all this; I have to trust the shutter speeds to be reasonably correct, as well as I have to trust the f-numbers engraved into the lens. So already there everything is lost by unknown factors.
But, here is a short description of what i do: The target is a wall with some printed USAF test charts on it. I let the camera decide the exposure time with the EV comp set to +1/3 stop. The raw files are then developed in ACR with correction for the white balance only.
As the test is aimed to give me an idea about resolution, CA and corner smearing the camera is on a steady tripod and all aperture values are tested.
The results, when comparing from f/1.4 to f/4 was that the exposure varied within 0.2 stops. I placed measure spot on a white area of the USAF chart, the same of course for all the images, the \"light value\" is readable in ACR. The difference was then determined by dragging the exposure handle until I got the same RGB values for each image.
Oh well, this is not of much practical value but it turns out that the G1 gives much better exposures than the 4/3 cameras I have owned does.
My guess is that metering the light from the sensor is much more reliable than it is measuring it from the viewfinder screen. (Different screens give different values and some of them has a metering fall-off earlier than other ones.
OK, this is getting long but now you know why I asked you if this was corner problem or something valid for the whole image.
My conclusion is that the µ4/3 cameras are better at taking advantage of the old legacy lenses than the 4/3 cameras as the practical light measure procedure works much better. I also find that the exposure difference between say 1/000 and f/1.4, 1/500 and f/2 and 1/250 and f/2.8 is veru small. All this with the g1 and lenses like Zuiko OM50/1.4, Leica Summilux-R 50/1.4 and Olympus Pen 42/1.2
regards,
/Jonas
Jan 28, 2010 at 07:13 PM
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