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03-04-2008, 04:34 PM   #1
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Exposure test: K10D and SMC-P M 100/4 Macro

After seeing threads about inaccurate exposure with non-A lenses, I hauled out my tripod, my K10D and my SMC-P M 100/4 Macro, and did some testing.

I found that in Av mode the exposure was virtually unpredictable, but I need to do some retesting to find out if it is a "one stop" mode. In M mode, I found that I could get consistent results only at f/5.6 through f/11, and to get an accurate reading on the exposure scale, I needed to stop down with the dof preview once, and then again. So my procedure is going to be
  1. Set the f/stop
  2. Move the exposure switch to dof preview
  3. release
  4. dof Preview again and hold while adjusting exposure

It looks like my macro is "f eight and be there" +/- one stop. On either side of that, it underexposes. 1 stop or thereabouts at f/4, and at f/22 my dark side blinkies outshine Darth Vaders light saber. I noted that the shutter speed recommendations did not change as I went from f/stop to f/stop outside the f/5.6, 8, 11 range.

The next tests will be to do the same with my M 400/5.6.

I would be interested in seeing how others have made out with various K and M lenses.

03-04-2008, 05:01 PM   #2
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glad to see some more "relevant" testing done. the av mode on M lenses is basicaly wide open only (the k10d at least will not close the aperture in that mode at all, no matter what, in my experience), so yes, one could say it is one-aperture-only.

the other findings are pretty much in line with what others have mentioned, however a bit shifted, we might find that the phisycal diameter of the aperture actually has more to do with it (not the fnumber, which is the relative aperture)

in my experiments so far, holding DOF preview and using the exposure scale, versus using the green button for a recommendation of shutter speed, gives the exact same results, every single time

can't wait to see your followup with the 400mm
03-04-2008, 05:20 PM   #3
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QuoteOriginally posted by nanok Quote
glad to see some more "relevant" testing done. the av mode on M lenses is basicaly wide open only (the k10d at least will not close the aperture in that mode at all, no matter what, in my experience), so yes, one could say it is one-aperture-only.

the other findings are pretty much in line with what others have mentioned, however a bit shifted, we might find that the phisycal diameter of the aperture actually has more to do with it (not the fnumber, which is the relative aperture)

in my experiments so far, holding DOF preview and using the exposure scale, versus using the green button for a recommendation of shutter speed, gives the exact same results, every single time

can't wait to see your followup with the 400mm
I found that the tests were readily repeatable - at least the exposures were consistent. If they had not been consistent you would have heard me screaming where you live!

It will have to be tomorrow before I try out the 400, or maybe Thursday - I shot the 100 inside, aimed at a window lit bookcase from 4 meters. The 400 cannot focus inside my house! It's an M with a minimum focusing distance of 5 meters (16.5 feet). I'll have to take the rig outside and take exciting neighbourhood shots.
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