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08-14-2010, 02:46 AM   #1
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So far so good, M42 SMC 50F1.4 wz K7, but

Hi all,

Ok it's been 2 months now, Dad's 1971nish s-m-c super takumar 50 F1.4 is on my K7. Been taking a lot of pictures, learning heaps (as in doing things manually), and enjoying some of the results.

As per the various stickies on how to's & instructions around regarding these types of lens/camera arrangements, i have been shooting this way;
-MF, M mode, spot metering.
-adjusting the required Aperture by manually rotating the aperture ring on the lens
-press green button so that the camera can read the amount of light that the aperture which was manually set at, and thus also automatically set shutter speed required.
-half press the shutter, and adjust focus manually, more often than not, relying on the focus indicator (hexagonal icon), blinking red square and the buzzing sound in view finder, then continued full press of the shutter to capture the shot.

Sorry about the silly question but why does the last part not work for F10 to F16? all seem to fine with from F1.4 to F8. The camera provides no assistance in focusing at F10 or lower.

Best Regards,
Ken.

08-14-2010, 03:47 AM   #2
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Not enough light getting to the focus sensor.

Cheers, Mike.
08-14-2010, 03:56 AM   #3
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You need to do your focusing at a wider aperture. Most people do it wide open, but anything up to about f4 (f5.6 at most) is fine. The focus indicator system really doesn't work too well (or not at all) when stopped down past that.

Focus first, then stop down to your shooting aperture. If you are using the green button method in M mode, then do your metering stuff at this point. If you instead put the camera in Av mode, the metering will be taken care of for you and you needn't bother with it.

Also, remember that the red square is NOT the focus confirmation indicator. The green hexagon is. The red square indicates which focus point is being used.
08-14-2010, 03:56 AM   #4
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With the reduction of light available (since the aperture size is reduced) the auto focus sensor that provides the focus indication, probably does not have sufficient light in which to fully operate. If I remember correctly, it operates off of contrast, thus with the reduced amount of light, there is an insufficient amount of contrast by which to make a determination.

In comparison to a more modern auto-focus lens (notice I did not say better), the camera controls the aperture, so it keeps it open during the auto-focus to help with the contrast detection. Sensing a lack of perceived contrast, the lens will go into focus hunting.



08-14-2010, 05:39 AM   #5
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That happens to all of my lenses too at the small apertures. You won't get the focus confirmation, which is why, as said above, you should focus wide open.

Have you also noticed underexposure if you ever shoot really closed down? I do, so with certain lenses, if I know I want to shoot at F11, I'll hit my button at like 22, and then open to 11.

I seldom shoot at 11, but the situation does come up now and then.
08-14-2010, 05:23 PM   #6
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Thank you All,

All clear now and appreciate the quick replies.

Regards
ken
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