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11-26-2013, 02:58 PM   #1
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can k-3 focus w/ 10 stop ND filter?

Curious if you can avoid doing the focus then put on filter thing for shooting water movement during the day...

11-26-2013, 02:59 PM   #2
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QuoteOriginally posted by kenyee Quote
Curious if you can avoid doing the focus then put on filter thing for shooting water movement during the day...
My guess would be that it would either focus much more slowly, or not at all, depending on the ambient light.

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11-26-2013, 03:26 PM   #3
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If you put the filter after focusing, the image will be a little out of focus, because filters usually change the distances, not geometricall, but optical. Maybe, if you have two filters, of different ND number, try first to focus with a lighter, than make the picture with the darker one.
11-26-2013, 03:30 PM - 2 Likes   #4
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There's no need for AF with a 10 stop filter. Stop down, switch to MF, use live view and focus peaking with the K-3, and focus that way. If you are using a 10 stop filter you are obviously not trying to capture any fast moving action

11-26-2013, 03:31 PM   #5
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Doesnt this also depend on the f-stop of the lens? And ambient brightness?
Also, if you are taking the time to do a long exposure, you will be using tripod and remote/timer anyway, might as well take time and focus manually, use DoF preview, maybe try zone focusing/hyperfocal..
11-26-2013, 03:45 PM   #6
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Can you see with sunglasses or welding glass? Well, it all depends on the ambient light.
11-26-2013, 03:54 PM   #7
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If you want to smooth moving water in bright sunlight, you can use less stops in the ND (or none) and use multiple exposure mode with Ev comp. In the K-3, you can apparently choose up to 2000 exposures for this instead of being limited to 9 like previous models, so the equivalent multiple exposure is virtually unlimited.

Depending on the lens (sharpness and contrast), Pentax SAFOX systems are essentially limited to something around f8 for AF in bright light -- I've personally achieved AF lock with lens/TC combos up to around an effective f10, but it was in direct sunlight, a contrasty subject, with a very sharp and contrasty base lens -- and focus time was not only very slow, but also very iffy. With a 10 stop ND, you'd be at an effective f32 (with an f1 lens) or slower, so there'd be virtually no chance for the AF system to find a lock.

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11-26-2013, 03:57 PM   #8
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QuoteOriginally posted by twitch Quote
There's no need for AF with a 10 stop filter. Stop down, switch to MF, use live view and focus peaking with the K-3, and focus that way. If you are using a 10 stop filter you are obviously not trying to capture any fast moving action
Had an 8 stop on this weekend and focused with no difficulty and no stop-down. Personal preference perhaps, but I wouldn't be using AF at this point anyway.

11-26-2013, 05:08 PM   #9
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QuoteOriginally posted by twitch Quote
There's no need for AF with a 10 stop filter. Stop down, switch to MF, use live view and focus peaking with the K-3, and focus that way. If you are using a 10 stop filter you are obviously not trying to capture any fast moving action
True...just an idle curiosity question w/ the claimed -3 eV focusing capability of the new AF module, I was just wondering how good it was
Though it sounds like it might work fine from jac's experience w/ an 8 stop filter

On my K20D, I do the hyperfocal thing anyways since you want everything in focus w/ a landscape w/ silked water...

Only other case when I might want to focus w/ an ND filter would be doing daytime video at f/2 but that should only be a few stops.
11-26-2013, 05:49 PM   #10
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The K3 can focus down to -3EV. That is pretty dark. So as long as the ND filter does not cut the ambient light lower than that as the camera sees it I don't see why it wouldn't auto focus.
11-26-2013, 06:24 PM   #11
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itunes has an app called ndtimer works well i recomend it
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