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02-01-2016, 09:53 AM   #1
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Entering focal length?

Hi,

Sometimes (not all the time) when I power on my K-r, it prompts me to enter the focal length of the lens. I usually have a zoom lens on there, so what should I select?

Also, in the Menu configuration, I noticed that the item for entering lens focal length is grayed out? Why is that, and is there a way to enable it?

Also, why does the camera want to "know" the focal length, in general?

Thanks,
Jim

02-01-2016, 10:06 AM   #2
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It will ask when it can't read the lens. Clean the lens mount, all the contacts on both the lens and the body.
02-01-2016, 10:07 AM   #3
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When SR is turned on the camera will want to know the focal length of the lens if the lens doesn't 'talk' to the camera. If the lens can report to the camera it'll report itself and you won't need to enter the focal length. With a zoom lens enter the longest focal length. Just my $0.02.
02-01-2016, 10:39 AM   #4
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if you are using a modern lens with 'A' contacts, then the camera should not be asking for focal length. If it is this is an indication that your contacts are dirty or misaligned.

02-01-2016, 10:42 AM   #5
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As far as I know, the older manual focus lenses (A, M, K types) will not send that focal length info. This will only come from an autofocus lens because the contacts on these do transmit focal length information.
02-01-2016, 11:10 AM   #6
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QuoteOriginally posted by mcgregni Quote
As far as I know, the older manual focus lenses (A, M, K types) will not send that focal length info. This will only come from an autofocus lens because the contacts on these do transmit focal length information.
Correct. I typed without drinking my coffee. I believe the F series is the first to transmit focal length. Apologies to the OP for confusing the issue.
02-01-2016, 12:49 PM   #7
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Thats the great thing about the forum....there's always some smarta....se ready and waiting to pounce and correct things
02-01-2016, 01:10 PM   #8
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QuoteOriginally posted by wtlwdwgn Quote
When SR is turned on the camera will want to know the focal length of the lens if the lens doesn't 'talk' to the camera. If the lens can report to the camera it'll report itself and you won't need to enter the focal length. With a zoom lens enter the longest focal length. Just my $0.02.
I think I read somewhere else that entering the shortest focal length makes more sense, since you don't want the SR to over-compensate for camera shake. (the longer the focal length, the more the sensor moves to compensate for shake)

02-01-2016, 05:41 PM   #9
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QuoteOriginally posted by starbase218 Quote
I think I read somewhere else that entering the shortest focal length makes more sense, since you don't want the SR to over-compensate for camera shake. (the longer the focal length, the more the sensor moves to compensate for shake)
Yeah, on a 70-300, I don't think I'd enter 300 unless I was always using the long end. Of course, if you aren't zooming that much, there is nothing wrong with setting it for 300 for this shot, 100 for that one, etc. But you do want to err on the low side in general if you're going to err. (once you are over 100mm or so +/- 10pts isn't a big deal)
02-01-2016, 07:43 PM   #10
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Original Poster
Sorry, but what is "SR"?

Thanks for all the comments/info!
02-01-2016, 07:59 PM   #11
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QuoteOriginally posted by ohaya Quote
Sorry, but what is "SR"?

Thanks for all the comments/info!
Shake reduction. That's the reason it wants to know -- so it can compensate properly. Longer focal length = more compensation. It should only ask you when using a manual focus lens.
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