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05-21-2011, 10:46 PM   #1
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Focus indicator k-r da 55-300

I'm thinking of getting a DA 55-300 as a reasonable and cheapish starter lens for zoom. I've just noticed in the k-r manual that the focus indicator is only available for lenses with maximum aperture of 5.6 or faster.
Since at 300 mm the DA 55-300 is 5.8 does this mean at 300 the focus indicator doesn't work or, in practice, is it so close it still functions?

05-22-2011, 07:04 AM   #2
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I have a DA L 55-300mm and a K-R. The indicator works for me. You should be OK with that lens.
05-22-2011, 09:23 AM   #3
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Me too -works fine and I tend to leave mine set at f8 in av mode for shooting pics of small birds and focus it manually. No problems from 55-300mm either with the indicator.
05-22-2011, 02:17 PM   #4
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Thanks all.
I thought it might have to do with not stopping down to focus and therefore there being not enough light with a max aperture of above 5.6 - what you set it at being irrelevant since it hasn't stopped to that yet. It possibly still does but seems this lens has enough light when at 5.8 and 300 mm - which is good
Might also explain why the lens can hunt a bit at longer focal lengths. Or does it sometimes hunt at all lengths?

05-22-2011, 02:50 PM   #5
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QuoteOriginally posted by Bill_R Quote
Might also explain why the lens can hunt a bit at longer focal lengths. Or does it sometimes hunt at all lengths?
AF system works on Contrast detection and Phase detection philosophy. Not Sure if K-r uses phase detection but at longer focal length even the slightest shake can cause great deflection. Just think of it as ripples in water, at the origin the ripples are barely visible but at the ends they can look like waves.
Since there is constant change in contrast in AF point. System finds it hard to focus it quickly. Hence, it keeps hunting for sometime.

Last edited by Swapnil; 05-22-2011 at 03:40 PM. Reason: grammar
05-22-2011, 03:50 PM   #6
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QuoteOriginally posted by Swapnil Quote
AF system works on Contrast detection and Phase detection philosophy. Not Sure if K-r uses phase detection but at longer focal length even the slightest shake can cause great deflection. Just think of it as ripples in water, at the origin the ripples are barely visible but at the ends they can look like waves.
Since there is constant change in contrast in AF point. System finds it hard to focus it quickly. Hence, it keeps hunting for sometime.
Thanks for the info Swapnil.

Specs for the k-r gives:

TTL: Phase Matching autofocus
LiveView: Contrast detection + Face detection, Contrast detection, Phase Matching. Phase Matching in LiveView performed by the AF Sensor.
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