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02-09-2010, 03:22 PM   #1
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'a' lens(es) .. locking focus.. help..

hi all... i just 'picked up' an smc a 200mm f4 lens that i'm going to use with my k-x.. now i've used my smc a 35-105mm f3.5 lens previously....
the issue is that getting the focus lock, (hexagon signal), is a little difficult... seems to take a great deal of delicate finesse to lock that focus in to then take a shot...(i've set the body to af-s)
let alone take an action shot, of say a bird in flight.....
i've taken some sharp pics of stationary items with an 'a' lens, but would like to expand it's usability....
would the catch in focus (focus trap) be the way to go??
(if so, please give simple, straight forward instructions and tips)...
an aging dog takes longer to learn new tricks.....lol !!!!
as always, thanks all for your consideration in helping... dave m

02-09-2010, 04:28 PM   #2
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If you're lucky your action shots happen at infinity or beyond and are all in focus.
02-09-2010, 05:08 PM   #3
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"A" lens and focus lock

Hi DCM,
had same with K20 & "A"s, does K-X have manual focus setting? might help .
With me,that indicator was like DOF indicator too,as I changed apeture,
with either E-wheel (in A mode on lens) or shifted via apeture ring,icon
would drift in and out. Cant explain it,but the more I used it, the more reliable
it was. Its going to be hard to do with moving subject regardless.
Focus trap is great, good light with fast shutter, and low apeture number
gives best results. Low light seems to increase latency between triggering incident
and shutter responce, plus, object of interest is usually moving so there could be
some blur in that respect.

Focus trap wont solve your situation in regards to trying to catch a bird in flight
its programmed so you might for example, bait a spot a short distance away,prefocus on that spot
and then "nailem" when event occurs.(bird comes to feed)
Like suggested above, you might try, faster iso setting, larger apeture number(for depth of field
and sharpness) and as fast a shutter speed as possible, with lens focused at infinity

Last edited by BillM; 02-09-2010 at 05:32 PM.
02-09-2010, 10:16 PM   #4
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QuoteOriginally posted by dcmsox2004 Quote
hi all... i just 'picked up' an smc a 200mm f4 lens that i'm going to use with my k-x.. now i've used my smc a 35-105mm f3.5 lens previously....
the issue is that getting the focus lock, (hexagon signal), is a little difficult... seems to take a great deal of delicate finesse to lock that focus in to then take a shot...(i've set the body to af-s)
let alone take an action shot, of say a bird in flight.....
i've taken some sharp pics of stationary items with an 'a' lens, but would like to expand it's usability....
would the catch in focus (focus trap) be the way to go??
(if so, please give simple, straight forward instructions and tips)...
an aging dog takes longer to learn new tricks.....lol !!!!
as always, thanks all for your consideration in helping... dave m
Despite the above comment, I see no reason not to try catch-in-focus with your A lens. I do it all the time with my M lenses. Probably 2/3 of my macro shots are taken with the body in AF-S. I set the magnification I want, set the aperture and exposure, decide where I want to get the focus, hold the shutter release and slowly move closer until the shutter releases. I've even used it with the 400, but it's so slow it's a bit iffy.

02-10-2010, 01:52 PM   #5
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QuoteOriginally posted by dcmsox2004 Quote
the issue is that getting the focus lock, (hexagon signal), is a little difficult... seems to take a great deal of delicate finesse to lock that focus in to then take a shot...(i've set the body to af-s)
let alone take an action shot, of say a bird in flight.....
i've taken some sharp pics of stationary items with an 'a' lens, but would like to expand it's usability....
would the catch in focus (focus trap) be the way to go??
I say no. You're almost always better off focusing by eye, with the camera's AF system not in th equation. With practice, doing it yourself is way more efficient - for exactly the reasons you state. And given the large size of the AF sensor that makes it impossible to know *exactly* what the camera thinks is in focus, doing it yourself is at least as effective too.
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