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07-28-2011, 04:58 AM   #16
Ash
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Telephoto lenses generally have large focus throws and will cause similar lengthy focusing times if sent from back to front and then back again on your camera. By far and away the best method to manage/solve the 'problem' is prefocusing.

07-28-2011, 06:21 AM   #17
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QuoteOriginally posted by Ash Quote
Telephoto lenses generally have large focus throws and will cause similar lengthy focusing times if sent from back to front and then back again on your camera. By far and away the best method to manage/solve the 'problem' is prefocusing.

I agree with you, however, what I find frustrating sometimes is that the lens focuses towards the wrong direction. In my case it does this with center point sometimes, but with other individual points or auto 5 it seems to happen much less...I wonder if it's the focus point/lens combination since the center point is the most sensitive one. I did learn to work around it though, since I like the quality of the photos the lens produces (DAL 55-300).
07-28-2011, 08:06 AM   #18
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QuoteOriginally posted by telly0050 Quote
so sounds like there's no best way to solve the problem
does sigma or tamron 300mm telescope lens have the same problem? will they go faster?
I thought you said that using 5 point focus improved things?

I've had 2 copies of the Tamron 70-300 LD Di whatever... it does focus noticeably (but not hugely) faster than the Pentax DA 55-300. However, the Tammy does have it's own demons - namely, purple fringing (sometimes extreme) and is softer wide open @ 300mm than Pentax. The Pentax has nicer color, too, and 55mm is useful.

The Tammy's 1:2 macro mode is fun, though!

Anyhoo, back to the 55-300... with some skill and forethought, you should be able to work around the slow AF most of the time. I've shot all kinds of wildlife and BIF successfully with the lens.
07-28-2011, 08:11 AM   #19
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I hope you aren't using a UV or other filter on your lens... that's often the cause of bad AF, since many UV filters block a lot of visible light, not to mention also introduce aberrations, ghosting, flare etc into the image which can muddy the lens and confuse the AF.

I have the DAL 55-300, as well as the Tamron 70-300 and two equivalent older Sigma's. None perform better than the other in relation to AF.

For best results I use center-spot AF only, but I am also not afraid to switch to MF when I need to. Even the best AF isn't infallible.

Pic related (shot with the K-x and DAL55-300). Only MF would work reliably for shots like this:



07-28-2011, 08:28 AM   #20
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5 points does improve a little, but a lot of times it just focused on sth i don't want (after trying a few times again)
and rawr i do have a cheap 5 bucks UV filter on it, i will take it off and try again
and nice bird right there!
07-28-2011, 09:19 AM   #21
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If you squeeze the lens release button, it will disengage the focus motor, allowing for a poor mans quick shift. Obviously be careful, and use at your own risk, but I can't see how retracting the focus motor will cause much wear. Now, now doing it quite right and wrenching the motor, or knocking your lens off -- that can cause some damage. If it hunts the wrong way, it sure is slow.
07-28-2011, 09:37 AM   #22
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QuoteOriginally posted by BillS Quote
If you squeeze the lens release button, it will disengage the focus motor, allowing for a poor mans quick shift.
Now thats an information I did not know! Thanks for the tip! I'm sure it will help the OP also.
07-28-2011, 01:34 PM   #23
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I have used my 55-300 with and without a Hoya UV(C) filter and have noticed no difference in focusing speed, hunting or 'confusion'.
Good UV filters hardly affect light transmission through the lens - it's the polarising and ND filters that do (and are designed as such).

07-28-2011, 03:20 PM   #24
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QuoteOriginally posted by Ash Quote
Good UV filters hardly affect light transmission through the lens
I agree. And Hoya UV(C) is one of the optically better examples of a UV filter.

But use a bad UV filter and you will be almost guaranteed to have AF issues, probably with any lens. I've experienced this myself with a Tiffen filter that came bundled with a lens I bought from Adorama (a FA 50 1.4). The AF became very indecisive with the filter on.

The pic below is related. You can imagine how AF would have problems working through such a dim and murky UV filter as the bad example below. Put a bad filter on a complex zoom lens like the 55-300 that already has a low level of light transmission and you compound the problem.

So it is always something worth mentioning when AF issues are involved.

07-28-2011, 08:06 PM   #25
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thx bills for your info, i will try it sometimes even tho it sounds a bit risky to use.

and wow rawr, i never know tat a good uv filter will actually effect the photo.
all i heard is tat "uv filter is a glass that protect the lens, go wit the cheapest option", and tat's why i pick up cheap zeikos off amazon. but somehow i don't really notice difference w/ and w/o the uv tho
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