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04-23-2021, 09:20 AM   #1
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Pentax DA* 300mm F/4 - Would focus be quicker if SDM de-activated?

I own the venerable DA* 300mm F/4 which I purchased used from a forum member. The SDM appears to work ok, but the focus time seems very slow, especially when compared to my HD Pentax-DA 55-300mm F4.5-6.3 ED PLM WR RE.

For those who own the DA* 300mm F/4 SDM, is this your experience as well? Or is the SDM on my lens maybe on it's way out?

In either case, for those that have done the conversion to camera focus drive, have you found that the lens focuses faster? Even compared to a fully working SDM version?

Thanks, Chris

04-23-2021, 09:25 AM   #2
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I observed the same thing, did the conversion and can't be any happier. From my experience I highly recommend. If you follow the procedure posted in the forum -did mine with a K200D- then you will be done in 5 minutes.
04-23-2021, 10:11 AM   #3
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DA*300 is not noted as a fast focusing lens. Mine is noticeably slower than my DA 55-300. I think that is normal and not a sign that the SDM is failing.
04-23-2021, 11:20 AM   #4
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I have both the DA* 200 & DA*300 and the 55-300 PLM. SDM is fine on both DA* lenses. Simply put, the PLM is much faster than either of them.

04-23-2021, 12:20 PM   #5
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Iíve got the 300 (one I bought new this year), and the focus is fine to me, even for birding. Aside from occasionally hunting, I havenít noticed any issue with focus performance, even when birding.
04-23-2021, 01:07 PM   #6
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I have the DA* and the PLM, the PLM is much faster focusing. I'm probably crazy but it seems faster on the DA 1.4TC. I've used it a lot lately so my technique is probably just better. Although today I went to my car and got the PLM to try to catch barn swallows in flight. Did not help, it's not the lens, I'm too slow to track them.
04-23-2021, 02:35 PM   #7
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The sdm motor could be dropping in performance after time of use. Try to see a YouTube video of the outofocus and see if it matches.
04-23-2021, 03:11 PM   #8
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QuoteOriginally posted by ramseybuckeye Quote
I have the DA* and the PLM, the PLM is much faster focusing. I'm probably crazy but it seems faster on the DA 1.4TC. I've used it a lot lately so my technique is probably just better. Although today I went to my car and got the PLM to try to catch barn swallows in flight. Did not help, it's not the lens, I'm too slow to track them.
I have the PLM and keep forgetting to give it a serious go. I was out an hour ago with the new K3 III and a *300 when I probably should have mounted the 55-300PLM

04-23-2021, 03:31 PM   #9
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QuoteOriginally posted by cdw2000 Quote
I own the venerable DA* 300mm F/4 which I purchased used from a forum member. The SDM appears to work ok, but the focus time seems very slow, especially when compared to my HD Pentax-DA 55-300mm F4.5-6.3 ED PLM WR RE.

For those who own the DA* 300mm F/4 SDM, is this your experience as well? Or is the SDM on my lens maybe on it's way out?

In either case, for those that have done the conversion to camera focus drive, have you found that the lens focuses faster? Even compared to a fully working SDM version?

Thanks, Chris
Yes I have both and the 55-300 is definitely faster but I don’t think I’ll convert it anytime soon unless the sdm starts dying. No issues for the 8 yrs I’ve had it
04-23-2021, 04:27 PM   #10
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QuoteOriginally posted by Kwong Quote
Yes I have both and the 55-300 is definitely faster but I donít think Iíll convert it anytime soon unless the sdm starts dying. No issues for the 8 yrs Iíve had it
Same here, it's not broke, don't fix it. But it's nice to have a lens with a "plan B".
04-23-2021, 04:39 PM   #11
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It focuses much faster on my K1 than it did on the K3 or K7.

What you really need is a K3iii : )
04-23-2021, 06:01 PM   #12
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QuoteOriginally posted by 11GTCS Quote
Aside from occasionally hunting, I haven’t noticed any issue with focus performance, even when birding.
One lens I wish had a focus range limiter on it, Though It does not focus that close, it's a nuisance for it to go all the way to the close stop when it does miss. Especially w/BIF
04-23-2021, 06:20 PM - 1 Like   #13
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QuoteOriginally posted by K-Three Quote
One lens I wish had a focus range limiter on it, Though It does not focus that close, it's a nuisance for it to go all the way to the close stop when it does miss. Especially w/BIF
This is my only complaint with this lens. I've found it focuses about the same as the older DA 55-300 but nowhere near as fast as the plm version. Few lenses do.
04-24-2021, 01:48 PM   #14
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QuoteOriginally posted by K-Three Quote
One lens I wish had a focus range limiter on it, Though It does not focus that close, it's a nuisance for it to go all the way to the close stop when it does miss. Especially w/BIF
Concur, thatís really my only issue. Not that itís too slow, just that without a limiter it has to move the glass a long way to get a shot. Iíve just learned to prefocus at ďinfinityĒ lock (actually past infinity, but you know). That forces it to start there and work back, which usually results in a practically instant lock.
04-26-2021, 06:09 AM   #15
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Thanks for all the helpful replies. It sounds like my lens is working normally based on all the responses.
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