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02-27-2020, 07:36 PM   #16
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QuoteOriginally posted by mikesbike Quote
I believe one main reason the Limiteds, with the exception of the 20-40mm zoom lens, remaining as screw-driven is the technology having less to it therefore develop problems- more long term reliability. The camera supplies the motor, so you get a new motor when replacing the camera. They do have a point there

I agree, the screw-driven system with the KP is noticeably better. So with this system, a new camera body can potentially include a lens upgrade as well.
But all Pentax lenses have had in-lens motors from some point after 2012, so that's not the reason. Let's not count the FA35/DA10-17 reissues, of course.

02-28-2020, 08:58 AM - 1 Like   #17
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QuoteOriginally posted by mikesbike Quote
I believe one main reason the Limiteds, with the exception of the 20-40mm zoom lens, remaining as screw-driven is the technology having less to it therefore develop problems- more long term reliability. The camera supplies the motor, so you get a new motor when replacing the camera. They do have a point there.
I don't shoot Canon, but I've read that almost every single EF lens they've released since 1987 has had in-lens focusing motors. And they seem to be doing okay on the reliability front.
02-28-2020, 09:12 AM   #18
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QuoteOriginally posted by ThorSanchez Quote
I don't shoot Canon, but I've read that almost every single EF lens they've released since 1987 has had in-lens focusing motors. And they seem to be doing okay on the reliability front.
The last independent reliability test I saw which if memory serves me well was done by Lensrentals.com had Pentax at the top of the list. And those numbers were released at the height of the SDM thing. Something a lot of folks consistently ignore. Sure SDM was bad, but not bad enough to knock Pentax out of the top spot.

I suspect because the screw drive lenses are so reliable even the SDM failures didn't affect the big picture. Yet you had salesmen every where telling people every where not to buy Pentax because of SDM.

I'm sure Canon is doing "ok." I feel like a commercial... "just OK is not OK."
02-28-2020, 09:16 AM   #19
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QuoteOriginally posted by Fogel70 Quote
They would also have to convert the lenses to "focus by wire", so the motor control focus even with manual focus.
Not something I would like to have on Limited lenses, as the distace scale and mechanical stops on focus ring would be removed.
I don’t see focus by wire necessarily „connected“ to PLM and vice versa. Focusing by wire on the 55-300PLM works ok for me. But I like real manual focusing more.

02-28-2020, 09:32 AM   #20
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I believe focus by wire on the PLM is more due to this being a retractable design, like the 18-50, which is also rectractable and focus by wire but use regular DC motor.

That said focus by wire is really horrible on the 18-50 (lagging and imprecise) but invisible on the 55-300 PLM, only the lack of any stop at close focus and infinity betray that it is indeed a focus by wire lens.
02-28-2020, 09:45 AM   #21
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QuoteOriginally posted by normhead Quote
The last independent reliability test I saw which if memory serves me well was done by Lensrentals.com had Pentax at the top of the list. And those numbers were released at the height of the SDM thing. Something a lot of folks consistently ignore. Sure SDM was bad, but not bad enough to knock Pentax out of the top spot.
I'd like to see recent numbers to satisfy my curiosity. But a two-minute Google search of camera and lens reliability brought up almost nothing recent or meaningful.

Apparently Consumer Reports has some kind of data on cameras, but I'm not curious enough to pay for it and then get the resulting deluge of spam emails from them begging me to come back after I cancel.

Last edited by ThorSanchez; 02-28-2020 at 10:06 AM.
02-28-2020, 09:46 AM   #22
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QuoteOriginally posted by Bertrand3000 Quote
I believe focus by wire on the PLM is more due to this being a retractable design, like the 18-50, which is also rectractable and focus by wire but use regular DC motor.

That said focus by wire is really horrible on the 18-50 (lagging and imprecise) but invisible on the 55-300 PLM, only the lack of any stop at close focus and infinity betray that it is indeed a focus by wire lens.
... and you can‘t focus when camera is set off.
02-28-2020, 09:57 AM   #23
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QuoteOriginally posted by ThorSanchez Quote
I'd like to see recent numbers to satisfy my curiosity. But a two-minute Google search of camera and lens reliability brought up almost nothing recent or meaningful.

Apparently Consumer Reports has some kind of data on cameras, but I'm not curious enough to pay for it and thencan get the resulting deluge of spam emails from them begging me to come back after I cancel.
All I've ever seen from consumer reports was an incredibly biased rating by some guy. They could have done straight reliability rating but they fudged it by letting the guy invent his own rating system and adding on top of their reliability reports.


Last edited by normhead; 02-28-2020 at 10:04 AM.
02-28-2020, 10:17 AM   #24
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QuoteOriginally posted by normhead Quote
All I've ever seen from consumer reports was an incredibly biased rating by some guy. They could have done straight reliability rating but they fudged it by letting the guy invent his own rating system and adding on top of their reliability reports.
I'm not impressed either. Closed-sourced, paywalled, and absolutely no guarantee that their rating criteria match mine. Going back 25 years I bought one of their car rating issues to compare small, sporty coupes I was looking at and had to wade through superfluous stuff like them marking down such cars for having a small back seat and cargo area. More recently looking at appliances and cars and half the models I was considering had no reliability score because they hadn't tested them long enough. I guess thanks for not inventing something out of whole cloth, but why did I just just pay for a subscription for this?

And then they spammed me for years with emails begging me to come back.
02-28-2020, 12:48 PM   #25
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QuoteOriginally posted by acoufap Quote
I don’t see focus by wire necessarily „connected“ to PLM and vice versa. Focusing by wire on the 55-300PLM works ok for me. But I like real manual focusing more.
AFAIK all lenses using this type of motor are focus by wire. This type of motor need a very little resistance in the focusing so it would be difficult to implement a mechanically connected focus ring. And also because the design of the motor that moves a small light lens element back and forth on rails with a small lead screw.
02-28-2020, 01:57 PM   #26
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QuoteOriginally posted by selfnoise Quote
I think you could actually put a small motor, like the stepping motor Fuji uses, into a lens like the 35 2.8 limited. But I don't think Pentax has the resources for a retrofit like this.

In any event the DC motors they use are decent and the more recent SDM lenses have seemed fine as well. The problem is more a lack of budget to replace older screw drive lenses.
The Pentax SDM also uses a stepping motor, but it’s a piezo-electric one, not electro-magnetic, which many people in the past ignored in the flame wars about SDM failure. I don’t know if you were aware of that, but the SDM motor is pretty small, too, as I found out when I dismantled my DA*16-50 upteen times to free up the drive. I’m not aware of the nature of the Fuji drive.

On other matters, I don’t know that ring drive motors actually increase lens body diameter any more than small shaft-drive ones like the Pentax SDM or DC motors, although the weight is probably greater. Consider that the whole of the body is increased to fit a shaft-drive motor, and not just the sector where the motor is mounted.
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