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10-21-2019, 05:37 AM   #736
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QuoteOriginally posted by Serkevan Quote
In that regard, what in lens motor would you guys bet on? New SDM? DC like the DFA tele zooms? I suppose the DC motor in those is different from the one in the 28-105 (mine is definitely louder than the DFA*'s, like a bird chirp), but I am not sure which one would be faster/cheaper/more accurate.
I have to be honest, I'm unclear what the relative merits of lens motors might be. While sdm lenses have a reputation for high failure rates it's the slowness of the system that bothers me when compared to competing systems. DC motor lenses aren't immune to failure, but more importantly they seem faster to focus and possible more consistent.

10-21-2019, 05:41 AM   #737
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QuoteOriginally posted by UncleVanya Quote
I have to be honest, I'm unclear what the relative merits of lens motors might be. While sdm lenses have a reputation for high failure rates it's the slowness of the system that bothers me when compared to competing systems. DC motor lenses aren't immune to failure, but more importantly they seem faster to focus and possible more consistent.
It may be incorrect to think of just two motors .... most likely it is two motor types. The PLM lens is very fast focusing, but I'm not sure how much to attribute to the motor and how much to the lens redesign that was necessary in order for the motor to work.
10-21-2019, 05:43 AM   #738
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QuoteOriginally posted by phoebus Quote
Hopefuly still won't happen - but I guess I'm in the minority...

So it's YOU that keeps on about another referendum vote just because you didn't get your way the first time.
10-21-2019, 06:14 AM   #739
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QuoteOriginally posted by UncleVanya Quote
I have to be honest, I'm unclear what the relative merits of lens motors might be. While sdm lenses have a reputation for high failure rates it's the slowness of the system that bothers me when compared to competing systems. DC motor lenses aren't immune to failure, but more importantly they seem faster to focus and possible more consistent.
The *new* SDM motors on the DFA 15-30/2.8, 24-70/2.8 and Star 50/1.4 seem to be different ring-type motors, so they should only have the name in common. They also appear, from the reviews, to be much faster.

10-21-2019, 06:25 AM   #740
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QuoteOriginally posted by UncleVanya Quote
I have to be honest, I'm unclear what the relative merits of lens motors might be. While sdm lenses have a reputation for high failure rates it's the slowness of the system that bothers me when compared to competing systems. DC motor lenses aren't immune to failure, but more importantly they seem faster to focus and possible more consistent.
I think the DFA*50 demonstrates that SDM can be fast and accurate. l understand that it is direct drive, unlike the smaller geared SDM of older lens. Whether it is used in the new 70-200/4 we’ll have to wait and see. My guess is it will DC like the 70-200/2.8 which seemed reasonably fast when I tried it.
10-21-2019, 06:31 AM   #741
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QuoteOriginally posted by Serkevan Quote
(...)

In that regard, what in lens motor would you guys bet on? New SDM? DC like the DFA tele zooms? I suppose the DC motor in those is different from the one in the 28-105 (mine is definitely louder than the DFA*'s, like a bird chirp), but I am not sure which one would be faster/cheaper/more accurate.
Ring SDM motors have more torque than DC motors, therefore allow to move heavier lens elements faster but they are bigger and more expensive. As for accurateness, I don't see it as a problem for either technology.
10-21-2019, 06:34 AM - 1 Like   #742
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The thing is that "DC" and "SDM" are basically marketing names mixed with technobabble. Both are "direct current" motors, by definition.

10-21-2019, 06:39 AM   #743
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QuoteOriginally posted by Serkevan Quote
The thing is that "DC" and "SDM" are basically marketing names mixed with technobabble. Both are "direct current" motors, by definition.
Doesn't all camera-based equipment start off as direct current?? 'DC' is a motor designation that may distinguish itself from modern 'SDM' as well as older 'SDM' in some useful way.
10-21-2019, 06:54 AM - 1 Like   #744
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QuoteOriginally posted by Serkevan Quote
The thing is that "DC" and "SDM" are basically marketing names mixed with technobabble. Both are "direct current" motors, by definition.
Hence my use of 'Ring SDM motors', which in Pentaxland designates a complete different beast from DC or 'old' SDM motors, both of which are micromotors.

In Canonland: Ring-Type USM vs. Micro USM.

10-21-2019, 06:58 AM   #745
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QuoteOriginally posted by Serkevan Quote
seem to be different ring-type motors
I know, this is what I said. My point is that the name does not necessarily mean anything substantial. And yes, obviously everything in the camera is DC, that's why calling a motor "Direct Current Motor" means between zero and nothing by itself.
10-21-2019, 06:59 AM   #746
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QuoteOriginally posted by Serkevan Quote
The *new* SDM motors on the DFA 15-30/2.8, 24-70/2.8 and Star 50/1.4 seem to be different ring-type motors, so they should only have the name in common. They also appear, from the reviews, to be much faster.
SDM is a name. Obviously the SDM in the DFA 15-30/24-70 is completely different as these lenses are rebadged Tamron lenses. The DFA *50 actually has a ring motor which is very different from the SDMs of the past.

But even within the SDM line up the speed varied. The DA *55 had by far the slowest focusing motor (and you could actually hear it power up when you zoomed). The DA *16-50 seemed a little faster than the 50-135. Anyway, just saying that the bigger question is what motor they are actually using combined with the length of the focus throw (shorter obviously makes for faster AF).

My guess for this lens would be a DC motor though. They could still call it SDM and have it be a similar motor to what is on a lens like the DFA *70-200.

Everyone seems to think the PLM system is awesome, but I'm not totally sold on focus by wire systems where they are unusable, even as manual focus lenses on older cameras. But maybe it is the way of the future...
10-21-2019, 07:06 AM   #747
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QuoteOriginally posted by Rondec Quote
SDM is a name. Obviously the SDM in the DFA 15-30/24-70 is completely different as these lenses are rebadged Tamron lenses. The DFA *50 actually has a ring motor which is very different from the SDMs of the past.

But even within the SDM line up the speed varied. The DA *55 had by far the slowest focusing motor (and you could actually hear it power up when you zoomed). The DA *16-50 seemed a little faster than the 50-135. Anyway, just saying that the bigger question is what motor they are actually using combined with the length of the focus throw (shorter obviously makes for faster AF).

My guess for this lens would be a DC motor though. They could still call it SDM and have it be a similar motor to what is on a lens like the DFA *70-200.

Everyone seems to think the PLM system is awesome, but I'm not totally sold on focus by wire systems where they are unusable, even as manual focus lenses on older cameras. But maybe it is the way of the future...
That's why I'm saying that I have no clue whether the new SDM ring-type is better than the DC motor in the 70-200/2.8 and 150-450 long teles. The teles have a "worse", in principle, motor, but they seem to perform decently well.
About the PLM, I'm afraid that the focus-by-wire is more or less a necessity of a linear motor. The 55-300 WR is still in production however, so hopefully Pentax takes a long time to phase the alternatives out.
10-21-2019, 07:06 AM   #748
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SDM of the past, belongs in the past - period. I had it and I sold it.
10-21-2019, 07:57 AM   #749
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PLM has nothing to do with focus by wire afaict.
10-21-2019, 07:59 AM   #750
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As for SDM (not DC and not ring type), buy and use an older Canon 50/1.8 'ultrasonic' and hear it tearing your ear.
Canon has (has had?) crap AF motors.
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