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03-20-2015, 07:40 PM   #271
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QuoteOriginally posted by RobG Quote
Lucky guy who got to try one out in NT and Queensland for the brochure! If you're prepared to spend that much on a lens, I don't think you can say you're cheap.
I think the 15-450 will deliver in terms of IQ, and i'm 100% sure it will deliver in terms of AF performance. As Ricoh said, the new D-Fa lenses are the first ones with focus motors quick enough to keep up with the SAFOX XI on the K3.
The only thing we'll have to worry about is finding the money to buy them...

03-20-2015, 07:55 PM   #272
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QuoteOriginally posted by RobG Quote
Lucky guy who got to try one out in NT and Queensland for the brochure! If you're prepared to spend that much on a lens, I don't think you can say you're cheap.
I have been trying all sorts of "long lenses" over the past few years and the only one that I find has excellent IQ is my "old" DA*300/4, so of course I will be expecting just as good from this 150-450 but perhaps I am setting the bar too high, who knows?

As for being "cheap" ... well I admit it to be true in the sense that I will wait for others to try it out first.
03-20-2015, 07:58 PM   #273
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QuoteOriginally posted by Stavri Quote
I think the 15-450 will deliver in terms of IQ, and i'm 100% sure it will deliver in terms of AF performance. As Ricoh said, the new D-Fa lenses are the first ones with focus motors quick enough to keep up with the SAFOX XI on the K3. The only thing we'll have to worry about is finding the money to buy them...
Fingers crossed; time will tell. I'm not being negative here. I really do hope that it's the lens I've been looking for, because I've contemplated getting a Canon (wash your mouth out, Sir) just to be able to match it with a long lens. I wasn't expecting the 150-450 to be that price, so it ought to deliver premium performance to match the price tag.
03-20-2015, 11:33 PM   #274
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QuoteOriginally posted by RobG Quote
[...] the AF speed improvement would want to be impressive.
They ARE. Believe me. It felt as anything but Pentax. I wrote a report, please read it:
https://www.pentaxforums.com/forums/16-pentax-news-rumors/290412-report-bruss...days-dfas.html

03-21-2015, 12:31 AM   #275
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They are, cause they incorporate now a large direct current AF engine. I tried to circle it on the picture below. Instead of a small, low power AF engine that drives the AF group with a reduction gear, this is a direct actuator of the AF group. Much faster, just as a car with a high power motor is fast. That's also the reason of the new shape of the pentax zooms, with a large diameter near the bayonet
03-21-2015, 12:45 AM   #276
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QuoteOriginally posted by thibs Quote
They ARE. Believe me. It felt as anything but Pentax.
Thanks for the pointer. Maybe I'll get my wish - IQ like the DA*300 and focussing speed like the Promaster (which sadly is the only fast focussing lens I have experienced). I should try the Promaster on the K3.

QuoteOriginally posted by goubejp Quote
They are, cause they incorporate now a large direct current AF engine. I tried to circle it on the picture below. Instead of a small, low power AF engine that drives the AF group with a reduction gear, this is a direct actuator of the AF group. Much faster, just as a car with a high power motor is fast. That's also the reason of the new shape of the pentax zooms, with a large diameter near the bayonet
Thanks. I didn't think the SDM of the DA*300 used an AF motor through a reduction gear though?
03-21-2015, 01:09 AM   #277
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QuoteOriginally posted by RobG Quote
because I've contemplated getting a Canon (wash your mouth out, Sir)
Rob, before you go to Canon... if the 150-450 doesn't suit you, try the Siggy 150-500.
I haven't had mine for long and haven't had much chance to use it, but I'm pretty pleased thus far.
03-21-2015, 02:35 AM   #278
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QuoteOriginally posted by RobG Quote
Thanks for the pointer. Maybe I'll get my wish - IQ like the DA*300 and focussing speed like the Promaster (which sadly is the only fast focussing lens I have experienced). I should try the Promaster on the K3.



Thanks. I didn't think the SDM of the DA*300 used an AF motor through a reduction gear though?
Have a look here (it is a 16-50) :
Pentax
You see how small is the sdm engine - thus the lack of power - and the reduction gear
Ths plastic dents of the gear are responsible of the lack of reliability of the sdm

03-21-2015, 03:29 AM   #279
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QuoteOriginally posted by rod_grant Quote
Rob, before you go to Canon... if the 150-450 doesn't suit you, try the Siggy 150-500.
I haven't had mine for long and haven't had much chance to use it, but I'm pretty pleased thus far.
Thanks for the suggestion, Rod!

QuoteOriginally posted by goubejp Quote
Have a look here (it is a 16-50) : Pentax
You see how small is the sdm engine - thus the lack of power - and the reduction gear
Ths plastic dents of the gear are responsible of the lack of reliability of the sdm
OK. I'm surprised that such a mechanism manages to be so quiet if indeed that's what's inside the DA*300.
03-21-2015, 05:33 AM   #280
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It is quite because made of plastic. A full metal version would be more Noisy - but will not brake.
03-21-2015, 03:01 PM   #281
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QuoteOriginally posted by goubejp Quote
Have a look here (it is a 16-50) :
Pentax
You see how small is the sdm engine - thus the lack of power - and the reduction gear
Ths plastic dents of the gear are responsible of the lack of reliability of the sdm
I though it was the micro motor on top that is breaking. The plastic gears couldn't be breaking or the lens wouldn't be able to work through the screw drive that is also attached to the plastic gears.
03-21-2015, 04:00 PM   #282
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QuoteOriginally posted by robjmitchell Quote
I though it was the micro motor on top that is breaking. The plastic gears couldn't be breaking or the lens wouldn't be able to work through the screw drive that is also attached to the plastic gears.
The plastic gears are part of the screw-drive AF (most lenses have plastic/nylon gears), they operate independently from the SDM...

Last edited by Stavri; 03-21-2015 at 04:28 PM.
03-21-2015, 04:26 PM   #283
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QuoteOriginally posted by goubejp Quote
Ths plastic dents of the gear are responsible of the lack of reliability of the sdm
My engineering knowledge of lenses is very limited indeed, but I remember reading some time ago that the SDM reliability issue was not related to the use of nylon gears per se.

Rather the problem was how some SDM lenses distributed the load of moving the lens elements across the mechanism. Specifically, all the workload in SDM lenses went to one motor point in the lens mechanism, instead of distributing the load more evenly. A better design approach, it was suggested, would have been to use two motors (one on either side of the lens), or a design that radially distributed the 'pushing and pulling' work of the motor and applied the torque across the lens mechanism completely evenly. This is how the DC motor in the new lenses works.
03-23-2015, 04:51 AM   #284
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Well the picture is rather clear
:
Pentax

The sdm transmit the load to the moving elements though a nylon gear which is subject to failure. Metal gear would be more resistant, but Noisy. Anyway the main issue is the (lack of) torque of such a small engine, thus the reduction ger needed to increase torque.
As you see one the picture above, the new "ring" DC engine, as described by the Pentax patent, has a much higher torque and power (power is torque multiplied by speed), cause it consists of a lot of small magnets distributed on a ring, and a mobile element with electromagnetic coils (and electronics) to drive it.
See
ROTARY ACTUATOR
03-23-2015, 06:14 AM   #285
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Aha. Thanks for the extra info.

I personally dislike nylon gears quite a lot. I once had a 4 door car with power windows that had nylon gears in the power window motor. In the first year of owning the car, every single power window failed, as the nylon gears in the window motors stripped, and the window would fall into the door, often at the most inconvenient time or location.

Touch wood, my only SDM lens (DA*300) has been very reliable to date.
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