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04-11-2012, 01:17 AM   #1
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Pentax SDM vs DC, my take

Pros and cons between the two;

1. SDM

Pro
-Silent


Con
-Expensive
-Slow (could be focus throw)
-Inaccurate
-Can 'die' on you

2. DC

Pro
-Silent
-Reasonably priced
-Fast (could be focus throw)
-More consistent AF
-Reliable motor with ZERO failure till to date

Con
-Only one lens with DC motor


I don't understand why Pentax is so fixed on using SDM despite all the cons. The only reason I could think of would be that Pentax had been suckered into signing a contract to buy all the lemons (SDM) from the lens maker until it expires. And we Pentaxians become the ultimate suckers to take over the crap.

This is not right if it is true and it would be nice if Pentax were to clarify on this issue.

What do you think?

04-11-2012, 01:22 AM   #2
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I don't know why Pentax is so shady about this matter- when we interviewed them, they only said that "each system serves a different purpose" and that the DC system is for budget lenses. Even that doesn't make sense, though, seeing that DC is more reliable and faster (even if it's only because of the rear-mounting). I would definitely like to see more DC lenses.

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04-11-2012, 01:29 AM   #3
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You hit the nail on the head! I smell a rat already and I think we Pentaxians deserve an answer. Pentax should explain to us why the SDM is more superior than DC!

I have a 18-135 for a year and when I picked up a 16-50 2 weeks ago I was so taken aback by the sluggish and inconsistent AF of the SDM. This just don't make any sense at all!
04-11-2012, 01:44 AM   #4
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When a product is mass produced, a company would buy material needed to build an item in bulk.
I'm guessing they either have tons of leftover parts for SDM, or still under a contract for a deal on SDM parts.

Until that runs out, why come out with a newer tech that'll make the other ones obsolete, and potentially lose money on that?

04-11-2012, 01:48 AM   #5
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I love the DC motor of my 18-135. It's not slower, compared to SDM. The DC motor is smaller too. (From what I was told.) So, the possibility of small limited lenses with DC motors really appeals to me a lot.
04-11-2012, 01:48 AM   #6
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Can't they con Canon and Nikon into taking over the SDM contract or remaining parts rather than let the Pentaxian unwillingly buy into it LOL!!!
04-11-2012, 02:14 AM   #7
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Overall I have not had a real need for the faster lenses that SMD supports. So, I have not really been a consumer of these lenses. However, my take on the matter, although I really do not disagree with the previous posts, is a bit more socially based.

In the Asian cultures - "the saving of face", is very important. I do think that there is a bit of this in the mix, at work here. I think that we have seen aspects of this in other problem areas within Pentax's line up. Pentax is very slow to acknowledge any type of less than stellar performance.

04-11-2012, 02:17 AM   #8
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Pentax haven't released a SDM driven lens since the release of the 55mm have they?

Who's to say it won't be a better version when the next DA* lens is released


Last edited by Mike.P; 04-11-2012 at 02:24 AM.
04-11-2012, 02:20 AM   #9
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QuoteOriginally posted by Adam Quote
I don't know why Pentax is so shady about this matter- when we interviewed them, they only said that "each system serves a different purpose" and that the DC system is for budget lenses. Even that doesn't make sense, though, seeing that DC is more reliable and faster (even if it's only because of the rear-mounting). I would definitely like to see more DC lenses.
Well not fully.
first off reliable.
There is only one lens with DC and yes there the DC works really well without fails but if we look at DA* primes we can say the samething with SDM so how much value can we give to that?
There are more lens models that have reliable SDM then there are lenses with reliable DC for example, it's just how you approach the matter.

Faster.
Same as before DC only one lens, the AF speed various with the SDM lenses so hard to say which one is faster.

Why the DC for budget, that's quite simpel. DC is not power full enough to move the bigger heavier elements and seals with the DA* lenses.

Last edited by Anvh; 04-11-2012 at 02:28 AM.
04-11-2012, 02:25 AM   #10
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QuoteOriginally posted by Mike.P Quote
Pentax haven't released a SDM driven lens since the release of the 18-135mm have they?

Who's to say it won't be a better version when the next DA* lens is released
the DA18-135 use DC, different type of motor.
DC is a brushless elctro motor SDM is a sonic motor, one uses magnetism the other uses vibration/friction to produce movement.

The last lens with SDM was the DA*60-250 i believe or the DA*55, pentx said in an interview that DC was for budget market but that they will keep using SDM for the pro market.
04-11-2012, 02:28 AM   #11
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QuoteOriginally posted by Anvh Quote
Why the DC for budget, that's quite simpel. DC is not power full enough to move the bigger heavier elements and seals with the DA* lenses.
And SDM isn't powerful enough in it's present form.
You only have to compare focus speeds between the Sigma 70-200mm HSM / 60-250mm and 50-150mm / 50-135mm to see that
04-11-2012, 02:30 AM   #12
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QuoteOriginally posted by Mike.P Quote
And SDM isn't powerful enough in it's present form.
You only have to compare focus speeds between the Sigma 70-200mm HSM / 60-250mm and 50-150mm / 50-135mm to see that
HSM is the same type of motor as SDM so what's your point?
It actual proves that sonic motors can be fast as well.

Pentax seem more aimed to focus precision and manual focus throw then autofocus speed.
04-11-2012, 02:32 AM   #13
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QuoteOriginally posted by Anvh Quote
the DA18-135 use DC, different type of motor.
DC is a brushless elctro motor SDM is a sonic motor, one uses magnetism the other uses vibration/friction to produce movement.

The last lens with SDM was the DA*60-250 i believe or the DA*55, pentx said in an interview that DC was for budget market but that they will keep using SDM for the pro market.
Sorry Stefan .. changed it just before your post.

I have changed the post as I wasn't being particularly clear. There have been no SDM lenses released since before the 18-135mm, the last being the 55mm.
04-11-2012, 02:32 AM   #14
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QuoteOriginally posted by Mike.P Quote
And SDM isn't powerful enough in it's present form.
You only have to compare focus speeds between the Sigma 70-200mm HSM / 60-250mm and 50-150mm / 50-135mm to see that
I thought that would be matter of gearing rather than power of the motor itself...
04-11-2012, 02:35 AM   #15
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QuoteOriginally posted by Anvh Quote
HSM is the same type of motor as SDM so what's your point?
It actual proves that sonic motors can be fast as well.

Pentax seem more aimed to focus precision and manual focus throw then autofocus speed.
My point is that you get both with the Sigma lenses.
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