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07-10-2009, 12:35 PM   #1
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K 3.5/28 vs. M 3.5/28

For those who have both the "K" and "M" version of the 3.5/28: is the K noticeably better? I currently have the M but I'm always looking out for the K (I already have the 2.5/135). But they sell almost twice the price of the M. Is it worth it? I'm pretty happy with the M: very good resolution, good edge performance, pretty contrasty and built to last. More resolution/sharpness is always tempting and that's what the K seem to offer compared to the M-line. According to this (http://www.takinami.com/yoshihiko/photo/lens_test/pentax_28-30.html) site the K almost reaches the A 1.7/50's resolution (which I have and which I find really sharp).

Oh, and a subquestion: can the Vivitar 28mm f/2.0 Close Focus keep up with these lenses in terms of sharpness and rendering?
I also have the Sigma 24mm f/2.8 Macro (1:4) without AF and I don't find it as good as the reviews on here made me believe it is. Contrast not even as good as my 18-55 II, not reasonably sharper edges, suffers heavily from flare.

The Vivitar gets similar ratings on here - so what do I have to expect?
Sigma: PentaxForums.com Third-Party Pentax Lens Review Database - 24mm f2.8 Super Wide II
Vivitar (f/2.8 version): PentaxForums.com Third-Party Pentax Lens Review Database - 28mm f/2.8 Close Focus


07-10-2009, 02:37 PM   #2
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I have both, in addition to the screwmount M42 SMC version, which is the K version in a different mount. The M mount 28 is an excellent lens in & of itself. The problem lies in the fact that the K & M42 versions are superb, one of the best Pentax lenses ever, & one of the best 28s manufactured by any company at any time. There happens to be two examples up on Ebay now, both Buy-It-Now offerings, one for $149, the other $199. The M42 versions, by the way, which go for less than the price of the K version, are also presently represented on Ebay in at least two auctions.

The other lenses you mentioned I have no experience with.

Last edited by raymeedc; 07-10-2009 at 04:21 PM.
07-11-2009, 09:14 AM   #3
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I wanted to keep it K-mount so M42 lenses aren't really an option (also you can't control the aperture from the camera which is possible on K-mount lenses).

So you say the (M42 and) "K" series 28mm is indeed better than the M-line. But is it clearly better?

I know finding the M42 version is quite easy, there are a lot to choose from.
But $149-199 is far more than I willing to spend on this lens. It seems these lenses get much more expensive in the US than they do here. A few months ago I found a "K" 3.5/28 which was sold for ~40/$56 - usual sales prices are around 70/$100.
07-11-2009, 09:40 AM   #4
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QuoteOriginally posted by Egg Salad Quote
[FONT="Verdana"][SIZE="2"]For those who have both the "K" and "M" version of the 3.5/28: is the K noticeably better?
It's noticeably bigger. The K version is such a big lens for its numbers. I think the M28/3.5 is really good, and gets overlooked because it's not the K version.

QuoteOriginally posted by Egg Salad Quote
Oh, and a subquestion: can the Vivitar 28mm f/2.0 Close Focus keep up with these lenses in terms of sharpness and rendering?
The Vivitar will be unmatched below f3.5! Based on my Vivitar (Kiron) 28mm f2.0 non-close focus, compared to my Pentax-F 28mm f2.8, I don't think the Vivitar will be as sharp in apertures they share. The K28/3.5 is supposed to be sharper than the A or F lenses, and my F28/2.8 is sharper than my Vivitar, though only in the corners (APS-C corners). My Vivitar also has a lot of flare, compared to about none for the F28/2.8. It's not a terrible lens by any means: center sharpness is great, and there are a lot of uses for f2.0-f2.8. The Close Focus version is made by Komine, and is possibly better, but similar coatings so I wouldn't expect less flare.

Here's a lens test I did at 28mm:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/61891-28mm-len...-pentaxes.html

QuoteOriginally posted by raymeedc Quote
I have both, in addition to the screwmount M42 SMC version, which is the K version in a different mount.
I am pretty sure that's not true. A couple of sources list the Super-Multi-Coated Takumar 28mm f3.5 as having 7 elements, and the SMC Pentax 28mm f3.5 as having 8. Plus the size difference. Yes, a lot of Takumars were simply given a new mount and bumped up to 52mm filter size, but I think the 28/3.5 is an exception.

07-11-2009, 10:23 AM   #5
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QuoteOriginally posted by Egg Salad Quote
I wanted to keep it K-mount so M42 lenses aren't really an option (also you can't control the aperture from the camera which is possible on K-mount lenses).
You can NOT control the aperture with the camera on K or M lenses, only "A" and newer generations. You will still have to manually set the aperture with the ring.

Another plus for M42 lenses is that you can use them in AV mode ( you will most likely have to take some test shots and apply some exposure compensation to get exposure right. )
07-11-2009, 11:43 AM   #6
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Size and weight is not an issue. Even it would weight 1.5kg/3lbs I wouldn't care as long as the performance is right.

And yes, it's not that much of a surprise the f/3.5 pentax lenses can't keep up at f/2.
But that's the reason I'm also looking for the Vivitar - the Pentax is good but not really fast. So the Vivitar (or any other f/2 lens) would be a useful complement.

I overlooked this but yes, the "K" 3.5/28 was a new developed lens from the M42 version.

It seems that's something only I have tried but you can control the aperture of pre-A-lenses by your camera. I'm still working on it but probably a guide on how-to will be here soon.
In short: You need the alu-foil-A-pin-shortcut-trick and some aperture lever modification (non-destructive) to make it work perfectly. But let me say I use both the said 3.5/28 and the 2.5/135 in full auto mode - including automatic aperture control.

Dave, I've already read your test (I was visiting this site months before I registered) but I didn't know the F 28 is somewhat compareable to the M and "K". The Komine made lenses are said to be better than the Kiron made so I don't know whether the Vivitar K12s performance is meaningful if you want to know the K01s. Anyways the Vivitar Close Focus gets a very positive rating here: http://noisetheatre.blogspot.com/2008/09/on-test-vivitar-28mm-120-close-focus.html

Last edited by Egg Salad; 07-11-2009 at 11:56 AM.
07-11-2009, 03:45 PM   #7
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QuoteOriginally posted by Just1MoreDave Quote


I am pretty sure that's not true. A couple of sources list the Super-Multi-Coated Takumar 28mm f3.5 as having 7 elements, and the SMC Pentax 28mm f3.5 as having 8. Plus the size difference. Yes, a lot of Takumars were simply given a new mount and bumped up to 52mm filter size, but I think the 28/3.5 is an exception.
Yes, that's true..... my mistaken recollection.
07-11-2009, 04:03 PM   #8
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QuoteOriginally posted by Egg Salad Quote
Size and weight is not an issue. Even it would weight 1.5kg/3lbs I wouldn't care as long as the performance is right.

And yes, it's not that much of a surprise the f/3.5 pentax lenses can't keep up at f/2.
But that's the reason I'm also looking for the Vivitar - the Pentax is good but not really fast. So the Vivitar (or any other f/2 lens) would be a useful complement.
That's how I use mine, as a complement, with the Pentax-F 28/2.8 for AF and cool camera features. I also can't decide which to sell.

QuoteOriginally posted by Egg Salad Quote
It seems that's something only I have tried but you can control the aperture of pre-A-lenses by your camera. I'm still working on it but probably a guide on how-to will be here soon.
In short: You need the alu-foil-A-pin-shortcut-trick and some aperture lever modification (non-destructive) to make it work perfectly. But let me say I use both the said 3.5/28 and the 2.5/135 in full auto mode - including automatic aperture control.
Some others have tried it, with some claims of success and others of failure. Based on those reports, I think an f3.5 lens would be a good candidate to work.

QuoteOriginally posted by Egg Salad Quote
Dave, I've already read your test (I was visiting this site months before I registered) but I didn't know the F 28 is somewhat compareable to the M and "K".
I used to have a Pentax-A 28mm f2.8 and a Pentax-M 28mm f3.5. The Pentax-M was definitely better. My current Pentax-F 28/2.8 is supposed to be the same as the A model in an AF package, so I assume both the M and K f3.5 models are better than the F28/2.8.

QuoteOriginally posted by Egg Salad Quote
But $149-199 is far more than I willing to spend on this lens. It seems these lenses get much more expensive in the US than they do here. A few months ago I found a "K" 3.5/28 which was sold for ~40/$56 - usual sales prices are around 70/$100.
I'm sure I saw some K28/3.5s sell for less than $100 a couple of weeks ago.

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