Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-22-2010, 01:51 AM   #1
Veteran Member




Join Date: Aug 2009
Posts: 381
pentax m f3.5 28mm

Is there a significant difference in the optical performance of the pentax m f3.5 28mm versus the f2.8 version, please? In fact, is there a difference between the IQ of the two versions of the f2.8 M? I note that the f2.8 v1 was noted for being lightweight and compact in the Pentax brochure, whereas the f3.5 stood out for price, resolution and contrast. Has anyone tested the variations side by side?

07-22-2010, 02:43 AM   #2
Veteran Member




Join Date: Jul 2009
Location: Berlin, Germany
Posts: 344
I suggest you to compare them in the lens review section. The f/3.5 is still regarded the better choice and there isn't much bad to be said about it.
I never had the f/2.8 version but the f/3.5 - which, used as it was intended is a great lens.

Pentax Lens Review Database - SMC Pentax-M 28mm F2.8 Lens Reviews
Pentax Lens Review Database - SMC Pentax-M 28mm F3.5 Lens Reviews
07-22-2010, 04:36 AM   #3
Veteran Member




Join Date: Aug 2009
Posts: 381
Original Poster
Yeah, I checked the reviews, and also searched the forum for a discussion of this. I added a review in a while ago for the f2.8 version 1, I am the third review from the end. I am interested in a head to head comparison. On the Takinami website, I see the f2.8 reaches a higher resolution than the f3.5:
http://www.takinami.com/yoshihiko/photo/lens_test/pentax_28-30.html
And in the Stan Halpin website there is some discussion of the testing of the 28mm's
Brief Comments
07-22-2010, 09:32 AM   #4
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
There's no getting around the fact that most people who have compared subjectively seem to prefer the 3.5 (as evidenced on Stan's site), but Yoshihiko's numbers do kind of suggest otherwise. My own quick haphazard comparison using my 2.8 and a borrowed 3.5) suggests that whatever difference there is, it's too small for me to care about.

The K (as opposed to M) version does better in the numbers, and indeed, most people call that the best of the bunch. But it's harder to find, usually more expensive - and also quite a bit heavier. Personally, if I were going that route, I'd hold out for the even better and slightly faster (yet somehow lighter) K30/2.8.

But as cheap and easy to find as the M's are - both f/2.8 and f/3.5 versions - and as good as they both are already - I'd be more inclined to just get one of those. If you're *really* looking to step us, there are always the M and A 28/2's.

07-22-2010, 10:08 AM   #5
Veteran Member




Join Date: Aug 2009
Posts: 381
Original Poster
Thanks, thats what I need to hear. I'll skip the f3.5 altogether and keep an eye out for the f2 Of interest, the lens diagram on Boj's website for the M 28mm f2: its wrong, unless the formula changed since the pulication of the Pentax marketing material. Looking in the Pentax brochure for the 28mm f2, its lens diagram is very similar, nearly identical, to the current Zeiss Distagon T* 2/28 10 element 8 group design.

EDIT: my mistake, thats the K 28mm f2 which I saw has the same layout as the Zeiss Distagon

Last edited by whojammyflip; 07-22-2010 at 10:26 AM.
07-22-2010, 08:09 PM   #6
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,416
QuoteOriginally posted by hoojammyflip Quote
...EDIT: my mistake, thats the K 28mm f2 which I saw has the same layout as the Zeiss Distagon
And that is one reason why the lens is so highly sought after.

Steve
07-23-2010, 05:02 AM   #7
Veteran Member




Join Date: Jul 2009
Location: Berlin, Germany
Posts: 344
Have you thought about the Vivitar alternative? I never used one (because I never had it) but it is highly regarded.
If you can find a Vivitar 28mm f/2.0 close focus you get several things at once no Pentax lens of that price will - obviously the joys of bright aperture but also a reproduction ratio of something around 1:4 (near limit is at 23cm/ 0.8ft).
More expensive than the M series lenses but still much more affordeable than the Zeiss clone.
07-23-2010, 06:07 AM   #8
Veteran Member




Join Date: Aug 2009
Posts: 381
Original Poster
For the low cost of it, buying the M 28 f3.5 and trying it out cannot hurt. I did something like this before when I was trying out longer lenses, and bought something like 5 tele lenses together for a head to head contest. Something startled me: aspects of the lenses I had not considered important, as they are consistent within the M series, started to matter. For example, colour balance, aperture ring movement, focus ring direction, heft.

Maybe a cheap way of improving the current 28mm I have is to get an old Takumar hood and tailor it to fit the FOV of the 28mm f2.8.

07-23-2010, 08:11 AM   #9
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
What's odd is that it's the M, not the K, version of the 28/2 that produces the much more amazing results in Yoshihiko's tests.

As for a hood on the M28/2.8, I tried a number of different unsatisfactory options (either ineffective, or produced vignetting) before happening on one that works wonderfully: the DA70 hood in its collapsed position.
07-23-2010, 08:33 AM   #10
Veteran Member




Join Date: Aug 2009
Posts: 381
Original Poster
Yeah, Ive been thinking the hood route could be a cheap way to improve the performance of a lens, although the veiling flare effect is more pronounced I believe with tele lenses. I picked up a Takumar 135mm hood this week for my M 135mm (its nearly 6cm long and fits the FOV perfectly, with digital sensors, you could use a 9cm hood on a M 135) and am very impressed at the internal design of the hood: ridged matt surface with velvet at the back. Definitely not equivalent to a rubber multi hood. I plan on taking another and cutting it down to length.
07-23-2010, 11:56 AM   #11
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
Flare is pretty common with wide angles too - it's that much more likey the sun is in or near the field. I used my hand a few times as a stop gap hood with my 28 and was shocked at how big a difference it made, which is what put on me my quest to find a hood.

I suspect buying a few stepping rings of the right size, as some others have discussed doing, would work well. It would take trial and error in the camera store to find the right combination, but if the employees don't object, that's probably what I'd do - assuming you don't just get a DA70 to solve the problem :-).
07-23-2010, 03:39 PM   #12
Site Supporter
gofour3's Avatar

Join Date: Oct 2008
Location: Vancouver, Canada
Posts: 5,334
QuoteOriginally posted by Marc Sabatella Quote
What's odd is that it's the M, not the K, version of the 28/2 that produces the much more amazing results in Yoshihiko's tests.

As for a hood on the M28/2.8, I tried a number of different unsatisfactory options (either ineffective, or produced vignetting) before happening on one that works wonderfully: the DA70 hood in its collapsed position.
The K28/2 is a little like the A & K/50/1.2, it’s not about sharpness. The K50/1.2 excels with its unique bokeh and the K28/2 excels when close focusing. That when the floating elements kick in and you get amazing aberrations free results. (3d like images) Both are specialty lenses and have sweet spots that you have to discover on your own.

Of course whether you need these unique features at the price these two lenses fetch is another matter.

Phil.
07-23-2010, 04:02 PM   #13
Veteran Member
Pentaxor's Avatar

Join Date: May 2009
Location: Vancouver, B.C.
Photos: Gallery
Posts: 6,513
QuoteOriginally posted by Marc Sabatella Quote
There's no getting around the fact that most people who have compared subjectively seem to prefer the 3.5 (as evidenced on Stan's site), but Yoshihiko's numbers do kind of suggest otherwise. My own quick haphazard comparison using my 2.8 and a borrowed 3.5) suggests that whatever difference there is, it's too small for me to care about.

The K (as opposed to M) version does better in the numbers, and indeed, most people call that the best of the bunch. But it's harder to find, usually more expensive - and also quite a bit heavier. Personally, if I were going that route, I'd hold out for the even better and slightly faster (yet somehow lighter) K30/2.8.

But as cheap and easy to find as the M's are - both f/2.8 and f/3.5 versions - and as good as they both are already - I'd be more inclined to just get one of those. If you're *really* looking to step us, there are always the M and A 28/2's.
I noticed the numbers as well. if we are going to go by the numbers, the M version would be the better lens. however, the question is, would those numbers show a much better image rendering or image illustration?

as was discussed before, the K28/2 is supposedly a wide portrait lens where sharpness is not it's purpose that is fast and has a shallow DOF. it would be the opposite of the K28/3.5 which is a wide sharp lens where it is primarily good for subjects of a more solid DOF. I would say the Yoshihiko numbers are pretty consistent to how the lenses are performing in real world.

this might be the reason why the K28/2 is much preferred over the M28/2. the M28/2 is as fast and maybe sharper than the K28/2 all over. but this made the lens less desirable because it doesn't have that certain image effect that the K28/2 has. the floating element could be the main factor here.

if I ever get some mad money, I might buy the CZ version instead since the K28/2 is really pretty scarce and I had let one slip by recently at a pretty decent and affordable price.
07-24-2010, 06:26 AM   #14
Veteran Member




Join Date: Aug 2009
Posts: 381
Original Poster
One thing which confuses me is how the front element on the M f3.5 is significantly larger than the f2.8, but it ends up being a slower lens.

I am a bit sceptical about lens testing using film. There are so many variables involved. Apparently, aerial resolution is the only pure test of a lens, where a microscope is placed behind the rear element and no film is involved.
07-24-2010, 09:00 AM   #15
Veteran Member
Pentaxor's Avatar

Join Date: May 2009
Location: Vancouver, B.C.
Photos: Gallery
Posts: 6,513
QuoteOriginally posted by hoojammyflip Quote
One thing which confuses me is how the front element on the M f3.5 is significantly larger than the f2.8, but it ends up being a slower lens.

I am a bit sceptical about lens testing using film. There are so many variables involved. Apparently, aerial resolution is the only pure test of a lens, where a microscope is placed behind the rear element and no film is involved.
having a larger element doesn't necessarily mean faster f-stops. e.g. telephoto lens versus standard lens. f-stop brightness or light gathering ability of the lens depend on the whole optical design.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
28mm, f2.8, f3.5, k-mount, pentax, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Super Takumar 28mm f3.5 vs Pentax-F 28mm f2.8? cheekygeek Pentax SLR Lens Discussion 12 10-16-2009 04:53 PM
Just for fun - Takumar 28mm vs Pentax-F 28mm vs Pentax-FA 31mm ltd thePiRaTE!! Pentax SLR Lens Discussion 6 09-16-2007 01:35 AM



All times are GMT -7. The time now is 03:37 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top