Disappointed with Pentax-A 2.8/28mm

fwcetus · 09-13-2015, 05:34 AM

Originally posted by Iberia

Hi,

I have bought a Pentax-A 2.8/28mm: the glass is clean, as are the blades and the focus ring is nicelly stiff but the image quality was a major disappointment.
Center is sharp but corners are soft/fuzzy at all apperture settings wider than f/11...the DA 21mm isn't particularly sharp in the corners either but it's definitelly not as bad.
Could this be a bad copy?

I was planning to get a Pentax-A 50mm next but I now feel like giving up on Pentax-A lenses altoghether.

Cheers,
Ric

The A 28/2.8 is, unfortunately, not exactly a star in the A series lineup -- it is known to be somewhat mediocre (which is NOT to say that it can't make useful images). Furthermore, I would definitely not judge an entire line from any one lens (in this case, from one that is not truly representative) -- there are some ~excellent~ A lenses (some carryovers from some M lenses, or even from K lenses), while some were brand new designs.

And, you just ~might~ have a bad copy of a not-so-great-to-start-with lens, one that, by your description, might have decentering issues.

Now, I suppose the next thing you could do is to get an A 50/2 for that "Pentax-A 50mm" you're planning on maybe getting, and then you'll think all A 50's are mediocre, too. [However, I do think the A 50/2 is actually better than the M 50/2, but that's another story.]

As has been suggested, take a look at some reviews -- Pentax A Prime Lenses - Reviews and Specifications - SLR and Interchangeable Lenses - Pentax Lens Reviews & Lens Database

However, I will defend your use of a brick wall for some useful lens testing -- sure, "it's not really photography", but it IS one useful way to quickly learn about SOME features of a particular lens. [However, there has to be a better brick wall to shoot somewhere near you than one with such worn, dull bricks, and with some of the bricks in a different plane than the rest of the bricks.]

Last edited by fwcetus; 09-13-2015 at 06:06 AM.

manntax · 09-13-2015, 05:44 AM

If we talking about a SMC-A 28mm then I would repeat tests with focus bracketing ( just to avoid possible field curvature problem) because my copy is definitely sharp sharp, stopped down really excels.

fwcetus · 09-13-2015, 05:57 AM

Originally posted by manntax

If we talking about a SMC-A 28mm [...]

But which "SMC-A 28mm"? (The A 28/2.8 is not the same as the A 28/2.)

In any event, the A 28/2.8 reviews on this forum site are "all over the place" with opinions of the design's IQ, so perhaps this is just one lens model that is not as consistent in quality, from lens to lens, as are many other lens designs. (?)

**interested_observer** · 09-13-2015, 06:04 AM

Originally posted by Iberia

Would the FA 28mm perform better or should I skip that as well and go for a Contax or a Leica?
I used the Contax SLR system for over a decade in the film days and the image quality was quite good...

Ric

Do you still have any of your Contax lenses? If so, you can use the Leitax.com remounting kits to convert your lenses from the C/Y to the K mount. It's reversible and does not harm/damage the lens. It does need the MM version of the C/Y mount.

I have converted two, the 28 and the 85.

manntax · 09-13-2015, 06:05 AM

Originally posted by fwcetus

But which "SMC-A 28mm"?

'SMC Pentax-A 28mm F2.8' - my copy closely matches my SMC-F 28 f2.8 and Kiron 28 F2

Iberia · 09-13-2015, 06:24 AM

Originally posted by interested_observer

Do you still have any of your Contax lenses? If so, you can use the Leitax.com remounting kits to convert your lenses from the C/Y to the K mount. It's reversible and does not harm/damage the lens. It does need the MM version of the C/Y mount.

I have converted two, the 28 and the 85.

Unfortunately I sold the 2,8/25mm (along with the 1,4/85mm and the 4/80-200mm) which would have been just right FOV wise.
I will try to get one from e-bay.

Cheers,
Ric

**Kerrowdown** · 09-13-2015, 06:37 AM

Originally posted by Iberia

It is quite unacceptable, that is why I started this topic.

Good luck on your quest of finding a "tack sharp" centre, edge to edge and corner to corner wide angle lens.

Originally posted by Iberia

I need a high performing lens with 24mm or 28mm focal length for a Pentax body, preferably manual focus for the reason stated above

Please do come back and advise us all of your final solution and findings, as I feel sure we can all benefit from your research.

**UncleVanya** · 09-13-2015, 08:25 AM

FA* 24 will not disappoint. FA limited 31 will not disappoint. The A version 28 isn't great. The 28 f2 in the K version is one of finest 28mm lenses ever made.

**interested_observer** · 09-13-2015, 08:37 AM

Originally posted by Iberia

Unfortunately I sold the 2,8/25mm (along with the 1,4/85mm and the 4/80-200mm) which would have been just right FOV wise.
I will try to get one from e-bay.

Cheers,
Ric

Zeiss stopped making the ZK line (with the K mount). However, you can still find ZK lenses around - either old stock, or used. I have a ZK 25/f2.8 that I like very much. Converted Contax lenses are still the affordable way to go compared to the Zeiss ZK's - even considering the cost of remounting.

The old K 28/f2 is exactly the same as the famous Zeis 28mm/f2 Distagon lens. It was part of the Zeiss/Pentax partnership.

Nick Siebers · 09-13-2015, 08:49 AM

I have the Zeiss ZK 28/2. It is a much larger lens than the A 28/2.8, so may not be as convenient for zone focus street shooting. I haven't really tested it corner to corner, either. It is remarkably sharp, though, even wide open.

I also have an M 28/ 3.5, which has many desirable features for a street shooting lens. It requires stop down metering, though, so may not suit the OP.

The Sigma Super Wide II is a 24mm f/2.8 lens with very nice optical properties, and the A setting. Some even have AF. Back when I had one it was better than the DA 21 wide open and/or up close. It didn't improve as much with stopping down, though, and I again didn't really assess the corners. The Miniwide 28/2.8 is also an option, comes with "a" setting in the II version, but not quite as good.

bassek · 09-13-2015, 09:28 AM

I am quite happy with my A24/2.8. Too wide maybe...

Seb

ChristianRock · 09-13-2015, 12:14 PM

I've had two different Pentax 28mm 2.8 SMC lenses - A and M. Sold both after I got my Rikenon XR 28 2.8 - the Rikenon was a lot sharper especially wide open.

tibbitts · 09-13-2015, 02:07 PM

Having just come from photographing a brick wall, I take issue with the comments about using one for testing. Admittedly it's not as good as a giant office-building-sized resolution test chart, but where are you going to find one of those?

Many of us do actually photograph buildings head-on, but also walls of foliage, horizons with grass or trees, etc. and it really is critical that all the parts of the image be sharp. Nobody expects that a lens will have optimal sharpness corner-to-corner, especially before stopping down, but at some point you do need good sharpness all across the frame, and testing with a brick wall (both up-close and at a distance) is effective. Sometimes I'll also test with street signs, but then I generally need 4 images (1 for each corner of the image) vs. 1 for a large brick building.

**todd** · 09-13-2015, 03:33 PM - **3 Likes**

I have this lens and shot it for almost exclusively for a month straight in the July "Single In" challenge here on the board, and have no complaints with it (though i will opt for my FA31 most of the time). I don't pay attention to corner performance though and DA15 is one of my fave lenses... The only time I would pay attention to corner performance is if something really caught my eye as a problem when looking at an image, and I've never had that happen... I don't have to care though. Just an unprofessional here using the lenses I have to make the best images I can with them for fun...

Some from July with this lens (none on a tripod)...

f/5.6

f/4

f/5.6

f/4

f/2.8

f/7.1

f/3.2

**Just1MoreDave** · 09-13-2015, 03:35 PM

I have taken lots of brick wall shots with my Pentax-F 28/2.8 which has the same optical formula, and a Pentax-A 28/2.8, usually 10-15 feet away. I think your shots should have been sharper in the corners. I do see some complaints about the Pentax-A 28/2.8 sharpness and they are typically like this thread. Some have trouble and some report no trouble. No one has ever suggested a solution besides another lens. There are certainly plenty of 28s out there to try.

09-13-2015, 05:57 AM	#18
fwcetus Site Supporter Join Date: Sep 2006 Location: New England Photos: Gallery \| Albums Posts: 1,286	Originally posted by manntax If we talking about a SMC-A 28mm [...] But which "SMC-A 28mm"? (The A 28/2.8 is not the same as the A 28/2.) In any event, the A 28/2.8 reviews on this forum site are "all over the place" with opinions of the design's IQ, so perhaps this is just one lens model that is not as consistent in quality, from lens to lens, as are many other lens designs. (?) Last edited by fwcetus; 09-13-2015 at 06:06 AM.

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09-13-2015, 05:34 AM	#16
fwcetus Site Supporter Join Date: Sep 2006 Location: New England Photos: Gallery \| Albums Posts: 1,286	Originally posted by Iberia Hi, I have bought a Pentax-A 2.8/28mm: the glass is clean, as are the blades and the focus ring is nicelly stiff but the image quality was a major disappointment. Center is sharp but corners are soft/fuzzy at all apperture settings wider than f/11...the DA 21mm isn't particularly sharp in the corners either but it's definitelly not as bad. Could this be a bad copy? I was planning to get a Pentax-A 50mm next but I now feel like giving up on Pentax-A lenses altoghether. Cheers, Ric The A 28/2.8 is, unfortunately, not exactly a star in the A series lineup -- it is known to be somewhat mediocre (which is NOT to say that it can't make useful images). Furthermore, I would definitely not judge an entire line from any one lens (in this case, from one that is not truly representative) -- there are some ~excellent~ A lenses (some carryovers from some M lenses, or even from K lenses), while some were brand new designs. And, you just ~might~ have a bad copy of a not-so-great-to-start-with lens, one that, by your description, might have decentering issues. Now, I suppose the next thing you could do is to get an A 50/2 for that "Pentax-A 50mm" you're planning on maybe getting, and then you'll think all A 50's are mediocre, too. [However, I do think the A 50/2 is actually better than the M 50/2, but that's another story.] As has been suggested, take a look at some reviews -- Pentax A Prime Lenses - Reviews and Specifications - SLR and Interchangeable Lenses - Pentax Lens Reviews & Lens Database However, I will defend your use of a brick wall for some useful lens testing -- sure, "it's not really photography", but it IS one useful way to quickly learn about SOME features of a particular lens. [However, there has to be a better brick wall to shoot somewhere near you than one with such worn, dull bricks, and with some of the bricks in a different plane than the rest of the bricks.] Last edited by fwcetus; 09-13-2015 at 06:06 AM.

09-13-2015, 05:44 AM	#17
manntax Veteran Member Join Date: Jan 2012 Photos: Albums Posts: 1,972	If we talking about a SMC-A 28mm then I would repeat tests with focus bracketing ( just to avoid possible field curvature problem) because my copy is definitely sharp sharp, stopped down really excels.

09-13-2015, 06:04 AM	#19
interested_observer Loyal Site Supporter Join Date: Jun 2009 Location: Tumbleweed, Arizona Photos: Gallery \| Albums Posts: 5,707	Originally posted by Iberia Would the FA 28mm perform better or should I skip that as well and go for a Contax or a Leica? I used the Contax SLR system for over a decade in the film days and the image quality was quite good... Ric Do you still have any of your Contax lenses? If so, you can use the Leitax.com remounting kits to convert your lenses from the C/Y to the K mount. It's reversible and does not harm/damage the lens. It does need the MM version of the C/Y mount. I have converted two, the 28 and the 85.

09-13-2015, 06:05 AM	#20
manntax Veteran Member Join Date: Jan 2012 Photos: Albums Posts: 1,972	Originally posted by fwcetus But which "SMC-A 28mm"? 'SMC Pentax-A 28mm F2.8' - my copy closely matches my SMC-F 28 f2.8 and Kiron 28 F2

09-13-2015, 06:24 AM	#21
Iberia Senior Member Join Date: Dec 2012 Posts: 135 Original Poster	Originally posted by interested_observer Do you still have any of your Contax lenses? If so, you can use the Leitax.com remounting kits to convert your lenses from the C/Y to the K mount. It's reversible and does not harm/damage the lens. It does need the MM version of the C/Y mount. I have converted two, the 28 and the 85. Unfortunately I sold the 2,8/25mm (along with the 1,4/85mm and the 4/80-200mm) which would have been just right FOV wise. I will try to get one from e-bay. Cheers, Ric

09-13-2015, 06:37 AM	#22
Kerrowdown PEG Moderator Join Date: Aug 2008 Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake Photos: Gallery Posts: 57,818	Originally posted by Iberia It is quite unacceptable, that is why I started this topic. Good luck on your quest of finding a "tack sharp" centre, edge to edge and corner to corner wide angle lens. Originally posted by Iberia I need a high performing lens with 24mm or 28mm focal length for a Pentax body, preferably manual focus for the reason stated above Please do come back and advise us all of your final solution and findings, as I feel sure we can all benefit from your research.

09-13-2015, 08:25 AM	#23
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,401	FA* 24 will not disappoint. FA limited 31 will not disappoint. The A version 28 isn't great. The 28 f2 in the K version is one of finest 28mm lenses ever made.

09-13-2015, 08:37 AM	#24
interested_observer Loyal Site Supporter Join Date: Jun 2009 Location: Tumbleweed, Arizona Photos: Gallery \| Albums Posts: 5,707	Originally posted by Iberia Unfortunately I sold the 2,8/25mm (along with the 1,4/85mm and the 4/80-200mm) which would have been just right FOV wise. I will try to get one from e-bay. Cheers, Ric Zeiss stopped making the ZK line (with the K mount). However, you can still find ZK lenses around - either old stock, or used. I have a ZK 25/f2.8 that I like very much. Converted Contax lenses are still the affordable way to go compared to the Zeiss ZK's - even considering the cost of remounting. The old K 28/f2 is exactly the same as the famous Zeis 28mm/f2 Distagon lens. It was part of the Zeiss/Pentax partnership.

09-13-2015, 08:49 AM	#25
Nick Siebers Veteran Member Join Date: Jun 2008 Location: Madison, WI Photos: Gallery \| Albums Posts: 2,165	I have the Zeiss ZK 28/2. It is a much larger lens than the A 28/2.8, so may not be as convenient for zone focus street shooting. I haven't really tested it corner to corner, either. It is remarkably sharp, though, even wide open. I also have an M 28/ 3.5, which has many desirable features for a street shooting lens. It requires stop down metering, though, so may not suit the OP. The Sigma Super Wide II is a 24mm f/2.8 lens with very nice optical properties, and the A setting. Some even have AF. Back when I had one it was better than the DA 21 wide open and/or up close. It didn't improve as much with stopping down, though, and I again didn't really assess the corners. The Miniwide 28/2.8 is also an option, comes with "a" setting in the II version, but not quite as good.

09-13-2015, 09:28 AM	#26
bassek Pentaxian Join Date: Feb 2011 Photos: Gallery Posts: 706	I am quite happy with my A24/2.8. Too wide maybe... Seb

09-13-2015, 12:14 PM	#27
ChristianRock Pentaxian Join Date: Jul 2013 Location: People's Republic of America Photos: Gallery \| Albums Posts: 9,910	I've had two different Pentax 28mm 2.8 SMC lenses - A and M. Sold both after I got my Rikenon XR 28 2.8 - the Rikenon was a lot sharper especially wide open.

09-13-2015, 02:07 PM	#28
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,193	Having just come from photographing a brick wall, I take issue with the comments about using one for testing. Admittedly it's not as good as a giant office-building-sized resolution test chart, but where are you going to find one of those? Many of us do actually photograph buildings head-on, but also walls of foliage, horizons with grass or trees, etc. and it really is critical that all the parts of the image be sharp. Nobody expects that a lens will have optimal sharpness corner-to-corner, especially before stopping down, but at some point you do need good sharpness all across the frame, and testing with a brick wall (both up-close and at a distance) is effective. Sometimes I'll also test with street signs, but then I generally need 4 images (1 for each corner of the image) vs. 1 for a large brick building.

09-13-2015, 03:33 PM - 3 Likes	#29
todd Site Supporter Join Date: Jul 2008 Location: Arizona Photos: Gallery Posts: 6,791	I have this lens and shot it for almost exclusively for a month straight in the July "Single In" challenge here on the board, and have no complaints with it (though i will opt for my FA31 most of the time). I don't pay attention to corner performance though and DA15 is one of my fave lenses... The only time I would pay attention to corner performance is if something really caught my eye as a problem when looking at an image, and I've never had that happen... I don't have to care though. Just an unprofessional here using the lenses I have to make the best images I can with them for fun... Some from July with this lens (none on a tripod)... f/5.6 f/4 f/5.6 f/4 f/2.8 f/7.1 f/3.2

09-13-2015, 03:35 PM	#30
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	I have taken lots of brick wall shots with my Pentax-F 28/2.8 which has the same optical formula, and a Pentax-A 28/2.8, usually 10-15 feet away. I think your shots should have been sharper in the corners. I do see some complaints about the Pentax-A 28/2.8 sharpness and they are typically like this thread. Some have trouble and some report no trouble. No one has ever suggested a solution besides another lens. There are certainly plenty of 28s out there to try.