Sorry, I missed this question. I did this the day after Christmas....so it's a little hazy in my memory. I'm pretty sure I manually focused using live view, even with the zoom. That's why the f/8 problem is hard to explain. Maybe I just slipped on that one.
I agree with everything you say about the Pentax. I wouldn't mind a few more over designed landscape oriented lenses, even if they are a little slow.
It will be interesting to see how the FE 28mm performs. It's not a Sony/Zeiss, not even sure it's one of their G lenses.
-Tim
Tariq Gibran wrote:
Did you pick the same spot(per the primes) and manually focus the FE zoom in these tests or did you rely on AF (which you mentioned could be a little wonky)?
That Pentax impressed me not only with distant/ scenic shots stopped down but even wide open at closer distances photographing people, etc. It's an over designed lens to be just F3.5 and it shows in the huge central sweet spot compared to other Alt lenses at brighter F-stops).
It is not the more recent, smaller/ compact "M" version, which is more readily available. Beyond the obvious size difference, the way to tell them apart is that this less desirable M version will show "Pentax-M" around the filter ring. The original K version will not (it will look like the picture I posted above).
Here is the page for the small/compact "M" version: http://www.pentaxforums.com/lensreviews/SMC-Pentax-M-28mm-F3.5-Lens.html
You're very welcome Tim. Telling the older Pentax lens options apart from one another can quickly become confusing as there are so many variations and designs.
Tariq Gibran wrote:
You're very welcome Tim. Telling the older Pentax lens options apart from one another can quickly become confusing as there are so many variations and designs.
The copy i bought is the "less desirable" M version. i like the look of Tim's K version so i will pursue finding one. i don't see getting to play with the M version for a bit as a loss because the reviewers of the M express some passion for the color that it gives and i expect to learn a bit before i sell it if i do.
amplexis wrote:
The copy i bought is the "less desirable" M version. i like the look of Tim's K version so i will pursue finding one. i don't see getting to play with the M version for a bit as a loss because the reviewers of the M express some passion for the color that it gives and i expect to learn a bit before i sell it if i do.
It may turn out to be a really nice lens. The difference between it and the older version will most likely show up on full frame at the borders and corners.
amplexis wrote:
The copy i bought is the "less desirable" M version. i like the look of Tim's K version so i will pursue finding one. i don't see getting to play with the M version for a bit as a loss because the reviewers of the M express some passion for the color that it gives and i expect to learn a bit before i sell it if i do.
are you shooting ff? if so, don't jump the gun on selling that lens, because it's a good piece of glass for landscapes, at ~f/10 on ff... f/11 on just about every wide prime that i've put on the a7r starts showing resolution loss in the center, due to mild diffraction.
here is a five-way 28mm lens test that i did on the a7r, shooting a landscape at medium distance... you can see how this little m28/3.5 more than holds its own, in terms of field curvature: 28mm lens tests
osv2 wrote:
are you shooting ff? if so, don't jump the gun on selling that lens, because it's a good piece of glass for landscapes, at ~f/10 on ff... f/11 on just about every wide prime that i've put on the a7r starts showing resolution loss in the center, due to mild diffraction.
here is a five-way 28mm lens test that i did on the a7r, shooting a landscape at medium distance... you can see how this little m28/3.5 more than holds its own, in terms of field curvature: 28mm lens tests
Jman13 wrote:
Have you used the FD 28/2.8? I'd love to know how it compares. I'm thinking of picking up an A7 II and using it as a digital FD body (I already have the FD 35/2, 50/1.4, 55/1.2, 85/1.8, 200/2.8 and 70-210/4 and 50-300/4.5L zooms. Just need a wide prime or two. ) Probably will get the 24/2.8, but also thinking of the 17 or 20 combined with the 28/2.8 since it's so cheap and has a great rep. I'm reviewing the a7II and 16-35 right now and like them both, but won't be investing too much in native lenses since it would be more for deliberate landscape shooting. My Fuji kit would remain my main daily carry. ...Show more →
I've got the 28mm f2.8 FD lens (nFD version) and I can't say that it's a very impressive lens. Even at f11 at infinity the edges and corners aren't good, but I might have a bad copy. The center is decent wide open (doesn't get much sharper stopped down), but it will lose out to my Contax 35mm f2 lens which is smaller and very sharp all over stopped down to f11, if not the best wide open. I can try and get some infinity samples tomorrow if you would be interested.
Tariq Gibran wrote:
Just out of curiousity, what part of the frame are these comparative "slices" taken from? Any corner comparisons?
the slices are all dead center; all of the glass that i've tested so far, at all focal lengths, has been focused on the "5610" street number, on the back of the building.
so many of these wide lenses have failed on the sides, without even looking at the corners... i'm nearly to the point where i have enough lenses with clean sides, to start comparing corner slices on those.
I recently became a bit obsessed with getting a nice copy of the Pentax 31mm Ltd. The first copy I bought was an early first batch MIJ specimen. In general use, it performs great and when tested with a resolution chart at a closer distance, it was sharp corner to corner. Oddly though, tested at infinity as used for a typical landscape, the corners and borders were just not what I would hope for. Maybe Pentax designed the first batch to "test" well on charts.
Fast forward to last week when I came across a MIJ copy that appeared to be a never used, NIB, though listed as Mint, but from a later production batch. I couldn't resist just seeing how it compared to the first copy on my A7r, as well as how it compares to the Pentax 28mm 3.5K which Tim has tested here. Turns out the earlier copy tested better on the resolution chart across the frame (at a distance of only about 3ft) but the newer version was clearly better at distance into the corners and borders. Even though this lens is a floating element design, apparently there is still some room for tweaking for one distance vs another.
With all that out of the way, here are links for the comparison of the later version Pentax 31Ltd to the Pentax 28/3.5 K on my A7r. Tripod mounted, same adapter (Rayqual) no additional sharpening in conversion through ACR. This also shows the difference in aspect ratio between the two lenses. The F-stop is indicated by the last number in the file name.
not a totally fair comparison because of the differences in focal length, but at f/11, the 31ltd pretty much blows the 28/3.5 away on that left side, and is also stronger on the right side.
at f/8 the differences are more dramatic, to the point that i'm wondering if the 28/3.5 is a bit weak on the left side... but then there are also bigger differences on the right side at f/8... wow.
did you refocus at every aperture?
looks like that 28/3.5 should be headed for ebay :-0
thx a bunch for posting that, 100% size is the only way to go, be it full pics or crop.
osv2 wrote:
not a totally fair comparison because of the differences in focal length, but at f/11, the 31ltd pretty much blows the 28/3.5 away on that left side, and is also stronger on the right side.
at f/8 the differences are more dramatic, to the point that i'm wondering if the 28/3.5 is a bit weak on the left side... but then there are also bigger differences on the right side at f/8... wow.
did you refocus at every aperture?
looks like that 28/3.5 should be headed for ebay :-0
thx a bunch for posting that, 100% size is the only way to go, be it full pics or crop....Show more →
No, I did not refocus. I will need to examine my earlier shots with the Pentax 28 as it has always performed well across the frame. As Tim has mentioned with his 28 + the rayqual adapter, I found that mine was right at the hard stop when focused on the middle medium distance tree. It may be that a different adapter that allows for a tiny bit more room to focus further might improve that left side. I don't know though since if one looks at the center and distant objects, things are sharp even wide open at 3.5. It may be we are seeing some sort of dip in sharpness in say zone B with the 28. The 31 is pretty much uniformly sharp.
The 31 looks very nice Tariq. I picked up another SMC 28mm 3.5 K and it doesn't perform quite as well as the one I tested here.
That left side does look a little suspicious, maybe a little like mine when I use the Rayqual. I wish you weren't so far away Tariq, I'd love to compare our copies.
tsdevine wrote:
The 31 looks very nice Tariq. I picked up another SMC 28mm 3.5 K and it doesn't perform quite as well as the one I tested here.
That left side does look a little suspicious, maybe a little like mine when I use the Rayqual. I wish you weren't so far away Tariq, I'd love to compare our copies.
-Tim
Yeah, it would be great to compare them together. I may do a test using a different adapter on the 28 as, like mentioned, the Rayqual may be just shy of true infinity focus with the 28 and/ or may just not play well with that lens for some reason. The 31 actually focuses a tiny bit past infinity with the Rayqual.
Here is the same 28/3.5K using a different adapter at F8 taken with the A7r. I'm not 100% sure but there may be a hint of softness at distance in one of the mid frame zones of the image. Things seem to sharpen back up at the border though. It might be interesting for you to test you 28 K at a further distance and see how it behaves. Unfortunately, this scene no longer exists due to development so I can't use it for a direct comparison with the 31 now. PK28F8 by tariqgibranstudio, on Flickr
