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03-30-2012, 10:14 AM   #1
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Pentax P-A 15mm F3.5 vs current glass?

Read up on the Pentax P-A 15mm F3.5 lens. But not much here and can't find any high quality sample photos or optical lab reviews.

How does the A-15mm compare to our current glass? Compare it to its digital equivalent 21mm 24mm...whatever it is?

I was looking for a Zeiss 21mm and was wondering how the Pentax A 15mm would do as a substitute for the Zeiss.

Thanks!

03-30-2012, 10:21 AM   #2
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SMC Pentax-A 15mm F3.5 Reviews - A Prime Lenses - Pentax Lens Reviews & Lens Database

Supposed it's pretty good. My understanding is that one of the manual 15mm lenses isn't so great on digital. I am not sure if it is the A-15mm or the K-15mm. I assume it's the K-15mm.
03-30-2012, 11:04 AM   #3
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QuoteOriginally posted by slackercruster Quote
Read up on the Pentax P-A 15mm F3.5 lens. But not much here and can't find any high quality sample photos or optical lab reviews.

How does the A-15mm compare to our current glass? Compare it to its digital equivalent 21mm 24mm...whatever it is?

I was looking for a Zeiss 21mm and was wondering how the Pentax A 15mm would do as a substitute for the Zeiss.

Thanks!
There is no "digital equivalent"... the A 15/3.5 is the same field of view as the DA 15/4. 15mm is 15mm, the field of view changes only when the camera sensor size changes, like going from APS-C to FF.

Comparing the A 15/3.5 to the DA 15/4 - and I don't have the A but I do have the DA - the A will likely having less contrast, less flare resistance, more warmth. This is do to the coatings of each lens. Modern coatings are generally cooler and more flare-resistant.
03-30-2012, 11:08 AM   #4
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QuoteOriginally posted by luftfluss Quote
There is no "digital equivalent"... the A 15/3.5 is the same field of view as the DA 15/4. 15mm is 15mm, the field of view changes only when the camera sensor size changes, like going from APS-C to FF.

Comparing the A 15/3.5 to the DA 15/4 - and I don't have the A but I do have the DA - the A will likely having less contrast, less flare resistance, more warmth. This is do to the coatings of each lens. Modern coatings are generally cooler and more flare-resistant.
The A15 may also have better corner resolution than the DA due to the fact that it is a full frame lens and you will be cropping it's corners away.

However, since the optical formulas are so different - comparing resolutions will require actual test data.

03-30-2012, 11:22 AM   #5
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From my limited testing and practical experience, it seems that both the A 15m and K 15 significantly overexpose on digital, unfortunately, and they produce a lot more distortion than the DA 15mm F4. I never shoot with either of these lenses any more (though I did on film, they work wonders with the Super Program), as I either opt for the DA 15mm or DA 12-24mm. Both produce better images.

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03-30-2012, 12:17 PM   #6
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QuoteOriginally posted by Adam Quote
From my limited testing and practical experience, it seems that both the A 15m and K 15 significantly overexpose on digital, unfortunately, and they produce a lot more distortion than the DA 15mm F4. I never shoot with either of these lenses any more (though I did on film, they work wonders with the Super Program), as I either opt for the DA 15mm or DA 12-24mm. Both produce better images.
I am sorry, but I would wholeheartedly disagree. I do not know the DA 15, I must say, though. I use the old K 15/3.5 from time to time, because it is a superb lens, even on digital. With really good resolution and very good contrast. The only problem I encounter is its flare resistance - or better, the lack of. The later A-version seems to be much improved in this respect.
Exposure may be off. But that was the case with ultra wide angle lenses all the time. Such a wide angle of view almost always leads to some ares in the image being too bright or to dark and to get the exposure right needs some knowledge. I know, the current version of matrix metering is quite good at calculating the matching exposure, but nevertheless, with ultra wide angles going fully manual and exposing in an educated way, is IMHO the best route.

Distorsionwise, the DA 16-50 is much worse, than my old K 15, which also holds its own, compared to the super-wide zooms I have (Sigma 15-30 and Sigma 10-20). The K 15 is one of those few lenses I would not part with, even if I bought a DA 15, which I might do one day...

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03-30-2012, 12:17 PM   #7
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QuoteOriginally posted by JinDesu Quote
The A15 may also have better corner resolution than the DA due to the fact that it is a full frame lens and you will be cropping it's corners away.

However, since the optical formulas are so different - comparing resolutions will require actual test data.
Yeah, I didn't want to say anything about sharpness because I haven't used the 15/3.5. I can say, though, that I have used a number of FF lenses on my Pentax DSLRs over the years and have still experienced edge softness, so IMO the whole "FF lenses on APS-C have better edge sharpness" is overblown. If you look at the Photozone reviews of Pentax FF lenses, you'll see what I mean.
03-30-2012, 01:52 PM   #8
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QuoteOriginally posted by Ben_Edict Quote
But that was the case with ultra wide angle lenses all the time.
The DA 15mm was spot-on exposure-wise when I tried taking the same shot with it (this was on a tripod an all, just never got published).

The overexposure issue with the A 15mm is actually quite interesting, as I think it's more of a camera problem than a lens problem. On the Super A, it would give the correct exposure. On a PZ-1, it was half a stop off, on the MZ-S, one stop, on on digital 1-1.5 stops (in outdoor light, which is where I tested it). This would imply that the lens data the newer cameras have is off in some way.

I might end up re-reviewing the DA 15mm and doing some comparisons. When I did so originally, we didn't have the in-depth review system.


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03-30-2012, 02:21 PM   #9
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The other thing to remember that on film, it is a super wide angle. It also excels on film. I have seen folks do some incredible work with it on digital though. The DA 15 has 2 pluses. #1 is price; #2 is AF. The DA probably has the Ghostless coating as well since it is a LTD lens. That didn't exist when the A and K lenses went into production. Some of the last of the A production ran into the 90s but never got that coating. I wrestled with the idea of whether 2 get a 15, 18 or the k 28/2 and opted for the 28/2 because on film, that is as wide as I like to go for the most part although I do have an old 21mm. I may eventually add a 15 or 18 to my line up though. We are talking about some of the finest glass Pentax ever made in the manual focus K mount lineup.
03-30-2012, 03:22 PM   #10
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Getting back to the other question I had in my OP

Should I keep looking for a Zeiss 21mm K as the 15mm A F3.5 would not be a good replacement for it?
03-30-2012, 03:49 PM   #11
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QuoteOriginally posted by slackercruster Quote
Getting back to the other question I had in my OP

Should I keep looking for a Zeiss 21mm K as the 15mm A F3.5 would not be a good replacement for it?
I would personally pick the A 15 over the Zeiss 21mm. But that is just me. However, it does have a large front element and the built in hood may not protect it enough. It is relatively heavy. But size and weight wise, they will be about the same.
03-30-2012, 04:19 PM   #12
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QuoteOriginally posted by slackercruster Quote
Should I keep looking for a Zeiss 21mm K as the 15mm A F3.5 would not be a good replacement for it?
The focal lengths are too different, so they are not comparable.
A potential "replacement" for the ZK 21/2.8 would be the A20/2.8.
03-30-2012, 04:44 PM   #13
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My brother has one (A version).
Pretty good on digital from what I can tell from his photos.
No issues with flare either.

Beautiful lens and no Pentax equivalent as its a FF lens.
The DA15ltd (I have this) is an APS-C lens though its unique too (small for a 21mm FF FOV)


The problem with this lens is its relevance today.
There is no digital Pentax FF, so its usage is confined to the same as the DA15, which is smaller/lighter/new.
On film, the A15/3.5 shines.
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