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08-15-2012, 11:00 AM   #1
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Pentax 645 25mm DA vs. D FA --any comparisons?

I'm curious if anyone out there has had a chance to compare the DA vs. D FA version of the Pentax 645 25mm lens.

I've got the D FA 25mm, which I purchased used from a forum member.

08-15-2012, 11:36 AM   #2
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Had to look through the database to confirm, but I'm quite sure there is only 1 version of this lens. Adorama has it listed as the 645D FA 25mm while BH Photo lists it as the SMC DA 645 25mm. All of the specs are the exact same, this lens was designed and released for use with the 645D only as far as I am aware.

To further confuse, on the Pentax website product page (Close to the bottom here), the lenses for 645 are initially described as "PENTAX D FA 645 lenses...designed exclusively for use with PENTAX 645D camera systems." But then the 25mm description is: "smc PENTAX DA 645 25mm F4."

While it appears that the updated for digital 55mm F2.8 is in fact usable on full frame 645 film cameras, the 25mm is for the 1.3x cropped digital 645D only.
08-15-2012, 12:04 PM   #3
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QuoteOriginally posted by pxpaulx Quote
Had to look through the database to confirm, but I'm quite sure there is only 1 version of this lens. Adorama has it listed as the 645D FA 25mm while BH Photo lists it as the SMC DA 645 25mm. All of the specs are the exact same, this lens was designed and released for use with the 645D only as far as I am aware.

To further confuse, on the Pentax website product page (Close to the bottom here), the lenses for 645 are initially described as "PENTAX D FA 645 lenses...designed exclusively for use with PENTAX 645D camera systems." But then the 25mm description is: "smc PENTAX DA 645 25mm F4."

While it appears that the updated for digital 55mm F2.8 is in fact usable on full frame 645 film cameras, the 25mm is for the 1.3x cropped digital 645D only.
there was 2 versions, the first was FF the second for the crop. the difference was in the hood i think, the DA the hood would Vignette on FF. I think they may have had some issues with FF performance so they limited it. 25 would be very wide on a full 645 frame (15mm on 35mm equivalent)
08-15-2012, 12:23 PM   #4
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QuoteOriginally posted by eddie1960 Quote
there was 2 versions, the first was FF the second for the crop. the difference was in the hood i think, the DA the hood would Vignette on FF. I think they may have had some issues with FF performance so they limited it. 25 would be very wide on a full 645 frame (15mm on 35mm equivalent)
No, there are two versions, one is DA (just released this spring in the US) and one is D FA (released a year or two ago in the rest of the world/asia).

DA means that it is only usable on the cropped sensor (33x44mm) on the 645D. The D FA is also usable on the other 645 film cameras (full frame 6x4.5cm)

What I'm trying to determine, mostly out of curiousity at this point as I already own the D FA 25mm, is whether the optical formula was actually changed for the DA, or if they just put a different lens hood on it (this causes the full frame to vignette on the DA version of the lens) and labeled it DA.

The D FA has pretty significant CA's, which are not ideal, but can be mostly dealt with in post. I'm wondering if these were correcty to an extent on the DA (newer) version of the lens.

08-15-2012, 12:47 PM   #5
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QuoteOriginally posted by Ryan Tischer Quote
No, there are two versions, one is DA (just released this spring in the US) and one is D FA (released a year or two ago in the rest of the world/asia).

DA means that it is only usable on the cropped sensor (33x44mm) on the 645D. The D FA is also usable on the other 645 film cameras (full frame 6x4.5cm)

What I'm trying to determine, mostly out of curiousity at this point as I already own the D FA 25mm, is whether the optical formula was actually changed for the DA, or if they just put a different lens hood on it (this causes the full frame to vignette on the DA version of the lens) and labeled it DA.

The D FA has pretty significant CA's, which are not ideal, but can be mostly dealt with in post. I'm wondering if these were correcty to an extent on the DA (newer) version of the lens.
I was under the impression that they had addressed the CAs in the newer one as well but couldn't find anything to support it
08-15-2012, 01:20 PM   #6
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QuoteOriginally posted by eddie1960 Quote
I was under the impression that they had addressed the CAs in the newer one as well but couldn't find anything to support it
Yep, that's the rumor I've heard as well, but haven't seen anything scientific to back it up so who knows if there's any truth to it or not. (hence my post!)
08-16-2012, 06:25 AM   #7
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ok there is some infor on the LL forum, but not directly first hand, it does look like the new version has improved CA performance (did version one have the drop in CPL filter?)

http://www.luminous-landscape.com/forum/index.php?action=printpage;topic=67627.0


QuoteQuote:
Hi larkis,

I'm certainly not qualified to give first hand experience with this lens, but I received various image files since it's release from various owners who shot with this lens on the 645D and also had a aquantence communicate with an overseas photohrapher who shot with both the original version on film and 645D and the new updated version of this lens. My comments are only a distillation of both examing such files and the feedback from that photographer and the most valuable info is of course from those that own and use this lens.

It has good central sharpness, especially when stopped down at least an f-stop from max aperture and edges and sides lag behind a bit (by approx 1 to 1.5 f-stops but when the lens is well stopped down, excellent sharpness is seen across most of the frame. I also found contrast good, but from the images I reviewed, I cannot make a good determinantion of microcontrast as the # of different lighting senario's was not all that varied.

The one area which was a surprise and in some cases I was personally dismayed about, was the high levels of CA in side and backlit scenes. It's easily provoked and readily apparent in most images that confront such lighting...of course it's subject dependednt. For certain types of subjects, it would be a serious issue, especially if printing large or if CA is prominant over much of the image. My hunch is Pentax is well aware of this and that is one of a number of reasons they revised the lens. The newer built in hood is obviously longer covering the front element to a greater extent than the 1st version of the lens. The photgrapher who shot with both versions felt upon visual inspection that the newer lens may have different coatings as well. His tests on the 645D seemed to show the newer lens exhibiting somewhat less CA than the old, especially in heavily backlit scenes, which was a great benifit. Which version of the lens were you contemplating? Some are balancing out having this lens vs. a D800 with the Zeiss 21mm. I wish it was somewhat less expensive.

There is another thread of someone who just tried out this lens and compared to his Pentax 35mm. He found the 35mm at f8 sharper but both were good. The link to that thread is third party lenses for Pentax 645D also quick/first impressions of DFA 25mm

I also felt from my impressions that the 35mm is also sharper but again two different focal length lenses.

Dave
08-16-2012, 08:46 AM   #8
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QuoteOriginally posted by eddie1960 Quote
ok there is some infor on the LL forum, but not directly first hand, it does look like the new version has improved CA performance (did version one have the drop in CPL filter?)
Thanks for sharing that info, I hadn't read that yet.

Yes, both versions come with drop in "normal" and cpl filters. I also purchased a 3-stop ND for mine. 40.5mm.

08-16-2012, 08:51 AM   #9
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QuoteOriginally posted by Ryan Tischer Quote
Thanks for sharing that info, I hadn't read that yet.

Yes, both versions come with drop in "normal" and cpl filters. I also purchased a 3-stop ND for mine. 40.5mm.
40.5 is a hard filter size to come buy, some of my RF lenses use it as well
08-16-2012, 08:53 AM   #10
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I think I got my 40.5 through Adorama, but I believe B&H also had them. Not all versions were in stock, though.
08-18-2012, 12:59 PM   #11
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Hi Ryan & All,

My post on LL regarding observations a photographer made while having used both versions of the 25mm lens, is from a reliable source and is the only comparison of the two versions I'm aware of. Speaking for myself personally, if I only shot 645 digital, I would opt for the new DA version, in order to gain whatever advantage I could in reducing the occurrence of CA. CA can be dealt with in post processing, but residual amounts often remain and sometimes removal can be moderately destructive in alteration of the image. since I still shoot 645 film too, then it appears I have only one choice and thus will ultimately be looking to purchase the D FA version.

Dave (D&A)
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