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06-20-2011, 02:19 PM - 1 Like   #1
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My first shots with the Pentax 645 25mm f/4

Hello dear friends,

I had the opportunity to "touch and try" the new and a bit awaited wide angle D-FA 25mm f/4 lens, as i poped up in the Paris' HD Forum a few days ago.

I was first of all very impressed with the size and weight of the beast : close to the FA 80-160mm zoom in dimensions, but even heavier du to the metal barrel and thick lenses. The lens cap is of the K "Limited" strain, metal cup plus inner black tissue. The lens tip is actually going frankly downwards, when the lens is hold at base ! It inspires a nice quality feeling, looks strong and solid / lifelasting altogether. The inner filter shelve is very practical to handle and stays well fixed, with the same conception as on former K primes as FA* 300/2.8 and FA*600/4.
The existing filter is a standard skylight/UV one, the polarizing brother being apparently still awaited.

The lens fits correctly equilibrated in terms of handling on both 645D and 645N bodies. The Focussing ring is very large and smoothly moving, a good news as it is not functionning with AF contacts of film 645 bodies, on which it scopes the equivalent of a 15,5mm lens in 135mm format.

Now, what about optical qualities ?

First, i have to state that this item was a "pre-serial" lens according to the Pentax France representative.

The main quick features i could notice on the few shots i took are :
1- no flare in backlight, or when pointed towards the sun : this seems to be a very scarce and appreciable quality, given the strongly curved front lens !
2- very good lineated or "squared" image design, with barely noticeable, and easily correctable barrel distorsion,
3- pretty good resolution, as from wide open to f/13 or even f/16 stops
4- excellent contrast,
5- slight blue-coloured chromatic aberrations against some green or contrasted subjects, this being easily correctable as only a few pixels large

I post thereafter 3 shots to give you an idea.







I impatiently await my film samples i.o. to confirm these impressions on a full frame 645 format.


Last edited by Zygonyx; 06-21-2011 at 03:18 AM. Reason: orthograph correction
06-20-2011, 03:02 PM   #2
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so do many others... Thanks for sharing your impressions and shots.
06-20-2011, 04:10 PM   #3
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Hello,
I have made the same test with the same lens at the same place the same day.
I can confirm the impressions given by Zygonyx.
The most impressive : Very solid resistance to flare and capacity to hold the black at a very good level with strong backlight but significant purple fringing at f:4.0 and f:5.6, less noticiable at smaller apertures.
Delivery for France is said to be not before mid september.

@ Zygonyx : your FA35 was a little bit better than mine !!. Have to check again the fine focus adjustment
06-20-2011, 04:49 PM   #4
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Am a bit surprised to hear about the fringing on this lens. Since the purple reduces with aperture, it is longitudinal not lateral chromatic. Maybe the production lens will use low dispersion glass to eliminate this problem.

06-20-2011, 05:18 PM   #5
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For $5000, I'd hoped for better than "pretty good resolution".
06-20-2011, 07:48 PM   #6
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Fabulous first post!
06-20-2011, 11:00 PM   #7
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Thanks for all your comments.

@marti : pleasant feed-back ! BF/FF is to check indeed and i thank you for this advice.
Looking for hearing from you soon for film remote controler (i think i will postpone the other lenses acquisitions i.o. to be able to get the 25mm first, by the end of the year) !

@desertscape : let's hope your wish will be accomplished, i agree on the fact CAs seem to be the weakest point of this lens.

@surfotog : my appreciation re. resolution is moderate as i did not measure anything, i just compared visually the samples to those taken with my 35mm in same conditions : quality is very close, minus AC for the FA 35mm. A real scientific statement is actually awaited !

@Douglas : thanks for encouragements !

Last edited by Zygonyx; 06-21-2011 at 03:20 AM. Reason: orthographic corrections
06-21-2011, 06:43 AM   #8
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I really appreciate your posting your inital impressions of this lens and the images you posted. It's an interesting offering for Pentax 645 users and provides an opportunity for some interesting can creative imagery. It's the only Pentax FA af 645 lens I haven't yet tested on the 645D and although theres been some significant sample variabilty with some of them, (especially when shooting at the more open aperturnes), I have high hopes that this lens is worth is considerably high price. Although of a more conservative focal length, I think some will want to know how this lens compares with the FA 35mm f2.8. Looking forward to hearing (and seeing) more from this lens. Thanks again!

Dave (DandA)

06-21-2011, 02:20 PM   #9
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Thank you Dave,
It is a pleasure to recieve such comments.
In my opinion, this lens is worth a high price (maybe not as expensive as the current 4199€ in France, but lens prices usually slightly drop with time) mainly because of its "paper" features, and also construction quality :
- unique and smallest rectilinear focal length in the medium format,
- "wheather resistant",
- with inside filter shelve.

Also, the close wide angles from concurrents are not that cheap if you consider for example the Mamiya 28/3.5 Sekor lens worth 3490 €, or the Hasselblad 28/4 HCD worth 4395 USD.

I would say that hopefully, the fact that no visible colour on the front lens cover was to be seen on this pre-serial copy gives hope that CAs will be better treated in the "selling products".

Re. comparison with FA 35/3.5, i shall post here a few examples to illustrate the scope and rendition.

An other backlight as i like them so much...


Last edited by Zygonyx; 06-21-2011 at 10:45 PM. Reason: orthographic corrections
06-21-2011, 03:47 PM   #10
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Hello,
Some other pictures :
- the first two : FA 25 / iso 400 / f:10.0 - "full frame" and +/- 100 crop
- the last two : FA 35 / iso 400 / f:10.0 - "full frame" and +/- 100 crop

All "small" jpeg from dng via LR3 (jpeg quality 70)

This lens is not cheap at all but terrific.
(and the one wich we have made the pictures is really a beta version and seamed to have some high milleage ...!)

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06-24-2011, 03:20 PM   #11
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I agree. For 5000$ I would think 'stellar' resolution across the complete 645D frame, would be a reasonable expectation. Hopefully, production lenses will exhibit this.
06-25-2011, 03:27 PM   #12
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This is just a P&S example to look at angular differences btw FA 35 (right) and DFA 25 (left photo) :

06-25-2011, 03:32 PM   #13
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+ You can now check on findings of harklee in the excellent review he posted in this same forum :

https://www.pentaxforums.com/forums/pentax-medium-format-645-6x7-645d/149579-...aw-review.html
06-25-2011, 04:07 PM   #14
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Now, an other "field comparison" btw respectively FA 35 and DFA 25 @ f/8, ISO 800 and 1/640s, plain shots and 2 x 100 % crops, as Jpeg from undiscriminant treatment with Silkpix :















CAs (visible on the last crop - D-FA 25mm) haven't been treated.

Last edited by Zygonyx; 06-26-2011 at 01:07 AM.
06-26-2011, 06:51 AM   #15
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Thanks for posting the comparison of the FA 35 vs. the new 25mm. If you compensate for camera to subject distance, so that the main subject is framed similary when shooting with the FA 35 and new 25....would you say the FA 35mm outresolves the new 25mm across the frame? It's of course hard to tell from the 100% crops posted, but it sort of appears that way. Any opinion would be appreciated.

Dave (D&A)
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