[ogl]

Well I guess all I can say is they've certainly picked pretty good subjects to put it to test by looking in the extreme corners - no pixel peeping required. At least the fringing is consistent

I'm 100% sure that this pictures converted in CS5 are much better.

[VoltMan]

Anything can be made to look better in CS5 or post - but lens IQ/distortion "is what it is" out of the camera - ask the film folks

I'm 100% sure that this pictures converted in CS5 are much better.

Clearly those aren't JPEG artifacts and are simply due to lens distortion (high CA) only seen in the outer ~1/3 of the frames and is clearly visible on a 30" monitor at about 24" viewing distance:



Given the price, the 95° angle of coverage on a 645D 33x44mm sensor (same as HCD 28@37x49 and 7° *less* than a Phase/Mamiya 28 which is 102°@40x53) and the certainty that the CA will increase even more on a full frame (film or digital) I'm not impressed at all. For all the hoopla of how this lens is "the widest for medium format" and designed for "landscape" if you look at the real facts its 3rd place in medium format digital SLR wides way behind what Phase/Mamiya & Hasselblad's platforms offer:

Make----/----Coverage @ max resolution----/----35mm Equiv.----/----My impressions
Phase/Mamiya 28/4.5- 102° coverage for 40x53 (80MP) - 17mm- sharp/low CA (~$4500)
Hasselblad 28/4 - 95° coverage for 37x49 (60MP) - 22mm - v. sharp/v. low CA (~$4500)
Pentax 25/4 - 95° coverage for 33x44 (40MP) - 19.5mm - looks sharp?/moderate-high CA? (~$4900)

(Note I'm a resolution bigot but arguably I could concede the HCD could be #1 as well for its sharpness and comparative lack of CA even given its angle of view)

So it looks to me the above is the "digital MF SLR wide angle state of the union" for quite a few years to come unless Phase/Mamiya/Hasselblad up the anty further. It will be interesting to see what comes out on Velvia or Acros etc.. Its also not encouraging that Pentax hasn't released the MTFs, nor coverage specs for 645 film/FF digital I might add.

In short their 25mm isn't a game changer but more like a loser to me. Which is a shame as I was holding out hope... and only time (which I don't have) and a Pentax full frame sensor (which they won't make for years to come) can prove me wrong.

[ogl]

In short their 25mm isn't a game changer but more like a loser to me. Which is a shame as I was holding out hope... and only time (which I don't have) and a Pentax full frame sensor (which they won't make for years to come) can prove me wrong.

the photos are good from 25/4 even in JPEG. and it's FF MF lens.
if you have a look at any FF or MF ultra-wide lens, you can see that all lenses suffer from some CA and distortion. in digital era is not a problem at all.

it will be time when Pentax could offer camera with bigger sensor.
nothing to compare with another brand.

[VoltMan]

Actually I've been looking intensely today at files from a Mamiya 28/4.5 - and in the frame area equivalent to the 25/4 from Pentax there is substantially less CA. On top of that it has more coverage (102 degrees) which gives me more scene in the frame. As an added bonus I get 80MP with ~12.5 stops of DR to work with.

To say CA and distortion isn't an issue in the digital era - well I guess if you're used to making compromises up front in the workflow its okay - in the end to me its like polishing a terd. Else if you have expectations of making the best images possible you have to rethink that approach. Not to mention the dozens of folks shooting B/W film here are going to have a really hard time compensating in CS I would think.

These claims of "the widest MF lens" to me are ridiculous in comparison to the Phase/Mamiya or Hasselblad. You can simply make a much higher resolution, wider angle digital photograph with a Phase/Mamiya platform with much less distortion, that will produce large prints far superior in detail and image quality. Given the costs of these lenses one would have expected them to be on rough par. From what Pentax has shown in the last several days it makes the choice v. easy for me not to get the 25mm, which means my 645D will remain in the role I bought it for - an inexpensive knock around MF digital with reasonable auto-focus. I was actually going to CP+ to look at this lens tomorrow (Friday) but now to be honest its not worth the 40 minute train ride.

the photos are good from 25/4 even in JPEG. and it's FF MF lens.
if you have a look at any FF or MF ultra-wide lens, you can see that all lenses suffer from some CA and distortion. in digital era is not a problem at all

---

Last edited by VoltMan; 02-10-2011 at 09:56 AM.

[Digitalis]

nor coverage specs for 645 film/FF digital I might add

they have actually, and it can cover full frame 645 giving a 35mm equivalent of 15.5mm - try doing that on a mamiya/hasselblad lens.

I don't think those samples are doing this lens any credit. I would wait for some RAW samples to be run through ACR before I make any judgements on IQ. Although I myself was a bit surprised at the amounts of CA present in the image, though I will point out the older hasselblad SWC with it's 38mm f/4.5 Biogon was considered at the time to be ground-breaking in terms of wide-angle photography and that lens had considerable CA at the edges too.


I was able to remove most of the CA in the image by using the lens correction filter in photoshop. The image need some heavy correction -21 /green/magenta fringing. But I have substantially reduced the visual impact of the CA. I agree it's not the best solution - it would have been better if they had designed the lens without this egregious optical design blooper but you work with what you have got.

this is corrected 100% crop from the uppermost left corner, bear in mind such corrections performed on raw files are going to deliver superior results:

[VoltMan]

Nice job cleaning up that file, and hopefully output from raw will significantly improve. Yet I'm still dismayed they would release a lens that produced images like that (even JPEG) without going the extra mile to clean up the design. Perhaps they've said somewhere it will provide FF coverage - its not on their specs page - but my point is a 645D can't use that coverage and if it did the CA would be as bad and probably much worse on the outer reaches of that coverage.

I've read the 38 Biogon design was ground-breaking - in 1954 (I wasn't even born yet), and continued to be so for something like 50 years, even with its shortcomings. Its simply amazing something like that could even arise from the ashes of WWII. But this is 2011 - some 57 years later, and I had much higher expectations from Pentax. I was actually hoping they could lower my kit costs or improve performance as well - that didn't happen.

With all that negativity you might assume I'm not happy with the 645D as a system - but not so - it provides a lot of practical advantages for me, but just not in wide angle applications, and I don't find the 25mm to be a good investment as I have other options which other people may not have.

they have actually, and it can cover full frame 645 giving a 35mm equivalent of 15.5mm - try doing that on a mamiya/hasselblad lens.

I don't think those samples are doing this lens any credit. I would wait for some RAW samples to be run through ACR before I make any judgements on IQ. Although I myself was a bit surprised at the amounts of CA present in the image, though I will point out the older hasselblad SWC with it's 38mm f/4.5 Biogon was considered at the time to be ground-breaking in terms of wide-angle photography and that lens had considerable CA at the edges too.


I was able to remove most of the CA in the image by using the lens correction filter in photoshop. The image need some heavy correction -21 /green/magenta fringing. But I have substantially reduced the visual impact of the CA. I agree it's not the best solution - it would have been better if they had designed the lens without this egregious optical design blooper but you work with what you have got.

this is corrected 100% crop from the uppermost left corner, bear in mind such corrections performed on raw files are going to deliver superior results:

[kuau]

Voltman
I shot with last year a mamiya 645 with a phase one p45+ and there 28mm lens
I was not impressed at all, soft corners and the mamiya 645 body even the latest df to me is very platic feeling to me not well built.
That's why at the time i turned to a used H3D-39 and there 28mm Hcd lens, results to me were great. Hasselblad does a lot in there phocus software that is specific to there 28mm lens.
I noticed a huge difference in opening a raw file in acr then in phocus and maybe now with the latest capture 1 software things have improved so my whole point is seems like both mamiya and hasselblad get good results with there 28mm lens because of software not just the glass.
The 25mm Pentax has the problem of no dedicated raw processor that has built in corrections for there lenses and what we are seeing is just that. The lack of quality raw support.
Maybe when adobe gets there hand on the 25mm lens things will improve, though i doubt it.
What a shame, i still feel in terms of a 40mp MF camera, in rems of body, the 645d is excellent.

Steven

[Digitalis]

I shot with last year a mamiya 645 with a phase one p45+ and there 28mm lens I was not impressed at all, soft corners and the mamiya 645 body even the latest df to me is very platic feeling to me not well built.

I have only had a week long encounter with the mamiya system and my instant impression is that it was awkwardly designed. The lenses are quite good, however the design of the camera lets the whole system down.

That's why at the time i turned to a used H3D-39 and there 28mm Hcd lens, results to me were great. Hasselblad does a lot in there phocus software that is specific to there 28mm lens. I noticed a huge difference in opening a raw file in acr then in phocus and maybe now with the latest capture 1 software things have improved so my whole point is seems like both mamiya and hasselblad get good results with there 28mm lens because of software not just the glass.

I was going to mention that, I have used the hasselblad phocus software and I did notice there was a lot of behind-the-scenes juggling of raw data. And to the uninformed that software correction gives the illusion that the lens is performing better than it actually is. that is why I like ACR - it levels the playing field. And I will also point out that none of the wide angle Hasselbald or Mamiya lenses are apochromatic which would, from a purely optical point of view render the lenses optical performance flawless...but this is not the case.

I think bringing the three primary colours into perfect focus at the sensor plane by means of software correction would be a much cheaper in the end, as opposed to designing a lens that is optically perfect in every way, To make such a wide angle lens truly perfect ED glass and advanced apochromatic designs would have to be used and would require microscopic alignment of the lens elements to tolerances so astronomically high it would be physically impractical to mass produce them.

[VoltMan]

Steven,

P645DF body aside (and I agree it doesn't "feel" well) I had good results from the 28/4.5 for urban exterior and street shots, granted a bit soft around the edges as you've noted - however I note that's FF coverage on a FF sensor. I won't argue the HCD either (see my earlier comparison post). What frustrates me is that in going with the 645D I'm willing to compromise resolution for a DSLR MF camera, but by gosh I'd expect to see a stellar lens for it at that price point - something that differentiates itself to justify buying it, especially given a 33x44 sensor.

Like you I think the 645D body itself is superb - the controls and everything about it make it a perfect (yet quirky) "on the go" platform, but its held back by its optics. For right now it does what I want, its just I'd hoped to get more out of it.

I'm ordering the IQ180 as an upgrade for the 65+ so for wide angle work I'm going to test the Hartblei Cam in May using a Canon 24mm TS and Hartblei/Zeiss 40/4 TS which both look promising from the files I've been shown. The new IQ interface is also a big leap ahead of the P series from what they've shown, and though I'm skeptical about the usability of its Live View function - if that function even works out at only 1fps it'd be perfect for my purposes. The Hartblei also takes the Zeiss T/S line which I drool over as well ..

[ogl]

You Tube

You Tube

[Digitalis]

For those who are interested in buying this lens(like I am) the internal filter holder accepts 40.5mm filters. The provided Polariser and clear filter from Pentax should be sufficiently well coated not to have an impact on flare performance on this lens however people who are fond of using neutral density filters may find it useful to know that B+W just happen to make neutral density MRC filters in this size (they only have one current model 4X MRC 40.5mm filter though)

The use of ND grads with this lens will prove challenging, I suspect Lee may be able to come up with something like what they did with the Nikkor 14-24mm f/2.8G - but suited for the much larger 645 lens.

[managger]

They sad that release date is 2 of April
Google „P„u„‚„u„r„€„t„‰„y„{

Does anybody from our community ordered this lens ?

[672]

Great thread. I spoke to my sales rep at Samys Camera L.A. who sold me my 645D and he laughed heartily when i asked when to expect the 25mm 645 lens. He reminded me that the cameras are almost non existent still. Furthermore they (the largest photo retaller east of B&H) have NO intention of having a demo or inventory of such a lens, even though they do stock mamiya and hasselblad.

I am getting great epson prints on the 7800 , so far all with P67 lenses and just got a 645 300mm from the marketplace at this forum, and the way things are going i plan to pay the price for whatever 645 glass i can get my hands on now , cause its only going to go up. Pentax are going to keep shipping bodies with little or no glass.....and it seems most of us rejected their 55mm as unacceptable anyway.

Now , i have to choose to sell off one workflow, i cant support three, so 1DSMK3 and glass or P67 and Imacon...I can tell you the labs are closing , with those open raising prices and quality and accountability falling rapidly.........

[Digitalis]

My sources tell me the Pentax D-FA 25mm f/4 will be available in July here Australia, So I would expect the new lens to be available in the US at a later date. The price of the new 645 lens is yet to be confirmed. There is at least one store here in Adelaide(of all places) that intends on keeping this lens in stock.

I have also made some enquires to Lee filters who do make a larger filter holder for the nikkor 14-24mm f/2.8 Lens - a similar filter holder will be needed for landscape photographers because the internal 40.5mm filter size is too restrictive on the use of graduated filters.

[harklee]

I've ordered this lens and supposed to get my hands on it this weekend, it is currently available in Japan and the lowest price is Y343,875, which is about 4100~4200 USD. I will keep you guys posted.

‰¿Ši.com - ƒyƒ“ƒ^ƒbƒNƒX smc PENTAX-D FA645 25mmF4AL[IF] SDM AW ‰¿Ši”äŠr

?????? D FA645 25mmF4AL[IF] SDM AW??????:????? ??????????

For the GND filters, since the lens is about 90mm wide, the conventional 100mmX150mm filters may work for 645d (probably not for any 645 full-frame sensors).