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09-22-2015, 05:22 PM   #1
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Difference between 645 FA and DFA lenses?

I recently moved from a 4x5 setup with a digital back to a Pentax 645Z. Mostly I am happy but find myself chasing the image quality I became accustomed to with Rodenstock and Schneider 4x5 lenses. I am doing indoor studio photography and mostly in the 90-200mm range. I need the images I create to be tack sharp. The sensor on the 645Z is excellent but the lenses I have tried leave something to be desired.

When I bought the 645Z I also picked up a 55mm DFA lens from B&H. This lens is very sharp. but a little too wide for most of what I do. I eventually bought a variety of F and FA lenses from eBay and they are, well, OK. I have a 45-85mm that I use occasionally, a 120mm, a 150mm that I use frequently, and a 200mm. The 150mm lens is a new(ish) FA model (4184570 serial #).

I understand that Pentax started releasing “DFA” lenses around the time the 645D came out. Can anyone explain the difference between a “D” and a non-“D” model lens? I understand SMC refers to the coating, “F” for focus, “AF” is autofocus, and “D” is digital? How are these digital lenses better or more suited for the digital 645 bodies than their older counterparts?

I also read recently that Pentax announced a whole slew of newer lenses that are now in stock at B&H. I’m most interested in the 150mm lens. Yet this new lens is not a “D” model. If I were to trade my older 150mm lens purchased on eBay (that was likely manufactured sometime in the past 10 years) for this newer model, am I likely to see any improvement in sharpness?

09-22-2015, 06:15 PM   #2
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QuoteOriginally posted by prohtex Quote
I became accustomed to with Rodenstock and Schneider 4x5 lenses.
I work with 4X5,5X7 and 8X10 formats so I know where you are coming from.

QuoteOriginally posted by prohtex Quote
I understand that Pentax started releasing “DFA” lenses around the time the 645D came out. Can anyone explain the difference between a “D” and a non-“D” model lens?
Perhaps the biggest operational difference is the lack of an aperture ring on the DA and D-FA lenses. Optically the DA lenses are supposedly optimized for a highly reflective imaging sensor, with coatings to reduce ghosting that would not occur with film.Optically, Pentax DA lenses have a smaller imaging circle than FA or D-FA lenses, this is an optimization that supposedly makes wider lenses lighter. The only two 645 lenses that I can think of that has made use of such optimization are the Pentax DA 645 25mm f/4 AL (IF) SDM AW* and the HD PENTAX-DA645 28-45mm f/4.5 ED AW SR lens**. DA optimizations only really have an appreciable effect on wide angle lenses, longer focal lengths are going to be large and heavy regardless of the format.

QuoteOriginally posted by prohtex Quote
I were to trade my older 150mm lens purchased on eBay (that was likely manufactured sometime in the past 10 years) for this newer model, am I likely to see any improvement in sharpness?
Most likely, a complete optical re-design of this lens with aspherical elements and ED glass would no doubt improve image quality substantially. Optical coatings haven't changed much over the years, Aero bright, ghostless coatings and physically protective coatings are the latest advances from pentax - these additions would in all probability provide a modest improvement in contrast and flare handling characteristics.


* This lens is discontinued according to B&H. The full format compatible Pentax D-FA 645 25mm f/4 AL (IF) SDM AW ultra wideangle lens, AFAIK is still available on Japanese markets, and it performs superbly on film.
** though this optimization doesn't prevent this lens from being a complete brick of a lens.

Last edited by Digitalis; 09-22-2015 at 06:25 PM.
09-22-2015, 07:14 PM   #3
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You may want to check out the user reviews on our forum:

Telephoto prime lens reviews
Zoom lens reviews

The 90mm and 120mm macro lenses are in high regard. The former is a newer design and might work better for you since you find 55mm too wide.

I find the FA 45-85mm zoom so-so, but I really like my FA 80-160mm zoom, which I find sharp and with good contrast.
09-22-2015, 07:42 PM   #4
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QuoteOriginally posted by Ole Quote
The 90mm and 120mm macro lenses are in high regard.
I agree - these two lenses are certainly worth a look.

09-22-2015, 10:53 PM   #5
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I would point you towards getting a hold of a 645 90mm DFA , a 645 120mm FA and a 67 100mm macro f4. The first one most expensive and the best . The other two very affordable and super sharp and clean. The last one needs an adaptor.

I have never heard any evidence to make me believe that the FA lenses were ever updated from the old days. Should be the same optics and coatings. So, replacing the 150 you have with newer stock shouldnt change anything.

---------- Post added 09-22-15 at 10:58 PM ----------

The non D lenses are an older design from the film days. The D lenses were designed and released since the 645 digital bodies arrived. In five years of the D and Z bodies pentax have given us four lenses, the 25, 55 , 90 and 28-45. We are still waiting for, well , anything that would improve our lot in the 90mm and up category...............hello , Ricoh ???? Pentax???? anybody.............
09-22-2015, 10:58 PM   #6
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So, just to clarify, both the DA and the DFA lenses are recent models designed to work well with high resolution, digital sensors (645D and 645Z). Of these, I have used the DFA 55mm, the DFA 90mm, the DA 25mm and the DA 28-45. All are good; the 90 and 28-45 are exceptional. I would say that these DA and DFA lenses are better than the average A and FA lenses, though the 120mm (A and FA) is very good indeed. The only difference between DA and DFA is that DFA covers full frame 645 and DA is designed specifically for the cropped 645 sensors on the 645D and 645Z. Be aware that the 25mm lens has existed in both DA and DFA flavours.

The FA lenses that were re-released in recent times (this includes the 150mm you mention) are not new digital designs, but re-releases of the latest pre-digital designs (presumably pending the release of more DA or DFA designs). I cannot rule out that the coatings have been improved when the FA lenses were relaunched, or that the quality control has been improved to make them more consistent on the demanding digital cameras, but I also cannot say that these things have happened. And in any case, the optical designs are not new - they are what the FA lenses have been for years.

So, in short, the DA and DFA lenses are the only ones specifically designed recently for digital use. They work very well. The FA and A lenses are older in design, even the FA lenses that you can buy new because they have been re-released. On average, they are not up to the standards of the DFA 90 and DA 28-45. However, many of them are very good and worth researching lens by lens (as mentioned above, the lens database on this site is a good place to look for that research).

Hope this helps.
09-23-2015, 12:12 PM   #7
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QuoteOriginally posted by Ed Hurst Quote
The FA lenses that were re-released in recent times (this includes the 150mm you mention) are not new digital designs, but re-releases of the latest pre-digital designs (presumably pending the release of more DA or DFA designs). I cannot rule out that the coatings have been improved when the FA lenses were relaunched, or that the quality control has been improved to make them more consistent on the demanding digital cameras, but I also cannot say that these things have happened. And in any case, the optical designs are not new - they are what the FA lenses have been for years.
Thanks to everyone for their thoughtful replies! This was very, very helpful and thorough. I'm so glad to know the community of Pentax users is strong. I'm really loving my 645Z and hoping to stick with the system for years to come.

As I'm doing indoor studio photography, I don't have much use for zooms. There is a tradeoff in image quality and for me the convenience is minor. My FA 45-85mm zoom covers me when I need to do anything on the wider side, but my 55mm DFA is always sharper.

Lately I've been shooting small-ish (around 24"-36" cubed) objects on a backdrop and have found that the 150mm focal length is perfect for my needs. I am also using my 200mm occasionally. I'd love to get a 90mm DFA but I think it probably too wide. So, its definitely a disappointment to hear that there aren't any "Pentax-D" lenses over 90mm. My 150mm FA is in excellent condition and produces images that are reasonably sharp, but I know it could be better. The question is, has Pentax really improved the design at all in the last 20 years? Obviously they haven't redesigned the optical system in any major way, but have there been other minor improvements?

I'm going to try to get my hands on a newer model 150mm to do some side-by-side comparisons. But what's keeping Pentax from updating these designs for digital?
09-23-2015, 01:23 PM   #8
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The designs are pretty much the exact same thing. If someone were to ask whether to buy new from a retailer or pay half as much or less on eBay, my answer would be pretty obvious.

You will be more likely to end up comparing sample variation than actual performance, as there do exist QC issues with Pentax lenses; for instance I have a "dud" FA 120mm that's much worse optically than my 150/2.8.

As fas as playing the sample lottery goes, you may be able to find lenses that edge out the ones you already have, but not because there's anything newer about them.

As far as the future is concerned, Pentax has a new normal and telephoto zoom slated for release sometime soon, possibly replacing the 45-85 and 80-160 by adding better optics, stabilization, and who knows what else. If these lenses will be DA optimized like the 28-45, I expect great things.

09-23-2015, 01:35 PM   #9
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I'm guessing they update the lenses that need it most first? Perhaps the 150, 200, 250 prime lenses are "fine" as they are and wouldn't benefit as much from optimizations?
09-23-2015, 01:54 PM   #10
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The 150/2.8 is honestly fine as it is - softer from f/2.8~5.6 for portraits and ultra-sharp from f/6.3~14 for everything else.

I can see why Pentax did things the way they did: a normal lens to make using the system easy, a wide to cater to landscape photographers, a macro to show what the sensor is capable of, and now a trifecta of zooms to cover the whole range from 28 to 160mm (or more).

After that they'll probably move on to more niche lenses, like a fast portrait lens (100mm f2?), or perhaps a fast normal wide, like a 45mm f/2. Having central shutters in these would basically result in a mass exodus of photographers switching to Pentax.

One thing I think we can all agree on, is that all of the film-compatible lenses have a terrible case of CA, Pentax needs to get on that. It'll take a while that's for sure.

Last edited by Kolor-Pikker; 09-23-2015 at 02:00 PM.
09-26-2015, 12:42 PM   #11
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QuoteOriginally posted by Kolor-Pikker Quote
One thing I think we can all agree on, is that all of the film-compatible lenses have a terrible case of CA, Pentax needs to get on that. It'll take a while that's for sure.
What's a CA? Thanks

asahijock
09-26-2015, 01:00 PM   #12
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I'm guessing chromatic aberration.

After testing an older 150 and a newer one in my studio, I could find no difference. Anyone who is interested in seeing my test images, PM me.
09-27-2015, 01:39 AM   #13
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Yes, chromatic aberration, specifically the kind that manifests as green/magenta fringes behind and if front of the point of focus.
Normally you would see it mostly on high-contrast subjects, but on the 150mm you can spot it on just anything that's not in focus.
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