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05-09-2023, 10:56 AM   #76
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Mark, your results are intriguing, but confusing to me! They are diametrically opposed to mine. I should qualify though that you're testing the three lenses on the same camera, presumably, whereas I only used the OM 35/2.8 shift on an APS-C Fuji X-T2 camera, and I compared the A and FA Pentax 645 35mm lenses on a GFX 50R. I can't explain why you get great results with your OM 35 shift and I got terrible results with two different copies. I don't have the FA 35/3.5 so I can't go back and compare. I do have the improved HD D-FA version, and it's not better in any way that is useful to me than the A. I compared those two very thoroughly.


As a side note, Fuji is having one of its regular sales, and I couldn't resist. I just tried out my new GF 35-70/4.5-5.6 lens on my 50R, and compared it side-by-side with my Pentax-A 645 35/3.5. The GF 35-70 has an outstanding reputation. I was curious how my old Pentax A 35 would do against the 35mm position of the modern GF lens. I shot the same scene from f/4.5, f/5.6 ... f/16.


At every aperture, the Pentax holds its own -- right across the GFX frame. As I compared the pairs of images, sometimes I thought the Pentax was better, and sometimes the Fuji, depending on what part of the scene I was studying. Most of the differences I noticed were visible only at 300% (either way).


This is one quick test, and the devil is always in the details. If I really cared to compare the two lenses, I'd check for field flatness, performance against flat targets, performance near, performance far, flare, etc.I might do more thorough testing one of these days, just out of curiosity, but the bottom-line for me is that I can use the Pentax-A 645 35/3.5 without worrying that I'm getting sub-optimal results relative to the native GF lens. This isn't a surprise to me because the A 35/3.5 is one of my most used lenses; I wouldn't be using it if it produced poor quality images.


The most obvious difference I see in the files is camera-related rather than lens-related. My GFX 50R does a poor job white balancing with adapted lenses, and makes everything too magenta and cool. My colour workflow automatically involves applying some minus tint and plus temp to most files. With the native GF lens, it's much better. Once I've corrected white balance, I can mix files from these two lenses together in a project without reservation.

05-10-2023, 12:30 AM   #77
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The truth lies in comparing multiple tests, but as you say, the details matter, and there are a few factors to bear in mind when comparing dissimilar results:

1. Results often look satisfactory until compared with something better. Remember how pleased we were with DVD quality? Compared to 4K, it now looks unbearable. And try watching VHS in 2023. This test caught me out twice: I wasn't impressed by the Olympus 35/2.8 Shift in 2007 because the Zeiss PC-Distagon made it look bad. And I wouldn't touch a Nikon 35 PC-Nikkor because – sat next to either – it seemed like junk. However, I was always pleased with the 645 FA35's sharpness - until now, testing this sample this way, leading to . . .

2. While I'm confident about the performance of these 645 35/3.5 samples, possibly they aren't great copies, and your A is better – but reviewing Pentax' MTF after the test, it predicts what I'm seeing with 4.3 micron pixels. However . . .

3. Your XT2 has a pixel pitch of 3.9 microns, so you'd be seeing defects of the Olympus I couldn't access with the S1R. Whereas those fat 'ol 50R pixels are 5.3 microns, and if you're cropping out most of Zone D, and not shifting, even this SMC-A resolves better in central zones at peak apertures, and focuses more accurately, than the FA. If you can live with that bokeh . . .

4. A while ago, I tried to distinguish between two similar 'full frame' lenses by moving them to Micro 4/3. I thought these were both elite-level optics, but the (3.3 micron) Lumix G9 shredded them, and revealed major differences between apertures. M43 (and APS-C) lenses operate at very high resolution: I don't now use any bare 35mm optics on M43 if pixel-level sharpness is a priority. Larger format lenses rarely hack it on smaller cameras: image circle is a trade-off between quality and quantity. That's partly why Speedboosters are such a good idea.

I'd love to lend you my Olympus 35 Shift to try on the 50R: if it doesn't perform better than your SMC-A, maybe I have a bad copy of both the A and the FA.

Last edited by 169; 05-10-2023 at 12:59 PM.
05-10-2023, 07:52 PM   #78
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I found a copy of the OM 35/2.8 shift (multicoated) for a very good price on eBay and almost bought it just to satisfy my curiosity. I went so far as to check if I could mount it on my F-Universalis, and I can because I have an OM lens board ready to go. But then my better judgment kicked in. It was too much money for a whim.


There are so many variables at play that make it hard to know why we're getting such different results. Pixel pitch could definitely be part of it; I have a GFX 100S arriving soon so it will be interesting to see how my lenses do on that sensor, with its smaller pixel pitch. I spent a lot of time comparing some samples made by a colleague who had the Pentax-A 645 35mm and could shoot it on both his 50R and 100S for me. Based on those results, I think all my lenses will be fine, but we'll see.


Other variables that I've noticed can have a huge impact relate to the adapter, and how the lens is adapted. Extremely small alignment errors can have a major difference on image quality. When I see someone complaining on a forum about "tilted elements" on an adapted lens, I immediately suspect adapter problems before tilted elements. The inside of the adapter is another major concern. Most adapters are too shiny and need flocking or coating. Even a tiny amount of bright metal can cause flare and ghosting. I've even had issues with long enlarger lenses where ghosting and flare were uncontrollable at the front side and could only be addressed with a rear-mounted baffle.


I'd be surprised if you had "bad" copies of your Pentax 645 lenses. I haven't noticed a lot of copy variation. Pentax made these lenses for professionals. I've owned enough P645 lenses to be confident that unless the lens has been dropped, it will perform as expected.

So I don't have an answer for you!
05-11-2023, 05:52 AM   #79
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Good point: adaptors can cause issues: the Pentax 645 > L mount adaptor is different to the OM35 one and could be a factor.

However, mindful of the possibility of accidentally creating a tilt lens, I made multiple tests of opposite sides of the outer zones. I focus bracket based on magnified views of the relevant section of each image, but the SMC-A made it difficult, because in Zone D you simply don't have enough resolution to see where you're focusing. It is a big ask in that setup and few lenses thrive there. I'm adding a comparison of the MTF charts at 16:9.net, which illustrates the problem I'm seeing.

If you're not shifting, I would expect the A and FA to perform equally - and well - but it now seems to me that purpose of the more complex FA design was to improve film-frame corners and wide aperture behaviour, refine the rendering and simplify distortion. I don't think Pentax improved centre-frame resolution stopped down at all, which accounts for the A's popularity when used on sub-MF sensors.

As to our different experiences of the OM35/2.8 Shift . . . it only seems like you and I care! I'm amenable to downgrading my view of the Olympus with the authority of the finicky GFX100S - but would want to re-test them on the even more ruthless M43 sensor - although I couldn't reach Zone D with it. There's definitely mileage in adapting 35mm shift lenses to GFX: in your shoes I would have the Samyang 24PC, but want my old Canon 24 TSE II. Enjoy!

07-29-2023, 01:26 PM   #80
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Rob.... can you tell me how far you can shift with your Pentax 645 A 35mm with the 100s? It would be great to get 10mm worth of shifting/rise. I'm not expecting compound movements with the Pentax lens. I don't own one yet but would consider if shifting results are in the range I am looking for.

Victor B.
07-29-2023, 07:24 PM   #81
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Hi Victor. A shift of 10mm on a GFX along the long edge of the frame at infinity technically requires a circle of good definition of 72mm. The 645 film format needs around 69mm, so 10mm is pushing it. Whether you'd be happy with the result depends on what's happening in the far shifted area. If it's sky above a building, you'll be fine. If there's lots of detail that needs to be resolved cleanly across the whole frame, you'll be less happy. At 10mm, you can also expect to see light falloff and moustache distortion if there are straight lines.

The lens is capable of producing excellent results on a GFX 100S. It's one of the lenses I never leave behind. However, good technique and well adjusted equipment are essential for best results.
07-30-2023, 08:25 AM   #82
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Thanks Rob..... I may pick up an A version since they are so reasonably priced. I have the GFX 35-70mm (my one and only zoom) which is a remarkable lens as has been reported by many. If needed I can pan with it but would really like to have some 'rise' capabilities to eliminate foreground. As far as distortion the GFX 35-70 seems to be very well controlled. Mustache distortion is difficult to correct. This was one of the great strengths of my Digitar 35XL - no distortion!

Victor B.

07-30-2023, 09:07 AM   #83
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Could you mount "Pentax 67" lenses on your tilt and shift adapters (with the Pentax '67 to 645' adapter)? Their illuminated circle is around 90 mm in diameter ...

Regards
07-30-2023, 06:38 PM   #84
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QuoteOriginally posted by victorbellehumeur Quote
Thanks Rob..... I may pick up an A version since they are so reasonably priced. I have the GFX 35-70mm (my one and only zoom) which is a remarkable lens as has been reported by many. If needed I can pan with it but would really like to have some 'rise' capabilities to eliminate foreground. As far as distortion the GFX 35-70 seems to be very well controlled. Mustache distortion is difficult to correct. This was one of the great strengths of my Digitar 35XL - no distortion!

Victor B.
You can't beat the SMC Pentax-A 645 35/3.5 for value and performance (except for the moustache).

I'd love to be able to use the wide semi-symmetrical lenses like your Digitar 35XL, but it's not possible with GFX on my F-Universalis. It's retrofocus or nothing at the wide end, unfortunately. I was briefly very excited by the release of the new APO Silvetar 35mm from Silvestri, but samples I've seen on GFX did not make me reach for my wallet. It might be better on smaller sensors.

What are you using for an adapter by the way? Are you going to stick that Pentax 645 lens on a tilt-shift adapter. They get the job done (but are not my favourite tool).
07-30-2023, 06:57 PM   #85
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QuoteOriginally posted by rdeloe Quote
You can't beat the SMC Pentax-A 645 35/3.5 for value and performance (except for the moustache).

I'd love to be able to use the wide semi-symmetrical lenses like your Digitar 35XL, but it's not possible with GFX on my F-Universalis. It's retrofocus or nothing at the wide end, unfortunately. I was briefly very excited by the release of the new APO Silvetar 35mm from Silvestri, but samples I've seen on GFX did not make me reach for my wallet. It might be better on smaller sensors.

What are you using for an adapter by the way? Are you going to stick that Pentax 645 lens on a tilt-shift adapter. They get the job done (but are not my favourite tool).
The adapter I have is a Kipon. If I were going to shift then I would more than likely use my Arca M-Two along with my 100s. I'm only concerned with rise. Even 7mm helps a lot - that is what I was able to get with my Digitar 35XL when I had my Phase 4150. I'm keeping all of my LF lenses as they may be useful in the future. Adding some horizontal info is many times much easier just panning but for vertical and keeping everything straight rise is necessary.

Victor B.
07-30-2023, 06:59 PM   #86
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QuoteOriginally posted by RICHARD L. Quote
Could you mount "Pentax 67" lenses on your tilt and shift adapters (with the Pentax '67 to 645' adapter)? Their illuminated circle is around 90 mm in diameter ...

Regards
I'm not using a T/S adapter on my 100s - just a dumb Kipon. For movements I would mount the lens on my Arca M-Two. Thanks for the info about the image circle on the 67. 90mm image circle is a big advantage.....

Victor B.
07-30-2023, 07:26 PM - 1 Like   #87
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The trouble with using P67 lenses is the wide angle options. I'm a big fan of many of the optics (especially the 75mm f2.8AL, the 55mm f4 [late], the 55-100mm zoom, the 300mm EDIF and the 400mm EDIF). But if you want a focal length that's wide when used on a 33x44mm sensor, there's not much going on. The 45mm is the widest rectilinear lens, and many of us don't rate it very highly optically. The 35mm is a fish eye. So your options run out at the short end of town.
07-30-2023, 07:27 PM   #88
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QuoteOriginally posted by victorbellehumeur Quote
The adapter I have is a Kipon. If I were going to shift then I would more than likely use my Arca M-Two along with my 100s. I'm only concerned with rise. Even 7mm helps a lot - that is what I was able to get with my Digitar 35XL when I had my Phase 4150. I'm keeping all of my LF lenses as they may be useful in the future. Adding some horizontal info is many times much easier just panning but for vertical and keeping everything straight rise is necessary.

Victor B.
You should get good quality shift over 7mm of rise. There are some interesting options in longer focal lengths if those would be useful to you. I have a friend in NZ who uses Mamiya RZ lenses, and likes the 50mm ULD. He's getting 15-20mm of shift. I get a clean 15mm on my hacked Mamiya G 50mm f/4, and more on my hacked Mamiya N 65mm f/4.5 L.


A really inexpensive and useful option is the good old Pentax-A 645 45-85. The 45mm end is excellent, and the image circle gets much bigger than needed for 645 in the middle of the range. On my F-Universalis, I find the 850 grams of the 45-85 is a bit too much; it pulls the standard into a bit of self-tilt. I don't know if your M-Two has a sturdier standard.
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