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Forum: Pentax Medium Format 07-30-2023, 07:27 PM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
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.
Forum: Pentax Medium Format 07-30-2023, 06:38 PM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
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).
Forum: Pentax Medium Format 07-29-2023, 07:24 PM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
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.
Forum: Pentax Medium Format 05-10-2023, 07:52 PM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
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!
Forum: Pentax Medium Format 05-09-2023, 10:56 AM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
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.
Forum: Pentax Medium Format 04-27-2023, 06:37 PM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
Indeed. In fact, I'd call those three the tip of the iceberg. There are so many other considerations. That's why I like the PentaxForums reviews. They give me useful clues about the camera used (native 645 or 67, Pentax digital, adapted), the style of photography (e.g., landscapes at f/11 versus portraits at f/2.8) and the skill level of the photographer. If you're careful, you can put all the pieces together and get some useful information before committing to buying or renting a Pentax lens.
Forum: Pentax Medium Format 04-20-2023, 10:11 AM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
Thanks for catching that Ed. The link is correct, it's just my intro that is wrong.

I couldn't believe how bad my copy was and agree that it was probably a bad one. The seller was reputable, but that doesn't mean they tested it in their store beyond putting it on a body to see if it operated. These were all serious, professional lenses; I just can't see Pentax releasing something as bad as the one I used. My effort wasn't wasted though because I ruled it out for my own situation based on the size and weigh alone. It's also challenging to use as a shift lens because something has to be done to control the aperture. For my testing purposes I just manually locked the lever in place at the positions I was testing, but that's not a solution for actually using the lens. I would have had to build a custom adapter with an aperture control mechanism.
Forum: Pentax Medium Format 04-19-2023, 07:01 PM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
Ed, I haven't tried the DFA that only covers 33mm x 44mm. However, the optics are similar (same?) as the older one. I bought a nice copy of the 25mm that covers 645 from a good camera store in Japan. SMC Pentax-D FA 645 25mm F4 AL [IF] SDM AW Reviews - 645 Wide-Angle Primes - Pentax Lens Reviews & Lens Database I tried it with GFX 50R. It's big and heavy, but if it had been good, I would have kept it.



Keeping in mind n=1... it was terrible. I don't mean "not as good as the GF 23mm". I mean seriously bad.


It was less sharp than my Samyang 24mm f/3.5 tilt-shift lens, had lower contrast, was worse at the edges at all apertures I tested, needs a special adapter, and was worse overall shifted. The Pentax also has a lot of strong purple fringing. I sent it right back.
Forum: Pentax Medium Format 04-17-2023, 06:28 AM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
I think your summary list is reasonable. I'd offer a few friendly amendments that can be taken with the usual grain of salt:

I haven't noticed flare as an issue on the SMC Pentax-A 645 35/3.5. I use it without a lens hood. To protect against stray light, I'll use whatever I can put in the way (usually my hat). It's one of the three lenses I use the most, so I'm confident that flare isn't a major issue. I can't comment on whether the later ones have better flare resistance.


A friend of mine, who isn't around to comment anymore, had the 33-55mm and use it as a shift lens on a GFX 100S outfit. He was extremely picky, but very impressed, especially given the negative reputation.


The 645 55/2.8 is an interesting one. I used it as a shift lens on a Sony A7R setup and thought it was fine. However, when I tried it on my GFX 50R outfit as a shift lens (two separate times), it wasn't. Centre performance unshifted was fine, but it fell apart at the edges until f/11 unshifted. I concluded at the time that it had significant field curvature because I could get better edges and corners if I focused on the edges.


The 67 55/4 third generation is a star. It's very sharp across the frame and has the big image circle I needed. I didn't keep it because it's large and heavy for my setup, and there are lighter options. Someone setting up a tilt-shift outfit who needed this focal length and didn't want to get into modifying lenses could be very happy with this one.


Everyone seems to say that the 45-85 is not good at the long end. I never saw that, and I explored that very thoroughly. I would use it without hesitation at any focal length. It has quite strong barrel distortion throughout the whole zoom range (stronger at 45 and weaker at 85). I'd have to check but I suspect there might be a moustache form in the whole image circle. For best performance across the frame you definitely want to close down to f/8, but it's absolutely usable wide open across the whole zoom range. I would describe this lens as ridiculously good given the price. It's without a doubt the best 45mm Pentax medium format lens (it's not even close). As a bonus, the image circle of the A is massive in the middle of the zoom range. The optics of the FA are supposed to be the same, but I've never used one so I'm not sure if the image circle is also massive on the FA. It's a property of some zoom lens designs (image circle increases in the mid-range), but the lens designers may have "choked" it -- like they did for the FA 150-300.


The reasons my A 45-85 stays in the drawer are it's too big to use comfortably on my technical cameras; the rotating front element is a pain with CPLs; and it's troublesome to use with tilt and swing. Having said that, if this was the only lens I had with me, I could do almost everything I need to do with it.


The 67 45mm is a real shame. It's small and light (relatively speaking), has nice colours, a big image circle, and moderate barrel distortion. It's only flaw for my purposes is it doesn't quite have the resolving power I wanted. I can see why people thought it was great on film. On digital, if you need the big image circle more than you need maximum possible resolving power, it's a good option. Some attention to sharpness in post does help. Unfortunately, I didn't use it enough to be able to comment on flare.


I came close to buying a 645 45/2.8 on more than one occasion, just to see if all the bad press was warranted. However, enough people whose opinion I respect said it was worse than the 55/2.8, and that one didn't cut it for me so I never bothered. It's a shame because it's a focal length I really like. Unless someone lends me one I'll never try this one because I have a superb Mamiya N 43mm f/4.5 L that I use now.


As a general observation about the whole lineup, I really like Pentax medium format because they're solid, no-fuss professional lenses. If my A 35/3.5 had to be replaced, I'm confident I could buy any one of the many available for sale that looked to be in decent condition and it would be fine; I wouldn't have to worry about copy variation. I think of them as the Honda of lenses: high quality, reliable tools. On my setup I'm only using one Pentax now (the irreplaceable A 645 35/3.5). The other lenses are Mamiya G and N, and Schneider-Kreuznach. But there's no question I could do what i need to do with Pentax medium format lenses.
Forum: Pentax Medium Format 04-16-2023, 06:57 PM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
The D-FA has a slightly narrower angle of view than the A. If the A is 35mm, the D-FA is 36mm (roughly).


To check the size of the image circle, I just put them both on my Arca-Swiss F-Universalis, which can shift to 25mm. There's no difference in the size of the image circle.
Forum: Pentax Medium Format 04-15-2023, 07:40 PM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
I'm not in the UK so can't help you with this project. However, I have the SMC Pentax-A 645 35/3.5 and the HD Pentax-D FA 645 35/3.5, and I've had the FA 645 35/3.5. I also have the 645 45-85 (A) and have had the Pentax 67 45/4. I've only used them on a GFX 50R as tilt-shift lenses if that's relevant.


Anyway, long story short, let me know if you want to buy my HD Pentax-D FA 645 35/3.5. ;) It's not better than my A as a shift lens in any way that I can measure or replicate. It's not sharper, and it's not better at the edges. The one thing it has going for it is Lightroom has a built-in correction profile (but that profile does a good job on the A too so it's not much of an advantage). The P67 45 is a very nice lens, but it's soft on my 50R once I zoom in. The 45mm end of the 45-85 leaves it for dead on my GFX 50R. I'm not saying you can't make excellent photographs with the P67 45. I know people who do. But if you need sharpness and detail, it comes up short.
Forum: Pentax Medium Format 02-27-2022, 05:57 PM  
Pentax Adapter K for 645 Lens - operation question
Posted By rdeloe
Replies: 18
Views: 1,882
So if anyone else has this problem... I figured out a solution. You need to be willing to drill a little hole in your lens. ;) However, if you're good with that and have the tools and skills, it's a reversible modification. In a nutshell, you can flip the sprint around so that it's always pulling on the lever that closes down the aperture.
Forum: Pentax Medium Format 02-27-2022, 01:57 PM  
Pentax Adapter K for 645 Lens - operation question
Posted By rdeloe
Replies: 18
Views: 1,882
Thanks Marco. Good tip.

It's a design flaw in the Fotodiox. The spring is strong enough, but the metal part doesn't have the right shape or texture to slide smoothly in the channel. I tried disassembly, sanding and grease, but that wasn't enough.

This is one of those problems that will cost a lot of money to solve. Accurate and secure mounting requires not only precision in cutting the front part of the adapter off the rest, but also a milling machine to add a rim that slides into the board and carries the weight of the lens; screws from the rear simply hold it in place.


It does work reliably to f/16, so I suspect I'm going to fall back on taking the board off the camera and giving it a little nudge from behind for those rare times I need f/19.


Here's what it looks like by the way.




---------- Post added 02-27-22 at 01:59 PM ----------




Indeed. Every adapter I've every owned, including the very expensive Mirex adapters from Germany that started the whole tilt-shift adapter thing, needed self-adhesive telescope flocking in the interior to manage stray light.


I've never tried a Rayqal, but apparently they do a good job through correct treatment of the interior surfaces, and the addition of light baffles. Those are very expensive though.
Forum: Pentax Medium Format 02-27-2022, 06:42 AM  
Pentax Adapter K for 645 Lens - operation question
Posted By rdeloe
Replies: 18
Views: 1,882
Richard, thank you. This is exactly what I wanted to know.

---------- Post added 02-27-22 at 06:59 AM ----------



I use a couple Pentax 645 lenses on my Toyo VX23D digital view camera, with a Fuji GFX 50R serving as the "back". I currently have the front part of a Fotodiox Pentax 645 adapter mounted to a Toyo lens board. The mechanism works reasonably well up to about f/16, at which point it won't close down to anything smaller. It's not a crisis because I rarely shoot beyond f/16, but occasionally I've had to go a bit past, and I can't with this adapter.

Pentax original parts are always the best, so I'm debating getting one of these and machining it to fit.


Thanks all for your help!
Rob
Forum: Pentax Medium Format 02-26-2022, 03:30 PM  
Pentax Adapter K for 645 Lens - operation question
Posted By rdeloe
Replies: 18
Views: 1,882
Thanks for responding ProfessorBuzz, but that's not what I meant.

I know it's manual. What I'm asking is does turning the aperture ring open and close the aperture when it's mounted on the adapter. When you turn the ring on an unmounted P645 lens, the aperture doesn't change unless you manually operate the spring-loaded lever. Third-party adapters for using P645 lenses on mirrorless cameras provide a spring-loaded mechanism for operating the lever on the lens, so when you turn the aperture ring on the lens, the aperture opens and closes. Is that what this Pentax Adapter K does?
Forum: Pentax Medium Format 02-26-2022, 10:04 AM  
Pentax Adapter K for 645 Lens - operation question
Posted By rdeloe
Replies: 18
Views: 1,882
Quick question about the "Pentax Adapter K for 645 Lens": when you attach the adapter, does it put spring tension on the 645 lens aperture control lever, so that turning the aperture ring on the lens actually opens and closes the aperture to the correct setting?

This is how adapters from Fotodiox and other manufacturers work, and it's what I need for an adaption project.
Forum: Pentax Medium Format 10-02-2020, 11:45 AM  
35mm favour
Posted By rdeloe
Replies: 15
Views: 2,237
Steve, here's a brand new thread about Hasselblad 40mm options: Hasselblad 40mm F4 CFE or CFE IF ? | The GetDPI Photography Forum
Forum: Pentax Medium Format 09-28-2020, 06:56 PM  
35mm favour
Posted By rdeloe
Replies: 15
Views: 2,237
Thanks for the link. It's nice to see Mirex is still in business, and making adapters for the GFX. I don't see them on their website so it must be a special order. Way back when I used a pair of Mirex adapters with a Sony A7R -- one for Sony E to Canon EF, and one for Canon EF to Pentax 645. Canon EF is good as the intermediate mount because it has the largest throat (so less chance of mechanical vignetting).


The lens he's using in this video is a SK 28/4.5. I've never seen one for sale so I have no idea what they cost (but I have a feeling the answer is "a lot"). Does he also have a video for the Hartblei 40mm TS?


The 9-shot flat stitch routine he's using is tricky to pull off without a lot of practice and repetition. He seems to do it a lot, so practice obviously makes perfect.

Rob
Forum: Pentax Medium Format 09-26-2020, 05:38 PM  
35mm favour
Posted By rdeloe
Replies: 15
Views: 2,237
Good luck in the quest! I believe I read some tests of the Hasselblad you're interested in at GetDPI, but I can't recall where. You could try on the medium format forum. If I had to place a bet here, I'd bet that you're not going to be happy. The older wides are just like that. Unfortunately, technical camera lenses are not going to make you happy either. On your sensor you'll be dealing with huge lens cast issues, plus they cost a lot of money and you have to mount them via something like a Cambo Actus because of the very short flange focal distance (so even more expense).

In my own quest for a wider lens than 35mm that can shift on my GFX, I hit a wall. I was briefly excited by the Nikon PC-Nikkor 28/3.5, but after a lot more use gave up on it. Here's the thread at DPReview where I talked about it: A 28mm shift (and tilt) lens for Fuji GFX cameras: Medium Format Talk Forum: Digital Photography Review There are some RAW samples you can play with from my GFX 50R. In the words of the great Mark Knopfler, "The bottle's empty, man, there's nothing left". ;)
Forum: Pentax Medium Format 09-24-2020, 07:39 AM  
35mm favour
Posted By rdeloe
Replies: 15
Views: 2,237
Hi Steve. Nice to meet you (virtually!)


If you're going to put up a series of these, I suggest you start a new thread. That way the conversation will be easier to find for other people.


I'm curious to see how you like the Pentax 67 lenses. The 45mm lens is nice and compact and has good colour, but I found it to be a bit on the soft side compared to the 45mm position of the Pentax 645 45-85/4.5 The Pentax 67 55/4 is really good. On the plus side, those 67 lenses will allow for as much shift as your adapter permits.
Forum: Pentax Medium Format 09-21-2020, 11:48 AM  
Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA
Posted By rdeloe
Replies: 87
Views: 10,576
diggles, I want to thank you for doing this and for publishing your results. You saved me a lot of money. I am (was) in exactly the same boat as you. In fact, today I posted a request on the forum asking for exactly what you'd already done. 35mm favour - PentaxForums.com Somehow I missed your work. Richard L. immediately pointed me to this thread, where all my questions were answered.

So here's my take on this: I am not buying a D FA 35/3.5!

I downloaded all the PEF files you supplied, loaded them into Lightroom, and then did a side-by-side with the compare tool. Interestingly, I had things setup so I didn't know what file was what (so it was a blind test). One of the files was noticeably better than the other in almost every respect. I assumed it was the D FA, but in fact it was the A. This held true across the two comparison scenes that you provided. Based on what I'd read about the D FA, I was certain going into this that it would be a lot stronger than the old A.

One should always be careful in making judgements about a lens based on one copy of a len and one test scene. Also, this test is only using the central part of the image circle, so it doesn't offer any insights into how the lenses do when shifted (which is how I use Pentax 645 lenses). Nonetheless, given how expensive the D FA is, and given that I already have a really good A and can't use the autofocus capability of the D FA, it seems pointless for me to buy a D FA and do my own testing. Thanks for saving me the time and money.
Forum: Pentax Medium Format 09-21-2020, 09:47 AM  
35mm favour
Posted By rdeloe
Replies: 15
Views: 2,237
Ha, jackpot! Thanks Richard. I don't know how I missed that post.

Here it is for anyone who is curious and hasn't seen it yet: Testing Pentax 645 35mm - SMC Pentax-A vs HD Pentax-D FA - PentaxForums.com


Rob
Forum: Pentax Medium Format 09-21-2020, 09:02 AM  
35mm favour
Posted By rdeloe
Replies: 15
Views: 2,237
Do you have a 645Z (or Fuji GFX 50R/S) and both the SMC Pentax-A 645 35mm f/3.5 and the HD Pentax-D FA 645 35mm f/3.5? If so, I'd be grateful if you could shoot a couple comparison frames for me and put the RAW files somewhere I can find them. Outside, focused long on the same subject, and f/11 would be ideal.

I am using the A and am very satisfied, but have read many times now that the D FA version is a significant step up. With a side-by-side comparison like this, I can figure out whether or not investing in the D FA will result in useful improvements.


Thanks!

Rob
Forum: Pentax Medium Format 07-13-2020, 05:36 AM  
Pentax 645 Helicoid Extension Tube inner diameter
Posted By rdeloe
Replies: 3
Views: 803
Thanks so much for checking.


So close! A few more mm and I would have been in business. Ah well, good to know.
Forum: Pentax Medium Format 07-12-2020, 11:12 AM  
Pentax 645 Helicoid Extension Tube inner diameter
Posted By rdeloe
Replies: 3
Views: 803
Do you own a Pentax 645 Helicoid Extension Tube? If so, can you quickly measure something for me?

From the front, what is the diameter of the inner "throat"?


Thanks,
Rob



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