Pentax 645 lenses on Fujifilm GFX

Maxrub1n said:

I know the fotodiox adapters have a smooth aperture ring built in without numbers. However I would love to use pentax 645 lenses in studio to set lighting and then transfer the exact aperture settings over to my rz67 to shoot alongside. Do older, manual pentax lenses work to turn the actual aperture ring on the lens? Or do you completely rely on the fotodiox ring for aperture?

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Let's say you're using an A lens; they're all manual.

You have the lens off camera and you turn the aperture ring. Nothing seems to be happening. However, there's a spring-loaded lever on the rear. Use your finger and you can move that. It will open the aperture to the position you set.

On an adapter like the basic Fotodiox one (which does not have its own aperture ring), there's a spring-loaded lever that engages with the one in the lens. As you turn the aperture ring, it pulls on the spring-loaded lever in the lens, so the aperture opens and closes as you adjust the aperture ring.

The adapters that have their own aperture ring are simply providing a mechanism to control the aperture lever on the Pentax lenses that don't have an aperture ring.

There is another option if you're willing to make a small modification to your lens and your handy. You can open up the lens from the rear, flip the spring around and attach it to a screw that you've added to hold the other end of the spring. With this modification, turning the aperture ring opens and closes the aperture on the lens.

I don't have any insights into your plan to use the Pentax 645 lens to set lighting, except that it sounds awkward and complicated! Wouldn't a light meter be simpler?

Maxrub1n said:

I know the fotodiox adapters have a smooth aperture ring built in without numbers. However I would love to use pentax 645 lenses in studio to set lighting and then transfer the exact aperture settings over to my rz67 to shoot alongside. Do older, manual pentax lenses work to turn the actual aperture ring on the lens? Or do you completely rely on the fotodiox ring for aperture?

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Hey welcome to Dpreview!

I have the fotodiox adapter and there is a work around to get the aperture number. The way I do it is to leave the Fotodiox to ''wide open'' and then set the lens to, lets say, f 8. Then you need to move then Fotodiox aperture ring until it stops... Its not very precise and do it carefully not to force anything. It's also easy to forget to turn the Fotodiox ring and shoot wide open...

I suggest another option: use another generic third party pentax 645 to gfx without a ring. You will end up being able to use the lens aperture all the time. I like it more if you don't need the tripod foot of the Fotodiox. But I have to say that my Fotodiox is very insecure and that I broke a lens because of it so be warned.

MF ratios said:

I have the fotodiox adapter and there is a work around to get the aperture number. The way I do it is to leave the Fotodiox to ''wide open'' and then set the lens to, lets say, f 8. Then you need to move then Fotodiox aperture ring until it stops... Its not very precise and do it carefully not to force anything. It's also easy to forget to turn the Fotodiox ring and shoot wide open...

Click to expand...

One (no doubt unintended) feature of this setup is that the aperture ring on the adapter does double-duty as a preview lever.

Simply rotating the aperture ring on the adapter from one side to the other lets you quickly and easily shift between between wide-open (for composing and initial focusing) and stopped-down (for final focusing), the same as many large-format lenses.

This is especially useful for me, as I photograph at night, so not having to count clicks or use a flashlight to open and close the aperture is a welcome lagniappe!

AudiiDudii said:

MF ratios said:

I have the fotodiox adapter and there is a work around to get the aperture number. The way I do it is to leave the Fotodiox to ''wide open'' and then set the lens to, lets say, f 8. Then you need to move then Fotodiox aperture ring until it stops... Its not very precise and do it carefully not to force anything. It's also easy to forget to turn the Fotodiox ring and shoot wide open...

Click to expand...

One (no doubt unintended) feature of this setup is that the aperture ring on the adapter does double-duty as a preview lever.

Simply rotating the aperture ring on the adapter from one side to the other lets you quickly and easily shift between between wide-open (for composing and initial focusing) and stopped-down (for final focusing), the same as many large-format lenses.

This is especially useful for me, as I photograph at night, so not having to count clicks or use a flashlight to open and close the aperture is a welcome lagniappe!

Click to expand...

great tip! I ll keep that in mind

These images are beautiful.

Do you have a portfolio or link to flickr / instragram?

cheers

Hello!
I recently purchased a GFX 100s and have acquired a few G lenses. But I have plans to fill in with additional P645 or P67 lenses and would like to know your thoughts on which would be the best. I have a little used P67II (in hope that Pentax or a third party would introduce a Digital conversion) and several good lenses. The remaining lenses of either model I have interest in are bargains right now. Which camera line would be the best of the best to go with?

Tom R53 in AK

These are Pentax medium format lenses that I have used, which do very well on GFX:

• Pentax 67 55mm f/4 third generation
• Pentax-A 645 35mm f/3.5
• Pentax-A 645 75mm f/2.8
• Pentax-A or -FA 645 45-85mm f/4.5
• Pentax-A 645 150mm f/3.5
• Pentax-FA 200mm f/4
• Pentax-FA 150-300mm f/5.6

Pentax lenses I have used and would not recommend include these:

• Pentax 67 45mm f/4
• Pentax-A 645 55mm

I have not used the Pentax-A 645 45mm f/2.8, mostly because the general reputation is that it's only OK.

I have just received a used, near mint condition, Pentax 645 45-85mm and tested it against my GF 35-70. I wasn't expecting it to equal the sharpness of the Fuji, but, based on various reviews, I was expecting it to come closer that it does. Also tested against my Canon EF 45mm ts which is far from stellar and no match for the Fuji. The Canon also beats the Pentax though not by as much.

The Pentax seems best in the middle of the focal length range but quite soft at the extremes and almost blurry away from center at the wide end. Typical for what it is? Or is it likely a bad copy?

I am returning the Pentax because it doesn't make sense to use a poor lens on a camera like the GFX 100s. Was I expecting too much? Should I give up on the idea of a 45-85 or try other copies? I hate to give up, because the idea of a zoom with tilt shift (via adapter) is so seductive and also because the lens does get a lot of praise. How to assess the praise?

ben sensler said:

I have just received a used, near mint condition, Pentax 645 45-85mm and tested it against my GF 35-70. I wasn't expecting it to equal the sharpness of the Fuji, but, based on various reviews, I was expecting it to come closer that it does. Also tested against my Canon EF 45mm ts which is far from stellar and no match for the Fuji. The Canon also beats the Pentax though not by as much.

The Pentax seems best in the middle of the focal length range but quite soft at the extremes and almost blurry away from center at the wide end. Typical for what it is? Or is it likely a bad copy?

I am returning the Pentax because it doesn't make sense to use a poor lens on a camera like the GFX 100s. Was I expecting too much? Should I give up on the idea of a 45-85 or try other copies? I hate to give up, because the idea of a zoom with tilt shift (via adapter) is so seductive and also because the lens does get a lot of praise. How to assess the praise?

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Your experience does not match mine. I consider the 45mm end of the Pentax-A 645 45-85mm to be the best 45mm adapted lens I've used. The other end has been described as less good between 75mm and 85mm, but I've never noticed that.

Here's Ye Olde Test Chart: Pentax-A 645 45-85mm at 45mm and f/5.6 on the left; Fuji GF 45-100mm f/4 at 45mm and f/5.6 on the right. Both images are 100% magnification. This is the upper-left corner of my decidely non-scientific test chart.

[ATTACH alt="Pentax on the left; Fuji on the right. This is at 100% from my 32" monitor."]2764367[/ATTACH]
Pentax on the left; Fuji on the right. This is at 100% from my 32" monitor.

I would have preferred to show you a real-world scene, but when I owned these two lenses at the same time I never got around to making a good side-by-side set.

One thing I have discovered over many years and a lot of adapted lenses is that much of the time when people think it's the lens, it's actually the adapter, or it's their technique, or both.

Adapter issues can make a massive difference in the performance of a lens. Some common adaptation problems include these:

• Inside of the adapter is shiny, or has a small shiny spot, causing stray light that destroys image contrast and thus the appearance of sharpness.
• Mount is not snug, causing the lens to droop, which makes the top or bottom look soft.
• Adapter is uneven from side-to-side or top-to-bottom, causing one side of the image to look bad in comparison to the other
• Adapter is the wrong length (e.g., slightly too long, so the lens doesn't quite reach infinity).

Common user error includes focusing problems, stabilization problems, not accounting for atmospheric conditions, etc.

A recent case in point for me: I thought there was something wrong with my new Mamiya N 65mm f/4 L lens. It was quite bad on one side. It made sense that the lens was the issue because I dropped it on the ground the day I got it! However, the lens was perfect. It was the adapter board I'd built for my F-Universalis camera. I realized it was the board because I happened to build a second adapter, to use the lens directly on my 50R. Lo and behold, the apparently "bad" lens became an excellent lens on a different adapter.

Thanks, Rob! Seems like I got a bad copy. The Fotodiox adapter works fine with my other Pentax lenses, including the heavy 120mm macro. So I'm ruling out blaming the adapter. The lens resolves better-- acceptably, in fact--at close distances with test charts, but resolves poorly at infinity if that tells you anything.

ben sensler said:

Thanks, Rob! Seems like I got a bad copy. The Fotodiox adapter works fine with my other Pentax lenses, including the heavy 120mm macro. So I'm ruling out blaming the adapter. The lens resolves better-- acceptably, in fact--at close distances with test charts, but resolves poorly at infinity if that tells you anything.

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My copy is just as good at Infinity as it is on test charts. If your other lenses do well on that adapter, then the case for a bad copy of the lens is much stronger.

I have finally pulled the trigger with the 50S II and the 35-70 zoom. Indeed it has taken some time but the 50S II comes with IBIS which makes a lot of sense and I could not resist with the cashback. Now I am trying to find the best adaptors for my Pentax lenses. What are your experiences with fixed or TS adaptors?

I have two Fotodiox adapters for Pentax 645, both the fixed and the TS. I use the fixed unless I specifically intend to tilt or shift, because the TS requires care to avoid bumping it out of neutral. I like both.

light_bulb said:

I have finally pulled the trigger with the 50S II and the 35-70 zoom. Indeed it has taken some time but the 50S II comes with IBIS which makes a lot of sense and I could not resist with the cashback. Now I am trying to find the best adaptors for my Pentax lenses. What are your experiences with fixed or TS adaptors?

Click to expand...

The Fotodiox tilt-shift now has a foot on the correct part of the adapter, which is a big improvement over the earlier model I had. I don't use mine much anymore, but when I did, I made it vastly more usable by building a collar that went around the front . This allowed for something you can't do with the current Fotodiox that has a foot, which is use swing without having to drop the camera on its side on the tripod head.

I think the best choice for tilt-shift if you want an adapter, rather than a more expensive and complicated setup like a Cambo Actus G or an Arca Swiss F-Universalis, is the Kipon P645 to GFX adapter. It costs more than the Fotodiox, but it gives you something that you'll find very handy, which is the ability to do rise and tilt, or rise and shift (and the same with swing). The Fotodiox uses the simpler design where you can do tilt and shift, or rise and swing.

The reason this is important becomes apparent when you use lenses where the axis of tilt does not run through the lens' rear nodal point. When you tilt with the Pentax 645 lenses that are shorter or longer than the 75mm, you're going to have to apply rise or fall to correct composition (depending on which focal length), and if you don't have the Kipon you have to lean the whole arrangement backwards or point it down more, which means more adjustments. I worked like this for years; it's quite do-able. But it's nice to be able to set tilt or swing, and then correct with rise/fall or shift.

The 75mm f/2.8 Pentax 645 lens is nice for tilt and swing because the axis of tilt does pass close to the rear nodal point. When you tilt or swing with that lens, the need for re-composition is greatly reduced. It's also a really nice lens (small, sharp).