Pentax 645 lenses on Fujifilm GFX

I am considering the GFX 100S and still have the following Pentax FA 645 lenses:

75 2.8, 120 4 Macro, 300 4

I know my Nikon mount 50 1.4 Art and Zeiss 135 2 APO may adapt well on GFX.

But how about the mentioned Pentax lenses? I do adapt the 120 4 on my D850, thus I guess it will perform well.

Any experiences with e.g. GFX50s?

light_bulb said:

I am considering the GFX 100S and still have the following Pentax FA 645 lenses:

75 2.8, 120 4 Macro, 300 4

I know my Nikon mount 50 1.4 Art and Zeiss 135 2 APO may adapt well on GFX.

But how about the mentioned Pentax lenses? I do adapt the 120 4 on my D850, thus I guess it will perform well.

Any experiences with e.g. GFX50s?

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Your Pentax 645 lenses will work very well. Obviously you won't have autofocus from your FA lenses, but the ones you have all allow manual aperture control with a standard dumb adapter.

It's always best to judge for yourself. If you go to this page, and scroll down to the bottom, you'll see a link to a Google Drive folder where I have posted full resolution JPEGs made with various adapted and native lenses on a GFX 50R. https://www.robdeloephotography.com/Pages/Toyo-VX23D-and-Fuji-GFX-50R I don't have samples for the 300/4, but I do have the 75mm and 120mm (manual versions, but same optics as your FA lenses).

The bottom-line is that Fuji GF lenses are superb. If you can afford them, and you don't have special needs (like tilt and shift), then they're the way to go on a GFX camera. However, there are lots of adapted lenses that are excellent too on a GFX camera; they're especially good value when you already own them!

In terms of adapters, I'm using a few: straight Fotodiox P645 to GFX, Fotodiox Tilt-ROKR for P645 to GFX, and my main adapter, a Toyo VX23D.

Hi,

I have the A version of the 120 I use it on a 50r and it’s a good performer. I’m sure your 150 and 300 will be good as well.

I have the Kippn adapter and it’s very good.

Rob uses a larger selection of 645 to excellent effect and I’m sure he will offer some advice, few examples of the 120 on the 50r below.

Hope this helps

Anthony

View attachment 0c8acc69faef474fb0fa32872a4777ff.jpg







View attachment f3fa2a40d38749c3b2bead82988ec470.jpg

And he’s beaten me to replying

78_Anthony said:

Hi,

I have the A version of the 120 I use it on a 50r and it’s a good performer. I’m sure your 150 and 300 will be good as well.
I have the Kippn adapter and it’s very good.
Rob uses a larger selection of 645 to excellent effect and I’m sure he will offer some advice, few examples of the 120 on the 50r below.

Hope this helps

Anthony

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I like the second one Anthony. I enjoy some ambiguity. At first glance those rocks could be forested islands. Well done.

I didn't keep my SMC Pentax-A 645 120mm macro, but not because it wasn't good enough; it is excellent and gets rave reviews on the Pentax Forum. At that focal length I found some smaller options that performed as well, so I sold it on.

Thanks Rob for adding your experience.

Thanks for this Anthony. Seems it has made sense to keep those lenses. I was thinking about selling them except for the 120 macro that performs well on my D850.

Another option is a TS adapter to bring new life to the lenses.

Another strength of a GFX 100S may be image stabilisation, provided that the focal length of adapted lenses can be dialed in. This is common with Olympus cameras but I don't know anything about this with the GFX 100S.

light_bulb said:

Another strength of a GFX 100S may be image stabilisation, provided that the focal length of adapted lenses can be dialed in. This is common with Olympus cameras but I don't know anything about this with the GFX 100S.

Click to expand...

You can provide the focal length of adapted lenses, and that information is written into EXIF.

Interestingly, on my Fuji X-T2 the camera would use the focal length information supplied in choosing a shutter speed in Aperture Priority mode. The X-T2 manual notes, "the camera will automatically choose a minimum shutter speed approximately equal to the inverse of the lens' focal length, in seconds...".

The GFX 50R does not seem to have that functionality. You can set the target minimum shutter speed for the Auto modes, e.g., 1/60th. I would prefer this value is linked to focal length. The manual for the GFX 100 (I don't own one) makes no reference to this functionality.

It would be nice if Fuji would implement the link between focal length, shutter speed and stabilisation in the 100S, and then bring those connections to the other cameras through firmware updates. Clearly they can do it because they did it for the X series.

Edit: Someone just posted a link to the GFX 100S user manual, and there it is (page 71): minimum shutter speed is linked to focal length as in the X-series cameras! Now let's hope they bring this to the other GFX cameras through firmware.

Thats good to know. It reminds me that when using the 120 on my D850 as a manual focus lens I first had to choose from a list of focal lengths and appertures to get the exposure right and to provide EXIF information. In the D850 it turns into a 135 because 120 mm does not exist in that list. This should also serve for calibrating IBIS.

Pentax 645 FA150/2.8 is excellent with GFX50(r/s). It causes aliasing to appear in the corners if there is fine detail @ f/5.6. It is very light and budget friendly option. Downsides are average sharpness wide open (quickly catches up), average handling of bright light sources (use a lens hood) and somewhat sloppy focusing ring due to the AF/MF clutch. It also has short focusing throw.

But, stop it down to f/5.6 and it behaves. My choices for the long lens option were adapted FA150 and Fuji 100-200. Not going to buy the Fuji now or in the near future.

Hi,

A Fuji 50s and my existing P645 lenses. With the new 100s, used prices of the 50s will drop nicely. But this would also be my plan with a Fuji 100. The only Fuji lens I would get is the 45-100. That being my main usage FL range.

Stan

Rob de Loe said:

I like the second one Anthony. I enjoy some ambiguity. At first glance those rocks could be forested islands. Well done.

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As a fan of your work Rob I am hugely flattered, thank you very much.

Anthony

78_Anthony said:

78_Anthony said:

I like the second one Anthony. I enjoy some ambiguity. At first glance those rocks could be forested islands. Well done.

Click to expand...

As a fan of your work Rob I am hugely flattered, thank you very much.
Anthony

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Now you're making me blush! But thank you.

Love the images, very nice.

light_bulb said:

Another strength of a GFX 100S may be image stabilisation, provided that the focal length of adapted lenses can be dialed in. This is common with Olympus cameras but I don't know anything about this with the GFX 100S.

Click to expand...

should be able to. the mount adapter setting is in the PDF manual. looks like this on the GFX100

I have the 645 45mm F2.8, 75mm F2.8, 120mm F4 macro, and 150mm F3.5. Pentax has a long and well deserved reputation for making fantastic lenses. I believe should you choose to use those lenses on a GFX body you'll not be disappointed.

Hi Rob

I'm hoping you can straighten me out with this one? I've recently purchased 2 Pentax 645 lenses from Ffordes, for my GFX 50R. The 45mm & 120mm Macro. Both are in very good condition and both have aperture control rings. But these rings do not physically alter the aperture size - only restrict movement via the mechanical lever. I've reported this to Ffordes and they say I need an adapter with built-in aperture control. Is that the Fotodiox P645 - GFX and/or Toyo VX23D you mentioned?

StonkinPix said:

Hi Rob

I'm hoping you can straighten me out with this one? I've recently purchased 2 Pentax 645 lenses from Ffordes, for my GFX 50R. The 45mm & 120mm Macro. Both are in very good condition and both have aperture control rings. But these rings do not physically alter the aperture size - only restrict movement via the mechanical lever. I've reported this to Ffordes and they say I need an adapter with built-in aperture control. Is that the Fotodiox P645 - GFX and/or Toyo VX23D you mentioned?

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Hi StonkinPix.

Look at the back of the lens. There are a couple levers sticking out. Close the aperture down, and then try to move the levers. One of them will close the aperture.

A proper adapter for P645 to GFX (or any other mount) will have a spring-loaded lever that engages the lever that closes the aperture down. When you mount the lens and turn the aperture ring, the spring-loaded lever in the adapter will press against the lever in the lens and close the aperture.

Be warned though that it's not a perfect system. On my adapter (Fotodiox), the spring isn't quite strong enough to push the lever all the way to the f/22 position. As a result, I never get more than around f/19. That's not a problem because I don't go past f/16 anyway. (Note that it could be that I damaged the mechanism, so a new Fotodiox might be just fine. You can tell if it's working by examining the shutter speeds. If the light doesn't change, then your f/22 shutter speed should be about 1/2 f/16.

I'd be interested in your opinion on the 45/2.8. I've always avoided that one because it has a reputation for being the weak link in the chain. The 120/4 macro is excellent. The 35/35 and 75/2.8 are also outstanding. If you ever wanted a nice three lens set, I'd get the 35/3.5, 75/2.8 and 150/2.8.

StonkinPix said:

I've recently purchased 2 Pentax 645 lenses ... and both have aperture control rings. But these rings do not physically alter the aperture size - only restrict movement via the mechanical lever. I've reported this to Ffordes and they say I need an adapter with built-in aperture control. Is that the Fotodiox P645 - GFX and/or Toyo VX23D you mentioned?

Click to expand...

The behavior of many lenses for SLRs is that the aperture setting on the lens only affects the taking aperture, and, as Rob said, the camera (or an appropriate adapter) mechanically moves the iris to the taking aperture, typically just before the shutter begins to open (or when the 'depth of field preview' button or lever is actuated). In an SLR, at least when the lens is mounted on the body, you want the iris all the way open (maximum aperture, f/2.8 or whatever) so that the viewfinder is as bright as possible and focusing is as easy as possible, only stopping down for the actual taking. Note that some SLR lenses--not sure about P645 ones--keep the aperture maximally closed (minimum opening, f/32 or whatever) when they are not mounted on a camera body.

So as Ffordes and Rob said, you need an adapter that has the lever to physically push the iris actuation lever in the lens to provide the aperture you set.