Fujinon GX lenses on digital medium format

[rdeloe]

Short version: Fujinon GX lenses for the Fuji GX680 system are an option if you need a large image circle on a camera that provides a focusing rail. Image quality is very good, and they’re inexpensive. However, to use these lenses on a digital camera you really need to disassemble and remount them; it isn’t difficult.

Fujinon GX 250mm f/5.6 on a GFX 50R, wide open

 

[rdeloe]

Long version: The Fujinon GX system is a robust professional 6x8 medium format camera that provides movements on a full range of lenses, from 50mm through 500mm. People still use this system as intended, but judging by the sale price of the equipment, it’s not popular.

Wikipedia has a good article that provides pictures and information about the lens lineup. https://en.wikipedia.org/wiki/Fuji_GX680

Some lenses from medium format film cameras are in heavy use on digital medium format cameras today because they’re easy to adapt. Pentax 645, Mamiya 645 and Hasselblad V are examples. Fujinon GX lenses are not readily adaptable; I have yet to encounter someone who uses them on a digital camera that isn’t the GX680 with a medium format back. The lenses are large, boxy, and just about impossible to attach to anything other than a Fuji GX680 camera body. As a result, they sell for very little money.

For most people looking to adapt lenses on digital medium format cameras, there are easier choices. I use many lenses that are smaller, lighter and don’t require rebuilding the lens. However, I was intrigued by the Fujinon GX line because it has a massive image circle (120mm for all but the 50mm f/5.6) and the lenses have register distances that work well with my setup and allow for huge movements.

I first looked at the GX line because I wanted a 250mm lens for my Toyo VX23D and Fuji GFX 50R outfit. Large format 250mm lenses don’t work because the register distance is too long for the VX23D body (unless custom long bellows and rails are used). Good medium format SLR lenses in the 250mm to 300mm exist, but they’re too long and heavy for my setup. For example, I’ve heard good things about the SMC Pentax-A 645 300/4, but that lens weighs 1,360 grams and is not usable on my VX23D.

I nearly passed over the GX line because of the awkward lens housings, but then I stumbled across a picture by a person on Flickr (Nokton48) who removed the lens cells from the Fuji housings and remounted them in various scavenged shutters for use on his Plaubel Makiflex. Ah ha!

I started with the 250mm f/5.6, and now also have the 210mm f/5.6, and the 65mm f/5.6 – all rehoused and remounted for use on my Toyo VX23D plus Fuji GFX 50R outfit. I have excellent lenses in the 65mm range already, but I bought the GX 65/5.6 because I’m exploring tall vertical stitched panoramas that begin with the centre of the image circle and go up; I needed a large image circle for what I have in mind, and the GX 65/5.6 is the only lens I’ve found that has the image circle and works on my camera; large format lenses like the Fujinon SW 65mm f/5.6 do not work because their register distance does not allow the needed shift of 30mm or more on my setup.

A "proof of concept" test image. Inspired by Lois Conner's 7x17 banquet camera vertical compositions, I'm exploring tall images that start at a normal viewing perspective. This requires a very large image circle to allow 30mm of rise from zero.

 

[rdeloe]

I’m really quite impressed by these lenses. Image quality easily meets my expectations for the GFX 50R sensor. I’ve compared the GX 65/5.6 to the 65mm position on my Fujifilm GF 45-100/4 lens (a fine optic), and the GX lens holds its own. I especially appreciate that image quality on the GX lenses I’ve used so far is good wide open, right across the frame. Optically, the only weakness I’m seeing is a tendency to some CA at the widest aperture; it cleans up easily in Lightroom, and is largely eliminated by closing down a stop, so this is not a deal breaker. Plus rarely shoot wide open.

In this 100% crop comparison, the lens is wide open at left and stopped down one stop at right. I've raised exposure, but that's it. Some CA is visible in the f/5.6 image, and it is a bit softer. Nonetheless, f/5.6 is completely usable -- not something I was expecting from these older lenses.

 

[rdeloe]

The circle of good definition (the good part of the image circle) is the highlight of these lenses for me. It’s actually larger than I can use on a GFX camera. At around 30mm rise in portrait orientation I start seeing hard vignetting from the opening of the cavity that holds the sensor; if I keep shifting, I don’t hit the edge of the image circle until past 36mm. I have long enlarger lenses that can pull this off, but nothing in the 65mm range.

In an earlier thread on the forum I asked about the register distance. I can confirm that it is different for every focal length. However, the register distances for the lenses are closer together than they would be if these were symmetrical lenses. Fuji used lens and housing designs that allow every GX lens to fit on the standard GX680 body. This means the long lenses are telephoto and the short lenses are strongly retrofocus. I estimated a register distance of 186mm for the GX 250mm f/5.6, and 125mm for the GX 65mm f/5.6. The housings add a “fudge” factor. In the wider lenses, the flange (the side of the shutter that would be in front of a lens board when mounted) is at the rear face of the housing, while on the longer lenses, the housing has an extension that locates the flange closer to the middle of the housing (and thus forward of the mount point).

A downside of these lenses for people who want to travel light is they’re big, and have large filter threads. The smallest front filter thread is 82mm (e.g., my 250mm and 210mm). Many are 95mm (e.g., my 65mm), and some are 105mm (e.g., the 50mm f/5.6). The housings only weigh around 300-350 grams, so on a lens like the GX 50/5.6, which weighs 1,250 grams, most of the weight of the lenses is the optics.

If you attach the unmodified lens to your camera, you can use the aperture by fixing the stop-down lever in place. You can’t use the Seiko #1 electronic leaf shutter because it’s controlled by the body. However, Fuji used a design that leaves the shutter open when the lens is off the body, so unmodified lenses are usable (unlike Mamiya lenses for the Mamiya 6 and 7, where the shutter is closed by default). I tried doing this, but I didn’t enjoy using the lenses this way at all; also, I didn’t want to haul around 300-350 grams of useless weight in the form of the housings.

I can provide details on how to disassemble these lenses if anyone is interested. In a nutshell, with a few simple hand tools you can strip the lens down to the front and rear cells, and the Seiko #1 shutter housing, with everything removed from the shutter except the aperture mechanism. The hardest part of the process is removing the lens cells. Fuji used thread locker to hold them in place so they don’t come out easily. Brute force will get the job done.

The "Simplified" GX 210mm f/5.6, and the bits left behind.

 

[rdeloe]

Note that if you do want to use the lens cells with a mechanical leaf shutter, this is possible. If the focal length you want matches or is close to another lens that uses a Seiko #1 shutter, you’re good to go. For example, the GX 180/5.6 can go into the mechanical Seiko #1 shutter of a Fujinon W S 180mm f/5.6 large format lens and the aperture scale will be correct. Nokton48 from Flickr also uses Seiko #1 mechanical shutters harvested from Mamiya RB67 lenses with the corresponding focal length. I didn’t need a shutter so I used the stripped down shutter that came with the lens as an “aperture mount”. In case you’re wondering, you can’t put the the lens cells in a Copal shutter. The Seiko #1 shutter uses M42x0.75mm thread on front and rear cells.

Once you have the lens cells out and the shutter stripped, there are many different ways to put the “simplified” lens on a camera. To reiterate, these are lenses that need a focusing system, and they have long register distances. My Toyo VX23D is ideal for these lenses, but I could see them working on other cameras with “view camera-like” designs (e.g., Cambo Actus, Arca Swiss F-Universalis).

The easiest way to mount a simplified GX lens in its stripped Seiko #1 aperture mount is to pop it onto a lensboard for your camera. You need a board with a hole for a Seiko #1 shutter (48mm). Copal 1 is not big enough, but it’s close and can be enlarged with a file and some elbow grease; a nice drilled hole is better of course. My GX 210/5.6 is currently mounted this way.

The simplified GX 210/5.6 lens, and mounted on a flat board on my VX23D

 

[rdeloe]

The GX 250mm f/5.6 has a register distance of 186mm; I can use it on a flat board, like the 210/5.6 pictured above, but that leaves me with a very long minimum focus distance and limited room for movements because the bellows is stretched to the maximum. The housing I designed acts like a “top hat” lens board for large format field cameras, in other words, it positions the lens forward of the place where the housing mounts to a lens board, thereby allowing the standard to be closer; this is the same trick Fuji used in the original mount. With this housing, which RAF Camera built for me, I have a very useful minimum focusing distance of just over 1 meter with my standard rail and bag bellows. Note that in my design, the sleeve just behind the front cell rotates and operates the aperture lever; it’s basically a large aperture ring. The rear of the housing uses M42x1 for the lens mount. I went with M42x1 because it slips through a slightly enlarged Copal 1 hole, which makes it easy to mount and dismount the board in the field.

The simplified GX 250/5.6 in its custom housing, and mounted to a flat board on my VX23D. I still need to add aperture marks on that central ring.

 

[rdeloe]

The 65mm f/5.6 required a different solution. It is very front heavy; the front lens group alone weighs 765 grams. The simplified lens will mount to a flat lens board like the 210/5.6, but it was so front-heavy that I couldn’t use it with tilt on my VX23D’s custom axis tilt solution. My solution was to mount it to a lens board around the front cell. This balances the lens perfectly on the front standard and makes tilt delightfully easy. The catch is that this puts the aperture mechanism inside the bellows. The solution for that was to mount the bellows to the rear of the lens using an adapter. The bellows adapter has a gasket that grabs onto the rear of the lens, and magnets that hold it to the bellows. This arrangement looks a bit Steam Punk, but it works very well. If I build a replacement version, it will look tidier.

 

[rdeloe]

I’ll be the first to admit that this is a niche option. I think I’m the first person to adapt these lenses for mirrorless medium format, and I may be the last because there are much easier options out there. Nonetheless, just in case anyone else has similar needs, I thought it might be worth documenting and sharing my experiences.

If anyone has any questions or comments, I’m happy to chat in this thread.
Rob

 

[Ed Hurst]

Not sure I will ever do this but want to thank you for the generous sharing of information and the very enjoyable read! And you never know, I just might....

 

[vjbelle]

Thanks for posting Rob..... Great info.

Victor B.

 

[rdeloe]

Not sure I will ever do this but want to thank you for the generous sharing of information and the very enjoyable read! And you never know, I just might....

My pleasure Ed.

In my day job I'm in the business of finding things out and then publishing the results. The habit is deeply ingrained, so when I learn something that might be of interest to someone else, I like to write it up and put it where others can find it! You never know.

 

[P. Chong]

Wow, thanks Rob. Superb resource to document your work to do the adaptation.

 

[buildbot]

Great info, thank you!

 

[itsdoable]

It's interesting the mixed feelings I have with this project.

The "Simplified" GX 210mm f/5.6, and the bits left behind.
View attachment 191466

On the one hand I'm sad to see a GX lens that will never be used as it was designed on a GX body.

The simplified GX 250/5.6 in its custom housing, and mounted to a flat board on my VX23D. I still need to add aperture marks on that central ring.
View attachment 191471

On the other hand, I'm happy to see a seldom used optic re-purposed in such a nice package.

I'd point out that you could have used the lenses with minimal modifications to fit the Toyo lens board, such that the it was reversible back to a GX. I don't have an issue with the GX aesthetics, but then I've shot with them for many years. But to be honest, the many "reversible" modifications I've done, despite carefully labeling and storing all the parts, will probably never be reversed!

Nice job, and we would be pleased if you could share more results.

 

[rdeloe]

It's interesting the mixed feelings I have with this project.

On the one hand I'm sad to see a GX lens that will never be used as it was designed on a GX body.

On the other hand, I'm happy to see a seldom used optic re-purposed in such a nice package.

I'd point out that you could have used the lenses with minimal modifications to fit the Toyo lens board, such that the it was reversible back to a GX. I don't have an issue with the GX aesthetics, but then I've shot with them for many years. But to be honest, the many "reversible" modifications I've done, despite carefully labeling and storing all the parts, will probably never be reversed!

Nice job, and we would be pleased if you could share more results.

Your mixed feelings are understandable. Part of me did feel a bit bad for destroying the original lenses; my "simplification" is not reversible. However, I took some comfort from knowing that the optics will live on and make pictures.

You're quite right that I could easily have used the lenses unmodified on a VX23D. The lens housing fits within the space for the Toyo 110mm lens board. It would have required building a custom board that mated with the mount, or perhaps adapting a part like the adapter Fuji made for large format lenses on the GX680. Locking down the step-down lever would be easy using one of several reversible techniques (starting with a piece of tape!)

I didn't go that route primarily because of the bulkiness and unnecessary (for me) weight of the housing. The pack I carry everything in is very tight already, so slimming the lenses down is an advantage for me. I confess the aesthetics of the lenses were also a factor. Elsewhere I've described the lenses as "f-ugly". They're a triumph of function over form. I'm all about function over form, but these are plastic fantastic ugliness! Beauty definitely is in the eye of the beholder.

 

[rdeloe]

Here are a couple examples, one with the GX 65/5.6 and one with the GX 210/5.6. They're quick work from what I could find during a short break from work today. My goal was to make some images that play to the strengths of the lenses.

For the 65mm, the main strength is the large amount of good quality shift that is possible. Nothing else in this focal length allows this much shift on my setup. In this case, I needed 25mm of fall. I didn't want to point the camera down because I wanted the plane of focus to align roughly with the tree on the left. The trees stand straight, so the camera needed to be level; pointing the lens down to get this frame would not have worked. The lens delivered 25mm of fall without noticeable light falloff. Carrying this one around is a pain because it's so big and it's semi-permanently on a lens board. But I think it's going to be worth it, especially if I don't want limitations on movements. My Schneider-Kreuznach Apo-Componon HM 60/4 is sharper, but the best it can shift before I hit the hard edge of the image circle is around 9mm (and light falloff will be strong).




I really can't resist ice and water. I should try to resist because it's almost a cliche. It's not like I haven't shot a lot of ice and water over the years. But I can't resist.... When I mentioned to someone I was looking for a long lens that could tilt, they couldn't understand why on Earth I'd want that. Tilt, for that person, was something that you only did with wide lenses. This kind of picture is why I want a long lens that can tilt. Many people love the fuzzy, indistinct look of long exposure water. I don't. I like my moving water to have a distinct form. In a fast moving watercourse like this, 1/12th to 1/15th of a second is about right to create the contrast I was looking for: hard, crystaline ice and soft moving water. I also wanted my ice to be in focus everywhere, which called for tilt; focus stacking would have made the ice sharp, but then the water would have become an indistinct mass. On top of all of these constraints, I couldn't get any closer because it was on the other side of a creek. That's a perfect use case for a long lens that can tilt!



Incidentally, the GX 210/5.6 is a really good performer. I'm sure there are sharper 210mm lenses out there, but this one is no slouch. The difference between wide open (f/5.6) and the aperture that appears to be as sharp as it gets (f/8) is minimal. Better still for my purposes, diffraction is very gentle at f/16 (an aperture I use regularly). A tiny bit of extra sharpening makes f/16 almost as good as f/8. That's quite something. Like it's bigger sibling the GX 250/5.6, there's a bit of CA wide open, but it's even less than the GX 250/5.6, and it cleans up easily. I never imagined I'd have a long lens that could be used wide open, so that's another bonus.

 

[4x5Australian]

Rob,
That second photograph is a cracker. Congratulations!
Rod

 

[stngoldberg]

Thank you for sharing
stanley

 

[rdeloe]

Rob,
That second photograph is a cracker. Congratulations!
Rod

Thanks Rod. I'm fortunate to live close to a fast moving little creek that throws up some very nice ice in winter.

 

[rdeloe]

In the previous post I offhandedly mentioned a pleasant surprise about the GX 210/5.6: very consistent performance from wide open through f/16.

Here's a small illustration. This is the same scene in evening light. The sign with "30" is 600m in the distance. The crops are 682x682 pixels out of the 8256x6192 full scene images. This part was in the shadows. I adjusted exposure to make it easier to see, but that's it (i.e., no extra sharpness, texture, clarity, etc.) . In the f/5.6 version you can see a bit of CA around the branches in the sky. It appears to be about 1-2 pixels width. The full scene is shown below.