Fuji/Fujica GSW cameras -- question

[rdeloe]

I have an oddball request for someone who has one of the Fujica GSW680/690 cameras. These are the ones with the 65mm lens -- so not the GW... cameras that have the 90mm. Any generation GSW will do (e.g., GSW690, GSW690II, GSW690III, GSW680III).

My request is this: can you measure the space between the rear of the lens cell and the film gate? I don't want you to scratch your glass, but ideally I need the distance between the farthest part of the cell, which might be the glass, and the film gate (those silver rails you can see in this picture).

Thanks so much!
Rob


Image source: ss_kobe_camera

 

[SCHWARZZEIT]

On my GSW690III it's 42.5 mm.

-Dominique

 

[rdeloe]

Dominique, than you so much! That's excellent news if you took the measurement with the lens set to infinity. (Sorry, I forgot to mention that's an important consideration.)


Can I bother you for one more measurement? If you can reach it, what is the diameter of that rear lens cell?

 

[SCHWARZZEIT]

I remeasured the rear lens element to image plane distance with the lens set to its infinity hard stop. It’s 42.0 mm.

The rear lens cell diameter is 37mm. I used a piece thin cardboard that I laid over the lens. I marked the edges of the visible rear element and then measured the distance on the cardboard.

-Dominique

 

[diggles]

Interested to see what you have cooking Rob!

 

[rdeloe]

I remeasured the rear lens element to image plane distance with the lens set to its infinity hard stop. It’s 42.0 mm.

The rear lens cell diameter is 37mm. I used a piece thin cardboard that I laid over the lens. I marked the edges of the visible rear element and then measured the distance on the cardboard.

-Dominique

That's super helpful Dominique. Thanks so much. I'm trying to avoid spending the money to get one and discovering that it won't fit for some reason. It's impossible to be absolutely sure until I get one in hand, but you've given me confidence to take the chance.
Rob

 

[rdeloe]

Interested to see what you have cooking Rob!

It's a crazy scheme Warren!

I'm not going to say I "need" a 65mm lens. I worked all summer with 50mm and 90mm and did just fine. However, I've wanted a 65mm lens for a while to get the 'normal' angle of view on 33mm x 44mm. The pickings are slim. I hacked a Fujinon GX 65mm f/5.6 and it's OK, but it's also huge and heavy for my F-Universalis, and for my back. I gave a Nikkor-SW 65mm f/5.6 a try recently, and found it only works for me at f/11, which is not good enough. The Mamiya N 65mm f/4 would be superb, but the rear element is too large for me to remount it for the boards I already use, so I'd have to build something custom. It's also quite expensive (relative to my modest budget) and would require a Mamiya technician to lock the shutter open. I'd do it if there was no other option. But this Fujica GSW 65mm lens seems like an option worth trying.

These Fujica GSW fixed lens cameras have a good reputation on film. This person put up a lot of scanned samples that give me some confidence that the lens could work for me: https://photojottings.com/fuji-gsw690lll-65mm-f5-6-camera-review/

• Image circle covers 6x9, so more than enough room for 25mm of shift in landscape
• The shutter is easy to lock open without modifying the lens
• Image quality at f/5.6 seems quite good, and f/8 seems excellent (from the film scans anyway)
• Distortion is moderate barrel and easily corrected
• Price is reasonable, especially if I can find a "for parts" camera that has a good lens but a damaged body
• Thanks to Dominique, it looks like the rear lens element will easily clear the Rotatfoot on my F-Universalis, giving me plenty of room for movements.
• Building a mount should be straightforward, and if the flange distance permits I think I can use a Pentax 645 mount and put it on my Arca-Swiss Pentax 645 board (which would be fantastic)
• And copies of the service manual are plentiful so I won't be going into a disassembly in the dark

So we'll see... The wild card is the flange distance. I think I'm going to be OK based on some information that Bill Claff provided over at DPReview, where I asked the same question for a different audience: https://www.dpreview.com/forums/thread/4693371#forum-post-66788114

And Dominique, I should mention that Bill Claff ran a diagram of the lens he found through his software and confirmed that your measuring skills are superb! Based on his modelling, he calculated a back focus of Back focus is 41.60mm. His work is at that above link.

 

[diggles]

What a fun project Rob. I looked through the high res film scans at the end of the article and the quality is excellent. Looking forward to seeing how it works on the 50r!

 

[SCHWARZZEIT]

That sounds like an interesting project, Rob.

When I laid my piece of cardboard on the lens and pushed it against the rear lens element it felt flat as if the rear end of the lens housing was on the same plane as the farthest part of the lens cell. Thus I used a caliper to measure the distance between the silver rails and the lens housing.
In Bill's schematic based on the original patent the rear lens element is about 1.4 mm recessed into the lens body. That doesn't seem to be the case with my lens. If it was then the actual spacing between rear lens cell and film plan would be slightly larger than I measured. There could be small changes to the mechanical and optical design between the generations of this lens. I see 1981 on Bill's site which I suppose is the year the design was patented.

I didn't have any complaints about the lens' performance and found it quite amazing for such a simple 6-element design of this age. But I mostly used it at f/16 for depth of field on 6x9. It has a slight amount of CAs towards the corners but less than the 90mm of the GW. You can check out a very large 716 MP sample scan on my website of an E100G slide shot with my GSW690III: https://www.high-end-scans.de/en/samples/dv121010_03/

It will be interesting to see how this lens performs on a digital image sensor. Keep us updated.

-Dominique

 

[rdeloe]

I spent some time studying the patent drawing Bill provided and noticed that the width of the rear cell including housing is larger than what you measured (estimate 46mm from the drawing).

What you mentioned here, combined with what I measured, does suggest they adjusted the design across generations and iterations of the lens. Conventional wisdom is that the optics are the same across the various GWS models, but on the Internet people pass on all kinds of dubious information. Only the lens designers will know for sure... or me if I buy one.

Your scanned sample looks promising. Still, I need to think this through some more. Working from the information I have, including your measurements and Bill's patent diagram, I've determined that I can't mount the Fuji lens as easily as I hoped. In order to get useful movements on my F-Universalis, I would have to mount it on a recessed lens board with a custom hole. This would be straightforward, but I'm not enthusiastic about going back to lenses on boards. Another option would be to remove it entirely from the housing, keeping only the shutter/aperture mechanism and the cells. This is what I did with the Fujinon GX lenses I rehoused.

I'm on the fence... I haven't seen digital samples from the Mamiya 65mm f/4 for the Mamiya 7, but given how my Mamiya G 50/4 and G 150/4.5 perform on my GFX 50R, I have a high degree of confidence that the Mamiya 65/4 would be excellent. Unfortunately, it also needs a custom board -- and would cost 2.5x the Fuji lens by the time I'm done.

Decisions decisions!

 

[SCHWARZZEIT]

Rob, I measured the diameter of what's visible from the rear lens cell which closely matches Bill's drawing. Including the lens housing your estimated 46mm diameter seems accurate.

Fotodiox has some full resolution samples shot with the Mamiya 7 80mm on a GFX50S on their flickr, but I couldn't find any of the 65mm.

 

[rdeloe]

Dominique, thanks for double-checking. I dug through the documents I collected and the drawing Bill used is from the "Version 1" SWD 65/5.6 -- the one in the original GSW690. It was in the service manual for the GSW690. I have the manuals for the GSW690 II and III, and unfortunately they stopped including the lens cross section diagram. I did look carefully at some pictures of the size of the GWS690 II and III rear lens relative to the housing around it and it seems about the same size.

After some more measuring and drawing, I've determined that the only way to mount one of these and have useful movements that aren't constrained by the lens being too close to the rear standard, I'd have to remove it from the helicoid and mount just the front part that holds the shutter and the aperture mechanism in a custom mount of some kind. The economics are starting to work against this. On top of which I received a PM from a forum member whose opinion on optics I respect tremendously; he has used the Fujinon SWD 65/5.6 and the Mamiya 6 and 7 lenses extensively with film, and confirmed my suspicion that they're not in the same league.

So... as much fun as it's been to puzzle this through, the smart thing to do is to suck it up and go with the Mamiya 7 65mm f/4. I have one full resolution sample image from a Mamiya 7 65/4 adapted to an IQ180, made with 7mm of left and right shift, and it looks superb. Changing the mount and fabricating a board to use it on my F-Universalis should be straightforward. I do wish the image circle was larger, but a circle of good definition that covers 6x7 film still gives me lots of room on a 33mm x 44mm sensor. Plus, the circle of good definition on my Mamiya G 50/4 is much larger than needed to cover 6x6 film, so perhaps Mamiya erred on the generous side with the 65/4.

Thanks for your help.
Rob

 

[rdeloe]

And that's the end of that for now... I found a good deal on a Mamiya 7 65/4, and it's on its way to Bill Rogers to have the shutter locked open and the bits I don't need removed.

Thanks again to everyone who read the thread and chipped in with advice and suggestions, including a couple people who emailed or PM'd me off line. What a great community!

 

[Ed Hurst]

We definitely need to see more on this project as it develops and, of course, some results at the end of it. Good luck!

 

[rdeloe]

We definitely need to see more on this project as it develops and, of course, some results at the end of it. Good luck!

I surely hope to be able to report that the Mamiya L 65mm f/4 is brilliant because the work Bill Rogers, the Mamiya repair expert, is going to do is irreversible! If it's a poor performer I will own a very nice paperweight and conversation starter about cautionary tales...

Fun fact: the remount *might* be dead simple. The diameter of the Mamiya 645 mount part that is held on with three M1.6x6 screws appears to be exactly the diameter of the Mamiya 7 mount. My plan is to drop a Mamiya 645 Extension Tube #1 through a hole in a recessed Arca-Swiss lens board to create the camera-side mount, and to use the lens mount part from the extension tube on the lens as a straight replacement. The only minor technical challenge is drilling and tapping new holes in the 645 mount to lock it to the lens. Hopefully in a few weeks I can report that it really was that simple!