Have you ever owned a Fuji 65mm f/8 for G(L)690?

[yessammassey]

This is a long shot, because it's a somewhat obscure lens. It also feels like a somewhat obvious question, but here goes:

Does this lens' diaphragm fully retract beyond the edge of the glass when set to its minimum aperture? Or does it always stick out just a bit?

Seems like an obvious question, right? A wide open lens is wide open. QED.

I suppose that there are at least a few historical lenses out there that didn't completely 'open up' at their maximum aperture, but this lens is fairly 'new' in terms of the entire history of photography, and was fairly advanced for its time, so I'm guessing that it did open up all the way by design, and that this copy is just the result of an inept servicing.

On the lens I am looking at, which is an otherwise nice example, there are aperture blades visible at f/8. They stick out just enough to give the entrance pupil a pentagonal shape.

I've heard that the Fujinon SW 65/8 large format lens is essentially the same optical design as the lens in question, just without the helicoid. So if you can share how that lens' diaphragm behaves at f/8, it's probably the same.

 

[Dan Fromm]

Where the diaphragm leaves sit when the diaphragm is wide open depends on the shutter, not on the lens.

FWIW, I have a 65/8 Fujinon SW in a Seiko shutter. When the shutter's aperture indicator is at "8" the entrance pupil is ever so slightly pentagonal. When the aperture indicator is moved wider open the blades disappear and the entrance pupil is round.

I've been shopping Fuji lenses recently, used Joe McGloin's very useful list of their lenses (see [URL]http://www.subclub.org/fujinon/index.htm[/URL]) as a guide. Its a little confusing so I used eBay listings to build small database of lenses' serial numbers and features. It appears that Fuji's LF lenses have six digit serial numbers and that the first two digits of the s/n indicate design type. This may not be true. If you want to believe it, the two 65/8 LF lenses I came across have serial numbers beginning 65 and are engraved Fujinon SW. I came across a couple of 65/8ers for GL690s. They're engraved Fujinon SW S and have serial numbers beginning with 65. So I suspect very strongly that LF and GL690 65/8 lenses are the same design in different mounts.

 

[MattKing]

What Dan said.
For lenses without a built in shutter, it would be much more reasonable to expect aperture diaphragms to be matched in size to the lens. But there wouldn't be anything other than concerns about excess lens size to stop a manufacturer from using a common aperture diaphragm in several different lenses.

 

[Dan Fromm]

Re serial numbers, there's a hole in my theory. I just did a sanity check, found a 65/5.6 Fujinon SW S in what appears to be a G/GL 690 mount. s/n 656575. By my s/n theory this should be an f/8er.

 

[yessammassey]

The lens in question has s/n 655567, so I think that fits with your theory.

Here is a photo of the lens in question, aperture set to f/8. 8 is the maximum aperture, but I can twist the ring a half-click past the point where '8' is engraved on the ring. It pushes the blades wider by less than 1mm. There is no way to get the diaphragm to 'open up' completely. Does this seem right to anyone?

 

[dynachrome]

I have seen lenses for other formats which have aperture mechanisms which do not appear to open fully even when the lens is set to its widest opening. The explanation I heard was that if you could open the aperture fully, the performance of the lens would suffer at that setting.

 

[Dan Fromm]

The lens in question has s/n 655567, so I think that fits with your theory.

Here is a photo of the lens in question, aperture set to f/8. 8 is the maximum aperture, but I can twist the ring a half-click past the point where '8' is engraved on the ring. It pushes the blades wider by less than 1mm. There is no way to get the diaphragm to 'open up' completely. Does this seem right to anyone?

Mine is noticeably wider open with the pointer at "8" than yours is.

Check the entrance pupil's diameter. At f/8 it should be 65/8 = 8.13 mm, at f/11 it should be 5.9 mm. Hold the lens at arm's length, lay a ruler across the front, and see what you get. Don't measure the exit pupil, which is what your pictures show. Measure the entrance pupil.

 

[moto-uno]

I hope this is of some use , I've 2 65/5.6 Fujica GL lens and both have serial #'s starting with 65 and on these
lens at 5.6 show the slightest pentagle (sp) shape when viewed through into bright light. Peter

 

[yessammassey]

I asked an eBay seller who was offering another 65/8 if the diaphragm on their lens behaved the same as the one in question, and they said that it did.

I have no experiential knowledge of large format lenses, but perhaps the ability to 'open up' the LF 'version' of the Fujinon SW is there as a creative option that was held back from the MF version, given the latter's original raison d'etre (tour group souvigner photography), where the possibility would just make your regular operations less foolproof. This is assuming that opening up the aperture past f/8 would significantly degrade the image quality in the periphery of the frame, which I think is pretty likely.

At this point I feel more confident that there is nothing too out of the ordinary with this lens' diaphragm.

Definitely going to measure it, too, though. And thanks for the instructions on how to do so.

Now it seems like my G690BL, which I've been considering this lens for, is finally starting to have issues with its blackout curtain. So I'm hopping from one issue to the other, which is what I figured would happen if I brought into this ancient system.

 

[Dan Fromm]

I have no experiential knowledge of large format lenses, but perhaps the ability to 'open up' the LF 'version' of the Fujinon SW is there as a creative option that was held back from the MF version, given the latter's original raison d'etre (tour group souvigner photography), where the possibility would just make your regular operations less foolproof. This is assuming that opening up the aperture past f/8 would significantly degrade the image quality in the periphery of the frame, which I think is pretty likely.

Good guess, but wrong. My 65/8's Seiko shutter's diaphragm will open much wider than needed. It doesn't stop opening when the pointer is at 8. And this can be seen with the front cell unscrewed from the shutter.

When, however, I move the lever past 8 the size of the lens' entrance pupil doesn't change from its size at f/8.

Lenses for RF and SLR cameras often (nearly always?) have mechanical stops that prevent the aperture control from going past wide open. Shutters for LF cameras have fixed maximum openings; #0 shutters, for example, can open as wide as 24 mm and no wider. A shutter doesn't know the maximum aperture of the lens mounted in it. If the maximum aperture is reached with the diaphragm partly open, well, then the diaphragm lever will often go past wide open and the entrance pupil's diameter won't change.

Reasoning from small format lenses to lenses for LF cameras isn't quite safe.

 

[outwest]

The 65mm f/8 for my Fuji GL690 shows a definite pentagonal opening when wide open. A great lens, by the way.