Fuji GX617 sharpness issues

[markymarkrb]

Forum,

Is anyone having any sharpness trouble with the lower left and right corners of their images from their FujiGX617 105mm lens?  It might just be technique but I thought that these lenses were supposed to be extremely sharp images corner to corner.  Any suggestions or help would be greatly appreciated.

[Slobodan Blagojevic]

Well, hard to comment on the sharpness of the lower left corner, for obvious reasons, but the lower right corner might just be a DOF issue, being the closest to the camera.

[Anders_HK]

Here is another guess;

617 means a great width and the lens perhaps has some variation in this plane. However since lower right and left are out of focus could perhaps indicate that the lens need readjustment to camera?? The fact you not see same issue at top perhpas shows no problem with lens but instead point at mounting of lens need to be adjusted for it to be at optimum to film plane?? Hence at shimming of lens mounting flange to camera. Any changes to mounting recent??

Regards
Anders

[alainbriot]

It's a depth of field issue.  The blurred areas are all along the bottom part of the image, not just in the bottom corners.  The background's sharp, so my guess is you focused on the background and didn't close the lens down.

The Fuji 617 lenses are basically 8x10 lenses.  Such lenses need to be stopped down all the way to give full depth of field, and hyperfocal focusing distance must be used.  If you didn't do this, then it's no surprise you have out of focus areas.  These are VERY sharp lenses, but you need to use superb technique to get the most out of them.  617 photography is definitely not point and shoot!

In fact, focus can be such a problem with near-far scenes that I used the groundglass focusing screen with mine.  It works fantastic.  The only thing is you have to shoot a full roll for each new composition.  But that's not much of a problem when you can take only 4 shots per roll.  I just bracketed: 1 exposure right on, 1 low and 1 high, finally one more right on for insurance, and voila, roll's done with !  

As a general rule, I blame myself or my technique before I blame my equipment.  Most of the time the problem is caused by me rather than by the camera.

[r944miller]

Suggest re-reading Alainbriot's post as, IMO, it hits about every point. If you need further evidence to convince yourself, find (or construct) a scene that has similar characteristics, vis-a-vis, foreground to background distances, sue a tripod, shoot an image, then invert the camera and take a second image. Compare the images.

(After writing the above it occurred to me that you should also be able to simply invert the lens assembly for the second shot. Obviously you would need to either use a second roll of film or to invert the lens inside a film tent/darkroom and then remount the camera on the tripod. The lens seems to mount eitherway with the only ill effect seeming to be that the contacts for the body release do not mate up so you would need to release the shuttter at the shutter itself. Since such an inverted mounting could easily be done in error, I would assume that Fuji's design of the electrical connections is such that no ill effect will result. If you were concerned you could simply remove the battery.)

Regards,

[LesPalenik]

I concur that the blur on the bottom is caused by relatively shallow DOF. The rocks in the front are much closer to the camera than the top of the falls, and even at a small aperture you need to aim for hyperfocal distance. I have experienced similar problems myself and for practicality reasons, I would try to aim the camera slightly higher and minimize the foreground.

Not to hijack the thread, some of these lenses exhibit noticeable fall-off to one side or all four corners. Your copy doesn't seem to have this problem, so you've got yourself a great lens.

[alainbriot]

Les,

I think he has a center filter on that lens. See his other thread:

http://www.luminous-landscape.com/forum/index.php?topic=51443.0

ALain

[LesPalenik]

Thanks, Alain

that explains it. I was already getting envious about his lens.

Les

[alainbriot]

In my experience all wide angles for large film format do vignette to some extent.  I've always considered it silly that manufacturers sell center filters separately from the lens. They should come with the lens since they are virtually indispensable. The only reason to not get one is if you have one from another lens that can work well, like the 90 on the 105 here.