Fujinon SW 90mm f8 won't focus in infinity

[eddymendoza]

Could it be possible that the lens I just purchased on Ebay is not as great as it seems? I am having thoughts that maybe the seller or someone else before the seller changed out the rear lens for a different lens. This lens looks great! It just won't focus on anything that's further than a few inches away. I am using a Cambo 4x5 monorail camera and no matter how I set the front or rear it just won't focus fa away. This is supposed to be a wide angle landscape lens but only works as a macro lens. My other lens is a Caltar 210mm f5.6 and it focuses at any distance meaning the bellows on my Cambo does the focusing as it should. 

 

Any help would be appreciated.

 

Ed

[Glenn McCreery]

Assuming that there is no problem with the lens, then it won't focus to infinity because the film plane is too far away from the lens. The distance from a point within the lens (the rear nodal point) to the film plane should be the focal length, 90mm, to focus at infinity. A recessed lens board might cure your problem.

The relevant (thin lens) equation is  1/fl = 1/f1 + 1/f2, where fl = focal length, f1 = distance from lens to subject, f2 = distance from lens to image plane. Substituting f1 = infinity, then f2 = fl. 

 

Edited September 30, 2023 by Glenn McCreery

[AJG]

Glenn has it--you need a recessed board for your Cambo to use this lens, especially if you want to use any camera movements with it.  A bag bellows would also be helpful for movements with wide angle lenses on 4x5.

[dan_fromm2]

Hmm.  I b'lieve that the OP posted the same question on LFPF.  Only there he admitted that he didn't try to focus on the GG, he use a Canon DSLR hung, via an adapter, on the Cambo's rear standard.  This adds considerable extension.  Good answers, Glenn and AJG, but not really to the OP's question.

[AJG]

2 hours ago, dan_fromm2 said:

Hmm.  I b'lieve that the OP posted the same question on LFPF.  Only there he admitted that he didn't try to focus on the GG, he use a Canon DSLR hung, via an adapter, on the Cambo's rear standard.  This adds considerable extension.  Good answers, Glenn and AJG, but not really to the OP's question.

If the OP wanted a useful answer he might have shared all of the parameters of his problem...

[eddymendoza]

18 hours ago, Glenn McCreery said:

Assuming that there is no problem with the lens, then it won't focus to infinity because the film plane is too far away from the lens. The distance from a point within the lens (the rear nodal point) to the film plane should be the focal length, 90mm, to focus at infinity. A recessed lens board might cure your problem.

The relevant (thin lens) equation is  1/fl = 1/f1 + 1/f2, where fl = focal length, f1 = distance from lens to subject, f2 = distance from lens to image plane. Substituting f1 = infinity, then f2 = fl. 

Thanks but I think I've exhausted all of the possibilities and will probably be purchasing a longer lens in the end. Let me see if I can surmised what I've found out from the good folks at Large Format Photography Blog. I tried all of the advise given like taking off the digital adapter and replacing it with the original ground glass, collapsing the bellows so it is completely closed, trying to focus with the lens off against a well lit subject and moving it back and forth and nothing seems to work perfectly. I did have better luck with the ground glass instead of the digital adapter and that does indicate that the problem is distance. I was able to see the subject a lot better once the bellows was completely closed but the critical focus wasn't there. Some people have suggested that the 90mm may not be able to work with my bellows because of the distance and I get that. I don't think getting a bag bellows will be of any use because even with the camera closed completely now I can't get critical focus due to the knobs. I wasn't looking for any movements with this 90mm lens because I just wanted something wider than the 210mm for landscapes so there's that. I appreciate all of the information here and at LFP blog but I think I've hit a dead end as it pertains to the 90mm. I will keep trying but just because I don't like to give up that easy. If and when I figure this out I will definitely update everyone here and elsewhere. 

Thanks for all of your help, I really do appreciate it.

 

18 hours ago, Glenn McCreery said:

 

 

[dan_fromm2]

Eddy, go back to LFPF.  I posted a complete solution to your problem there, to which you took offense.  You should read my response, which might soothe your hurt feelings.

So you'll know, I have several Cambo SCs, also several 90 mm lenses including a thoroughly broken 90/8 SA that I bought for its shutter.  They all focus to infinity on my 4x5er.  So, for that matter, does my 35/4.5 ApoGrandagon.  The 35 doesn't cover 4x5.