Question for techs: extending focus beyond infinity (1 Viewer)

Patudo · Oct 27, 2018

Hi,

A couple recent comments on Cloudynights:

Rich V. said:
I had Cory S. tweak my Fuji FMTs so that I had more + focus range for my far-sightedness; worked great because the Fuji's short ER didn't play well with my strong + eyeglasses.

SMark said:
Cory has adjusted many 7x35's to accommodate my nearsightedness. I've had at least 3 FPO Rangemaster's that would not reach focus for me, and Cory made all of them work for me, along with a couple others in addition to those.

Could any kind person with technical experience enlighten me on how this is achieved and (more pertinently) how difficult it is? I have a Swift 7x35 (model 766) that I would like to focus just a little further beyond infinity - it is just about acceptable now, but stretches the accommodation of my left eye more than I'd like. I'd gladly sacrifice close focus - a minimum focusing distance of 30 or even 40 feet would still leave me with plenty of room. The optical tech here who had a look at them informed me that adjustments of the type mentioned above weren't possible. I would welcome any comments.

Regards,
patudo

dries1 · Oct 27, 2018

If done, I assume one would lose the close focus ability on a glass.

Andy W.

WJC · Oct 28, 2018

Patudo said:
Hi,

A couple recent comments on Cloudynights:

Could any kind person with technical experience enlighten me on how this is achieved and (more pertinently) how difficult it is? I have a Swift 7x35 (model 766) that I would like to focus just a little further beyond infinity - it is just about acceptable now, but stretches the accommodation of my left eye more than I'd like. I'd gladly sacrifice close focus - a minimum focusing distance of 30 or even 40 feet would still leave me with plenty of room. The optical tech here who had a look at them informed me that adjustments of the type mentioned above weren't possible. I would welcome any comments.

Regards,
patudo

You move the objectives in or out, depending on the need. All else will be fine—except collimation. :cat:

Patudo · Oct 28, 2018

Thank you sir. Is this something that can be done for most binoculars (1960s era Swifts in particular), and how troublesome would moving the objectives be, in terms of reseating them within the barrel (and any other quirks that might not be immediately apparent to the layman)? The chap I sent my Swifts to informed me that there wasn't enough space. He's well regarded and I've been happy with his work on other binoculars. I didn't ask for a more detailed explanation, but maybe I should have.

WJC · Oct 29, 2018

Patudo said:
Thank you sir. Is this something that can be done for most binoculars (1960s era Swifts in particular), and how troublesome would moving the objectives be, in terms of reseating them within the barrel (and any other quirks that might not be immediately apparent to the layman)? The chap I sent my Swifts to informed me that there wasn't enough space. He's well regarded and I've been happy with his work on other binoculars. I didn't ask for a more detailed explanation, but maybe I should have.

If that guy was Tony or Gary, they are quite good. But the US Navy taught things that didn't come to mind for many others. Yet, if there is not enough "meat" to recess, the solving of the problem can still be achieved, but not cost-effectively. :cat:

Bill

18000bph · Oct 29, 2018

Interesting that the original post complains about short ER of the FMT. I thought the Fujinon to be among the most generous ER available.

richard866945 · Oct 31, 2018

adjusting infinity

Patudo said:
Thank you sir. Is this something that can be done for most binoculars (1960s era Swifts in particular), and how troublesome would moving the objectives be, in terms of reseating them within the barrel (and any other quirks that might not be immediately apparent to the layman)? The chap I sent my Swifts to informed me that there wasn't enough space. He's well regarded and I've been happy with his work on other binoculars. I didn't ask for a more detailed explanation, but maybe I should have.

There are three things I would look at.
1. is there room to add a spacer in front of the OG within its mount?
2. Is there any metal that could be removed from the back of the assembly that contains the OG to allow the whole assy to sit further in?
3. Can the ledge that the OG assy sits on, be reamed out a mm or two?

I have a repair workshop (Action Optics) and would be happy to examine these possibilities.

Patudo · Nov 1, 2018

WJC said:
If that guy was Tony or Gary, they are quite good. But the US Navy taught things that didn't come to mind for many others.

Bill

Ah, well; sadly, much though I'd like to, the cost of sending mine back across the pond to one of that exalted brotherhood outweighs the utility I'd get from having the adjustment done. The "quite good" will have to do for now.

Gracias,
patudo

WJC · Nov 1, 2018

Patudo said:
Ah, well; sadly, much though I'd like to, the cost of sending mine back across the pond to one of that exalted brotherhood outweighs the utility I'd get from having the adjustment done. The "quite good" will have to do for now.

Gracias,
patudo

I can’t trust this program with ONE BLOODY SENTENCE!

I said (using Word, this time):

They are not across the pond; they’re next door. :cat:

Bill

Question for techs: extending focus beyond infinity (1 Viewer)

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