FUJI Rangefinder Infinity focus

[danni_suskin]

I just aquired a Fuji GSW689III. I noticed that when focusing at a

distant subject, the rangefinder indicates focus is achieved just

before the lens cannot be turned any further ie. not at the final

travel point of the focusing ring. Rather like many of my Nikkor

lenses (35mm). Is this typical for these cameras and should I trust

the rangefinder, or should I turn it to it's full extent for infinity

focus?

Thank toy.

[jim schwaiger]

Some cameras focus "beyond" infinity which is probably what you are experiencing. Things contract and expand with temperature changes, so this allows focus at infinity over a wide temp. range.

[jay_.]

Not hardly. That only applies to long telephoto lenses and mirror lenses. For a rangefinder to be accurate, the images *must* coincide exactly at the point the lens reaches the infinity stop. However "infinity" is just that. To truly check the rangefinder's infinity adjustment, focus on a sharp vertical target (like a radio tower) *at least one mile away*. Some folks use the edge of the moon at night. If the images don't line up when the lens is at infinity, the camera needs adjusting. Otherwise it will be off at ever other distance, even if DOF covers some of the error.

[steve_hamley]

Folks,

 

I've noticed the same behavior with my Mamiya 7 rangefinder and heard the arguments that if the images don't line up at the lens stop, the rangefinder is off. There is an unspoken assumption here that when the lens stops, it is designed to be at infinity focus. If the lens designer for some reason designs the helical focusing mount to focus beyond infinity, then the preceeding argument is not true and the rangefinder is not necessarily off. Mamiya at least has reportedly stated that they design lenses to focus beyond infinity.

 

I tested my Mamiya 7II rangefinder on the moon and noted slight disalignment of the images. Next, I set up a suitable subject at 6 feet plus a few inches (6' closest focusing for the 150mm lens) for the 150mm lens, and focused carefully and shot wide open. The depth of field was where I expected it to be, so I concluded the rangefinder accuracy was correct as far as I could tell.

 

Be careful before you start fixing problems that may not exist or be of significance. You can easily end up in worse shape.

 

Thanks!

 

Steve

[john_bright]

With your first roll of film just make sure that it focusses OK at close distances and then trust the rangefinder for everything else.

[jerry_friedman]

I have owned a bunch of Fuji MF cameras and this is what I have

found on all of them. The infinity focus is more variable than with

other cameras. Usually, on 35mm cameras, you hit infinity focus

at about 60 feet and that is all there is. The Fuji's however are

more thoughtful. At about 60 ffet or even 100 feet, you will find

the rangefinder focusing on the first part of the infinity loop. To

focus all the way at the "end" of the infinity focus, you have to be

looking at something in Denver. All this means is that if your RF

is accurate (try focusing on something 60 feet away and then in

Denver and put the infinity on the first loop and then at the end)

and see the difference. One more good idea from Fuji.