Speed Graphic Rangefinder Question

[axs810]

Hello,

I have a Speed Graphic with a 135mm lens and a calibrated rangefinder. I was wondering would it be possible to swap out the lens with a Rodenstock APO-Sironar S 135mm and still have accurate focus with the rangefinder?




Thanks,
axs810

[Lachlan 717]

Without knowing what the in situ lens it, it's impossible to say. Its flange focal distance would need to be compared to the R'stock's.

If it's the Kalart side mounted version, it should be an easy fix, though, with a simple screw being loosened, a slide correction and then retightening of the screw.

[Tin Can]

I have not found it not 'easy' to readjust any RF and have tried several times with muliple KalArts. If you have one working 'perfectly' I suggest you do not fiddle. Off course you can mount any lens you want and use GG to 'sight in or focus'.

Ymmv, but I have learned my lesson and have several that are a joy to use in 'original' condition.

You may find yourself very 'unhappy' in short order.

Or not.

[Corran]

If you have one working 'perfectly' I suggest you do not fiddle.

Yep.

The simple thing to do though is lock the camera at the infinity position (confirmed by the RF), put your 135mm APO-Sironar on and move the front standard till it focuses to infinity on the GG, and then test it yourself. It's possible it will work, but really the only one who could say is you. I have calibrated a lot of Kalarts and about 20-30% of them are just out of whack so much they can't be [re]calibrated, at least by me. I've bought a couple of mechanisms and replaced the whole part, which solved the problem, but again if it works with whatever 135mm you have accurately I'd leave it be.

[Dan Fromm]

In general, no. The focal length engraved on a lens is rarely the lens' actual focal length and two randomly selected lenses with the same engraving rarely have the same focal length.

By all means swap lenses if you want to, but be prepared to recalibrate the RF. Simply adjusting the bed stops almost certainly won't be enough.

[Jim Jones]

There is some variation in the actual focal length of 135mm lenses. For the top rangefinder Speed Graphics, cams for focal lengths of 132, 133.5, 135, 136.4 and 138.7mm were available to compensate for this. If two lenses are close enough in focal length but have different flange distances, readjusting the infinity stops is all that should be needed with either type of rangefinder. It's been decades since I've had to adjust Kalart and Meyer side rangefinders, but managed to get the job done.

(edit) Dan and Bryan type faster than I can do research. Good. The more people chime in, the more we learn.

[BrianShaw]

I certainly agree with all of the above, but you never know until you try it. I replaced a 135 Optar with a 136 Symmar-S on a SuperGraphic and found the swap to be within reasonable tolerances. Maybe that was a lucky break, but it was my lucky break and only could be determined by experience.

[Jac@stafford.net]

[...] If it's the Kalart side mounted version, it should be an easy fix, though, with a simple screw being loosened, a slide correction and then retightening of the screw.

True, and permit me to caution that the simple screw is tiny, of soft brass and almost always mangled or broken. We had a thread with pictures on the work-around to fix that. I can find it if there is new interest.

[Lachlan 717]

True, and permit me to caution that the simple screw is tiny, of soft brass and almost always mangled or broken. We had a thread with pictures on the work-around to fix that. I can find it if there is new interest.

Jac,

Thanks for mentioning this.

I ruined the screw on my current SG. I've just finished replacing it with a 2.5mm screw. I had to tap a thread into the brass slide base, which is easy. I then superglued the nut in place, allowing me to tighten the setting with a small socket.

I think it's a much better design than the screw, as it allows greater tightening of the assembly.

[axs810]

Thank you all for your replies!


Unfortunately I just checked the rangefinder again and it's focusing closer than the targeted area. Looks like I'll have to try adjusting the rangefinder once I read up and understand how to do it lol.



Thanks again!



edit/ I guess I thought it was calibrated because when I last used the rangefinder I was shooting at f/16 and everything seemed fine. I wanted to be sure so I tested it against the ground glass with an x8 loupe and found it wasn't as accurate as I thought it was.