Infinity Focus - how far it should be?

[lucwc]

Hi,
I am new to forum and have epson r-d1 for months. I tried to adjust patch in order to get more accurate focus. Checked all related topics on this forum and also get lot good info from here. Now I have one question (may be it is foolish question):
How far away I should look at when adjust the infinity focus in the patch. I tried mile way but my 90 elmerit-m won't focus at the closed distance. If I tried just 15~20m away then Infinity focus (means mile away) is not clear focused). Any suggestion here?
Thanks in advance!

 

[Finder]

Rangefinders are very sensitive. A mile is too close to judge infinity.

You also need to figure out is the rangefinder needs calibrating or the lens. Calibrating the rangefinder to a lens that is out of calibration compensates for that lens, but the rangefinder will no longer be acurate for the other calibrated lenses.

 

[lucwc]

Thanks Finder for your response. I am thinking of the lens calibration since my 35 and 50 are both okay with the settings. I am not sure if 90's need calibrate. I try to do calibration to RF myself here😀 .

 

[peter_n]

I use the moon to check alignment with the lens set at infinity.

 

[lucwc]

I use the moon to check alignment with the lens set at infinity.

nice suggestion, Peter, I will try out at night. Thanks!😀

 

[ClaremontPhoto]

I remember reading somewhere that Leica check rangefinder accuracy at 1m, 10m and 50m.

 

[Gabriel M.A.]

I use the moon to check alignment with the lens set at infinity.

I hereby call this the Ralph and Alice Rule 😀

 

[awilder]

Actually anything beyond 3/4 mile is just fine for Leica style rangefinders even with lenses as long as the 135/2.8. I find the moon or stars problematic due to the high contrast and internal reflections making subtle rf errors more difficult to detect.

 

[lucwc]

Read above messages that I would try 1/10/50/ 0.75 mile/ mile/ moon all together😱 , Too many to me. So what is the practical way I should use, I need experienced master here!🙂

 

[Xmas]

It depends what you got outside your den window, on a clear day I have a white washed cottage about 3 miles away that a Kiev will just resolve. On a hazy day it dissappears, and I use a clock tower about 300 yards, the Kiev can just about detect the clock tower is not at infinity. I'm not too worried.

Noel

 

[M4streetshooter]

For the life of me, I can't ever understand why anyone would focus on infinity.......well, 1 reason, to alter the near focus....other than that...the focus scale/aperture scale is certainly more accurate and using hyperfocal distance, your not focusing on infinity anyway....why waste the near distance by focusing on infinity....?

 

[lucwc]

For the life of me, I can't ever understand why anyone would focus on infinity.......well, 1 reason, to alter the near focus....other than that...the focus scale/aperture scale is certainly more accurate and using hyperfocal distance, your not focusing on infinity anyway....why waste the near distance by focusing on infinity....?

Hi, I am trying to figure out the infinity point when doing RF patch adjustment. Cetainly I will do closed point adjustment after get the correct infinity point focused. That is my question. Thanks.

 

[Uwe_Nds]

I remember reading somewhere that Leica check rangefinder accuracy at 1m, 10m and 50m.

Jon,

IIRC, the calculated infinity setting equals 1000 x focal length.
Therefore, with a 50mm lens, infinity would be @ 50m.

Best regards,
Uwe

 

[payasam]

Uwe, for a separate range-finder the focal length of the lens is of no consequence.

 

[Rob-F]

Jon,

IIRC, the calculated infinity setting equals 1000 x focal length.
Therefore, with a 50mm lens, infinity would be @ 50m.

Best regards,
Uwe

And even if you assume a distance of 10,000 times the focal length, infinity would be just 500M away. That's only three-tenths of a mile.

ANother way would be to figure some multiple of the rangefinder base. Let's see what happens if we use the distance of the RF window from the center of the VF window on a Leica M. That's 2 and 5/8 inches, roughly. 2.625". We are ignoring the magnification factor here. And let's take 1,000 times that. Now we have a distance of 2,625 inches, or 219 feet. Can the rangefinder discriminate such a small angle? OK how small is this angle? Taking the inverse tangent of .001, we get 0.0573 degrees. Okay, maybe the rangefinder is so precise that this small an angle makwes a difference. So to be on the safe side, let's now try 10,000 times the finder's base. That's 2,190 feet. And ATAN .0001 is .00573 degrees. I don't imagine my Leicas, good as they are, can detect such a small angular difference.

Conclusion: I would say that a target a half-mile or so away has to be as good as the moon for adjusting a camera rangefinder.

Agree or disagree?

 

[pvdhaar]

I've two M-mount cameras that were repaired/overhauled in different places last year. Both agree to within 1 cm for an object placed along a tape measure at 2 meters. Something I find astonishing given all the adjustments possible. Both think infinity is a chimney less than 100 meters away. Neither will entirely line up the windmill at 1000 meters away.

But I don't care much, as focus accuracy is more important in the 1 to 3 meter range.

 

[Xmas]

If you are calibraing a rgfdr infinity is as far away as you ccan get, moon is ok. the repair person will have a collimator...

Noel

 

[ClaremontPhoto]

Infinity for photographers does mean the same as infinity for astronomers or mathemeticians.

A typical lens goes to 5m or 10m, and then infinity.

There is no 100m or 500m marking. The twist between 10m and infinity is tiny.

Feel free to test your rangefinder on a building a block or so away.

 

[rxmd]

A typical lens goes to 5m or 10m, and then infinity.

Depends, telephotos often have more. My 2.8/180 Sonnar has a 50 meter mark. Not common with rangefinder lenses, though.

 

[iUser]

epson say adjust off something =>30 meters