Author Topic: Does infinity calibration always need to be that hard?  (Read 1683 times)

Zang

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Does infinity calibration always need to be that hard?
« on: August 01, 2022, 14:32:18 »
I found infinity calibration very cumbersome and here is why. First, I need to fully assemble the lens with infinity being passed to be able to pinpoint it. Then I need to disassemble the lens, sometimes almost completely, to be able to adjust. I don't think there is a way around that. Second, I need to find a fairly far object to test the infinity. Believe me, it is not simple in my case :) In my location, I need to drive from home a bit to have a good testing terrain.

I was thinking about (and I actually tried) calibrating using the shorter distances but I don't think that is accurate and I still rely on calibrating real infinity. What is your experience working with infinity calibration?

Jack Dahlgren

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Re: Does infinity calibration always need to be that hard?
« Reply #1 on: August 03, 2022, 04:34:46 »
“Real infinity” is pretty far away. How about calibrating using the moon?

Zang

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Re: Does infinity calibration always need to be that hard?
« Reply #2 on: August 03, 2022, 16:28:06 »
%u201CReal infinity%u201D is pretty far away. How about calibrating using the moon?

I know, real infinity is not far nor near, it is nowhere LOL

The moon is currently only 10% and comes out low and late, but yes, it is my favorite calibration tool!

SLR

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Re: Does infinity calibration always need to be that hard?
« Reply #3 on: August 12, 2022, 02:37:48 »
I have learned that infinity is at a factor 1000 x focal length, with a 50mm lens that would be : 1000 x 50mm = 50 mtr.....unless specialized lenses are at play, such as macro lenses.
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Zang

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Re: Does infinity calibration always need to be that hard?
« Reply #4 on: August 12, 2022, 14:30:14 »
I have learned that infinity is at a factor 1000 x focal length, with a 50mm lens that would be : 1000 x 50mm = 50 mtr.....unless specialized lenses are at play, such as macro lenses.

What you are telling is interesting, but I think the relation might not be linear. The distance resolution of my Nikkor 180mm f2.8 is far beyond 200m!

pluton

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Re: Does infinity calibration always need to be that hard?
« Reply #5 on: August 18, 2022, 01:46:08 »
I have learned that infinity is at a factor 1000 x focal length, with a 50mm lens that would be : 1000 x 50mm = 50 mtr.....unless specialized lenses are at play, such as macro lenses.
That formula has been published and repeated for many years but, as Zang suggested, it doesn't seem to apply to photographic lenses in actual use. Might be part of a famous theoretical argument in optics/physics?
Keith B., Santa Monica, CA, USA

Nasos Kosmas

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Re: Does infinity calibration always need to be that hard?
« Reply #6 on: August 18, 2022, 12:06:07 »
That formula has been published and repeated for many years but, as Zang suggested, it doesn't seem to apply to photographic lenses in actual use. Might be part of a famous theoretical argument in optics/physics?
This is a very general formula, the more of the lens mm the less accuracy to  infinity
Physics is applied to any lens no mater is a macro, tele or anything else

Moon is a safe object for infinity focus unless you have a super tele or telescope :)

There is a simple way for dyi-ers to make an in-house infinity focus system
Find a binocular objective lens let’s say 500 mm and position a low light source in the exact position of 500 mm ( like a reverse telescope )
If you go to the opposite side of the light source you need infinity focus to see clearly the light source  ;)
This is because the light beams are parallel as the source is on infinity

David H. Hartman

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Re: Does infinity calibration always need to be that hard?
« Reply #7 on: August 18, 2022, 20:54:46 »
“Real infinity” is pretty far away. How about calibrating using the moon?

The moon moves in the sky and we view the moon through a lot of atmosphere so I doubt that the moon is a useful infinity target.

I've used a light pole 0.3 miles (0.5 kilometers) distant as an infinity target to adjust a 50mm f/1.4 AIS Nikkor. The air temperature was probably about 75 °F (24 °C) and clear so these did not interfere. I used a Nikon F5 with a 6x waist level finder.

If infinity isn't set perfectly I'd much prefer a lens to focus passed infinity.

I'm not sure how much this might help.

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Hugh_3170

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Re: Does infinity calibration always need to be that hard?
« Reply #8 on: August 18, 2022, 23:16:23 »
Nasos, optical labs have similar equipment for calibrating the infinity focus of lenses - as per your last line.


.....................................

There is a simple way for dyi-ers to make an in-house infinity focus system
Find a binocular objective lens let’s say 500 mm and position a low light source in the exact position of 500 mm ( like a reverse telescope )
If you go to the opposite side of the light source you need infinity focus to see clearly the light source  ;)
This is because the light beams are parallel as the source is on infinity

Hugh Gunn

Nasos Kosmas

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Re: Does infinity calibration always need to be that hard?
« Reply #9 on: August 19, 2022, 13:50:05 »
Nasos, optical labs have similar equipment for calibrating the infinity focus of lenses - as per your last line.
I know it’s not my idea I show it on a camera repair house many years ago 8)

Hugh_3170

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Re: Does infinity calibration always need to be that hard?
« Reply #10 on: August 19, 2022, 14:20:58 »
Yes, but your DIY solution is still of interest to those that need to perform infinity adjustments.  Thanks for this.

 :)

I know it’s not my idea I show it on a camera repair house many years ago 8)
Hugh Gunn

Zang

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Re: Does infinity calibration always need to be that hard?
« Reply #11 on: December 15, 2022, 00:05:47 »
At the end, I have found a lens whose focusing adjustment does not require tearing down almost everything :) Contax Zeiss 50mm f1.7 allows infinity adjustment with the optical assembly installed. Only the front barrel needs to be removed and that is easy. It is pretty clever and I wish every lens had that ability.

Øivind Tøien

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Re: Does infinity calibration always need to be that hard?
« Reply #12 on: December 15, 2022, 02:19:29 »
A litte note here that in deep space astrophotography we always want the lens to be able to focus slightly past infinity. For longer lenses we use a Bahtinov mask at magnified live view to find focus on a star before each imaging session and often several times during a session if the lens is not at a stable temperature. The focus point might even change depending on how far above the horizon it is imaged due to optical bending of light rays by the atmosphere, so it is best to use a star close to the imaging area for the focus. If a Bahtinov mask is not available, using the weakest star visible in magnified live view provides good focus, perhaps guided by a brighter nearby star to initially narrow it down.

With a lens with ED elements, if the hard stop is at infinity at one temperature, one could risk not getting to infinity when the temperature changes. I find that even most of my non-ED AIS lenses will have the hard infinity stop very slightly past infinity (tested on multiple bodies). It is not very far off though so for regular near infinity landscape imaging with the lens stopped down in daytime the hard stop is usually sufficient.

Øivind Tøien

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Re: Does infinity calibration always need to be that hard?
« Reply #13 on: December 15, 2022, 11:11:06 »
Why does the infinity marking NEED to be calibrated?

As long as the lens focuses past optical infinity then the mark one eyeball and the auto focus can focus over the required range, can it not?

Zang

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Re: Does infinity calibration always need to be that hard?
« Reply #14 on: December 15, 2022, 14:24:28 »
Why does the infinity marking NEED to be calibrated?

As long as the lens focuses past optical infinity then the mark one eyeball and the auto focus can focus over the required range, can it not?

The thread is more relevant to MF lenses. The problem is bigger for the case when the lenses cannot reach infinity but in a few occasions, I found the lenses went pass infinity too much hurting the close focus ability. Also, hard stop at infinity saves us time when we need go there with manual focusing.