Infinity Focus is not quite right

[mehguy]

Hello,
I own a Nikon FE where I believe the Infinity focus isn't quite right. Whenever I try to focus on something in the distance, like a far away building, using the focusing aid, it focuses right up a smidge right before infinity, not *at* infinity. If I were to focus at infinity, the building in the focusing aid would look slightly misaligned.

I'm just wondering if this is normal or there is some type of misalignment.

 

[BrianShaw]

Is there ever a situation where normal DoF, even at the most open aperture, would not result in a crisp image at infinity (either way)?

Which "focusing aid"; the split image? And which screen? If you are using a screen with microprism I'd consider that a better thing to check than the split image.

Which lens?

On a tripod?

 

[mehguy]

Is there ever a situation where normal DoF, even at the most open aperture, would not result in a crisp image at infinity (either way)?

Which "focusing aid"; the split image? And which screen? If you are using a screen with microprism I'd consider that a better thing to check than the split image.

Which lens?

I would have to develop a roll of film to find out.

I'm using the split image on the Nikon type K screen.

I'm using a Nikon Series E 50mm 1.8 lens

 

[BrianShaw]

No, I don't think you need to use film to answer that question. A DoF table or even the DoF markings on the lens should give youy the answer.

There has been lots of writings on the internet over history that suggests that sometimes lenses "overfocus at infinity" to accomodate temperature shifts. That may be so but the difference seems to me to be either inconsquential to practical photography or the result of erroneous measurement/testing.

Check your lens on medium and close distances. That is where any measurement/focus errors will matter.

And double check that the screen in your FE is properly installed.

 

[ic-racer]

One would use an autocollimator (or distant object) and a known good body and/or known good lens to diagnose the issue.

Do you have any other Nikon bodies or lenses?

 

[xkaes]

In addition to the screen, I'll add that the focusing aid might be the problem. Does it have a diopter adjustment -- as many do? Does it seem out of focus without the focusing aid? Does anyone else also see it as out-of-focus?

Do you use glasses?

 

[MattKing]

Are you assuming that the infinity marking on the lens is correct, and your focus system is wrong?
That may not be the case.

 

[loccdor]

I have lenses that don't quite focus to infinity (very common), and lenses that focus past it (rarer, usually only long telephotos).

I have cameras where the mirror might not be precisely in place (my Pen F's mirror actually moves very slightly if you tilt the camera above the horizon line, I assume something is loose).

How much is is a smidge? 20 ft before infinity? 40 ft? This may actually be desirable. In general you never want to shoot 35mm wide open at infinity with a vintage lens. Stopping down once or twice, depth of field should cover it.

 

[Kodachromeguy]

One would use an autocollimator (or distant object) and a known good body and/or known good lens to diagnose the issue.

Do you have any other Nikon bodies or lenses?


View attachment 419124

How did Leitz check or adjust the focus of their thread mount cameras? These bodies had a solid back without a door or panel.

 

[mehguy]

In addition to the screen, I'll add that the focusing aid might be the problem. Does it have a diopter adjustment -- as many do? Does it seem out of focus without the focusing aid? Does anyone else also see it as out-of-focus?

Do you use glasses?

The Nikon FE doesn't have a diopter adjustment. I also do not wear glasses.

One would use an autocollimator (or distant object) and a known good body and/or known good lens to diagnose the issue.

Do you have any other Nikon bodies or lenses?


View attachment 419124

I have another 50mm lens, but it is currently 4 hours away from me right now. Nothing on hand at the moment.

 

[MattKing]

The Nikon FE doesn't have a diopter adjustment. I also do not wear glasses.

People use diopter adjustments eyepiece attachment accessories for cameras that lack built in adjustments.
I would reiterate - the camera may be focused on infinity - both the viewing system and the film - and the lens markings may be wrong or may sometimes be wrong, depending on temperature.

 

[mehguy]

People use diopter adjustments eyepiece attachment accessories for cameras that lack built in adjustments.
I would reiterate - the camera may be focused on infinity - both the viewing system and the film - and the lens markings may be wrong or may sometimes be wrong, depending on temperature.

So it was a conscious decision to put a bit of over-focus?

 

[BrianShaw]

So it was a conscious decision to put a bit of over-focus?

Probably not for a 50mm Series E. That’s more likely in long telephoto and mirror lenses.

If I were you, I’d work on verifying your observation using either matte or microprism parts of the K screen. Or a collimater if you’re not convinced that the “error” is insubstantial to practical photography. TBH, that might be where the potential discrepancy is more likely.

Regarding diopter, never heard of an aftermarket adjustable diopter viewfinder attachment gizmo for a Nikon, but there were corrective diopter eyepieces. They are marked with the diopter strength.

 

[MattKing]

Regarding diopter, never heard of an aftermarket adjustable diopter viewfinder attachment gizmo for a Nikon, but there were corrective diopter eyepieces. They are marked with the diopter strength.

A difference in plurality here, I'm afraid. I intended to refer to the set of options as covering the various options available.
When I refer to "diopter adjustments eyepiece attachment" I'm intending to refer to a set of different options, where each attachment in the set adjusts the eyepiece a set amount, and the entire set of them gives the user a choice in order to match their eyesight correctly.
Historically, people would be able to go into a store and try out the demonstration set that the store had on hand by placing and removing different ones on to their camera and looking through the viewing system. When they had the correct demonstrator for them in place, the customer would buy one with that strength, and the demonstration set would go back in the store's display/drawer.

 

[MattKing]

So it was a conscious decision to put a bit of over-focus?

Or a slight misplacement, or a slightly incorrect re-assembly.
With SLRS, people go years without ever using those numbers to scale focus or even measure/estimate distance. Lens mounts can also wear.

 

[xkaes]

Hello,
using the focusing aid,

What "focusing aid" are you referring too?

 

[ic-racer]

Possibilities are as follows and one would need to use the usual testing to elucidate the problem:
a) Lens infinity stop is wrong
b) Lensmount to film plane distance is wrong
c) Mirror angle is wrong
d) Focus screen distance is wrong

Curiously I have about 30 Nikon bodes and about 30 Nikkor lenses. None have ever tested wrong at the 4 points listed above.

Other brands....yes to all 4.

 

[BrianShaw]

What "focusing aid" are you referring too?

See post #3. Split image on the K screen...