Subject: FM2 and FE2 focus precision (on glass) at infinity.

[marck mcgill]

I have an FM2 and an FE2 bodies, and I've recently noticed that when

I focus at infinity, all of my lenses < 50 mm (specifically: 50 1.8;

28 2.8; 20 2.8) still show some lesser image "fragmentation" on the

microprism area of the glass. I'm talking of a VERY SLIGHT effect,

something that can't even be noticed with the split-image

stigmometer. That happens with both cameras.

 

Since nothing similar happens with any of my longer-focal lenses (>

85), do I have to worry or some tolerance with shorter lenses has to

be expected?

[leslie_cheung]

Are you saying that they just won't focus slight short of infinity or

they focus a little past infinity.

[leslie_cheung]

Up too early...do you mean they are slightly short or passed

infinity?

[jim_gifford]

There is a difference between "focus at infinity" and "twist the focus ring all the way toward infinity."

 

Focus rings often allow focus beyond infinity. This is so you can take pictures of what happened BEFORE the Big Bang.

 

If your microprism area allows crisp focus on objects at the horizon, regardless of whether the focus ring is at its stop, you're fine.

 

-Jim

[david_h._hartman]

The micro prism can�t be optimized for all focal lengths of lens or all maximum apertures. The important question is when you focus these lenses to infinity and take a photograph at maximum aperture is that photograph sharp in the center. Now if it�s sharper at f/5.6 that to be expected so don�t let that upset you. Also few lenses are really sharp at the edges wide open so don�t worry about that either. At this point I don�t think you have a problem from what you describe.

 

It�s 5:20 AM and I just woke minutes ago so I�ll check back later when the head is clears.

 

Regards,

 

Dave.

[marck mcgill]

@ Leslie: I mean that I'm slightly short of infinity.

 

Yes I see your point, but it's hard to tell if you're slightly out of focus, or if the image is soft because of the full aperture...

[roy_g]

I have two FE's one FE2 and one F3HP, my 50mm 1.8 (2 samples) lenes do as you describe on the FE/FE2 but not the F3HP. I think it has something to do with viewfinder magnification and eye placement. If I make sure I'm looking center of viewfinder all is ok, any slight shift off center (right side of center for me) then the lens seems to come up short of infinity. This doesn't happen on the F3HP.

[alex_lofquist]

The split-image "rangefinder" in the center of the screen has a definite depth to it, so it is the least capable of giving accurate focus. The microprism is better, but still not as precise as the matte screen. Best of all is the aerial image using parallax viewing on cross hairs to focus. Unfortunately the trade-off in ease of use leave the last method to astronomy or other scientific applications. If critical focussing is paramount, the focal length of the field lens in the screen should closely match that of the camera lens. The bright-view, and similar screens attempt to accomplish this with the introduction of microlenses to give a broad range of focal lengths on the screen. I don't know if Nikon makes a "Brite View" for the FM or FE, so if they don't Beattie may have one to fit.