Two D60's, both with focusing problems.

[Dave Ringoen]

Stephan, you got me thinking about this a bit more.

I don't have a D60, but I'm going to posit that the focus sensor is down at the bottom of the mirror chamber near the tripod mount, and opposite the pentaprism. If that's where it is, the problem likely lies with the position of the mirror. If the mirror is too high (or too close to the lense), for example, it would shorten the optical path from the lens to the pentaprism, but lengthen the path to the focusing sensor, causing front manual focus, and back autofocusing.

Dave

 

[Stephen DeNagy106674]

Dave:

Yes! A subtle problem in mirror position would wreak havoc with the whole system. Let's hope this is not a pervasive problem.

Others reading this who own D60's--please test your units and see if this is isolated or if there is indeed a mechanical problem with the mirror and focusing accuracy.

--Steve

Stephan, you got me thinking about this a bit more.

I don't have a D60, but I'm going to posit that the focus sensor is
down at the bottom of the mirror chamber near the tripod mount, and
opposite the pentaprism. If that's where it is, the problem likely
lies with the position of the mirror. If the mirror is too high (or
too close to the lense), for example, it would shorten the optical
path from the lens to the pentaprism, but lengthen the path to the
focusing sensor, causing front manual focus, and back autofocusing.

Dave

 

[Don Lashier]

Exactly. In my case I believe that the sensor plane was off since AF and viewfinder agreed, but focus plane was always in front of subject. Also, absolute focus error decreased with focal length.

My replacement 1D is arriving tomorrow so we'll see.

• DL

I think David is going about all of this just fine. Are forgetting
how SLR's work?

Though I am not an optical expert, I see that the Canon D60 has
three optical axes.

1. 1: Lens-> Mirror-> Screen -> Pentaprism -> Human Eyeball (Manual

Focus)

1. 2: Lens-> Mirror-> Semi Silvered section-> secondary mirror->

Contrast Detection (Auto Focus)

1. 3: Lens-> Film Plane (CMOS detector, our film)

 

[George Richardson]

My replacement 1D is arriving tomorrow so we'll see.

• DL

I think David is going about all of this just fine. Are forgetting
how SLR's work?

Though I am not an optical expert, I see that the Canon D60 has
three optical axes.

1. 1: Lens-> Mirror-> Screen -> Pentaprism -> Human Eyeball (Manual

Focus)

1. 2: Lens-> Mirror-> Semi Silvered section-> secondary mirror->

Contrast Detection (Auto Focus)

1. 3: Lens-> Film Plane (CMOS detector, our film)

----------------

Many many years ago the British Journal of Photography got a well known (film) SLR,and tore the focusing accuracy to bits.

From what i remember-they had a graph which looked like a roller coster-with a line going through the centre,and where the wave passed that line,that was where it was 100% sharp (on the film plane),and it showed how the camera went in and out of focus on the FILM PLANE,as one changed the focus distance (manually) on the lens.

In other words-what one saw in the viewfinder-as sharp was not always sharp on the film plane.

They put this down to inacuracy between what the mirror sends to the eye,and the distance to the film plane.

And im sure nothaing has changed.

Regards

George Richardson

 

[Stephen DeNagy106674]

George:

Perhaps what we need now with digital SLRs now is "focus bracketing" so that each shot could blast a couple fore and aft of the assumed plane of focus.

Either that, or we all go back to ground glass focusing!

--Steve

Many many years ago the British Journal of Photography got a well
known (film) SLR,and tore the focusing accuracy to bits.

From what i remember-they had a graph which looked like a roller
coster-with a line going through the centre,and where the wave
passed that line,that was where it was 100% sharp (on the film
plane),and it showed how the camera went in and out of focus on the
FILM PLANE,as one changed the focus distance (manually) on the lens.

In other words-what one saw in the viewfinder-as sharp was not
always sharp on the film plane.

They put this down to inacuracy between what the mirror sends to
the eye,and the distance to the film plane.

And im sure nothaing has changed.

Regards

George Richardson

 

[Mike Fulton]

Did they say WHY it's possible to fall out of adjustment during
shipping?

This is very disconcerting to me. Just how careful do you have to
be with these bodies not to upset the AF-adjustments?

If one is getting bad results from MANUAL focus, as has been described here, then the electronics in the lens or camera are irrelevant. It's got to be a problem in the optical path between either the lens and the viewscreen or the lens and the focal plane.

It sounds like either the mirror, the prism, or the viewscreen itself is physically in the wrong position within the camera.

I can't think of anything else that would cause bad focus at the focal plane while things look OK in the viewfinder. It cannot be the lens mount, because you'd see that in the viewfinder.

It might LOOK ok through the viewfinder if it's only off by a millimeter or two, but that would be enough to cause the focus point to be different on the viewscreen than at the focal plane. This would cause either autofocus or manual focus to fail.

BTW, I'd think the viewscreen being out of position is probably the MOST likely suspect.

Mike

 

[Don Lashier]

BTW, I'd think the viewscreen being out of position is probably the
MOST likely suspect.

In the case of my 1D I think that the sensor plane was wrong because both AF and MF were off similarly. The replacement is all but perfect.

• DL