Question about infinity focus problem

mporter012 · Jul 31, 2013

Hi!

I have an FE2, and a 28mm ais 1.8 lens and a 50mm af 1.8 -

Last year I noticed that when I focused to infinity, the subjects far away were slightly out of focus, so I had to adjust the focus just slightly. For the landscape work I do, I often just set the focus to infinity, and did this many times before I realized the focus was off.
After developing and printing some negatives, I've noticed that many of them aren't that sharp, with either lens. I use a tripod and a cable release.

I'm looking for any advice you can offer on what could be the issue. I'm assuming it is something with the mirror on the camera??? but I'm not sure.

Thanks,

Mark

illumiquest · Jul 31, 2013

Could your focusing screen be loose? Doesn't seem likely but I can't see anything else if both lenses are giving you bad results. Maybe a loose film plate?

Tom1956 · Jul 31, 2013

One can only speculate.

mporter012 · Jul 31, 2013

Tom1956 said:
One can only speculate.

Well, this doesn't sound promising
Of course, I can buy an FE or FE2 in mint condition for $100 bills.

Tom1956 · Jul 31, 2013

Sorry for the trite answer. Without seeing the camera it could be several things. Speculation on this forum would be useless. Mirror out-of-place would be #1 suspicion.

cliveh · Jul 31, 2013

mporter012 said:
Hi!

I have an FE2, and a 28mm ais 1.8 lens and a 50mm af 1.8 -

Last year I noticed that when I focused to infinity, the subjects far away were slightly out of focus, so I had to adjust the focus just slightly. For the landscape work I do, I often just set the focus to infinity, and did this many times before I realized the focus was off.
After developing and printing some negatives, I've noticed that many of them aren't that sharp, with either lens. I use a tripod and a cable release.

I'm looking for any advice you can offer on what could be the issue. I'm assuming it is something with the mirror on the camera??? but I'm not sure.

Thanks,

Mark

If you had to adjust the focus for subjects far away, this would imply that you are focusing on something nearer than the infinity setting and thus throwing out the focus at infinity. Is this correct?

Ian Grant · Jul 31, 2013

I have an old focus screen from a junked SLR and it's great for checking true ficus on the actual film pane, I use a ground glass on 120 folders & TLR's to check focus accuracy.

You need something similar to check the camera. You need to set for the hyper focal distance rather than infinity, tha'll give you far better DOF.

Ian

Alan Gales · Jul 31, 2013

Early Bronica 6x6 cameras (S2a and older) had this problem when new. It was do to a misalignment of the focussing screen.

flash26c · Jul 31, 2013

I don't know but DOF at infinity should take care of slight focus problems at infinity --- are the lens' stopping down when shutter is released?

ic-racer · Jul 31, 2013

Look up "lens collimation."

mporter012 · Jul 31, 2013

cliveh said:
If you had to adjust the focus for subjects far away, this would imply that you are focusing on something nearer than the infinity setting and thus throwing out the focus at infinity. Is this correct?

Not exactly, if I understand your question. If lens is set on infinity, after x amount of feet, everything should be in equal focus. Well, if i set the camera to infinity, it appears everything is JUST slightly out of focus, so I have to adjust slightly back on the focus. Does that make sense? In other words, the lenses are reaching infinity focus just before the lens in set on infinity.

Mark

mporter012 · Jul 31, 2013

Ian Grant said:
I have an old focus screen from a junked SLR and it's great for checking true ficus on the actual film pane, I use a ground glass on 120 folders & TLR's to check focus accuracy.

You need something similar to check the camera. You need to set for the hyper focal distance rather than infinity, tha'll give you far better DOF.

Ian

I'm not entirely sure I understand how to do this... Can you explain in a bit more detail how I would do this?

Mark

asteroid_death · Aug 1, 2013

Let me ask you...what are the chances of both lenses having the same problem?

I know you said you were developing & printing yourself, but I had a similar issue with my wide angle Nikkors appearing soft at infinity. I was also taking landscapes. I quickly came to the conclusion that although the old Nikkor's are built tough, they weren't that sharp in comparison to modern glass. BUT In the end it turned out that the scanner I was using didn't have the resolving power to dig out all the information in the minute details of those wide angle shots and was thus producing a softer image. It wasn't until I got a blowup done in the lab that I realized the lenses were not the problem. A scan of a portrait with a 50 or 80mm would appear reasonably sharp, but the landscapes were always soft.

I'd recommend investing in a dedicated film scanner. You can get a really good one for less than $150 if you're timing is right.

Andrew K · Aug 1, 2013

easy to check.

put the camera on a tripod, and tape a piece of "Scotch Magic Tape" across the film rails form top to bottom (this is a frosted, easy to remove sticky tape - I've used it for years as a rough and ready way to check focus on cameras where I don't have a piece of ground glass the right size to sit in the film plane.

Better still if oyu have some ground glass cut it to size and use that.

Now using set the shutter to B and lock it open (use a cable release). Now focus the lens on something thats easy to focus on - a brick wall or a power pole. It doesn't matter - neither does the distance - say 10 feet or so. Now look through the viewfinder and see if the image is in focus.

If it IS then we know the mirror alignment and focussing screen are set correctly. The lens then needs to be re-adjusted so it hits infinity at the infinity mark.

If its OUT OF FOCUS then the mirror is out of adjustment, or the focussing screen is not sitting where it should be, or the flange depth is out(the distance from the front of the lens flange to the film plane) and this needs fixing.

I was a camera technician full time for too many years, and this can be a fun problem to fix....

E. von Hoegh · Aug 1, 2013

mporter012 said:
I'm not entirely sure I understand how to do this... Can you explain in a bit more detail how I would do this?

Mark

The chances of both lenses having the same trouble is vanishingly small.
Forget about hyperfocal trickery, too - you want accurate focus first.
For an SLR to focus properly, the focussing screen must bear the same relationship to the lens that the film does. For this to happen, 1)the lens flange must be the correct distance from the film, 2) the mirror must be in precisely the correct position, and 3) the focussing screen must be in precisely the correct position.
What you need to do is place an old screen on the film rails and see if the focus at the film plane coincides with the focus in the viewfinder.
Open or remove the back and put the camera on a tripod for this, and use a high quality magnifier to look at the screen at the filmplane. Check at infinity, medium, and close distances and report the results

Question about infinity focus problem

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