OM-10 split image microprism w/ Tokina 80-200

[broncc]

I just got a Tokina 80-200 f/4.5 lens for my OM-10. That's my first zoom lens and I am noticing that often when I focus one half of the focusing ring stays black (it's not one particular half, it's usually one of the two and when I move around/try to focus it switches to the other or disapperas). I also noticed that the matte part looks more than black dots rather than the matte way it looks on my Zuiko 50mm f/1.8. Do you think there is something wrong with the lens or I just can't focus it with properly? I tried to capture it with my smartphone.

 

[Ap507b]

Nothing wrong with either the camera of the lens. What you are seeing happens with split image focusing aids with slower lenses.

As the OM10 is an entry level camera, I wouldn't be surprised if it has a fixed focusing screen. Higher specification OM's, like the 1 & 2 have interchangeable focusing screens & you can get one that doesn't have the focusing aid which is better for slower lenses.

Here is a page that shows the screens available for the OM1 & 2 & explains their differences:

http://www.mir.com.my/rb/photograph...mpusom1n2/shared/accessory/screens/index1.htm

Imagine that the OM10 has something like the 1-1 at the top. It says that it darkens with lenses slower than F5.6. I have a 1-1 in my OM2 & have seen it darken with an F3.5 lens.

 

[bdial]

If you keep your eye centered on the optical axis of the prism you will see both halves. You will notice, as you shift your eye and the camera around a bit, the dark half switches, find that in-between point where both are clear.

 

[broncc]

Thanks! I was a bit worried that there is something wrong with the lens.

 

[albada]

Olympus made a few f/5 lenses, which must have been even more difficult to use with the microprism or split image.
As the prior poster said, you must center your eye perfectly so that both halves are clear.
BTW, there are many 80-200 zooms out there that are faster than f/4.5 (and thus easier to focus).
My collimator-tests show that the following lenses are sharp wide open:

Kiron 80-200/4
Zuiko 75-150/4
Tamron 70-210/3.8-4
Tamron 70-210/3.5
Vivitar Series-1 70-210/3.5
​

Mark Overton

 

[broncc]

I got the Tokina for $10 so it was hard to resist. Thanks for the tips

 

[Sirius Glass]

If you keep your eye centered on the optical axis of the prism you will see both halves. You will notice, as you shift your eye and the camera around a bit, the dark half switches, find that in-between point where both are clear.

That is exactly it. This occurs more pronounced when the effective aperture is smaller than the normally used lenses.