I've been looking for a good long telephoto lens for some time. In another document I described one particular failure, in which
I came to the conclusion that no telephoto lens, no matter how long, is worth having unless
it can produce better images at its focal length than digitally enlarged photos from my
ED 70-300mm f/4.0-5.6 telephoto lens.
In August 2009 I bought a Rokinon 800 mm f/8 mirror
telephoto. I compared it with my Zuiko 70-300 lens and decided that it wasn't worth the
effort, so I sold it again.
What's wrong with the lens?
It doesn't have a tripod mount, but it desperately needs one. With the camera mounted
on a tripod, it was almost impossible to get it to stop wobbling. In the end I propped
up the front of the lens with a second tripod:
The focusing mechanism has a very short travel, making it very difficult to focus. The
only way I could get anything sharp was to use live view and 10x magnification, and as a
result it took me up to a minute to focus on anything. It didn't help that I had to
remove the second tripod, and that the image wobbled badly,
Basically, it failed the comparison test. See the comparison photos below.
The following photos are in three columns:
A photo taken with the Zuiko lens at f/8 and 300 mm.
A cutout of the same photo approximating to the field of view of the Rokinon.
A photo taken with the Rokinon.
Clearly the third photo should be better than the second to justify the lens.
The photos were taken with the camera on a tripod (two for the Rokinon), with remote shutter
release, and with image stabilization turned on. The angle of view is different in some
cases, because it's so difficult to point the things.
On the face of it, it seems that the Rokinon fails this test. Further magnification makes
that clear. Here we have the images reduced to about the equivalent of 3200 mm (i.e. ¼ the
size for the Rokinon, and about 10% for the Olympus). Again, the Olympus comes first, not
only in the sequence:
Summary: the mirror lens is an order of magnitude better than the supplementary toy that I
bought in February 2009, but not good
enough. I'm going to have to accept that the only real alternative is a longer real lens.
Maybe Olympus will make one some time.