Questions about a Tokina 500mm Mirror Lens

[Stan]

The Tokina RMC 500mm Cat lens arrived today. I promptly put it on my D300 and shot a few test shots down the street. It's in excellent condition complete with case, hood, caps and the 3 35.5mm filters, but no instructions. So I have a couple of questions and hopefully some one has some experience with this lens.

* What is the front filter thread size? I've seen it listed as 72mm, but it's bigger than that. I tried a 72mm filter and it was too small, but not by much. So it's not 72mm, but certainly not 77mm either. I don't intend on putting an actual filter there, but I want a lens cap for it. The one that comes with the lens fits over the lens hood which is bigger than the barrel of the lens, and I can see myself not wanting to use the hood at times, but will want a cap.

* I've read before that mirror lenses are designed to always have a filter on them. It came with the 3 original 35.5mm filters (1 Skylight, and 2 ND). But I don't have the instructions so I can't confirm whether that's the case on this lens.

Any help would be greatly appreciated.

Thanks,
Stan

[Stephen]

It should be a standard filter size, but maybe Tokina have not bothered to thread it to standard as the large sizes are costly for good ones.

Yes, the usual rule is the filter at the back should always be fitted, but it is open to try the lens without it on test shots and compare the result.

For B/W an orange or red is useful as it raises the low contrast.
For colour, a polariser on the front can be used, but we are back with the size problem, and cost!

The hood should always be used, as all mirror lenses suffer from stray light from out of frame hitting the internal barrel, and lowering the contrast.

Stephen

[julio1fer]

Hmmm, I am a sinner. Never used a filter on my 500mm f/8 mirror lens, although it also came with a 3-piece set.

The hood is an excellent idea, why didn't I think of that? Maybe that is why I had such a low contrast.

[Stephen]

Apr 26, 2013 19:16:14 GMT -5 julio1fer said:

Hmmm, I am a sinner. Never used a filter on my 500mm f/8 mirror lens, although it also came with a 3-piece set.

The hood is an excellent idea, why didn't I think of that? Maybe that is why I had such a low contrast.

It's worth checking with both the filter in and out, in theory the classic MTO Russian design does not mind in or out, as the light is near a perfect path at the back, with the lens correctors well forward in the design.

But the camera designs from Japan and now China, are seeking to reduce the size of the lenses and the rear elements are far nearer the film or sensors.

The light path is a much smaller cone and the filter has the light going through at a greater angle, which is allowed for by the designer, the flat glass acting as the final element. However after saying that, the effect is slight, and it appears in practice that they work OK without the filter in place.


a hood is generally vital, any out of frame light illuminates the interior of the barrel and reflects on the mirrors losing contrast in the image. Again, the shorter the type of body, the worse the effects are.

Stephen.

[Stan]

I just wrote a blog piece about my little mirror obsession and discussed the reduction in size from the MTOs and what the Japanese ended up doing with them in the next few years. I kind of suspected that this reduction might have something to do with the filter situation since I've never run across anything saying that it was necessary for the Russian lens. However, I certainly didn't have the technical knowledge, much less the expertise to explain the issue!

Thanks; this helps a lot. I always like to know "why" I'm doing something!