Tokina 100 Macro as Tube Lens?

[Deanimator]

Would a Tokina 100mm macro lens be acceptable as a tube lens for an infinite objective?

I have one that's my regular lens for outdoor live specimen use and was wondering if it could do double duty.

[Pawel]

for lenses corrected to infinite distance of F = 100, certainly yes. An example of such a lens is Mitutoyo Qv 2,5x. Most lenses require F = 200mm, so with your Tokina will get 1/2 magnification and weaker image quality.

[Deanimator]

for lenses corrected to infinite distance of F = 100, certainly yes. An example of such a lens is Mitutoyo Qv 2,5x. Most lenses require F = 200mm, so with your Tokina will get 1/2 magnification and weaker image quality.

Thanks.

I'll eventually look for something else.

[Macrero]

It depends on what objective(s) you would use it with. I do use 100mm tube lenses with Mitutoyo objectives (5, 7.5, 10 and 20X) on APS-C camera and coverage is still more than acceptable.

Yeah, you would be working at half the nominal magnification, but if image circle is big enough that's not an inconvenience, rather the opposite since (with Mitus) you work at 2.5X with NA 0.14, at 3.75X with NA 0.21, at 5X with NA 0.28, at 10X with NA 0.42, etc...

I never tried the Tokina 100 Macro as tube lens though, so I can't tell how it will work, the best way to find that out is trying it

One thing I learned about "tube lenses" after trying a lot of lenses for that purpose is that the "tube lens" not necessarily has to be optimized for infinity, actually none of the lenses I currently use as tube lenses is. I use mostly enlarging, repro, copy lenses which all are optimized for close distance and I am pretty happy with the result.

Here is a test-stack with Mitu 7.5X and Componon 5.6/100 at 3.75X on APS-C sesnor:

https://images2.imgbox.com/fd/4a/640ZwDAO_o.jpg

Best,

- Macrero

[Macro_Cosmos]

You want a tube lens that is corrected for infinity, which the Tokina macro lens isn't. There are far cheaper options, such as the Raynoxes (Raynoi?).

Depends on your objective lens as well. It usually has f=x00 written on it, most require 200mm tubes.

By the way, BH has a sale on Raynox:
https://www.bhphotovideo.com/c/product/ ... _Lens.html

10% off, pretty good.

[Macrero]

You want a tube lens that is corrected for infinity, which the Tokina macro lens isn't. There are far cheaper options, such as the Raynoxes (Raynoi?).

Depends on your objective lens as well. It usually has f=x00 written on it, most require 200mm tubes.

By the way, BH has a sale on Raynox:
https://www.bhphotovideo.com/c/product/ ... _Lens.html

10% off, pretty good.

That might be right according to theory, tube lens is focused at infinity, so you will get the best of your infinity corrected objective if you use a tube lens optimized for infinity. But as I stated above, in my experience that's not always true in real life. There are lenses optimized for infinity that does not work great as tube lenses and other which are optimized for close distance that makes an excellent tube lenses.

The Raynox are by no means optimized for infinity, but they work great, another examples are the Apo-Gerogon, G-Claron, Apo-Ronar, etc, etc...

You'll never know how a given lens would work as a tube lens till you try it, no matter optical formula, correction, etc.

- Macrero

[mawyatt]

Like others I've tried lots of different tube lenses with my Mitty's (5, 10, 20, 50X).

I tried the Nikon 105mm F2.8 VR as a tubes lens, it wasn't good, neither was the superb Rokinon (Samyang) 135mm f2, yet the old Vivitar (Komine) 135mm f3.5 and Zeiss Jenna 135mm f3.5 work very well.

Mitty infinite objectives are designed around 200mm for the tube lens, and thus 100mm pulls the lens well away from it's design center, which might be the reason for the poor performance, also the image circle will be very small likely vignetting on larger sensors.

Like mentioned above the Raynox 150 (208mm) and 250 (125mm) work well as tubes lenses, are inexpensive, and I've used both for many years now with good results with the Mitty's. The old Nikon 200mm F4 "Q" lens also work well are are cheap (<$50).

The best overall tube lens I have at the moment is the Sigma LSA 200mm, I've had this for some time and its my favorite 200mm tube lens. These were very inexpensive when I got it ($20~30) long ago, but now it's much higher probably because of it's value as a tube lens.

Hope this helps,

[ChrisR]

Mitty infinite objectives are designed around 200mm for the tube lens, and thus 100mm pulls the lens well away from it's design center, which might be the reason for the poor performance, also the image circle will be very small likely vignetting on larger sensors.

As I understand it, an infinity objective isn't affected/pulled by the tube lens. Bundles of rays go out of the back parallel, ie focused at infinity. It's what you do with those is all that matters. (There may be cases where aberrations cancel out, but I haven't heard of, or found any.)
If you use a "short" tube lens you get proportionately lower magnification. But you're spreading the resolvable dots (subject side) out less (sensor side), so you should expect to see a higher quality in terms of resolved dots per mm, sensor side.
The rub, of course, is that the usable image circle is also reduced. At 100mm, you're likely to see darkening, cutting off, or quality reduction towards the corners of an APS sensor.