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I want to take my macro photography to the next level and would like to use the Nikon CFI Plan 10x microscope objective. I read that this objective has to be mounted on another lens also called the tube lens. So my question is:

Can I use my Nikon 105mm f/2.8 macro lens as a tube lens?

I read that dedicated macro lenses are not the best choice for a tube lens but I would like to confirm that.

Thanks Greg

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Yes, you can use a Macro lens as long as you are able to attach the Nikon CFI Plan 10x microscope objective to the front filter threads and have it close to the front element.

If the Nikon 105mm f/2.8 macro has a recessed front element, it may not be possible to get good results.

There will be no vignetting with lenses that 100mm or more.

Source: Extreme Macro

An infinity objective is a model objective that is designed to be used in connection with another lens, a tube lens, also known as relay lens. For extreme macro, a tube lens can be a standard non macro telephoto lens: macro lenses tend to be optimised for nearby focus and can have quite far recessed front lenses. Zooms also work but use them at the long end. Dedicated tube lenses are also available.

When used this way, the Nikon CFI 10x objective will still cover an APSC-sized sensor, but the Mitutoyo will not. Both objectives cover APSC on a 135mm tube, and give 6.75:1. You don't want to go under 100mm for a tube lens as this may give vignetting in the corners.

  • Yeah 200mm would be sweet but it's ridiculously expensive. You can mount it with an M-25 adapter coupled with a 62-52 step down adapter. Have a look at this video (click the play icon at the bottom of the screen). He is using 3 adapters. microsculpture.net As for the front lens being recessed, I just looked at mine and the lens begins when the thread ends so it isn't retracted. Anyway, I will give it a try. – Greg Apr 27 '16 at 12:28
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You would be able to form an image on the sensor with it focused to infinity but you're likely to have some vignetting - it could be quite bad.

It's worth trying, but don't spend a lot on the adaptors! In fact you may want to try a cardboard adaptor first to judge the field of view.

The magnification onto the sensor won't be 10x using a 105mm tube lens. Reference tube lenses range from 160mm to 200mm for common microscopes and their objectives (MicroscopyU).

I've put my Canon 350D on top of a microscope with a standard tube lens and got vignetting but nothing terrible - I had to crop but was only interested in the centre.

  • If I use a 105mm lens the magnification will be more or less halved if I'm not mistaken. I will give it a try anyway and will try to spend as little as possible. – Greg Apr 27 '16 at 10:30
  • That's right - Nikon use 200mm tube lenses (here's the link I couldn't find on my phone) – Chris H Apr 27 '16 at 12:08
  • What is a card adaptor by the way? Thanks – Greg Apr 27 '16 at 12:21
  • As in make something out of cardboard and sticky tape before spending money on adaptors. – Chris H Apr 27 '16 at 13:37
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Most if not all focusable lenses can be used as a tube lens, which is simply a lens always focused at infinity, and therefore does not need to be as complex as a photo lens. Also, typical tube lens would not have variable aperture / stop capability. To calculate magnification you need to remember that Nikon mag (10x in your cases) is quoted with 200mm tube lens, e.g. has EFL = 200/10=20mm.

If you want to try it, it's fine. If you want a permanent setup, it might be easier / more economical to purchase standard 200mm tube lens and objective with desired magnification.

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It's a microscope objective, so no, you can't use your Nikon 105mm f/2.8 macro lens as a tube lens. Only tube lenses are tube lenses.

However, with extension tubes (not lens) and close up filters, you may be able to achieve the same magnification with you Nikon 105mm (10x is possible as in this case, while 100x times require an actual microscope objective).

Nikon CFI Plan 10x is a microscope objective,it's not a tube lens:

https://www.nikoninstruments.com/en_EU/Product-Selectors/Objective-Selector

This is a Nikon tube lens:

http://www.edmundoptics.com/microscopy/infinity-corrected-objectives/nikon-cfi-60-infinity-corrected-brightfield-objectives/58520/

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