Advice for getting 5:1 on APSC sensor

[Davids]

I was hoping to get some advice in regards to getting around 5x magnification on my fuji xt1. I have a 2:1 Laowa 60mm, also a Raynox DCR-250 converter. With those two I can get around 3x magnification. I'd like to go higher, but not so high that it wouldn't be useful in the field. I figure 5x is about as high as I'd like to go in the field (it would still be mounted to a rail). I'm having a hard time figuring out which objective would be best, and how to best mount it.
I don't currently own any lens that is >100mm, so would a tube lens be the cheapest route?
Any advice would be greatly appreciated!

David

[ctron]

I was hoping to get some advice in regards to getting around 5x magnification on my fuji xt1. I have a 2:1 Laowa 60mm, also a Raynox DCR-250 converter. With those two I can get around 3x magnification. I'd like to go higher, but not so high that it wouldn't be useful in the field. I figure 5x is about as high as I'd like to go in the field (it would still be mounted to a rail). I'm having a hard time figuring out which objective would be best, and how to best mount it.
I don't currently own any lens that is >100mm, so would a tube lens be the cheapest route?
Any advice would be greatly appreciated!

David

Hi David,

I'm not really familiar with your camera and lens combination, but you're welcome to take a look at a thread I started last week:

http://www.photomacrography.net/forum/v ... hp?t=29842

Basically, I've been using my DSLR with 2.25" of macro tubes and my DSLR's reversed kit lens, which zooms from 18-55mm, to get from 2.5 to 7.5:1.

With what I'm using, the bottom line I've discovered is that my lens performs much better at the lower range than the upper. I am losing a *lot* of clarity and contrast as I approach 7.5:1, but I'm getting much better results at the lower range. Your mileage of course will vary, but you're welcome to read the long thread. HTH.

[Davids]

After looking around, what I think I may do is get an 11 mm extension tube for my fuji xf 56mm, that 67 mm is equivalent to a 100 mm full frame, then put an "infinite"-style objective in front of that.
Does anyone know if that will work or do I need a true 100 mm (or it's APS-C equivalent) lens?


David

[Charles Krebs]

David,

For this you do not use format "equivalents", but actual focal lengths.

If you put an infinity type Nikon 10X on a 56mm lens you would get a magnification of about 2.8X (56/200 * 10). And even though some of the Nikon objectives work well over a larger than expected field, you would probably not get good performance out past the center of the frame, even on an APS-C sized sensor.

When you put an objective onto a camera lens, the lens should be focused at "infinity", so you would not want extension tubes.

[Davids]

Thank you for clearing that up Charles.

So, since I already have a Raynox dcr-250, it seems logical to use it as a tube lens with 125 mm of extension tubes between it and the camera, like this:
http://www.photomacrography.net/forum/v ... e6dd589f04

Using 125 mm of extension tubing should give me 0.625 x whatever the objective magnification is. I could increase the length of that tube, but it would not work if it were less than 125 mm, correct?

I appreciate all the help.

[Charles Krebs]

Using 125 mm of extension tubing should give me 0.625 x whatever the objective magnification is.

A little more accurate would be to say that with the 125mm lens (DCR-250 in your case) focused to infinity, a microscope objective designed for a 200mm tube lens will give .625x the marked magnification.

Remember there is some depth to your camera body, so you really set up the "tube lens" to be visually in focus at "infinity" rather than just adding 125mm of extension tubes. You'll need a bit less than 125mm of tubes.

I could increase the length of that tube, but it would not work if it were less than 125 mm, correct?

It will "work" either way, but if the tube lens is focused at something other than "infinity" you alter the working distance for which the objective is designed. How much this will negatively impact image quality will vary with the NA (numerical aperture) of the objective, and the amount you deviate from infinity focus of the tube lens. A 10/0.25 objectives has a relatively low NA, so the impact will likely be pretty low and a modest deviation might not be noticed. But is is always best to start at the proper distance so you have an image quality benchmark to compare to before you change things.

[Chris S.]

David,

I'd consider getting a 5x objective and putting it on an older ("non-AI") Nikkor 200mm lens, with a converter that adapts it to Fuji X. An eBay search for such lenses turns up specimens for as little as $14. These are built like tanks, and were professional lenses in their day--just make sure, with a lens of this vintage, that it has no fungus.

A likely-looking adapter to the Fuji X might be the Fotasy AFNK Nikon Lens to Fujifilm FX Mount Camera Adapter for $15. This combination of lens and adapter would not have autofocus or auto-iris, but for use as a converging lens (tube lens), these have no importance.

On the front of the 200mm lens, you'd need a 52mm to M26 adapter to hold either a Nikon 5x CFI or Mitutoyo 5x lens. Here is such an adapter from eBay vendor jinfinance for $15.50. Altogether, this would give you a rock solid, high-quality converging lens assembly for about $45, plus shipping. (Note that I haven't tried this combination personally; am suggesting it based on experience with a number of converging lenses, and on considerable time spent shooting older Nikkor glass.)

--Chris

[ChrisR]

Minor note - Nikon's objectives range has a number of 4x, fewer 5x.

An obvious addition - if you try your existing Raynox reversed as a tube lens, then you could use the same adapters, on more extension, to use the dcr-150 version which has a focal length 208mm, giving you just slightly over the marked magnification.

For field use, you're very likely to find the depth of focus less than useful, above about 4x. The options are to add a diaphragm, which will apparently increase DOF but actually give you a diffraction-blurred deeper image, or venture into focus stacking. The latter is only really viable on stationary subjects.

[Davids]

Excellent information as always, thank you!

Just a question - and I realize this is a significantly more expensive option, but do you see Mitutoyo MT-1 tube lens for sale much on this site? I've only seen them on EO, but was wondering if they come up for sale used.


Thanks again!

David

[Chris S.]

David,

A small number of Mitutoyo MT-1 tube lenses came up for sale on eBay by a single vendor just once, as long as I've had a search going, which is quite a few years. They went quickly, but I picked up a couple. While I'm not in a hurry to part with them, I could spare one. Would have to dig through records a little bit to see what I my cost was. PM me if interested. I have never seen one for sale anywhere else, save new at full price.

I use a Mitutoyo MT-1 tube lens in daily work, and am very pleased with it. For details, see here.

--Chris S.

[rjlittlefield]

I also own an MT-1, as well as Raynox DCR-150, Thorlabs ITL200, and Nikon MXA20696, and I have tested those lenses head-to-head against each other.

Having done that, I mostly use the Raynox.

See http://www.photomacrography.net/forum/v ... 487#175487 and the link therein, for discussion and test results.

--Rik

[Davids]

Say I were to use the MT-1 setup but used 100 mm of extension tube with a 10x objective, would that be the same as 200 mm extension tube with 5x objective?


David

[Charles Krebs]

Say I were to use the MT-1 setup but used 100 mm of extension tube with a 10x objective, would that be the same as 200 mm extension tube with 5x objective?

No. The tube lens should be set-up so that it is in focus at "infinity" by itself, with no objective attached ("think" focusing on a distant treeline, or distant street light, or the moon). Then you attach the objective. Don't think of extension tubes here as the traditional "macro" accessory that you would vary to get different magnifications. Think of them simply as the means to extend a lens (the tube lens) so that it is focused at "infinity" in the camera body. If you want to change the magnification of an objective you need to use either a longer or shorter focal length tube lens, but in all cases the lens should be set to infinity focus.

The MT-1 is a 200mm lens. To focus it at infinity will take much more than 100mm of extension. (With only 100mm of extension you will not be even close to "infinity" focus). I don't use one, so I don't know the exact extension (Chris S probably does). There is a correct extension "number", but since adapters are different and body depths are different, you would typically set it up by actually establishing focus on a very distant subject (rather than a specific length of tubes).

[rjlittlefield]

The MT-1 is a 200mm lens. To focus it at infinity will take much more than 100mm of extension. (With only 100mm of extension you will not be even close to "infinity" focus). I don't use one, so I don't know the exact extension (Chris S probably does)

There is a nice picture on the "Technical Information" tab at http://www.edmundoptics.com/microscopy/ ... ses/54774/.

Hot-linked from there:



--Rik

[Davids]

One set up that has intrigued me is this one by Craig Gerard:
http://photomacrography.net/forum/viewt ... 5d814673a8

I like the low profile of it, but am a bit confused by the use of the SK unifoc and the relatively short distance between the objective and sensor - it does not appear to be 200 mm. I have PMed him to get a bit more information. Has anyone else used a similar setup?