Between 10 and 20x

[kaiotaku]

Hi everyone,

I've been using an infinite Nikon objective on a 200mm lens to get 10x magnification, but for some subjects that I've been doing recently I find that it's not enough magnification.

I've just ordered a 20x objective, which I expect to be useful but there will be times when I want more than 10x but less than 20x. I imagine I could get 15x by using the 20x at 150mm on a 70-200mm zoom. The specific objective that I've ordered is the Mitutoyo 20x NA 0.42 (highly regarded on this forum). Can anyone confirm that they have experience doing this sort of thing, with good results?

The subjects I'm photographing are tiny seashells. The smallest that I've photographed is 0.475mm (fully adult, measured by SEM). I have a project where I'll be doing quite a few in the 0.5 - 0.8mm range.

Lynton

[ChrisR]

Zooms usually cause vignetting, somewhere away from the long end - can't predict exactly where.
One good option is to use a relatively cheap 135mm - a search on 135mm should bring up options.

[kaiotaku]

Thanks for that idea. I should have mentioned that I'm using a crop camera (Canon 70D). I'm quite surprised if vignetting would occur at f/4 with an objective on a crop camera. I guess that would give about 13x and something like a Samyang or 2nd hand Canon might be suitable. I do the 10x imaging currently on a Canon 200mm f/2.8.

[Lou Jost]

There are several reports on this forum about vignetting withe Samyang as tube lens.

[mawyatt]

Lynton,

The Samyang 135mm f2 (Also called the Rokinon) is not a good tube lens, a spectacular 135mm lens but not as a tube. Th IQ is well below what can achieved with say a Raynox 250.

The Raynox 250 is an inexpensive 125mm magnifying lens thats works surprisingly well as a tube. Others are using the Zeiss 135 and Vivatar 135mm too.

Best,

Mike

[Pau]

I haven't any Mitutoyo but my 7D with the 70-200 F4L IS as tube lens doesn't vignette with Nikon microscope objectives at 150mm, it can be used down to 140mm.

[Lou Jost]

I should add that Royalwinchester got really excellent results using a 125mm Apo-Lanthar. It is very expensive though, >$2000 and only available second-hand.

[ohdeeremee]

I use a Nikon infinity 10x on a Nikon 70-300mm f/5.6 on a D90. Zoom to 150 has vignette, 175 is OK, or at least very usable. At 200mm I measure 10.6x, at 300mm, 15.0x.
I chart all my lens combo's and here is my chart for this one.
I do not have a 20x, so do not know how well that will work, but suspect it will be nearly the same except for the multiplier. (20x, not 10x). I suspect you will only get down to around 18x with the 20x objective before vignette starts.


And here are 4 pix, so you can see the vignette. I was not picky about focus on these, as I was looking for measuring the ruler across the sensor, so please ignore this.


@150mm

@175mm

@200mm

@300mm


Hope that helps....
George

[Lou Jost]

Recently Nathan showed that the Mitu 20x had an exceptionally large image circle (it covers the medium-format Phase1 sensor with high quality to the corners) relative to other Mitus and so it could be pushed down to much less than 18x. See this thread:

http://www.photomacrography.net/forum/v ... 6&start=45

[Chris S.]

Lynton,

You might look into whether a Sigma 150mm macro lens vignettes or not with a 20x Mitutoyo objective. I myself have no idea. But if works, it would deliver 15x. And as this lens is very highly regarded for close-up work, it might be a multi-tasker for you.

If this should interest you, there are probably members of this forum who have this lens and can say with authority how it performs for converging Mitutoyo optics.

--Chris S.

[kaiotaku]

Thanks Chris and others for the info and ideas.

Actually the idea of the 150mm macro had occurred to me already. I found one thread devoted to this but it seemed like nobody had tried it.

Of course, I've found myself thinking "do I not have enough enough macro lenses already?" (Canon EF-S 60mm, Canon 100mm, Canon 65mm MP-E 1-5x...)

I mainly photograph subjects centred on a black background, so a little vignetting in the far corners wouldn't be a concern actually, admittedly it is nice not to have it at all. Might be a question of experimenting and seeing what I can come up with. I'll read more about the Raynox and other options too.

[rjlittlefield]

It may sound a little crazy, but if you have a 1.4X teleconverter in your kit, try that in combination with your 100 mm. Focused at infinity, this creates a 140 mm tube lens, giving 14X with a Mitutoyo 20X. I don't recall having tested that full combo. But certainly my Mitutoyo 20X plays nicely with my Canon macro 100 mm f/2.8L IS USM to give a very sharp 10X that covers APS-C, and I've also had good results pairing my teleconverter with the 100.

--Rik