My MPC 90mm super macro lens

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MarkSturtevant
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My MPC 90mm super macro lens

Post by MarkSturtevant »

Here I show a "super macro" lens that I had built a while ago. I think it turned out interesting, but this posting is not just to show it to readers here. I would also like to solicit some advice about how I might improve its image quality.
I have dubbed the lens the "MPC 90mm", although it is certainly longer than 90mm. "MPC" stands for "Mark's Personal Contraption". Central components of this lens in its current form is the Pixco 36-90mm helical extension tube and the Neewer electronic reversing ring. The lens is a reverse mounted Canon EF 50mm f/1.8 II. Fitting everything together are a bunch of different adapter rings.
Image

The insides are masked with Protostar paper, although the internal threaded areas of the Pixco helical extension tube can not be masked. I did as much masking as I could, I feel.
Image

At full extension, this lens gets 3.14 :1 magnification on my T5i camera body. Over 4 : 1 if I add extension tubes. It is surprisingly light weight, but that is because most of the components are aluminum. I can use it hand-held easily enough (although extensively propped on things) at less than its full extension. Toward full extension I need a tripod and remote shutter cable. Those who make good use of the famous MP-E 65mm lens have my deepest respect!

Here are some pictures of results.
Image
Image
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So in general I am liking but not yet wowed by this lens. I somehow don't feel that it is as sharp as I was hoping (am I imagining that?), and on some occasions it seems to me that the contrastyness is just not there. The 2nd ant picture and the leafhopper picture are examples. These are taken in bright light. For that issue, perhaps I could cut down on internal reflections by mounting a fixed aperture near the 50mm lens? Not sure how to do that.
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Pau
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Post by Pau »

Yes, the relative lack of contrast can be due to the unflocked parts of the tubes, I suppose it can't be flocked because the variable length mechanism. A rectangular flare cutting stop placed near the camera side could be more effective than at the lens side.
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Post by Lou Jost »

Mark, I think it is still a 50mm lens even though reversed. In what respect do you find that it behaves like a 90mm lens?

mawyatt
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Post by mawyatt »

Mark,

Agree with Pau, the 2nd image shows some internals that could reflect. You might be able to remove the adapters and moveable pieces for flocking, then reassemble or use a long loose tube of Protostar or Beetle Black that could slide inside the lens and move with the length changes. If you use the Protostar for the tube leave the paper backing on of course.

The Neewer reversing ring is nice, do you know if they make one for Nikon? Google didn't give me anything positive.

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

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Post by ChrisR »

You could try black paper discs/rectangles, strategically positioned:
Image
Last edited by ChrisR on Sat Jan 13, 2018 7:28 am, edited 2 times in total.
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Post by MarkSturtevant »

Pau wrote:Yes, the relative lack of contrast can be due to the unflocked parts of the tubes, I suppose it can't be flocked because the variable length mechanism. A rectangular flare cutting stop placed near the camera side could be more effective than at the lens side.
Thank you, Pau. I will try to work on that. It seems likely that the remaining internal reflections cause enough problems to be noticable in bright light, and are just not so noticable in lower ambient light.
I thought I read somewhere about putting a rectangular screen near the lens. Do you think doing both -- placing one near the lens and the camera -- will be more insurance, or would that cause a new issue?
Mark Sturtevant
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Post by MarkSturtevant »

Lou Jost wrote:Mark, I think it is still a 50mm lens even though reversed. In what respect do you find that it behaves like a 90mm lens?
I know my silly name for the lens is wrong. The 90mm is from the max extension of the Pixco tube. A better one might be based on measuring the actual length at full extension, from the camera sensor to ...? I don't know really.
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Post by MarkSturtevant »

mawyatt wrote:Mark,
Agree with Pau, the 2nd image shows some internals that could reflect. You might be able to remove the adapters and moveable pieces for flocking, then reassemble or use a long loose tube of Protostar or Beetle Black that could slide inside the lens and move with the length changes. If you use the Protostar for the tube leave the paper backing on of course.
The Neewer reversing ring is nice, do you know if they make one for Nikon? Google didn't give me anything positive.

Best,
There are some stacked adapters, and maybe I could flock these as a unit. There is not much surface on their inner edges for adhering flocking, but I can look. I had though about making an inner tube of flocking. Either of fixed length or extendable/collapsable (tricky!). What has held me back is some consideration of what could happen out in the field. If the inner tube got loose or out of line while miles away from home I would not have the tools to do a proper fix.

I think there was a different company that very recently came out with the electronic reversing ring for Nikon. I just remember reading about it a couple months ago. The Chinese companies blatantly copy other companies seemingly at will, and we benefit from that. I will look for it.
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Lou Jost
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Post by Lou Jost »

Mike, you can easily make one of those yourself for any fully-electronic lens, as I did for my Olympus.

mawyatt
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Post by mawyatt »

Lou Jost wrote:Mike, you can easily make one of those yourself for any fully-electronic lens, as I did for my Olympus.
Lou,

Thanks, yes I recall when you did this. I'm too lazy to actually build one now, got some electronics stuff (Live View EFCS with Flash for Nikon D500 & D850 specifically for stacking with Stackshot & WeMacro controllers, should work with other cameras also) I'm in the mist of designing and building (waiting on parts).

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

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Post by Pau »

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Post by MarkSturtevant »

This is useful! So if I can pick up on key points in that thread, an optimal shape for an internal baffle should be circular if near the lens (near the ~ circular aperture), and rectangular if near the rectangular sensor. Is that right?
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Post by Lou Jost »

And the optimal region for the baffle is near the middle, not near the sensor nor near the aperture.

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Post by MarkSturtevant »

mawyatt wrote: The Neewer reversing ring is nice, do you know if they make one for Nikon? Google didn't give me anything positive.
I tracked down a new brand of these rings, and its shown here: https://www.dpreview.com/news/835689415 ... ny-e-mount for Sony. Likely that is what i saw earlier. In any case, it seems one could make one with extension tubes and a cable, as shown here:
http://www.photomacrography.net/forum/v ... 6663#96663

Admin edit RJL: make second link point to specific post.
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Post by Chris S. »

Lou Jost wrote:And the optimal region for the baffle is near the middle, not near the sensor nor near the aperture.
Lou,

To my thinking, the optimal placement for a flare-cut stop is as near as possible to the sensor, in order to place this stop in a location where it will block reflectance from as many flare-inducing surfaces as possible.

But you assert an idea contrary to this. And knowing you, my bet is that solid thinking supports your assertion. Would you mind elucidating it?

Cheers,

--Chris S.

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