Nikon + summar = nikmar

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seta666
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Nikon + summar = nikmar

Post by seta666 »

I just discovered that if take the optical elements off the summar 65mm I can fit RMS microscope lenses on it, giving them a nice round aperture ring, based on morpha´s sumray and his aperture adapter for microscope lenses
Image
aperture ring
Image
The final lens on the adapter
Image
regards
Last edited by seta666 on Wed Jun 23, 2010 3:27 pm, edited 2 times in total.

rjlittlefield
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Post by rjlittlefield »

Nice! What does that provide for a rear thread?

--Rik

seta666
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Post by seta666 »

The rear thread is m25*0.75, so you can use step down ring or this adapter I had made before I knew that
Regards

PaulFurman
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Post by PaulFurman »

I'll be curious if it performs OK. I did similar with regular lens and 1:1 macro lens and it selected the not-so-good parts of the lens for edges. Should still be useful for framing & setup though. I've got an old spiratone 35mm bellows macro that I could use, though it doesn't have such a nice round opening - just 5 blades.

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Post by PaulFurman »

Well, I tried and it seems to work fine. It is indeed useful for modeling & framing, or if I'm just not in the mood to do a stack of 100 frames :-) The mounting is awkward, even though it has RMS thread, the way the aperture is adjusted is you turn the little gnurled lip on the front:
Image
... so not very stable having to attach to that. Next, I tried the JML lens threaded inside that lip. The part that reads F=35 SPIRATONE, etc, came unscrewed. But I had to fudge it on with gaffer's tape to fill the gap to the threads so is not quite squarely mounted and things move when rotating to adjust aperture. And it has a little bit of play too.

I would have thought the aperture needed to be inside the lens, closer to the glass. Here's where I got bad astigmatism with rear added aperture on an 85mm 0.5x macro lens.

seta666
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Post by seta666 »

PaulFurman wrote: I would have thought the aperture needed to be inside the lens, closer to the glass.
I thouht that too before seeing morpha´s tests; when I recieved the mikrotar 15mm I was surprised, as it has all the optical elements in front of the aperture ring.
I still hve to test this hybrid, I hope it does not vignete
Regards

PaulFurman
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Post by PaulFurman »

OK this must be the post you mention with morfa putting an aperture behind a microscope objective. That happens to be the very same one I'm using. Note that stopping down did increase CAs, but it's still useful for getting the background to transition to out of focus more gradually by adding one or a few shots stopped down.

When I get my D700 back from repairs with it's live view, I'm eager to use the aperture as a framing aid. It is painful setting up a shot with a 10x .30 NA - I can barely tell what I'm even looking at, even when I know what it should look like. With the optical viewfinder on my D200, I don't have enough light to see much stopped down.

Here's a very quick stack with the JML stopped down to 'f/8' at 6x. That's only 7 frames; it would have taken a heck of a lot more frames wide open. The aperture is designed for 35mm but also starts at f/3.5 so ignoring that, it works out to an effective aperture of f/56. If I figure 35mm f/8, that's 4.4mm dia. and at 21mm it's f/4.8, effective f/34. That can close down 2 more clicks to effective f/70.

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Post by rjlittlefield »

PaulFurman wrote:I'm eager to use the aperture as a framing aid.
For this application, watch out for changes in perspective between wide open and stopped down. For example with the added aperture being so far behind the optics, the combination is likely to have "inverted perspective" where things look bigger the farther away they are. Then when you open up, the lens will revert to its designed perspective which will be different -- maybe normal or at any rate less inverted. This will change the framing of the assembled stack. If you frame tightly using the added aperture, the framing may end up too tight when it is removed.

--Rik

seta666
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Post by seta666 »

You can see a test here http://www.photomacrography.net/forum/v ... hp?t=10082
Aperture can be closed to a maximum of one stop and 1/3 (acording to flash exposure compensation), still enough to save some shots

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Post by PaulFurman »

Looks like it worked fine. I see you just did a few stopped down to transition the background so I guess the geometry didn't change.

BTW, sorry again to hijack your thread but... I figured out I can mount an RMS objective in mine with some tape and don't need to rotate the objective (messing up framing), just the knurled lip, and I can swap in the JML. It's less useful for the JML because vignetting occurs at low magnification and at high magnification it's already stopped down too much wide open. With the 10x objective, it stops way the heck down, which is indeed handy for getting a quick preview before committing hours to a detailed stack.

seta666
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Post by seta666 »

No worries, I wish I had more aperture frames to experiment with but I have not. I guess is that somene made an aperture adapter for RMS lenses it would sell well. RMS male-round aperture-rms female ;-)
I plan to use it with microscope lenses to get a smother transition from focused part and background. Something for the JML would be nice too
Regards

seta666
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Post by seta666 »

I just found another interesting lens for this purpose, The M42 Industar 50-2 50mm f3.5 which can be found very easy on ebay. It has 2 group elements which are very easy to unscrew, the front element happens to be just bigger than rms, so by applying some plumber tape on an RMS microscope lens you can screw it on the lens.
so you end with an M42 microscope lens with aperture ring; the only downside is that the aperture is not as pretty as that of the summar, it is only 6 blade one.
I will post pictures later on

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