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Mitutoyo objective lens coins
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abpho



Joined: 17 Aug 2011
Posts: 1426
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PostPosted: Thu Feb 16, 2017 7:33 pm    Post subject: Reply with quote

Nice work Rocky.
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rockycarter



Joined: 27 Jan 2017
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PostPosted: Fri Feb 17, 2017 6:23 pm    Post subject: mitutoyo objective mounted on an el-nikkor enlarger lens Reply with quote

thank you abpro.
here is a test with an el-nikkor 80mm F 5.6 enlarger. attached as a relay lens with the mitutoyo 10 X as per PM requests. i set the apecture at F8 as requested. here is the results, the nikon el-nikkor 80mm cost around 100 to 125 dollars on average. i will attach a list of the pieces required. to mount the nikkor relay lens to the bellows.
M42 Screw Mount Lens to Nikon F AI Ring Adapter
Leica M39 Lens to M42 Pentax screw mount 39mm to 42mm step up screw adapter ring
NIKON EL-NIKKOR 80mm 1:5.6 ENLARGER LENS
40.5mm to 52mm Step Up Ring Filter Adapter
52mm to 58mm Metal Step Up Lens Filter Ring Adapter
Nikon CFI M25 microscope objective to M58 58mm filter adapter
Metal M25X0.75 mount female to M26X0.706 Mitutoyo microscope adapter leica
this is all you need to mount this lens. the first ring 40.5 will also fit the rodenstock enlargers
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s58y



Joined: 06 Apr 2011
Posts: 8
Location: USA

PostPosted: Fri Feb 17, 2017 8:39 pm    Post subject: Reply with quote

With the 80mm El-Nikkor lens, are you getting 4X rather than 10X, or is this some sort of non-typical setup where you can get other magnifications?
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rockycarter



Joined: 27 Jan 2017
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PostPosted: Sat Feb 18, 2017 8:35 am    Post subject: mitutoyo objective 10 X with a nikon el-nikkor 80mm Reply with quote

s58y i think i am still getting close to 10X magnifaction. here is a picture of a metric ruler taken with the last set up. all i can get in view is 2 mm. so it is the same as the image chris checked. so i believe it is 10x mitutoyo works great with an enlarger lens. here is the ruler image. as you can see with the enlarger lens. you can take advantage of the built in apecture.
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19392
Location: Richland, Washington State, USA

PostPosted: Sat Feb 18, 2017 9:11 am    Post subject: Reply with quote

Right, the image indicates 10X (more accurately I measure 9.85, but that difference in the noise).

With an 80mm tube lens, the "expected" magnification would be 10*(85/200) = 4.25X.

But that expectation depends on the 80mm lens being focused at infinity. As used here, the 80mm lens is extended much beyond that, which raises the magnification but drags the objective away from its design point.

Objectives with small NA, like this 10X NA 0.28, are pretty tolerant of this sort of change. So, changing the extension is a handy way of changing the magnification.

The technique works less well at higher magnification / larger NA. I don't think you'd like what happens to a 50X NA 0.55 in similar usage.

--Rik
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mawyatt



Joined: 22 Aug 2013
Posts: 1664
Location: Clearwater

PostPosted: Sat Feb 18, 2017 9:30 am    Post subject: Reply with quote

Rik,

Would this be true with something like the 5X Mit (lower NA)? It seems this is a good way to get magnification coverage between the set-point of 200mm on the Mittys. Had thought about this long ago (think I may have asked here but in a different way) but figured this was a dumb idea since I know nothing about optics.

If this can work it seems one could use a bellows (variable extension) with the Mittys (5X and 10X) and accommodating tube lenses (Raynox 150 & 250 maybe?) to get in-between magnification coverage with good IQ....poor man's macro zoom! Rolling Eyes

Maybe these could be made telecentric also?

http://www.photomacrography.net/forum/viewtopic.php?t=33317


Best,

Mike
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Sat Feb 18, 2017 7:17 pm    Post subject: Reply with quote

mawyatt wrote:
If this can work it seems one could use a bellows (variable extension) with the Mittys (5X and 10X) and accommodating tube lenses (Raynox 150 & 250 maybe?) to get in-between magnification coverage with good IQ....poor man's macro zoom!

Yes, this is a good course to pursue, but you'll have to try it and see. I have not tried doing this with the 5X at all, and with the 10X only a little, so I don't know for sure what will happen.

As further explanation...

The combination of an infinite objective and a tube lens essentially forms a finite objective. Varying the extension of the infinite combo is like varying the tube length of the equivalent finite.

The classic analysis and experiments about varying tube length have focused on spherical aberration at image center. That is well understood and simple. The wavefront aberration varies as NA^4, and at NA 0.14 it would be so small as to be irrelevant.

So from a practical standpoint, the important issues will be other aberrations that kick in towards the corners and edges. Unfortunately those are not simple, either to understand or to predict, so ultimately you have to try it and see.

As an example of the issues that may creep in, take a look at what I found when shortening a Nikon finite conjugate 10X NA 0.25 so as to give only 6.9X. That is documented at http://www.photomacrography.net/forum/viewtopic.php?p=57815#57815 and http://www.photomacrography.net/forum/viewtopic.php?p=57849#57849 (same thread, different pages).

It seems to me, based only on general principles, that smaller changes will be better than big ones, so I would proceed by choosing whatever tube lens gives nominal magnification as close as possible to what's needed, then adjusting from there.

--Rik
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rjlittlefield
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Joined: 01 Aug 2006
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PostPosted: Sat Feb 18, 2017 7:43 pm    Post subject: Reply with quote

mawyatt wrote:
Maybe these could be made telecentric also?

The 5X is nearly telecentric by itself. It will remain so with different tube lenses and different extensions as long as you do not add an external aperture. That's because the internal aperture establishes the entrance pupil, which (in my sample at least) is already pretty far out. All external positions will reposition the entrance pupil to be closer to the lens, with inverted perspective.

The 10X is a little less telecentric, but there's nothing you can do about that. The required position for a telecentric aperture would be inside the lens. You could get perfect telecentricity by adding a weak correction lens in front, but that would mess up the image quality because the Mitty is not designed to look through glass.

There's another issue that I'll mention mostly for completeness. The issue is that a lens can be perfectly telecentric near the center of its field, while being non-telecentric away from center. That's caused by physical vignetting, which chops off one side of the entrance cone so that the center of the remainder no longer parallel to the optical axis. My best guess is that if corner darkening is not obvious, then the change in telecentricity won't be either. But if you start seeing strange effects especially on large sensors or at reduced magnification, this is something to consider.

--Rik
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mawyatt



Joined: 22 Aug 2013
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PostPosted: Sat Feb 18, 2017 8:59 pm    Post subject: Reply with quote

Rik,

Thanks, looks like I'll have some tests to run when I get my setup back together.

Best,

Mike
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rockycarter



Joined: 27 Jan 2017
Posts: 70
Location: Canada

PostPosted: Wed Feb 22, 2017 8:02 pm    Post subject: Reply with quote

This is a image of a 1968 Canadian pure nickel dollar. This is what i look for in collecting errors coins. This condition is called flat field doubling. I can see how focusing stacking is going. To take my coin photography to the next level. I can see the roller marks on the metal as well.


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abpho



Joined: 17 Aug 2011
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PostPosted: Wed Feb 22, 2017 8:05 pm    Post subject: Reply with quote

Have you heard of coinimaging.com? There might be some useful information for you.
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rockycarter



Joined: 27 Jan 2017
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PostPosted: Fri Feb 24, 2017 8:12 pm    Post subject: Reply with quote

abpro thank you for the link. I have read his books he does very good work with coins. I picked up my piece of granite today. 34" by 36". I will start to wire up my new lighting system. That will be my next project. Here is a image of my coin setup.

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rockycarter



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PostPosted: Tue Mar 21, 2017 5:35 pm    Post subject: Lighting Reply with quote

I have received my power supply AC to DC converter. The first Cobb led rings lights has arrived as well. I have one Cobb led that. I will mount directly to the mitutoyo objective. i am still waiting on the DC dimmers. I will post some photos once i start to wire this system up.
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rockycarter



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PostPosted: Mon Apr 03, 2017 7:27 am    Post subject: Reply with quote

I have my power supply max 12V DC with a max 5 Amps. I mounted one of the angel eye 80mm ring light to a macro lens. I wanted to test the light on a pristine coin. This coin is made of pure silver. It is in cased in plastic. here is the results. Just waiting for a 40 mm angel eye ring light. To mount it directly on to the mitutoyo objective. This coin was lite directly by the angel eye ring light. The scratches is on the plastic holder


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ray_parkhurst



Joined: 20 Nov 2010
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PostPosted: Mon Apr 03, 2017 5:10 pm    Post subject: Reply with quote

Those Angel Eye lights are very interesting Rocky! I ordered some 40mm and 50mm to test them out. Thanks for the tip...Ray
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