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Need advice on macro lens choice
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ChrisR
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PostPosted: Thu Apr 23, 2015 9:02 am    Post subject: Reply with quote

The EDF's are the MM series, that I'm referring to.
Measuring Microscope just being the thing they fit.

The MPE working distances ( engraved on the lens) are
1x 101mm
2x 63mm
3x 51mm
4x 44mm
5x 41mm

It's quite a fat lens which gets in the way of lighting sometimes, and at 5x it's not quite as sharp as at lower mags.

Perhaps your best bet on a Nikon would be a Mitutoyo 5x objective, which I think covers 24 x 36, though I'd do a search to confirm. I don't recall trying it.

The EDF / MM lenses would not cover 24 x 36, though you've probably got enough pixels to "enlarge the middle" for many purposes.
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rjlittlefield
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PostPosted: Thu Apr 23, 2015 9:57 am    Post subject: Reply with quote

Nick, my reference for EDF / MM lenses is http://www.nikonmetrology.com/en_US/content/download/5132/47708/version/4/file/MM+series_2CE-IDYH-9.pdf , brochure page 24 (Adobe Reader "Page 13 of 16") and brochure page 28 (Adobe Reader "Page 15 of 16"). This is the "apparently updated brochure for the MM-400/800" that I linked above.

--Rik
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Macro Photog



Joined: 13 Dec 2014
Posts: 81

PostPosted: Thu Apr 23, 2015 10:42 am    Post subject: Lense choice Reply with quote

Rik/ChrisR

Sorry I misunderstood. Got it now. I saw the machine, really nice. I also saw some of them for sale at various places. "Fat" should not be a problem for most of my work however, the quality and listed WD do set off some cautions for me. It is also a shallower working distance than I've been told by someone who wants to sell me one. This person is quoting a WD of 70mm. I think this person is being honest so am I missing something? They say they are filling the frame at a 1.5 magnification factor with 110mm of extension tubes. Is this helpful?

Chris, I found a Mitutoyo 5x M-Plan APO objective, the WD is 34mm (way less than I would prefer). Is this the one you are referring to in your email? I found detailed specs. (below) but I don't know which one(s) relate to sensor coverage.

Also, it seems the lower mag objectives, though they have very good WD would duplicate my existing capability and may not be worth the effort. ...or am I losing the plot again?

Best,

Nick


Type Microscope Objective
Primary Magnification PMAG 5X
Numerical Aperture NA 0.14
Working Distance (mm) 34.0
Focal Length FL (mm) 40
Resolving Power (µm) 2.0
Depth of Focus (µm) 14.0
Field of View, 24 Diameter Field Eyepiece (mm) 4.8
Field of View, 18 Diameter Field Eyepiece (mm) 3.6
Field of View, 2/3" Sensor (mm) 1.8 x 1.32
Field of View, 1/2" Sensor (mm) 1.28 x 0.96
Compatible Tube Lens Focal Length: 200 mm
Maximum Diameter (mm) 34.0
Length excluding Threads (mm) 61.0
Mounting Threads M26 x 36 TPI
Weight (g) 230
Style Infinity-Corrected
RoHS Exempt
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rjlittlefield
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PostPosted: Thu Apr 23, 2015 11:42 am    Post subject: Re: Lense choice Reply with quote

Macro Photog wrote:
"Fat" should not be a problem for most of my work however, the quality and listed WD do set off some cautions for me. It is also a shallower working distance than I've been told by someone who wants to sell me one. This person is quoting a WD of 70mm. I think this person is being honest so am I missing something? They say they are filling the frame at a 1.5 magnification factor with 110mm of extension tubes.

Nick, please clarify: are you talking about the MP-E 65 here? If not, then what?

--Rik
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Macro Photog



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Posts: 81

PostPosted: Thu Apr 23, 2015 12:48 pm    Post subject: Reply with quote

Rik,

I've emailed the individual to get the exact model number and will post as soon as I receive it.

Best,

Nick
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rjlittlefield
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PostPosted: Thu Apr 23, 2015 1:17 pm    Post subject: Reply with quote

Macro Photog wrote:
I've emailed the individual to get the exact model number and will post as soon as I receive it.

OK.

Just to try sorting things out here...

When ChrisR wrote:
Quote:
It's quite a fat lens which gets in the way of lighting sometimes, and at 5x it's not quite as sharp as at lower mags.

I believe that he's talking about the MP-E 65, whose table of magnifications and working distances he had just given.

My concern now is that you might be talking about some MM-type objective, so I want to make sure that we're not talking past each other.

--Rik
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Macro Photog



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PostPosted: Thu Apr 23, 2015 2:46 pm    Post subject: Objective decision Reply with quote

Rik,

The lens information is:
EDF20052
TM Objective Lens 5x

I looked it up and according to an old Nikon MM-200 brochure
the working distance for a 20052 is 64mm
Hope this helps.

Best,

Nick
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rjlittlefield
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PostPosted: Thu Apr 23, 2015 3:11 pm    Post subject: Reply with quote

Well, I don't know about anybody else, but I'm confused so let me spell out my confusion and maybe it'll help somebody else.

The brochure I mentioned earlier says that EDF20052 is a TM objective Lens 5x, and it lists working distance as 64 mm for what appears to be the same lens. That's the same information you have, so no problem, not the source of my confusion.

But you wrote that
Quote:
This person is quoting a WD of 70mm. I think this person is being honest so am I missing something? They say they are filling the frame at a 1.5 magnification factor with 110mm of extension tubes. Is this helpful?

I now have the feeling that this quote refers to the EDF20052, and if it does then I see some big disconnects. Granted I don't have one of those lenses to play with, but based on what I think I know about its construction, I really cannot see how that 5X lens could be pushed down to 1.5X and still fill a frame with anything resembling a decent image, or for that matter have only 70mm WD at 1.5X. If somebody else can confirm that it actually does these things, I'll be very tempted to buy the next one I see just so that I can figure out what the magic is. If the story said 4.5X then OK, but 1.5X no way.

At the moment, my working assumption is that part of the story got scrambled in observation, interpretation, memory, transmission, or some combination of those.

I would ask for more details, preferably to include both an image made that way and a snapshot of the optical setup.

--Rik
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Macro Photog



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PostPosted: Thu Apr 23, 2015 3:33 pm    Post subject: Reply with quote

Rik,

I think my wording may have been confusing so I am including the relevant part of the email below for clarification (hopefully!).

I took some measurements here with 5x objective and my camera

- The working distance of the 5x objective is 70mm
- My extension tubes are 110mm long
- 7mm is filling the frame (across as seen in the picture). Please note I use a Sony camera with 1.5x magnification factor compared to a full frame DSLR, so about 10mm would fill the frame in case of a full frame DSLR.

You can use this data to see if 5x will work for you.


Nick
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rjlittlefield
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PostPosted: Thu Apr 23, 2015 5:06 pm    Post subject: Reply with quote

OK, that helps a lot.

So now I see that "1.5X" is not the optical magnification but rather the crop factor of the APS-C sensor that he's using.

Working from there, suppose we take his sensor size to be 23.5 mm width (A6000, NEX-7 etc.) and presume that "7mm" might mean anything from 6.5 to 7.5 mm. Then his optical magnification is someplace in the range of 3.62X to 3.13X. Nikon's value of 64 mm WD at 5X might mean 63.5-64.99, and the focal length of that lens is probably around 40 mm, so using the usual formula that relates extension, magnification, and FL, I calculate expected working distances from 66.5 to 69.8. Those are certainly close enough to 70mm that we can take it as a rounding error.

Summarizing all this, what this fellow is telling you is that the lens will tolerate a slight reduction from its nominal magnification and still cover an APS-C sensor well enough to keep him happy.

His statement that "10mm would fill the frame of a full frame DSLR" casually assumes that the objective would produce a good image that far out, which according to ChrisR it won't, even at rated magnification. I wouldn't count this as dishonesty, but incautious optimism does come to mind.

--Rik
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ChrisR
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PostPosted: Thu Apr 23, 2015 8:36 pm    Post subject: Reply with quote

Just tried it quickly. It's late so I didn't set up a demo.
I adjusted to 5x with a EDF20050 5x lens by imaging a ruler. The distance between the rear lens flange and camera was about 150mm.
There's an image over the whole sensor (D700, 24 x 36) but only the center 2mm diameter or so looks to be even sharpness, outside that it falls off, ie ~10mm on sensor.

Extending the bellows I'm using to full extent, with 60mm or so of tubes on the lens as well, I get about 7x.
There seems no point trying lower magnifications because the image circle is so small.
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Macro Photog



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PostPosted: Fri Apr 24, 2015 9:08 am    Post subject: Need help with lens choice Reply with quote

All,

As the 5x MM series is the only lens that met my WD criteria I purchased an example this morning before it got away. I know it is not a "perfect" lens but considering my distance requirement it was the best decision. I am now looking forward to my initiation into the micro objective world.

I want to thank everyone for their input and especially patience as you interpreted my lay person input into technical requirements. I learned a great deal and have much more to go. I will post impressions once I've had have some shooting time with it.

Best,

Nick
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rjlittlefield
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PostPosted: Fri Apr 24, 2015 12:41 pm    Post subject: Reply with quote

Sounds good.

If you happen to have a teleconverter, then you might try placing that on the camera, behind all the other stuff. That will expand the center part of the image to fit your sensor better, without requiring a lot of extra extension. At this narrow aperture, both techniques can work well and you just have to try and see which is better.

--Rik
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PostPosted: Fri Apr 24, 2015 1:51 pm    Post subject: Reply with quote

Rik,

Thanks for the tip. I do have a TC-201 (2x). I'll have to try that.
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ChrisR
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PostPosted: Fri Apr 24, 2015 4:28 pm    Post subject: Reply with quote

Hold the converter!
I revisited this 5x because it was not quite how I expected it to be. I'd never taken a photo with it...
Long story short, the rear lens group was in backwards. Without a twin to compare it with I'd not have known. If yours looks concave Nick, turn it round! Now mine match. The good image circle is better than before.
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