Lenses for use at 4-5X on an APS-sized sensor

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rjlittlefield
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Lenses for use at 4-5X on an APS-sized sensor

Post by rjlittlefield »

Here's an assortment of lenses that I've recently tested for use at 4-5X on an APS-sized sensor.

Except for the JML 21 mm f/3.5 in the back row, these are all lenses that either can be purchased new or come up fairly frequently on eBay.

Image

They're roughly in order by overall image quality, worst at lower left, increasing across the front row, increasing again across the back row starting at left and ending up with highest quality at back right.

The test images were shot as stacks and processed through Zerene Stacker PMax to bring out difficulties in the corners. The target consisted of 600-grit silicon carbide sandpaper, scored with a spring steel pin so as to crush particles and produce lots of fine detail. The target is described in a separate thread, HERE.

Camera-resolution images for evaluation can be found here (in order matching the above photo):

no-name achromat, commonly found on eBay shipping out of China, very small image circle, severe aberrations on sides and corners of APS sensor at 4X. This objective is advertised as DIN, but it appears to actually be JIS, with a parfocal distance of only 36 mm instead of 45 mm for DIN. As a result, the working distance is shorter than you'd think also. For our purposes, avoid this one.

Nikon E achromat. This old objective appears to be in the CF line, but it actually has obvious color fringes. It's also not very sharp in the corners. Not shown above but tested separately, the Nikon Finite Conjugate 4X sold by Edmund Optics is very similar. Avoid both of these.

AmScope plan achromat, optically similar to the Cnscope, both lenses have differences from one corner to another. With both lenses corners are softer than the EL Nikkor but the center looks better.

Cnscope Plan Achromatic, covers most of the frame with high quality image. If you need an inexpensive DIN format objective, this is well worth the price at $25. What appears to be this same lens is widely advertised on eBay shipping out of China, not always advertised as "Cnscope".

EL Nikkor 50 mm f/2.8 at f/4, more uniform across the field than any of the small objectives, but not as sharp in the middle. At typically low prices, definitely a Good Buy.

Olympus 38 mm at f/2.8. Somewhat sharper than the EL Nikkor, with more uniform corners.

JML 21 mm f/3.5, similar sharpness to the Olympus and the absence of false colors is striking. An outstanding lens, if you can snag one.

MPE-65 at f/2.8 and 4X, slightly sharper than all except the Nikon CFI combo, better uniformity especially in corners.

MP-E 65 at f/2.8 and 5X. For direct comparison with the CFI combo, next.

Nikon CFI 10X Plan Achromat on Canon 100 mm macro lens, giving 5X. This combo is much sharper than the MP-E 65, not surprising since the MP-E is running around f/16 effective while the combo is about f/10. What is surprising is that the combo holds up well clear to the corners, despite that this far exceeds the field size that the objective was designed to handle.

Comparing up and down the line, there's really not much difference in central resolution until you get up to that last combo.

Edges and corners are a different story. The small fields of the finite objectives are a bit of concern for use on bellows, since any misalignment of the front standard will shift the optical center back on the sensor. For critical work it'd probably be a good idea to check that.

I hope this is helpful.

--Rik

Edit: to add test results for the Nikon Finite Conjugate 4X sold by Edmund Optics.
Edit: to add link to target description
Last edited by rjlittlefield on Fri Sep 15, 2017 4:42 pm, edited 3 times in total.

harisA
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Post by harisA »

Nice work thank you.
Nikon cfi is far better from all others.
I was wondering if you Know the working distance of chinese 4x cnscope.

seta666
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Post by seta666 »

Nice comparison; in my opinion the JML image looks better that that of the MP-E, more "clean", with less CAs but both are very good. The pupil ratio of the Olympus may affect it a little bit because of higher efective aperture but still is a very nice lens to use.
I do not own the MP-E but both the JML 21/3.5 and the Olympus 38/2.8 give great results in full frame cameras even at lower magnifications

Regards
Javier

ChrisRaper
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Post by ChrisRaper »

Excellent test - thanks Rik :D Where does that non-name Chinese 4x Plan Achromat fit into the list?

Saul
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Post by Saul »

Thank you very much for the article, it answered my question, what to use for 5x range !

Any information about quality of:
http://www.ebay.com/itm/NIKON-10X-0-30- ... 424wt_1101 ?

Eric F
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Post by Eric F »

Rik, thanks very much for bringing this info and your excellent tests together for us!

One question about the MP-E: ever since Charles' discussion on the best f-stop (at 5x) for this lens (Feb. 2007 - here), I have followed his advice and happily used f/4; you are testing this lens at f/2.8...what gives?

Eric

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Post by rjlittlefield »

harisA wrote:I was wondering if you Know the working distance of chinese 4x cnscope.
15.0 mm at 4X. The Amscope has a bit more working distance at 15.7, but because of the shape of the barrel it provides slightly less angle for illumination.
ChrisRaper wrote:Where does that non-name Chinese 4x Plan Achromat fit into the list?
Not sure I understand the question, but the objective I think you're asking about is the one I've labeled "Cnscope". That's what the web page said when I bought it, from eBay HERE. Looking closer at the ad and email, I see that "Cnscope" looks like the name of the company, not the objective. I was a bit confused by that because the eBay member id I bought from is "hunter20099". Exactly the same barrel design and markings, including the "Plan" designation is available from other sellers also.

There is also a very similar looking objective labeled "SP" (Semi Plan), available from other sellers. I have no experience with that one.

I see also that there are numerous objectives that look almost identical to the Nikon E that I tested. But they are designated Semi Plan and can be distinguished by details of the silver ring:

Image vs Image

Again I don't know anything about these.
Saul wrote:Any information about quality of:
http://www.ebay.com/itm/NIKON-10X-0-30- ... 424wt_1101 ?
I believe the optics in that lens are the same as the non-BD lens that I tested HERE. If so, then it's very good at 10X over an APS-sized sensor, but the image quality drops badly outside that. The lens will extend farther for magnifications above 10X, but expect the corners to go bad if you reduce the extension for lower powers. See details HERE.
Eric F wrote:One question about the MP-E: ever since Charles' discussion on the best f-stop (at 5x) for this lens (Feb. 2007 - here), I have followed his advice and happily used f/4; you are testing this lens at f/2.8...what gives?
My MP-E 65 is sharper at f/2.8 than at f/4. Here are single frames at 5X, viewed at 200% of actual pixels.

Image

I don't know why the difference from Charles' results. Diffferent sample, different camera. That's why all these test results should be taken for general guidance only. For critical work, you really need to test your own equipment.

--Rik

Eric F
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Post by Eric F »

Thanks Rik; good advice!

By the way, a lens I really like -- which we don't see often on Photomacrography -- is the Canon Macrophoto 35 f/2.8. (Dave Millard showed some tests here).

Eric

Admin edits: Link corrected.
Chris R. 4 Dec 2013
Rik L. 18 Jan 2014

ChrisLilley
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Post by ChrisLilley »

Great series of tests, very informative.

I note that in another thread, Rik also tested the Mitutoyo 10X NA 0.28 (working distance 33.5 mm) at 5x

Charles Krebs
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Post by Charles Krebs »

Nice work Rik.... thanks! (and it is a lot of work to do this!)

Saul,
Any information about quality of:
http://www.ebay.com/itm/NIKON-10X-0-30- ... 424wt_1101 ?
Rik:
I believe the optics in that lens are the same as the non-BD lens that I tested HERE.
The appearance is similar but the lens Saul indicated is an infinity M Plan type. (I know nothing about it's performance).


Eric:
One question about the MP-E: ever since Charles' discussion on the best f-stop (at 5x) for this lens (Feb. 2007 - here), I have followed his advice and happily used f/4; you are testing this lens at f/2.8...what gives?
Eric... don't forget the examples I posted back in 2007 were made of a 3-dimensional subject using a 12.7Mp, full-frame (24x36mm) sensor (Canon 5D). So this minor difference does not surprise at all.

ChrisRaper
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Post by ChrisRaper »

rjlittlefield wrote:Not sure I understand the question, but the objective I think you're asking about is the one I've labeled "Cnscope". That's what the web page said when I bought it, from eBay HERE. Looking closer at the ad and email, I see that "Cnscope" looks like the name of the company, not the objective. I was a bit confused by that because the eBay member id I bought from is "hunter20099". Exactly the same barrel design and markings, including the "Plan" designation is available from other sellers also.
Thanks Rik - you're right - I just hadn't seen "Cnscope" on the ad. :) It's interesting that it is so close to the EL-Nikkor but they have complimentary faults ... the EL-Nik being not quite as sharp in the middle but the Cnscope is worse on the edges. I think I will try a Cnscope because that central sharpness will be useful for what I am doing :)

I wonder how some of the older lenses stack up ... like the Watson, Reichert & Vickers lenses out there? There are always more questions and more lenses to test :D

EDIT: Ohh, I just thought - how about having a special subforum for equipment tests? That would be a great reference :D

Eric F
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Post by Eric F »

Excellent point Charles -- thanks (I did forget about the sensor difference; I'm accustomed to an APS-C camera).

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Post by rjlittlefield »

Charles Krebs wrote:Rik:
I believe the optics in that lens are the same as the non-BD lens that I tested HERE.
The appearance is similar but the lens Saul indicated is an infinity M Plan type. (I know nothing about it's performance).
Oops -- good catch! I didn't scroll over far enough to see that last image. :(

--Rik

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Post by rjlittlefield »

Diligent readers of this thread will notice that I've split off the discussion of pixel counts into a separate thread of its own: "Pixels for use at 4-5X on an APS sensor".

Please continue each discussion in its own place. Thanks!

--Rik

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Post by rjlittlefield »

I found a very good lens I would like to share with you:

Image

This is a Nikon CFI BE Plan Achromat 4X NA 0.10, part number MRN70040. As of March 2021 update, this lens is available in the US as new manufacture for normal list price of $69 at Microscope Central. I have no idea about availability in other countries except it should be available directly from the local Nikon.

This is an infinity objective that has to be used in conjunction with a tube lens. It's designed to deliver 4X on 200 mm, but it can be pushed cleanly down to 2.7X on a 135 mm, or even down to 2X on a 100 with some softening and a bit of transverse CA in the corners. At 2.7X and above, the image is sharp and clean corner to corner -- very nice! (Remove the black barrel covering the lens to avoid darkening of the edges & corners, especially at lower magnifications. See HERE for discussion.)

Of course you can push it to higher magnifications on a longer tube lens, or by adding a teleconverter. That works fine but it won't get you much more detail, because even at 4X the objective is already running at effective f/20.

In addition to corner-to-corner sharpness, this lens has very nice color characteristics. It's not as color-free as the JML 21, but it's hugely better than my MP-E 65 or the Olympus 38 mm. More like the Nikon CFI 10X shown in the initial post.

Sample images from this objective can be viewed at these links. (Shot with black barrel still in place as shown above.)

Nikon CFI BE Plan 4X at 4X on Vivitar 200mm

Nikon CFI BE Plan 4X at 2.7X on Vivitar 135 mm

Nikon CFI BE Plan 4X at 2X on Canon 100 mm f/2.8L USM macro

One potentially handy feature of this lens is that it can be focus stepped using the AF motor of the tube lens. In fact, the DOF of this low-mag objective is large enough that it can even be focus stepped using a front-focusing lens such as the Canon 55-200 mm f/4.5-5.6 that came as a kit lens with my first Digital Rebel. Focusing with EOS Utility, single press of "<", here's what came out.

Full frame:
Image

Crops resized to 67% of actual pixels.

Image

I was pleased to see no evidence of focus banding. An increment of 2 "<" might be OK, but that telephoto has a little play in the mechanism and I'm not sure that would work reliably. By the way, the spectral colors in some areas are due to the fly, not the lens. I used undiffused illumination coming from a fiber bundle over 6 inches away, so the illumination was quite harsh. See the spectral fly thread for more discussion of this issue.

Note that unlike the Nikon CFI objectives that we're most familiar with, which are CFI60's, the BE objectives use a standard DIN thread and parfocal distance. This means that BE objectives need an RMS thread adapter, different from the Nikon CFI 10X objective seen earlier in this topic.

I did test this objective on bellows, with no tube lens. It got soft. And anyway, it's still a 50 mm lens, so using it on empty extension would have no advantage over doing the same thing with say the EL Nikkor 50mm.

I hope this is helpful. I actually ordered this objective expecting to test it and send it back. That's not going to happen -- this one's a keeper.

--Rik

Edit Sep 21, 2012: to add note about removing the black barrel to avoid darkening of edges and corners.
Edit Mar 23, 2021: provide current information about availability.
Last edited by rjlittlefield on Fri Sep 21, 2012 2:43 pm, edited 2 times in total.

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