Quick Test of WeMacro vs. Mitutoyo 5X

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mawyatt
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Quick Test of WeMacro vs. Mitutoyo 5X

Post by mawyatt »

Attached are a couple images of the WeMacro M Plan Apo HL 5X 0.15 NA Inf 200mm objective and the similar Mitutoyo 5X.

First off the WeMacro looks like the Mitty except it's shorter, even has the same threads and comes with the same style case. Very nicely built.

I did a very quick test with a Vertical Setup using a Nikon D800E and a Nikon 200mm F4 "Q" as the 200mm tube lens. Lighting from 3 strobes and a foam cup diffuser.

Subject is a chip in a QFN package, and I took a single shot. Unfortunately the in focus locations didn't line up, but the results show the WeMacro has very good resolution but higher CA than the Mitty. Check out the small square metal "fill pattern" which is scattered everywhere.

I'll try and get more testing done, but this will have to wait for some time until I get other efforts completed.

Image

Mitty 5X
Image
WeMacro 5X (Note slight CA)
Image
Mitty 5X
Image
WeMacro 5X (Note resolution)


Anyway, as you can see outside some slight CA the WeMacro seems like a pretty good lens and value IMO.

Best,

Mike

mawyatt
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Post by mawyatt »

I redid the Mitty image to better line up with the WeMacro.

Best,

Mike


Image
Mitutoyo 5X
Image
WeMacro 5X

Sorry I have no idea why these are coming out like this, I did PS and forced 1023 pixel wide with 4/3 ratio, then had to do LR to force under 300KB.

rjlittlefield
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Post by rjlittlefield »

mawyatt wrote:Sorry I have no idea why these are coming out like this, I did PS and forced 1023 pixel wide with 4/3 ratio, then had to do LR to force under 300KB.
I'm guessing you have Lightroom set to shrink the image if necessary to make the file smaller.

But you should be able to export direct from Photoshop with no problem. The function you want is "Save for Web". In recent versions of Photoshop it is under File > Export > "Save for Web (Legacy)..." In earlier versions it was File > "Save for Web & Devices..."

--Rik

mawyatt
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Post by mawyatt »

Rik,

I used the "Save for web" feature and tried another set to get better alignment. Think that works...thanks.

So here's a better comparison between the WeMacro and Mitutoyo 5X. Outside the higher CA the WeMacro looks pretty good IMO.

Best,

Mike


Edit: The focus areas aren't exactly lined up, but if you pixel peek into the lower right corner and look near the wire-bond surface bonds you can see some surface texture details (note the angled line). Here if you compare the two images you can see the very slight resolution (sharpness) advantage of the Mitutoyo, but it's very slight indeed!


Image
WeMacro

Image
Mitutoyo

Image
WeMacro

Image
Mitutoyo

ray_parkhurst
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Post by ray_parkhurst »

Hey, not bad at all. Both show a bit of LatCA. It's tough to tell with the subject how much LongCA there is in either one. Keep in mind that Apo optics have no claim to elimination of LatCA, only LongCA. The Chinese 5x seems to be well worth its price.

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Post by Pau »

ray_parkhurst wrote: Both show a bit of LatCA. It's tough to tell with the subject how much LongCA there is in either one. Keep in mind that Apo optics have no claim to elimination of LatCA, only LongCA...
Are you sure?
AFAIK Apo usually refers to lateral CA. Some lenses well corrected for lateral CA like the Apo Rodagon D do show some longitudinal CA. The CA shown seems to me more due to longitudinal CA (only shown at out of focus zones)
Pau

Lou Jost
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Post by Lou Jost »

It seems to be red/green, which I normally see from LoCA.

ray_parkhurst
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Post by ray_parkhurst »

Pau wrote:
ray_parkhurst wrote: Both show a bit of LatCA. It's tough to tell with the subject how much LongCA there is in either one. Keep in mind that Apo optics have no claim to elimination of LatCA, only LongCA...
Are you sure?
AFAIK Apo usually refers to lateral CA. Some lenses well corrected for lateral CA like the Apo Rodagon D do show some longitudinal CA. The CA shown seems to me more due to longitudinal CA (only shown at out of focus zones)
Apochromatic means that the lens is corrected for 3 wavelengths at the same focal plane, ie for Longitudinal CA. Lateral CA can be corrected in post processing if you can characterize the lens well enough, but Longitudinal CA can't really be corrected for.

The Apo Rodagon D 1:1 is not actually Apo, but really a well-corrected achromat.

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Post by ray_parkhurst »

Lou Jost wrote:It seems to be red/green, which I normally see from LoCA.
I'm mostly looking at the ball-on-stitch bonds at lower right corner. They are not quite at the same focal plane, but are pretty close. The Mitty shows very slight fringing between shadow and bright areas, but the CN lens shows them more severely, and is also starting to show a general green shift when OOF-low.

edited to add: looking closer, those appear to be stitch-on-ball, which I find strange to see on an Au surface. To ensure bondpull, I usually do ball-on-stitch.
Last edited by ray_parkhurst on Sun Jul 30, 2017 9:56 am, edited 1 time in total.

mawyatt
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Post by mawyatt »

All,

Here's some additional crops that may help.

Best,

Mike
Image
WeMacro 5X

Image
Mitutoyo 5X

Pau
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Post by Pau »

ray_parkhurst wrote: Apochromatic means that the lens is corrected for 3 wavelengths at the same focal plane, ie for Longitudinal CA...
Sure, but this is accomplished only at the focus plane, not at OOF, so it can show loCA at OOF parts of the image, see a typical graph (Wiki):
Image
To be Apochromat the focal plane must be well corrected, so lateral CA that applies at the focus plane must be very small

(at least this is my interpretation...)
Pau

ray_parkhurst
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Post by ray_parkhurst »

Pau wrote: To be Apochromat the focal plane must be well corrected, so lateral CA that applies at the focus plane must be very small

(at least this is my interpretation...)
I don't think this is generally true. There are lenses and objectives that are apochromatic yet have poor LaCA, even at the best focal plane. The 4xPlApo comes to mind. There are also lenses which are fully corrected for both LoCA and LaCA, such as the 105PN.

hero
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Post by hero »

After comparing the two images in Photoshop (the WeMacro shot needed to be scaled up by about 102.51% to match the Mitutoyo) I see some very minor differences in chromatic aberration, but I couldn't determine whether this was due to the lens or the focus or some other processing step. One of the challenges is that the subject is very strongly monochromatic yellow. Overall, I'd say the differences are surprisingly minor.

The question of whether "apochromat" is a term used to refer to correct longitudinal (axial) color or lateral (transverse) color is an interesting one; my understanding is that it is the former. Axial color is primarily a result of the surfaces of sharpest focus being variable as a function of wavelength. Lateral color as it is commonly understood is a result of the focal length of the system being variable as a function of wavelength (i.e. magnification varies with wavelength). Rarely do these occur in isolation--as consequences of optical material dispersion, they are almost always simultaneously present to some degree (diffraction also varies with wavelength but does not normally lead to the kind of spurious color we observe in photography).

mawyatt
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Post by mawyatt »

hero wrote:After comparing the two images in Photoshop (the WeMacro shot needed to be scaled up by about 102.51% to match the Mitutoyo) I see some very minor differences in chromatic aberration, but I couldn't determine whether this was due to the lens or the focus or some other processing step. One of the challenges is that the subject is very strongly monochromatic yellow. Overall, I'd say the differences are surprisingly minor.

The question of whether "apochromat" is a term used to refer to correct longitudinal (axial) color or lateral (transverse) color is an interesting one; my understanding is that it is the former. Axial color is primarily a result of the surfaces of sharpest focus being variable as a function of wavelength. Lateral color as it is commonly understood is a result of the focal length of the system being variable as a function of wavelength (i.e. magnification varies with wavelength). Rarely do these occur in isolation--as consequences of optical material dispersion, they are almost always simultaneously present to some degree (diffraction also varies with wavelength but does not normally lead to the kind of spurious color we observe in photography).
These images were from the D800E in 16 bit TIFF format, then using Rik's suggestion "Saved for Web" in PS as JPEG under 300KB for use here. No other post processing was done. My goal was to compare the lenses and nothing else. There is a slight difference in color and brightness from each lens as in CA and sharpness/resolution.

Everything considered, especially since comparing to a Mitty 5X, this WeMacro 5X seems pretty good to me, and a very good value IMO. This is my reason for posting, so others might take advantage of this lower cost Mitty alternative.

I'll let you lens gurus discuss the aspects of lens design, CA and whatnot.

Best,

Mike

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Post by rjlittlefield »

About the word "apochromatic", I checked in a few books that I have conveniently at hand. Here is what I found.

"Optics in Photography" (Rudolf Kingslake, page 39) says that
Secondary Spectrum
When we speak of a lens being "achromatized," we mean strictly that the spectrum has been bent back on itself, and that the images in two of the colors of the spectrum have been united at a common focus. The remaining colors, however, will in general depart slightly from the common focus of the two selected colors. Thus, an achromatic lens may show a slight residual of color in the image (secondary spectrum), which in a lens of long focus may be great enough to be significant, especially for the ultraviolet and infrared. The light in both these spectral regions comes to a focus slightly beyond the best visual or photographic focus, so tat when using infrared-sensitive film, it is advisable to move the lens forward away from the film by about 0.5% of the focal length, to secure the sharpest possible definition.

By the use of crystalline fluorite or unusual types of optical glass, however, it is possible by careful design to construct a lens in which the secondary spectrum is reduced to the point where it is completely negligible. Such lenses, used commonly in three-color process cameras, are known as apochromats.
"A History of the Photographic Lens" (Rudolf Kingslake, page 316) says
Apochromat. A lens in which three wavelengths instead of the usual two meet at a common focus.
"Modern Optical Engineering" (Warren J. Smith, fourth edition, page 428) says that
A lens in which three wavelengths are brought to a common focus is called an apochromat. Often this term also implies that the spherical aberration is corrected for two wavelengths as well. By properly balancing the glass combinations given above one can achromatize the triplet for four wavelengths; such lenses are called superachromats.
"Optical Design of Microscopes (George H. Seward) does not define apochromatic, but instead (page 129) simply uses the word in one description.
However, the plot does not display the "S shape" of an apochromat, where a vertical line indicates three corrected wavelengths. The lens is certainly an achromat; however, it is not apochromatic.
Of course the phrase "common focus" is pretty vague. But Kingslake and most of the discussions that I find on the web seem to be treating "common focus" in terms of what you would control with the focus ring, hence longitudinal (axial) color.

--Rik

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