Lenses and Optics

Finally, Some m4/3 MTF Testing: 25mm Prime Lens Comparison

This blog is a little different. It’s geekier than most, of course. Also, I don’t use it to make income, and that makes it a bit scattered. A mainstream blog has to cover all the hot topics. I get to cover what I’m interested in at the moment. More importantly, I don’t have to cover everything, so you rarely see me writing about stuff I don’t understand.

Another benefit is I get to watch with great amusement as various Fanboys speculate on why I don’t write about their favorite product. The actual reason is usually that the company hasn’t released lenses that interest me (Nikon in 2017, for example) or I don’t have mounts to test them (Fuji and Pentax).

Micro 4/3 is a bit different. I can test most of them (the m4/3 mount we have can’t handle linear electromagnetic focusing lenses, but can handle all the others) but it requires taking time to set up the machine differently. Since most of our contract testing is for full-frame lenses, that makes it a little inconvenient to do m4/3, and because I’m old and grumpy, I tend to avoid inconvenience.

25mm Micro 4/3rd shootout

But now it’s the holidays, we don’t have any contract testing lined up, so I am going to test some of the more interesting m4/3 lenses. So now you m4/3 shooters are getting equal opportunity to read too-long articles full of charts and graphs just like everyone else. Like they say, “be careful what you ask for, you might get it.”

As we start looking at these, I want to emphasize a couple of things, because many m4/3 users will be new to this blog. First, we’re testing the lenses with no camera involved; all we’re evaluating is the optics. My interest is in the lenses, and the lenses only. Making lenses for a smaller imaging circle has some distinct theoretical advantages. Whether the lensmakers use those advantages for good and make better lenses, or for evil to cut corners and raise margins, well, that interests me quite a bit.

When you take a picture, you’re using the system (the camera and lens each add their limitations). Despite what many self-described experts say, it is very, very rare that just the lens or just the camera limit the output of the system. In practical terms, unless you have a really horrid lens, or a 4 megapixel camera, both camera and lens contribute to the final output. (If you have both a horrid lens and a 4 megapixel camera then you don’t need to be reading this.)

One other point: with m4/3 lenses you can’t make broad generalizations about the name on the outside, because that doesn’t necessarily reflect who made the components on the inside. So if the Olympus 25mm f/1.2 is pretty awesome (it is), for example, don’t take that to mean all Olympus lenses are pretty awesome (they aren’t). The name on the outside means “We paid the people who designed the lens, made the different components, and assembled it. Some of them actually work for us, some don’t, and the ones who did this lens didn’t necessarily do that other lens.”

Let’s Meet Today’s Players

We have several lenses that meet the criteria of being 25mm primes and being testable on our machine.

Notably missing from this list is the Panasonic 25mm f/1.7, because, as its Fanboys will probably tell you shortly, everyone knows it’s far better than all the others, and I wanted to keep that a secret. Or because it has an electromagnetic focusing motor and we can’t test it on the optical bench. Take whichever theory best suites your degree of paranoia.

I’ll also mention that while we usually test 10 copies of each lens, but when we get into m4/3 mounts, ten copies can be hard to come by. For that reason we’ve only tested five copies of the Voigtlander, that’s all we had in stock.

The Olympus 25mm f/1.2 ED Pro

We start with this lens because it’s considered an excellent new design that has been very popular. It’s by far the most expensive of this group at about $1,200. It contains multiple low dispersion and high refraction, as well as a single aspheric element. On the other hand, 19 elements make this a very complex lens, which made us wonder what copy-to-copy variation would be like.

Courtesy Olympus.com


Olympus Digital 25mm f/1.8

The other extreme is the little Olympus Digital 25mm. At $249 it’s the bargain lens of the bunch and it’s also the smallest. It doesn’t have as wide an aperture. It has two aspheric elements, but at this price range, we expect those are molded. So, we started with low expectations, but at this price, just a decent showing would make this a lens worth considering.

Olympus. com

Panasonic Leica DG Summilux 25mm f/1.4 ASPH

At $600 this lens has a reasonable price, it’s not very large physically, has an f/1.4 aperture, and despite what I consider the stupidest hood design in all of photography history, has a fairly rabid following who love it. It has two aspheric elements and the simplest design of all the lenses we tested. Plus, it says Leica and Summilux on the front, and we all know what that means — they paid Leica to put ‘Leica’ and ‘Summilux’ on the front. In case I wasn’t clear, I went into this test a little cynical about this lens. It’s an older design, and I expected the newer design of the Olympus might have passed it by.


Voigtlander 25mm f/0.95 Nokton Type II

I maintain complete impartiality when it comes to lenses. Except I despise all things Voigtlander. Not because their lenses are bad, but because customer service is nonexistent and repairs nearly impossible to obtain, at least in the U. S. But at f/0.95 and a reasonable (for that kind of aperture) price tag of $800, this lens has to be considered for those who are willing to focus manually. Plus it has an all-metal construction which provides two advantages. First, it weighs a lot more. Second, you can describe it as ‘built like a tank’, which, of course, means ‘I don’t know anything about lens construction, but this one sure is heavy.’

Courtesy Voigtlander


MTF Results

These results are all taken at widest aperture, so it’s not a direct comparison optically; a smaller aperture gives a better MTF. They’ll all improve stopped down a bit (more on that later). These MTFs are the average of 10 samples for all except the Voigtlander, which is the average of 5 samples.

Olympus 25mm f/1.2 ED Pro

This is actually very good for an f/1.2 lens, much better than the Canon 50mm f/1.2, for example. It maintains excellent sharpness in the center half of the image. It’s still quite sharp, although with some astigmatism, out to the edge.

Olaf Optical Testing, 2018

Olympus Digital 25mm f/1.8

Here’s my first surprise of this testing batch. The little Olympus is really quite good. It falls off and has some astigmatism in the outer 1/3 of the image a bit, but not badly.

Olaf Optical Testing, 2018

Panasonic Leica DG Summilux 25mm f/1.4 ASPH

The Panasonic was a bit disappointing. Even though it’s tested at a smaller aperture than the Olympus Pro, it doesn’t resolve nearly as well in the center. This is especially true of the higher frequencies (green, blue, and purple lines) which are critical for fine detail resolution on cameras with smaller pixels. It does maintain good resolution out to the edge of the frame, though.

Olaf Optical Testing, 2018

Voigtlander 25mm f/0.95 Nokton Type II

This one was also better than I expected. It resolves decently in the center and falls off at the edges. But at f/0.95 that’s unavoidable. I was impressed that it could do this well. Lenses with apertures this wide are rarely this good. Right in the center, it resolves as well at f/0.95 as the Panasonic does at f/1.4.

Olaf Optical Testing, 2018

Stop-Down Tests

We picked an average copy of the Voigtlander and Olympus 25mm f/1.2 to retest at f/1.4, to get a little more even comparison. (And used an average copy of the Panasonic for comparison, so we weren’t comparing single lenses to a group of lenses.)

Panasonic – Olympus

The Olympus was clearly better at higher frequencies (blue and purple lines). If you’re shooting with (or looking at a test done on) a 12-megapixel camera, the high frequencies are less important.

Olaf Optical Testing, 2018


The Voigtlander surprises me yet again. It can match, perhaps slightly exceed, the Olympus in the center 1/2 of the image, although it can’t (like all ultra-wide aperture lens designs) keep up in the outer 1/3 of the image.

Olaf Optical Testing, 2014

Olympus 25mm f1.8 and Olympus 25mm f/1.2 Pro at f/1.4

I didn’t test the Pro at f/1.8. To be honest, I didn’t think there would be enough competition that I’d be interested. So I’ll have to compare the Pro at f/1.4 to the Digital f/1.8 at f/1.8. Not really fair, since the Pro would do better at f/1.8. On the other hand, you can buy 4 of the little Digital f/1.8 for the price of one Pro, so . . . . .

Olaf Optical Testing, 2018

It’s kind of shocking to me that the Digital f/1.8 is significantly sharper in the center. Things even up away from the center, but still, that’s impressive. Really. Impressive. Good job little-inexpensive-lens.

Comparisons at f/2.8

Because sometimes people stop down.

Olympus vs. Olympus

At f/2.8 the Pro is definitely superior in the outer 1/3 of the image, but the baby Olympus still impresses me with its performance at f/2.8.

Olaf Optical Testing, 2018

Panasonic Leica vs. Olympus Pro

At f/2.8 there’s not a lot of difference between the two. The Olympus is a bit better at the edges of the image, but it’s a small difference.

Olaf Optical Testing, 2018

Voigtlander vs. Olympus Pro

Not surprisingly, the Olympus is now a tiny better than the Voigt in the center, and far better in the outer half of the image.

Olaf Optical Testing, 2018

Field Curvature (MTF vs. Field vs. Focus)

For those of you who don’t read our technical articles very often, the field curvature may be the most useful thing we give you. This is NOT distortion; rather it’s how the plane of best focus curves. The tangential and sagittal fields often curve differently; when they do you know, there will be astigmatism in those areas.

There’s other information you can get from field curvatures and if you’re interested here are some background articles: Fun with Fields of Focus 1, Fun with Fields of Focus II, Field Curvature and Stopping Down. I should mention these are done at f/5.6 because that gives a nice, clear picture of the field. Stopping down (or opening up) doesn’t change the curvature significantly. Keep in mind that when you’re shooting at a wider aperture, the field is much narrower.

We haven’t done these on many m4/3 lenses, so I had no idea what to expect. Because there’s less side-to-side distance to cover, it seemed likely that the field curvature would be less apparent.

Olympus 25mm f/1.2 ED Pro

There’s a gentle curve with this lens, but note that the sagittal field (right side) curves differently than the tangential field (left side). This means that while the overall field is flat, there is going to be some astigmatism off-center. The MTF graphs above reflect that.

Olaf Optical Testing, 2018

Olympus Digital 25mm f/1.8

Here we see a more dramatic curve, but more of a tendency to be in the same direction. At wide apertures, though, the edges of the image are not going to be in focus at the same point that the center is. With this one, the field will truly curve. This also explains that the MTF curves above drop off at the edges, not because the lens is weaker, but because the field is curving away.

Olaf Optical Testing, 2018

Panasonic Leica DG Summilux 25mm f/1.4 ASPH

Here we have two very different curves. The sagittal is almost perfectly flat; the tangential is in a W shape. This lens will have some mid-field astigmatism that will clear up near the edges, but will be pretty flat otherwise.

Olaf Optical Testing, 2018

Voigtlander 25mm f/0.95 Nokton Type II

Here’s yet another surprise to me. I really expected the ultra-wide aperture lens would have severe field curvature, but it’s not too bad. There will be edge astigmatism (where the U-shaped tangential curve continues up, while the M-shaped sagittal curve turns down). There will be a slightly curved overall field.

Olaf Optical Testing, 2018

Copy-to-Copy Variation

Micro 4/3 lenses, in general, have a lot of sample variation. Why this is I can’t say. What I can say is it’s not the fabled “QA check” that people imagine happens. Optical tolerance is done during the design of the lens and the assembly line, not by running a test at the end of manufacturing. Micro 4/3 lenses, as a rule, don’t have any compensating adjustable elements, so what you get at the end of the assembly line is what you get unless something is broken inside.

With these lenses, I wasn’t sure what to expect. The Olympus Pro is a complex lens; complexity and wide aperture tend to create a lot of variation. The Panasonic Leica and Olympus Digital f/1.8 are much simpler designs.

I’ve added the Variance Number to these graphs, although I want to point out that a number is a blunt tool; it’s not nearly as useful as looking at the graphs. As a rule, we consider prime lenses to be acceptable if the Variance number is less than 40, and random crap shoots if it’s over 80. So here are the graphs and variance numbers for the three lenses we could run them on. (We don’t consider five copies enough to comment on variance, so we skipped the Voigtlander in this part of the post.)

Olympus 25mm f/1.2 Pro

It looks better than the variance number suggests, but there’s some significant variation particularly in overall sharpness (notice how even in the center, there’s a fairly thick area).

Olaf Optical Testing, 2018

Olympus 25mm Digital f/1.8

The variance number says it’s quite good, but the widening as you go away from center shows that there’s likely to be some difference in one side or the other on a given copy. The current variance number doesn’t take this into account as much as I would like it to.

Olaf Optical Testing, 2018

Panasonic Leica Summilux f/1.4

Any way you look at it, there’s a lot of copy-to-copy variation, more in overall sharpness. This is getting close to the point where your copy and Bob’s copy are probably noticeably different.

Olaf Optical Testing, 2018


So What Did We Learn Today?

Well, there are several good choices if you’re interested in a 25mm prime lens for your m4/3 camera. There’s not a bad choice in the bunch; I think most people would be happy with whichever one they have.

If you absolutely need an f/1.4 or wider aperture lens, the Olympus 25mm f/1.2 Pro is probably the best overall lens, although it comes at a hefty price. If you want the widest aperture possible and are willing to manually focus and realize you probably can’t get it repaired, the Voigtlander Nokton Type II is much better optically than I had expected.

The Pansonic Leica Summilux is a good lens, and at 2/3 the price of the Olympus Pro is a reasonable choice for a lot of people. It’s certainly not better, and the copy-to-copy variation makes me hesitant to recommend it very highly. On the other hand, as I said to start with, I’m a little cynical about that lens so maybe that’s affecting my judgment. It’s still a good lens at a reasonable price.

Me personally, though, I love a bargain, and in this case, I’d be willing to give up some aperture to get it. The little Olympus 25mm f/1.8 isn’t as wide an aperture as the others. Even stopped down, it’s not quite as sharp at the edges as either the Olympus Pro or the Panasonic Leica. But at that price and that small size, it’s a great bargain and a really good lens. This one surprised me in a very positive way.


Roger Cicala and Aaron Closz


January, 2018


Note: It’s been a while since we did an m4/ test. For those of you m4/3 Fanboys and Detractors who are so vocal in some forums, this isn’t those forums. We welcome informed discussion and opinions. We do not allow snide, or ugly personal comments to other posters. I’m not a poster; you can be snide and ugly to me if you like.

Author: Roger Cicala

I’m Roger and I am the founder of Lensrentals.com. Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

Posted in Lenses and Optics
  • There are also some interesting old Four Thirds lenses that might be considered, including the amazing Oly 14-35mm f/2 and the Panny 25mm D Summilux f/1.4. I know: legacy, one is not a prime, but still excellent and available. AFAIK there are no MTF comparison tests between FT and MFT lenses, which I would find useful because I wonder if the newer models are ‘that much’ better (or not).

  • Brandon Dube

    The path of light through that is not very similar to Olympus’ lens.

  • Someone

    Some fast zooms do something similar. See for example Sigma 18-35/1.8: https://www.sigma-global.com/common/lenses/cas/product/art/a_18_35_18/specifications/images/construction.gif

  • Lo-Wok Li Ya

    Thank you so much! You are great and supportive!

  • Meier Kurt

    Hallo Roger,
    Thanks for leaving your comfort-zone and thanks for your time.
    I really enjoyed reading.
    But: There are many more m43-Lenses out there:
    So please stay grumpy but don’t get really old
    (you are not) before you had them all.

    (ohhhhhhh…come on; at least 200 f/2.8 vs. 300 f/4 and….)

    Thank you for sharing.

    May the (m43)-Light always be with you

  • Brandon Dube

    I doubt we will ever take a stab at bokeh, it’s too subjective.

  • Ivar Brekke

    The PL15 is my favorite M43 lens 🙂

  • Ivar Brekke

    That would be great! Bokeh would also be interesting, It might be a little hard to define the rules of what good bokeh is. Leica thinks that bokeh should have a contrast “falloff”, whichs than make the in focus object pop more for example. Some reviews I have seen thinks that good bokeh is circular bokeh balls, which is a silly parameter, as cateye bokeh for example svirls more, which might be what you are after.

  • Jonas Palm

    Thanks a lot for these tests!
    I particularly appreciate that you stopped down for comparisons – I very rarely shoot at full opening.

  • I agree. I did some side by side comparisons between my 2 lenses Oly 17mm 1.8 and Pana 15mm 1.7 and there is definitely a difference. All ‘Leica’ lenses seem to delivery more contrasty images. So out of camera jpegs do have a bit richer colors. I would even say that they somehow look more 3Dish whatever it is.

  • Claudia Muster

    Ok, now that everybody seems to place their wishes what µ4/3 lenses should be tested, I’ll add mine: I think it would be interesting to see and compare the MTF curves and their variation of the Oly 300 and the Panaleica 200, both with and without the 1.4 converter. Even when their price tag is certainly out of the range for most amateur photographers.

  • Brandon Dube

    Color is forthcoming from us 🙂

  • Ivar Brekke

    Thank you for your test, find your tests very interesting, please bring up more m43 stuff! Resolution is an important parameter on any lens, and as you say in that regard the Olympus 25mm f1.8 is really good for the price. However, I have been looking up many picture comparisons with the PL 25 and I must say that it is a really good performer in color “pop” which is hard to test. If you look at this comparison you might see what I mean:

    I find the PL to have more color dynamic range, while the olympus are more grayish/flatter. Look at the red and green in the first comparison (or the colors in all of the comparisons). Also the highlights are lighter and the shadows darker, giving it a nicer look in my perception. I have seen the same on all other comparisons around the web, still very few reviewers even mentions it. Here is another comparson with the voightlander included:

    The difference is noticeable, I think it shows in all PL lenses in comparison with simialr focal length olympus ones. Panasonic have managed to create a consistent look in their PL lens range, which is why I think the users love the lens range (me included). The old 12-35 which I also own, does not have the same PL character, which is why I do not use it as much and should probably have sold it a long time ago.

    I wish reviewers around the web had better tools/methology to better compare these kind of differences (color and bokeh) when comparing lenses.

  • Hal Knowles

    Thanks Roger et al., for the awesome Micro Four Thirds lens camparison! Should you ever have the optical bench set up for future Micro Four Thirds lens testing, I’d like to kindly request if you could add the SLR Magic 25mm t0.95 Hyperprime to this existing 25mm comparison. It is a lens you carry and though it is a bit more niche than the others, some of the few reviews available suggest that it may be sharper than the Voigtlander 25mm lens.



  • Impulse_Vigil

    Thanks for this! Any and all M4/3 tests from your are most welcome IMO.

  • James Whitehouse

    Thank you, I really find these tests useful and informative. Is there any chance you could include CA, though, as a lot of times sharpness is only one factor of interest for me, and I often find CA bugs me even with quite expensive lenses.

  • Impulse_Vigil

    DxO’s T-stop measurements vary even on the same mount/format (e.g. E-M1 II w/25/1.2 vs other M4/3 bodies with the same lens)… I’ve read some theories on why but I’m still not totally sure it isn’t simply testing error.

  • mohammad mehrzad

    “hehe” is all I can say.
    I can actually use this argument the next time there is an equivalency war (not that uncommon these days) , to stop the madness.

  • Carleton Foxx

    You’ve stumbled into the Sophie’s choice one faces when trying to compare two formats using equivalence. Do you compare them with all settings being the same, in which case larger formats always come out ahead? Or do you handicap the larger format by increasing ISO or stopping down to an “equivalent” aperture so the results are the same? I wish someone would come up with a definitive answer.

  • Made my day!!!!!! 🙂

  • Maya

    Thanks for the article ! Now I guess that I know why I never managed to find a 25mm f1.8 which wasn’t badly misaligned. My own real-life experience with this lens is in line with the article.

  • zapatista

    When are you gonna review some Canon stuffz?!? It’s not fair, all this panolympusjunk.

  • Brandon Dube

    Astigmatism and field curvature are invariant with aperture. They are reduced in apparent magnitude when the aperture is closed, because the depth of field is increased. If a lens has focus shift from spherical aberration, the plane selected in the MTFvFvF plots may move to one that is more astigmatic (e.g. if the T and S fields move away at the edge, which is what astigmatism is).

    The separation of the T and S lines in an MTF vs Field plot is not directly indicative of astigmatism; there can be several causes for that (astigmatism being one of them.)

  • Lo-Wok Li Ya

    Thanks, Roger and Brandon! A true joy to read.
    What I find strange is that many lenses (OM 1.8, Pana Leica, Voigt) exibit the increase of astigmatism when stopped down. How is that possible since we know that astigmatism decreases at lower apertues?!

  • Franck Mée

    That makes sense. Thanks for the details!

  • Hal Knowles

    Roger, Aaron, et al. Thanks for another incredible blog post and testing run! AS a Micro Four Thirds (m43) user, I am excited to see you finally testing lenses for the system. In the future, should you have the optical bench set up for additional m43 lenses, I would love to kindly request that you consider testing and adding the SLR Magic 25mm t0.95 Hyperprime Cine III. It is a lens you carry in stock and some reviews suggest it may outperform the Voigtlander 25mm (at least some copies a f some apertures).



    P.S. While sharpness is certainly a critical feature of all lenses, for some situations other lens characteristics may take precedence. For example, I am fortunate to have a nicely centefed and very sharp copy of the Panasonic Leica 25mm f1.4 lens. However, I often find that in environmental portraiture (which is presumably a major use of thu lens and its focal length), I am consistently underwhelmed with the point light source bokeh balls. At all apertures, they have pretty horrible onion ring abberations and at the f1.4 and f1.6 aperture in the image edges they take on a very unattractive truncated shape that I find highly visually distracting. It’s a shame because I find the other aspects of it’s bokeh (outside of the distinct balls) to be quite nice (e.g. front/rear blur smoothness and transitions). It is so close to being a near perfect lens for my needs in that focal range, but I find myself preferring the performance and portability of the Panasonic 20mm f1.7 over it and I am considering replacing the Panasonic Leica 25mm f1.4 with the aforementioned SLR Magic 25mm t0.95 for its more pleasing bokeh and wider aperture, despite its presumed considerable drop off in sharpness.

    Out of curiosity, has the Lens Rentals Blog ever written any posts about the various lens characteristics and abberations and how lens designers and manufacturers balance their correction (or lack of correction) for desired aesthetic and performance

  • Brandon Dube

    Why does the diameter of the lens matter? Aberrations work in normalized coordinate systems.

  • Phillip Reeve

    But a f/1.2 aperture for M43 is quite a bit smaller than a f/1.8 for FF?

  • Brandon Dube

    The field of view (~40 degrees for a “normal” lens) and F/# set the difficulty. Same field of view, quite a lot bigger aperture, harder design.

  • Phillip Reeve

    I think the distortion numbers would be valuable to judge how much the sharpness of the final image will be affected by the forced distortion correction? That’s less of an issue for these normal lenses of which only the 1.4/25 forces distortion correction in most Raw converters but it will be more important with other M43 lenses which heavily rely on distortion correction. Oh and it would be interesting to know how much weaker or stronger distortion correction affects image sharpness. We have this older article from you but it only covers one lens at one focal length: https://www.lensrentals.com/blog/2013/01/you-can-correct-it-in-post-but/

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