Equipment

The Zeiss FE Batis 25mm f/2.8 & Loxia 35mm f/2 Lens MTF Charts

For quite a while now, some you have asked where the MTF results were for the Zeiss Batis and Loxia lenses, and my answer has been not done yet. There were a lot of reasons for that. Chief among these was the lenses are so popular that we can’t get as many as we want and keep them in stock long enough test them. There were also the issues we had modifying our optical bench for testing lenses with an electromagnetic focus for the Batis lenses.

So this arrives pretty late, way after most of you have made whatever purchasing decisions you are going to make regarding these lenses. But better late than never. With that in mind, though, I’m going to post all of our Batis and Loxia results in one place (here) just like we did in summarizing the Sony FE lenses so that it can serve as a reference.

One thing I will mention, because I think it acts as a good example. Unlike most manufacturers, Zeiss publishes measured MTF curves with their lenses, not computer simulations. When you ask me why my results are different from ones released by Canon or Nikon, I quickly say mine are real; theirs are idealized computer simulations.

When you ask me why my results are different from Zeiss’ results, the answer is that they are different measurement techniques. Some will have to do with various machines; Zeiss uses their K-8 and K-9 machines, we use a Trioptics Imagemaster vertical MTF bench. The light source is slightly different, for example. The Imagemaster uses a photopic light; Zeiss uses (I believe) a broader spectrum source. It may also have to do with the number of points measured, the number of samples tested, and a host of other things.

For example, we measure each lens at four different rotations, taking cuts from side-to-side, top-to-bottom, and from each diagonal, so each lens is measured at 84 points. The main reason we measure this way is that we’ve written software to give us an easy way to compare lenses to see how they differ.

OlafOpticalTesting, 2016

OlafOpticalTesting, 2016

That may be a very different measuring technique from what Zeiss uses. Other differences are going to be our mount, which cuts the 20mm edges in some measurements, or the thickness of sensor glass utilized in the test. (I can only obtain optical glass in 1,2,3 or 4mm thicknesses, and the sensor glass is between 2.3 and 2.5mm thick.) This may make a slight difference, and more importantly, the amount of difference varies somewhat depending on the lens in question.

So why bother to publish this data instead of just letting you look at Zeiss’s data? Because Zeiss doesn’t test the other lens brands. If you want to compare MTF between, say, a Loxia and a Sony FE, then these are worthwhile.

MTF Results

Markus has written an excellent new piece of software that lets me put up side-by-side comparisons just by pushing some buttons. Since I want to play with my new toy, I’m putting each Zeiss lens MTF next to a Sony lens of similar focal length. Remember, though, that they are all measured wide open, so don’t look silly and say this f/2.8 lens is sharper than this f/1.4 lens. Because aperture. And, of course, if you want to compare these to other FE mount lenses, the MTF charts are here.

Zeiss Batis 25mm f/2.8

The closest comparison I came up with is the Sony FE 28mm f/2.0. It’s a fair comparison since they’re both f/2.0, although the Sony lens is far less expensive. The Sony does pretty well from a resolution standpoint in the center where it’s as good or perhaps a tiny bit better than the Batis, but away from the center, the Batis shines, maintaining its sharpness well and with little astigmatism.

OlafOpticalTesting, 2016

OlafOpticalTesting, 2016

 

Zeiss Loxia 35mm f/2.0

I chose the Sony 35mm f/2.8 ZA Sonnar as the comparison lens, so remember, of course, that it is being tested at a stop’s smaller aperture. The Loxia would improve stopped down to f/2.8. Even given its disadvantage, though, it’s apparent the Loxia 35 isn’t the fastest horse in Zeiss’s FE mount fleet. It’s an older design so we shouldn’t be too surprised at that. And yes, I know you’re all curious as to how much better the Loxia would be at f/2.8. So am I but time takes time, and I don’t have any right now.

OlafOpticalTesting, 2016

OlafOpticalTesting, 2016

 

Zeiss Loxia 50mm f/2.0

In this test, I gave the Loxia a full stop advantage by choosing the new Sony 50mm f/1.4 ZA as it’s comparison. On the other hand, the Loxia is considerably less expensive. Despite giving up that stop of aperture, the Sony ZA clearly has higher resolution. However, the smooth, fairly astigmatism-free MTF curves of the Loxia suggest it will have a very different ‘look’ that some people will prefer.

OlafOpticalTesting, 2016

OlafOpticalTesting, 2016

 

Zeiss Batis 85mm f/1.8

The comparison here is with the Sony 85mm f/1.4 GM lens, which is more expensive, but gives up some aperture. Even considering the aperture difference, the 85mm Batis puts in a most impressive performance. Excellent resolution and very flat curves across the field. It’s not an inexpensive lens, by any means, but its performance is most impressive.

 

OlafOpticalTesting, 2016

OlafOpticalTesting, 2016

 

Conclusion

I haven’t gone into great detail about this set of lenses for one fairly obvious reason: they’ve been out quite a while and photographers who love them love the look of them and don’t seem anxious about what the MTF is like. I think this does show, to some extent, why the Loxia Biogon 35mm f/2.0 isn’t as popular as the other lenses, perhaps, but that’s about the most significant thing I see here.

I know some of you are asking where the results for the 21mm and 18mm Batis are, and the answer is ‘not done yet.’ I’ve made a solemn oath not to post data like this until we’ve finished ten copy sets, and those are still so popular that we haven’t finished testing yet, we can’t keep them in stock long enough. Stay thirsty, my friends (and patient).

Roger Cicala, Aaron Closz, and Markus Ruthacker

Lensrentals.com

August, 2016

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 Equipment
  • Sean T

    turns out I was prescient! More or less.

  • Omesh Singh

    I guess , with it being an affordable alternative, many people probably would just buy it outright rather than want to rent. I suspect there will be some more alternatives from Sigma and Canon in the near future so would be nice to log the Tamron’s performance.

    p.s. Don’t worry about sending me digging through all those old blog posts. In all honesty you’ve earned so much respect from me over the years that it is easy to forgive a tiny slip like that.

  • Omesh, I apologize. I was thinking of the 35mm. We don’t have enough of the 85s to do a full test.

  • Omesh Singh

    Hi Roger, I went through the blog all the way back to Feb and couldn’t find it. I only found 35/1.8 and 45/1.8 VC tests, not the 85/1.8 VC test. Was the 85mm bundled together with another lens test or does it have an obscure title?

  • Thinkinginpictures

    This blog site might just be the most awesome thing I’ve ever found on the internet. I’m dead serious.

  • Damir ?olak

    Yes, but so does Sigma 30mm 2.8

  • I agree. Using it from f 4 on and at 5.6 to 11 most of the time.

  • Oskar Ojala

    The Zeiss 35/2 has a lot of aberrations at f2, improving significantly at f2.8, so I wouldn’t make conclusions based on only performance wide open. Stopped down, it’s a sharp lens with many nice imaging properties.

    My experience from using the Batis 85 has been that it’s clearly better in most regards than its CaNikon equivalents. Your MTF measurement indicates that measurements might agree.

  • Chris

    Looking forward to copy variation data. I’ve had challenges getting good performing copies that are not decentered. Wondering if I just have bad luck, or it’s a common issue.

  • Omesh, we tested it a while back if you want to google for it. I know searching through our table of contents is pretty worthless.

  • Omesh Singh

    How does the Tamron SP 85mm f/1.8 VC do?

  • plekenut

    will fe28/2 performs great on a6000?

  • Daniel

    No worries, I’m still new in the ‘reading MTF charts’ business, so I was just wondering. BR, Daniel

  • Daniel, they are wrong – pulled in from a different graph. We’ve corrected the software but I’m out of town so it will be a week or so before I can get around to posting new graphs with the correct legend.

  • Daniel

    Is it just me, or are all legends wrong regarding the colors used for the different mtf-curves ? (or at least for 20,30,40 and 50mm ?)

  • David Braddon-Mitchell

    The Loxia 35 is full of SA wide open; but at least mine shines brighter than any other 35 I’ve tried at f5.6 and 8. And an amazing thing about it is that while the edges are excellent at those apertures, it still has some curvature of field .. So of you focus on the edge or corner they are better still … About as good as the centre. So for an off centre subject stopped down its great. And if you focus stack centre and edge focused frames for landscape it’s miraculous. Still it’d be nicer if they could keep that goodness and have better performance wide open…

  • Eric PK

    The Batis 25 is F2.0, not 2.8

  • Brandon Dube

    Careful what you wish for, Sean…

  • Sean T

    Neat. Very curious about the Loxia 35. Thank you guys for all your work on these many hundreds of lenses you’ve tested and presented to us.

    Now if only you’d do the same thing for the super-tele-zooms (Tamron 150-600 and its Sigma rivals)…

  • User Colin

    I know you say they are tested wide open and so it would be silly to compare, but then you go and place them mirror-wise alongside and that just invites comparison. Surely the correct thing to do would be to say “Sorry folks, I’m not going to stick that next to the other, because that wouldn’t be a responsible way to present the data”.

    Some of these lenses will be used wide-open, but most won’t. Many will be used a stop or so closed down. Some will be used heavily closed down for DoF. So I’m wondering if this wide-open testing is as problematic as your concerns about IMATest charts being used only so many feet away, rather than at infinity.

    Is there any way you can test these at f/2.8? That would at least give a level playing field for most primes, and for some of the pro zooms. And testing a few at f/5.6 or f/8 might be interesting wrt what real gains spending more $$$ really buys you at those apertures.

    It seems perverse that people use f/1.4 to render much of the image as an out-of-focus blur and yet that is the aperture being assessed for sharpness. And the portrait photography that most needs such wide apertures is also the style most likely to be forgiving of having soft corners.

  • Lee

    Oh man for a second I thought the 28/2 was the most bizarre lens ever until I noticed you’d flipped that chart so that it was “back to back” with the 25/2 chart! Now that I know about it haha I like that presentation very easy to read.

  • obican

    Hi Andrea from SAR. I know you are looking at the article, trying to find which sentence to paraphrase. Here they are:

    “The 85mm Batis puts in a most impressive performance. Excellent resolution and very flat curves across the field. It’s not an inexpensive lens, by any means, but its performance is most impressive.”

    “The smooth, fairly astigmatism-free MTF curves of the Loxia suggest it will have a very different ‘look’ that some people will prefer.”

    “The Sony does pretty well from a resolution standpoint in the center where it’s as good or perhaps a tiny bit better than the Batis, but away from the center, the Batis shines, maintaining its sharpness well and with little astigmatism.”

  • Alan Yuen

    The Batis should be 25mm F2 instead of 2.8

  • Considering the testing differences, the parallels to Zeiss’ own MTF’s are clear. There are no surprises here.

    Thanks for the effort and thanks for posting the Sony 28mm’s results!

  • joel richards

    Thank you, thank you, thank you!

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