This is the second in a series of three posts about Imatest results on m4/3 mount lenses. The first post covered most of the lenses of 25mm and wider focal length. Most of the zoom lenses in that test were done at, or near, their widest focal length since we were concentrating on the wider angle lenses. This test run started by retesting most of the zoom lenses at 25mm, which we hoped would show a bit better performance since most zooms are weakest at their extremes.
We also did some confirmation testing at 25mm. First retesting the Panasonic - Leica 25mm f/1.4 because it just didn't seem as great as we expected on the initial set of tests. Then we did some comparison testing, testing the same lenses on both the Panasonic GX1 and the Olympus OM-D E-M5. I won't bore you with all the numbers, but testing 6 copies of the Panasonic-Leica f/1.4 didn't change our initial results much. (The results have been updated on the previous article.)
I had assumed, since we test only unsharpened raw files, that camera brand would not make any difference, and it did not. We tested copies of the Panasonic 14mm f/2.5, the Olympus 9-18mm zoom, the Panasonic 7-14 f/4 zoom, and the Olympus 12-50 zoom on both cameras and there was no difference in MTF 50. This doesn't mean there is not some distortion correction or other manipulation going on when using a same-brand lens on a given camera. It just means there's no obvious manipulation of the raw image that affects MTF 50.
Testing the Zooms at 25mm
In the last article, we tested the Olympus 12-50 and 14-42mm f/3.5-5.6 II R lenses at 14mm. I thought that focal length might be weak points for those lenses, so today we retested them at 25mm, more towards the center of their zoom range. We also tested the Olympus 12-50 f3.5-6.3 (we were out of stock during the wide angle test), Olympus 14-150 f/4-5.6, and Panasonic 14-140 f/4-5.8 OIS all at 25mm. Two or three copies of each lens were tested, and testing was done as described for the other article.
I'll present the numbers in two tables:
In the first table, we'll look at the MTF50 of each lens at the widest aperture it can use at 25mm
|Oly 14-42 II R||f/4.3||690||580|
In the second table, we'll look at the MTF50 with each lens at f/5.6
|Oly 14-42 II R||f/5.6||710||630|
There are few comments to make about the zooms. Using the rule of thumb that a difference of less than 50 lp/ih is probably not noticeable, only the Olympus 14-42 lags a bit behind the others in resolution. The two superzooms, the Oly 14-150 and Panasonic 14-140 were both pleasant surprises. It's quite a good showing they made, keeping up with the smaller-range zooms. Have to give some props to the Panasonic 14-45, too. It's a low cost ($275) lens but hangs right there with the others. Finally, the zooms haven't changed much between their wide end in the previous tests and the middle of their range we tested now.
Testing the 45mm Primes
We have two 45mm lens choices for m4/3: the Panasonic-Leica 45mm f/2.8 and the Olympus 45mm f/1.8. There are a lot of differences in the two. The Olympus gives a wider aperture, is smaller, and $250 cheaper. The Panasonic-Leica has built in Image Stabilization. I've presented this table a little differently so you can compare the two lenses at equal aperture.
In our tests the Panasonic-Leica 45mm does outresolve the Olympus by what is probably a noticeable margin if you compared them side-by-side. Results from both are excellent, though, and I can't imagine anyone being disappointed with either one.
Oh, and One More Thing
I was just about to break down the testing set up when the receiving people brought me a present: several copies of the Sigma 30mm f/2.8 and 19mm f/2.8 in m4/3 mount. These were spectacular on the NEX system so I had to go ahead and run the tests on these before they went out on rental.
Several things are interesting here. First, the Sigma lenses give excellent resolution on m4/3 mount like they do in NEX mount. No surprise there. Second I would have expected the resolution to be lower on m4/3 mount since we are measuring in line pairs / image height and the NEX-7 has 4000 pixels of image height versus the m4/3 3460 pixels and Imatest measure system (camera and lens) resolution, not just the lens.
As expected, the Sigma 30mm has slightly lower resolution on m4/3 cameras. However, the Sigma 19mm was had nearly the same resolution in m4/3 mount as it did in NEX mount. In m4/3 mount, therefore, the Sigma 19mm and 30mm were had about equal MTF50 (the 19 actually a tiny bit sharper in the edges and corners at f/2.8). (In NEX mount the 30mm was slightly sharper than the 19mm.)
I'm not sure why the difference, so what follows is purely speculation and I welcome other people's ideas. In looking at our m4/3 results overall, it seems there is a tendency for wider focal lengths to resolve at least as well as longer focal lengths. In most systems we've tested that hasn't held true: wider lenses, with a few notable exceptions, tend to be a bit weaker. Perhaps the m4/3 sensor format makes designing wider lenses easier or more effective. Perhaps the m4/3 sensors, particularly the newest 16-megapixel sensors have a better or more effective microlens array? Perhaps there is some sharpening or contrast boost going on in-camera to the raw images? Note: Please read Thom Hogan's excellent comment below: it makes more sense than any of my ideas did.
It's also possible there is some defect in our testing set up that's giving an advantage to wider focal lengths on m4/3 cameras. I don't think this is likely, we've run 5,000 lenses through our Imatest lab and I think we've worked the kinks out. But it's always possible. I'll look forward to seeing the results from other testing labs to see how theirs compare.
Part 2 Summary
Having been through most of the m4/3 lenses now I think there are some very obvious conclusions: 1) there are a lot of good prime lenses available for m4/3 from 14mm to 45mm. It's interesting that the new Sigma lenses stand out as superb compared to other NEX lenses, but are just another good prime lens on the m/4/3 system.
Things are a bit different on the zoom side. There are some good consumer quality zooms, but other than the Panasonic 7-14 f/4, there are not any that I would consider 'top' or 'pro' quality zooms. Several of the zooms have good resolution, but they are all aperture-impaired. I think this is a big hole that needs to be filled, especially now that we're getting reasonably fast autofocus in mirrorless bodies. An f/2.8 range 35-100mm would kick some serious butt, even at a premium price. Even a reasonably long wide-aperture prime, something like an 80mm or 100mm f/2.8 would be welcome.
The biggest gap in the m4/3 lens lineup, though, is certainly going to be at the long end and we'll cover that in the third part of this series. I'd love to find an exception, but having spent a weekend shooting every one of the m4/3 mount long zooms and comparing them to what's available for SLRs, I don't expect a lot of good results.
Addendum: Wouldn't you know, the day after I wrote my little diatribe about needing good quality f/2.8 zooms for m4/3 the first preliminary reviews of the Panasonic 12-35 f/2.8 OIS come out and are very positive. Now, just give me that good telephoto, guys, and I can stop juggling mirrorless systems