After seeing some disconcerting results from a new Panny 15/1.7 and concluding focus shift was likely an issue, I resolved to test all my m43 lenses. I'm fairly recent to m43, and was hoping this particular harpy had been banished from the realm, but my results indicate that it isn't, at least not entirely. I think these tests are probably useful to others, so I'm sharing here. Here's a quick introduction on focus shift for those not familiar: fast lenses with uncorrected spherical aberration can focus at a slightly different points wide open and stopped down. The EM-5 (and I believe, other m43 cameras) preferentially focuses wide open, just like DSLRs. So what appears to be a properly focused image in the EVF may end up backfocused. The fact that the EVF uses contrast-detect doesn't solve the problem unless you use the DOF preview button while manually focusing. For more information about focus shift in general, see here: http://photographylife.com/what-is-focus-shift The testing setup: EM-5 on a tripod, in purely manual focus mode. I manually focused wide open using the LCD with magnification, then took a picture both wide open and stopped down. The target was slanted at about 40° so that the depth of field is apparent. The vertical lines and Hs and &s was printed at a slanted angle, I was hoping it'd help but it didn't. I tried to keep everything level with the camera directly facing the paper target but there is some slop, I wasn't using rails. It shouldn't be enough to affect the test substantially. Focus was on the center of the X and the line directly through it. Let's start with the Olympus 60/2.8 macro in close focus (about 1:1.3 magnification) since it's easiest to see the shift here. Wide open, f2.8, the focus is nearly on the center line through the X. It looks slightly behind it, so I missed by a touch. Now, stopped down to f5.6, the focus plane has shifted backwards even more, at least halfway between the center line and the one above it. This corresponds to a shift of about .5mm, which is probably not very noticeable, even in macro. But the magnification makes it easy to see what's happening overall, it's harder at wider angles. Now for the Panny 15/1.7, which kicked off this entire testing suite. Wide open. Note that the colors change very close to the point of focus. Stopped down to f4. It's a little hard to tell where the exact focus point lies, but using symmetry and color shifts, I'd estimate it somewhere between the & and the H behind the X. That's about 9mm. This is enough to severely alter an image's impact. If you're having trouble seeing the shift here, try downloading the images and viewing them in separate photoshop layers (or preview on a mac), which let you toggle between them. You should be able to see the zone of focus "sliding" backwards. Here's the Olympus 12/2.0 wide open. Rather hazy but still possible to focus accurately with care. And now, stopped down. I can't detect any focus shift at all. :smile: And here's everyone's favorite lens, the Panny 25/1.4 wide open. Again I may be slightly backfocused here, it's hard to say with the green and violet fringing. And stopped down. I'd say that peak focus is around the bottom of the & behind the X. That's a shift of about 4mm. Testing of assorted objects around my room (not test charts) indicates that it's just enough to be noticeable if precise focus is required. I also tested my Oly 12-40/2.8 zoom at 12mm, 25mm, and 40mm; the Oly 45/1.8, and the Oly 60/2.8 further away. For the sake of brevity I'll omit the pictures and just say that no focus shift was detectable in any of these cases. It seems Olympus' designs prioritize spherical aberration, a laudable approach. Conclusions: If you get the Panny 15/1.7, be aware that if you aren't shooting wide open, you'll get backfocus. These tests were necessarily done at close focus (sensor was about 30cm from X for the 15mm), but I did some landscape testing near infinity, and saw substantial shift there as well. One workaround is to manually focus while holding the DOF preview button down, which works within its many limitations. Personally I'm very disappointed in this lens design and returned mine. I'd give up some overall sharpness for the ability to accurately focus easily. For the Panny 25/1.4, consider doing the same for some subjects, though it's far less critical. For the Olympus lenses, it looks like we're all clear, let's hope they keep up the good work.