The evening of December 23rd found me out scouting for Christmas lights. Several days of rain had finally dissipated that afternoon, and it was the first opportunity I'd had this season to add to my portfolio. Coming down out of the hills above San Carlos, my attention was caught by pearly, low-hanging clouds over the Bay Area, and I decided a nighttime panorama had some artistic potential.
I set my Olympus OM-D on its tripod with the fabulous 45mm ƒ/1.8 M. Zuiko lens set to ƒ/4 and exposure times in the 2- to 3-second range at ISO 200. I made two sets of five exposures each, using the camera's built-in 2-second self timer to trigger the exposure. (I've found this so convenient a way to get vibration-free photographs that I don't think I've even touched the cable release I paid good money for in more than a year.)
The next day I pulled one of the photos up on my 27" iMac screen in Adobe Bridge, and right away saw a problem (figure 1). The right side appeared a lot less sharp than the left, and I wasn't even viewing at 100%. Well, Bridge can be a bit weird about rendering at non-1:1 sizes, so I pulled up a full-size view, hoping that this was just rendering cruft. Damn, there really was a problem. You can see this in figures 2 and 3, which are 100%-size crops from the right and left sides of figure 1. (I've posted full-frame, full resolution JPEGs of the photos used in this article at my website for any readers who wish to engage in further pixel-peeping.)
Maybe it was really in the scene—turbulent air, or fog, or rain? Hoping against hope, I pulled up the photo (figure 4) that was to the right of figure 1. The right-hand part of the scene shown in figures 1 and 2 is centered in this frame and, as the 100% crop in figure 5 shows, atmospheric conditions are just fine. The details are sharp.
All 10 frames showed the same phenomenon; nicely sharp over 75% of the width of the frame and lousy over the remaining 25%. Condensation on the lens or the sensor, maybe? I don't recall any when I was photographing, but, honestly, I wasn't looking.
How about camera shake or vibration, either innate or due to some weirdness in the image stabilization system? Shutter recoil can cause only one part of a frame to be blurred, if most of the shaking occurs while most of the frame is blocked by the shutter blades. Seconds-long exposures exclude that possibility—even if there were anomalous vibration when only part of the sensor was exposed, that time span was only milliseconds out of the total exposure. It wouldn't produce a visible effect.
The photo in figure 6 provided another clue. There is a bit of detail in the lower right—some closer-by black tree branches silhouetted against a lit house and street lights—that's also present on the left in figure 1. Looking at a 100% crop from left side of figure 1 (figure 7) it looks to me like the more distant lights are sharper than the closer tree branches. In figure 8, cropped from the right side of figure 6, the closer tree branches appear much sharper to me, while the distant lights are fuzzier.
If I'm reading the photos correctly (it's kind of hard to pick out these details), that's telling me the plane of sharpest focus is much closer to the camera on the right side of the photograph. Folks like Lloyd Chambers and Joe Holmes have reported this sort of thing in misaligned lenses. Me, I have trouble wrapping my head around the idea that an alignment error can cause only one side of the photograph to go out of focus, but I'm not going to argue with those guys.
It looks like something knocked my lens out of kilter and it needs to go into the shop. Except for one puzzlement. None of the rest of the photos I made that night or since have shown this problem. Figure 9 is an example. It's not a perfect match (ƒ/5.6 instead of ƒ/4) but it's close enough. The icicle lights on the eaves look equally good on both sides of the photo (figures 10 and 11). The fine detail on the right might be even slightly crisper than on the left, although that's surely splitting hairs.
I made some test photos last week, duplicating the exposure conditions in the problem photographs: Focused on a subject at infinity, made sets of exposures with the target point framed left, center, and right. I repeated this several times and pixel-peeped the results like mad. I can't see a clear pattern. I might be able to convince myself that the left side of the frame is a bit better, on average, than the right. Except when it's not. If that average difference is real, it's subtle. I'd never notice it in practice if I weren't looking terribly hard for it. It's not like the glaring, consistent problem in those panorama photos.
That's what puzzles me. Can a lens be knocked that far out of alignment and then just casually shake itself back into proper position? The camera did go back of the car and got driven around after I photographed the panorama, before I photographed any Christmas lights. Could the vibration have put everything back where it was supposed to be? It seems unlikely to me, but I'm no lens repair expert.
Obviously I haven't had time to send the lens off to a repair service to be checked out (I haven't even gotten a quote, yet). That might...or might not...give me a definitive answer. You know how that goes. In the meantime, what do you folks think? Have you ever seen anything like this, where a lens goes wonky for an entire series of photographs and then goes back to normal? It's sure a new one for me.
Note: All the JPEGs were converted from RAW files using my default ACR settings. No massaging; this is what the camera gave me.
Ctein either presents or solves mysteries on Wednesdays on TOP.
Original contents copyright 2012 by Michael C. Johnston and/or the bylined author. All Rights Reserved. Links in this post may be to our affiliates; sales through affiliate links may benefit this site.
(To see all the comments, click on the "Comments" link below.)
Featured Comments from:
Bruce Norikane: "I am really enjoying this thoughtful diagnostic discussion. Although it seems an unlikely cause, have you ruled out the vertical tilt of the camera? The images with the problem appear to be tilted a bit down while the Christmas light shots look like they are tilted up. I would be quite surprised, if this could cause the problem, and you would have probably spotted it in other shots with this camera and lens combination."
Frank Grygier: "Cameras are now complex computer systems. The total automation of the photographic process on a platform of this nature is bound to produce a glitch now and then. As with any computer I would simply re-boot the camera and see what happens."
Olivier: "Oh yes, it happened to me for most part of the summer of 2007 when I was traveling in Austria with my D70 and one lens, the AFS 18–70mm (a fine lens when it works). All of the sudden I got pictures very sharp on the left side, and very out of focus on the right side. Since I had no alternative I defined ths as my new style and actually started playing with it. I was finally disappointed when all went back to normal after I accidentally dropped the lens. It worked flawlessly until now...."
toto: "Perhaps the floating IBIS sensor got skewed out of proper alignment temporarily that night. Rebooting the camera (shutting it off and turning it back on) might have fixed the problem."
John Camp: "I'm thinking you bent over the camera to look at something, and a little stream of warm breath got on the lens, or got your warm hand close to part of a cold lens, and got very very thin condensation on the lens. I'm sure you've had that happen with your glasses, where you get a little condensation that you can easily see through, but can be really annoying."