Shifting (and Tilting) Your World

Architecture photographers in the old days must have hated their jobs. They'd either end up with a photo of a tapered building or, when they stepped back and shot straight, with the ground filling half of the frame. Of course there are some solutions to this (climbing a nearby building up to half the height of your subject, stepping way back and using a telephoto lens), but those tricks are not always practicable (nothing to climb on, objects blocking the way when shooting from afar). And cropping the floor, whether in the darkroom or in post-processing, will chew at your resolution, which is of course not desirable either. So eventually someone came up with the fairly complex optical device called the “tilt-shift lens”. Like the name says, this type of lens actually combines two different techniques of bending the incoming light in order to achieve certain visual effects. The physics behind effects are not exactly easy to grasp, so if you're able to explain the relationship between focal length, aperture and shooting distance to non-photographers without problems, your next step would be to explain the physics of tilt-shift lenses. I'll try it nevertheless.

Shift: Let's get back to your tall building from the intro paragraph. You're standing in front of it and it looks really tall and majestic and all that stuff. But exactly because of this enormous size, you just can't squeeze it into a photo, because it either gets cropped at the top, or it bends backwards when you shoot upwards. So you're standing and thinking “Man, I wish I could move my camera up”. Of course you can't do that, but shifting the lens will do something similar, albeit not quite the same: since you never leave the ground, you can only pan the view upwards. So, imagine a lens that doesn't cover just the size of your sensor (or film, if you're into that), but a much bigger area. And then you take a piece of that area (coincidentally it will be the size of your sensor/film) for your photo. The special trait with this is that you can actually move that area about freely within the wider area that's provided by the lens. This, exactly this is done when shifting the lens. This means that you can stand in front of the building, pointing your camera straight ahead (not up), so that the building gets cropped at the top, and then you just slide (or in another word: shift) the field of view upwards. After doing that, you will have the full height of the building in your frame, and at the same time, less of the annoying ground that has filled up all your previous architectural photos. Goodbye earth, hello sky! Of course, the shifting range is still somewhat restricted, so you won't be able to stand in front of the Burj Dubai and shift your lens up 800m to get a close-up of the top.

Tilt: Normally, photos have a focus point that lies somewhere between your camera (or more exactly: your lenses' closest focal point) and infinity. Everything at the focus distance will be sharp, and everything behind and in front of it will be blurry. On a side note, it is not only your camera that works this way, but also your eyes. The plane of focus is always parallel to the recording plane, but it a film, a sensor, or your retina (well, the retina is a bit more complicated). Tilting your lens will break this fundamental optical principle, and in that, will blow your mind right away. Well, not really. It's difficult to explain technically (see?), but bending those lens elements lets you bend your focal plane in the three-dimensional space in front of your lens. Thus, the focal plane is not longer restricted to being parallel to the sensor. This means that the area of sharpness in your image can extend from front to back (infinity), while the sides of your images drown in blur. You can position the place of focus somewhat freely in space (some restrictions apply). Since the human eye is not at all prepared for such an optical phenomenon, the images will look really strange and unusual. When shooting from high up, you can place the selective focus in such a way that the world beneath you will look like a model set in the photo. Cars look like toys, people look like little plastic figures. Tilting your shots will give them a whole new depth, quite literally. Tilting is also often used in product photos. Let's say you're shooting a bottle of water slightly from above. Since your place of focus is parallel to the sensor, the top and bottom of the bottle will be out of focus, unless you use an aperture of at least f/350 or so, which would require something like a pinhole camera and lots of patience (due to the insanely slow shutter speed). To avoid this, you can also use a tilt-shift lens and place the focal plane along the length of the bottle.

There are even more possibilities to use the lens. For instance, you can use the shift function to create a panorama. Just shift the frame to all extremes of the lens, take shots each time and stitch them in post-processing. And I am sure there are more uses that I don't even know about yet.

As you might have guessed already, there is a reason for me writing this article: I just got one of these mamas. Lenses that is. It's called Canon TS-E 24mm f/3.5 L. TS-E is Canon's term for tilt-shift lenses (who knows what the “E” stands for). Now, I've bought other “special” lenses before (fisheye, Lensbaby), but I never used them much. This was mainly because the effect they provided was too special, or because I never got to terms with how they work. So why do I think that I'll use this one more frequently? Well, mainly because you can use it in a very inconspicuous way. In fact, people who don't know much about photography will probably never realize that a photo was taken with the shift technique. On the other hand, you can do mind-blowing stuff with the tilt function. That said, it's never good to overdo an effect like this, because it can end up tiring quickly.

Using lenses like this comes at a price. And the biggest price is...the price! I bought my lens used from Ebay, but it still claims its place as the most expensive lens in my lineup. On the other hand, Canon released new tilt-shift lenses earlier this year, an update of this 24mm lens as well as a brand new 17mm lens (which was deemed impossible to do before). They are both reported to be extraordinary lenses, but for the price of each of these, you could almost get a new 5D Mk II camera body (or two months on a cruise ship in the Caribbean, but hey, you gotta prioritize, right?). Contrary to the new lenses, mine isn't digitally optimized, which led me to fear that there would be a lot of Chromatic Aberration, as I've seen in many other older lenses. I'll have to do some more testing, but right now it looks like the CA is not too strong.

Further drawbacks? No autofocus, slight barrel distortion (nothing that can't be handled in post-processing though. PTLens even supports the lens, so it's not a big deal). Light metering gives some funny results sometimes, specifically when shifting, so it's best if you meter with the lens set to “zero” and then save the exposure settings and tilt/shift away. Also, the lens is quite heavy at 570g. Now if you're routinely carrying your 400mm f/2.8 lens around, you'll laugh at 570g, but I like my equipment to be as lightweight as possible, since I usually do a lot of walking on my photo tours. On the other hand, the lens is very sturdy, so you could double-use it as a device to knock down someone who wants to steal your camera, or your soul for that matter. And luckily, the lens is still quite small and it fits nicely into my camera bag.

I'm looking forward to the genuinely new perspectives that this lens offers. Watch our for pictures at Daily and all the other notorious places on the web.

Comments

Karthik Abhiram – 2009-09-03 19:45:24

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Photography