I had a brief opportunity to test the Canon 17mm tilt/shift lens yesterday afternoon and, in poor weather, opted to visit the Glasgow University cloisters to carry out a “real-life” trial.
The cloisters offer an enclosed space out of the rain, which protects the large front lens element, and a beautiful grid of columns and paving to check out the distortion and edge-to-edge sharpness of the lens. The lens was trialled on a Canon EOS 5D MkIII at 100 Iso and at apertures of f8, f16 and f22 (continued below).
The first thing to notice (apart from the weight of the lens and the size of the front element) is that this lens really slows you down. As well as having to get the framing spot on, the lens has two axial adjustments; the front half of the lens, which includes the tilt mechanism, rotates through 90 degrees, so that the tilt can be adjusted horizontally or vertically (and anywhere in between). Similarly, the rear part of the lens , which includes the shift mechanism, also rotates through 90 degrees so that the shift can be adjusted both horizontally and vertically. It’s not rocket science but when you set the camera and lens up, properly framed, you then have to work out how both sections of the lens should be rotated to ensure you get the tilt and shift adjustments you have in mind. You also have to bear in mind that the initial framing should allow for any T/S adjustments you are going to make. All of this means a littler bit of trial and error, although I suspect the more you use the lens the easier and more intuitive this becomes. I certainly hope so, because the lens could otherwise become a bit of a mixed blessing in rapidly changing light.
Put simply, the shift mechanism slide the lens on the shift axis whilst keeping the plane of focus parallel to the sensor. This works by unlocking the mechanism and turning a small knurled wheel on the side of the lens to shift the lens. This effectively moves the image up and down or side-to-side on the sensor and allows the photographer to, for instance, keep the camera horizontal to ensure straight verticals but include higher parts of a building. In this example you would lose some of the foreground (the field of view remains unchanged). The shift would also allow the photographer to get parts of a subject in where tight space would normally restrict access to raise the camera or move it from side to side. All in all a fairly simple concept that works really well and is very intuitive.
The tilt mechanism is equally simple to operate and seems fairly straight-forward in concept too. A second adjustment wheel on the lens barrel tilts the front element of the lens, tilting the view along the plane of adjustment. As an example, in the building example given above, if you had to tilt the camera to include the top of a building, you can use the lens tilt mechanism to adjust the converging verticals back to parallel . However, the mechanism tilts the plane of focus away from the plane of the sensor and, because of this, focussing becomes very critical and it is important that all four corners of an image are checked for sharpness before packing up and going home. Clearly, with a 17mm lens at f16, the hyperfocal distance generally compensates for any focussing shortfall, but I find it’s always best to be sure.
The tilt mechanism can also be utilised to extend the depth of field. For example, by tilting the lens downwards in landscape photography the plane of focus becomes closer to the plane of the ground and, by setting the hyperfocal distance of the lens, the photographer can achieve in the order of 35cm to infinity in focus at f16. It can also be used to narrow the depth of field; by tilting the lens to its maximum and opening the aperture up you can achieve, for example, that “toy-town” effect so often seen on the internet these days.
In use the lens shows minimal distortion (I can’t really detect any distortion in the photographs taken yesterday, although you may be able to pick a little up on a chart). Central sharpness is exceptional at f8 although there is some drop off at the edges. At f16 the lens is probably a touch softer at the centre but is much more consistent across the frame, whereas at f22 diffraction begins to rear its ugly head and starts to soften the image.
Vignetting is well controlled as is chromatic aberration, with only a little of the latter visible at bright/dark edges at f16. This is very easily corrected in post processing.
So, this specialist lens is optically superb and has many uses. Even though it is slow to use, many people would argue that that’s probably a good thing. Just be aware of the potential limitations in rapidly changing light; have the camera set up and the view framed before the anticipated and spectacular sunset begins!
As for me, I’d love one and this is another lens to add to the “wanted list”.