Buildings are usually taller than people, and so if you want to take a picture of one, you will be tempted to tilt you camera up so that you get the whole building on the picture. But that leads to converging lines, and the buildings seem to tilt back. This is illustrated quite nicely at photo.net.
The right way to correct this problem would be to move the camera up so that it is at half the height of the building. Now that is often easier said than done, so an optical trick would be the preferred way.
A shift lens can be moved perpendicular to the film plane so that a different part of the picture is projected onto the negative (or slide) without having to tilt the lens. It is important to understand that the image is shifted, because the movement of the lens is negligible compared to the objects usually depicted (houses). So this way, you can leave the camera in a position where the lens is horizontal, but move the lens up, and thus select a part of the image that contains the whole building, but not the foreground. This way, you get a picture of your house upright and still fill most of the available negative or slide space.
The perspective is of course changed by this, so that pictures taken with shift lenses always look a bit unnatural. But that is the smaller evil compared to houses that seem to tilt and crumble ...
The Arsat 2.8/35 is available for different lens mounts, the one I have is for Nikon. It does not have Auto Focus, of course, neither does it have the AI feature that tells the camera the relation between the selected and the maximum f-stop. Thus, you can only measure exposure when stopped down. And with the F80 (called N80 in the US), you can't do any exposure metering at all, because there is no electronic circuitry, without which the F80 won't activate the exposure meter.
The aperture can be changed continuously between 2.8 and 22, the aperture preselection locks at whole f-stops (see below). The lens can be shiftet 11 mm from its "normal" position, the direction of the shift can be changed 360° and locks at eight angles.
The procedure when taking a picture is as follows:
The important part is not to forget stopping down again if you change the composition or refocus (which you have to do at maximum aperture, of course). But this is made easier with a nice feature of the Arsat lens: you can preselect the f-stop, then you cannot stop down more than the selected f-stop, which makes it a lot easier (i.e., you don't have to look) to go back and forth from 2.8 to the desired f-stop. In addition, you will can often just set the lens to infinity, so focusing isn't such an important issue.
The lens does not cover enough area to be shiftet the whole 11 mm without vignetting (i.e., dark areas in the corners). You can get rid of the vignetting by stopping down. Just how far you have to stop down is shown in the following table that I came up with by taking pictures of the same building 72 times ...
| 0 mm | 7 mm | 8 mm | 10 mm | 11 mm | |
|---|---|---|---|---|---|
| Vertical Shift | 2.8 | 2.8 | 5.6 | 5.6 | 8 |
| Horizontal Shift | 2.8 | 5.6 | 8 | 8 | 11 |
"Vertical" and "horizontal" are meant relative to a landscape picture, so "vertical" means shifting along the shorter side of the negative, and "horizontal" along the longer side.
I used Kodak EliteChrome 100 slide film for the test, and my tripod of course.
Using my 50 mm lens as a loupe, I could see no distortions at the edges. The test also showed that the sharpness of the lens is quite good, but I don't have a comparison with the Nikon PC lenses.
The Arsat shift lens seems to be a decent shift lens that is much cheaper than the Nikon PC lenses but has quite good quality. Especially if you don't do a lot of architecture shots, you probably don't want to spend so much money on a lens you only use occasionally.
One thing you should really think of getting for your camera if you buy a shift lens is a focusing screen with a grid so you can really get the buildings upright. But that type of focussing screen is very useful even without a shift lens, because it makes aligning the horizon and other features a lot easier.