The tilt-shift lens is probably one of the most special lenses available. It allows the photographer to turn, shift, and tilt the lens in many different ways. In this article, I explain when and how to use the shift function.
A tilt-shift lens looks pretty amazing. It has dials and knobs and can rotate or move in different directions and angles. Every tilt-shift lens I know of has manual focus, although there are rumors of autofocus in the future Canon RF versions of their tilt-shift lineup. I use the Canon TS-E 17mm f/4L and the Canon TS-E 24mm f/3.5L II lens for my real estate work and sometimes for landscape photography also.
When every movement of the tilt-shift lens is visualized, as seen in the animated gif, it looks like a very complicated lens to use. In some ways, it is. But there are basically two functions that can be seen separated from one another. The first one is the shift function, and the second one is the tilt function.
The shift function is the lateral movement of the lens relative to the camera. It is also the easiest one to use. In this article, I’ll explain how it works and when you can use this function. The tilt function will be addressed in the upcoming part two.
The Shift Function Explained
With the tilt-shift lens, it is possible to move the lens relative to the camera. Because the image circle of the tilt-shift lens is significantly larger compared to a regular lens, you won’t get any vignetting when the lens is shifted.
The shift function allows you to choose a different part of the image circle to be captured instead of the center part. This can easily be understood when comparing the above visualization of the image circle against the image circle of a tilt-shift lens below.
The shift function allows the photographer to choose the part of the image circle that will be recorded, up to a certain point. The shift function only allows a limited amount of movement, depending on the size of the image circle. For a Canon tilt-shift lens like the TS-E 17L, this is 12 mm to either side. But it may vary if you have a different lens.
Why Is Shifting Necessary?
To understand why the shift function is helpful, we need to have a closer look at something that is called perspective. Every photographer who owns a wide-angle lens has seen it. Just tilt your wide angle lens upwards and look at any vertical line in the frame. The lines will tilt inwards. It looks as if the lines originate from a vanishing point in the far distance. This is called perspective distortion.
This is something that every lens and focal length suffers from, but it will become more obvious if the focal length shortens. If you are photographing buildings and trees from a close distance, and you need to tilt your lens upwards to capture the complete building or tree in one frame, and the perspective distortion kicks in.
If you hold your camera perfectly horizontal, you will see the lines become normal again. There might be some regular barrel distortion, but that is due to the physics of the lens. Let’s just ignore that one for a moment. So, if you can hold your camera perfectly horizontal, the perspective distortion is absent. The vertical lines of buildings will be vertical, but the building might not fit into the frame. At the same time, there will be too much ground or pavement in the frame. That is the moment when the shift function of the tilt-shift lens comes in handy.
Shifting To Prevent Perspective Distortion
Now comes the fun part. Because of the large image circle, the whole building or tree will be visible within that image circle. You just have to place the part that will be registered by the sensor in the correct location. This can be done by shifting the lens relative to the camera, in this case, upwards. This is shown in the before/after image below.
By shifting the lens, the vertical lines will stay vertical. After all, the camera is still in its horizontal position. The lines are not tilted anymore by the perspective distortion. But it will only work if you keep your camera exactly horizontal. The moment you tilt your camera again, the perspective distortion will kick in again.
Using Photoshop To Correct Perspective Distortion
With all the clever photo manipulation software, it is easy to correct any perspective distortion in post-processing. So, if you don’t own a tilt-shift lens and you have tilted vertical lines in your photo, it is possible to straighten these lines.
But the correction will come at some cost. By removing this distortion, you will lose a lot of the image. How much you need to crop depends on the amount of perspective distortion. The more distortion you have, the more you will lose.
If I take the example I have used to show the perspective distortion and remove it in Photoshop, you can see how much of the image will be lost. I need to transform the image in the horizontal direction as well as the vertical direction. This is necessary to keep the correct proportions.
There is another downside to this kind of image correction. By stretching the image in the horizontal and vertical direction, pixels will be pulled farther from each other and thus, the image detail will be reduced. On the other hand, modern software can correct this up to a certain level, and you will have to look at 100% magnification or more to see the difference.
Who Will Benefit From the Shift Function of a Tilt-Shift Lens?
Tilt-shift lenses aren’t cheap. But it is possible to find some budget version on the market. Laowa is one brand that comes to mind, just like Samyang. But perhaps there are more alternatives available. I used the Canon version for this article. Of course, Nikon also has its own versions.
Nevertheless, most tilt-shift lenses are much too expensive to buy without a good reason. If you have to correct perspective distortion just once in a while, it might be perfect to do so in post-processing. Just keep in mind to capture enough extra space to allow cropping.
But if shoot a lot of buildings or other objects that have vertical lines and you need a perspective distortion-free capture, it might be worth investing in such a lens. Also for real estate photography, these lenses are perfect. That is the reason why I bought these lenses.
Do you use tilt-shift lenses for your photography or would you like to start using these lenses? Or do you think perspective distortion correction in post-processing will do the job just as well? Please share your thoughts in the comments below.