Paul Jolly Photography Chapter 9

Shift Lens

When taking a photograph with the camera horizontal any vertical lines, for instance buildings, will look correct.
To photograph higher sections of the photograph you could use a wider lens, but this will take in more of the scene and lower the number of pixels available on your intended subject, or tilt the camera up.
Tilting the camera results in the vertical lines seeming to move together from the bottom to the top of the frame.
If we re-think of the image on the camera sensor with the camera horizontal we realise that the image will include the top of the building with the correct verticals, the sensor is just in the wrong place. The shift lens allows the sensor to move into the required area of the image by moving the lens and this moving the image relative to the sensor.
We do have to look with care at the result of these lenses because the normal method is to move the front element or elements of the lens but this is not quite the same as moving the sensor in the image: The difference being in the movement of the lens as this actually changes the image; although, for most uses of these lenses, the difference is not often apparent.
Shift lenses tend to be larger then the equivalent ‘normal’ lenses because, as we have to move the image over the sensor, we need to have a larger than normal image for the sensor to move within.
shift_lens