Metering with a Tilt-Shift Lens

Question

The manual of the Canon TS-E 17mm F/4 states that metering only works when the lens tilt and shift are set to zero (in the same position as a standard lens would be). Logically this implies that the meter indicator in manual mode would be incorrect as well.

What techniques then would be recommended to meter with such lens? Does the light entering the lens depend on the shift and/or tilt positions? If you meter from a highlight the the lens and camera straight, would that be still valid after tilt, shift and the orientation adjusted? (Obviously for reflective surfaces the answer to the latter is no).

Answer 1

It is very simple: Metering does not work when the lens is shifted, metering does not work when the lens is tilted. The workaround is also very simple: Shoot in M mode. Adjust the exposure to your satisfaction with the lens untilted and unshifted. Then shift and/or tilt, and take the actual photo.

Note: It is the metering that is affected by tilt/shift, not the actual exposure. If 1/200, f/f5.6 is the correct exposure with tilt/shift set to zero, 1/200, f/5.6 is still the correct exposure when the lens is tilted and shifted.

Answer 2

Note that the advice to meter before shifting or tilting a lens does not seem to be necessary when using a mirrorless digital camera.

The problem with metering in an SLR or even a DSLR is that the light is actually measured by a separate, dedicated metering system near the eyepiece, based on light reflected by the mirror. Tilting and shifting reportedly causes accuracy problems for this form of reflected metering.

But when using a mirrorless digital camera (or even "live view" in a DSLR) the image sensor itself is used for metering. And because the light which hits the image sensor is the light which will make up the final image, using it for metering should exactly represent how bright the final image will be.

I've spent a fair amount of time wandering around the streets of London capturing architectural shots on a mirrorless Canon EOS R and second-hand TS-E 24mm f/3.5 Mark II lens. And despite taking hand-held shots with amounts of shift from 0 to the maximum +12mm of shift, metering has worked absolutely fine for me even while the lens is heavily shifted. For example, this shot taken in City Of London.

I've also captured a number of product shot close-ups, where the lens is only two or three centimetres from the subject, and tilted almost to the maximum of 9°. Again, despite metering each shot while the lens is strongly tilted, I've had no problems at all. For example, this recent product shot.

In short: when metering with the image sensor itself, this advice can probably be disregarded. In fact, given that you're metering using the image sensor itself, this old advice probably should be disregarded.