Night test of another wide angle lens
The 24mm Canon TS-E f/3.5 doesn't check out as well as some of the others have, but it's decent.
The above image (too dark again, thanks to Substack…grrrrr) is a 5 minute exposure from my back yard with an unusual lens (about which, more shortly). It was taken at ISO 50 (thus, no compromises as to gain) and f/16 (in a desperate attempt to get sharp stars).
(Yes, I use parentheses too much.)
A little background, to help explain why this lens is unusual. Larger-format cameras often use lenses that ‘see’ a wider area than the film in the camera can record. This is desirable because such cameras make the lens (and the film) moveable, to take advantage of that oversize image.
I won’t get into the moves themselves (that is a whole photography career worth of information), but it is advantageous to be able to move your lens around because you can correct certain types of problems. For example, a vertical shift can deal with those pesky converging side of tall buildings. For now, just accept that there is a very good use for such lenses.
They just have been rare in the 35mm format.
This Canon lens is made for 35mm, and it does include tilt and shift. The image circle (the size of the circle that is reasonably illuminated by the lens) is significantly larger than 35mm film. A typical 35mm camera except to make any image that covers 24x35mm; the diagonal there is about 42.4mm, so a typical 35mm lens will have an image circle at least that large, maybe even a little larger.
The Canon TS-E has an image circle of just over 67mm, so you can move the lens around and still adequately illuminate the film (which does not move).
The diagonal of the sensor in my digital cameras is…67mm as well, so I can fully illuminate it with the Canon lens. (But I cannot take advantage of shift and tilt, because the lens just covers my sensor with its image circle.)
Which, in short language, means it provides a useful circle of illumination for a medium format camera that is equivalent to 6x4.5cm film.
The next question to ask is: how good is the image out there past the usual domain of 35mm cameras? The answer is: just OK. The center (still a bit bigger than 35mm format) is really really sharp, as you’ll see as I post daytime images taken with the camera (there are a few posted from today).
The good news is that it is about 80% cheaper than a true, high-end medium format lens. Which also matters. :)
For fun, the image at the top is at 100% of full size. I let the exposure go long enough that most of the stars are showing the earth’s rotation with their tracks, but the lines they make are clear and crisp, so it’s really quite a good lens.
I cropped out the bottom because it was just dark dirt. What remains is, as I said, full size and a reasonable way to evaluate the lens.
I will next to a critically focused test image to see how well it resolves stars in the corners. A lazy attempt at focus showed some issues slightly out of focus, and I need to check to see if they remain when focus is essentially perfect.
There are two daytime images taken with this lens here. <- click to follow link.