I was wondering about the effects of shooting with the new Canon EF 17-mm f4 L Tilt and shift lens?
How well will such a wide lens work when using movements?
What are the theoretical limitations of such a wide lens.
Do any of you have one yet? Can you show examples?
Hi Will,
I've been doubting which one (the new 17mm or 24mm) I had to get, and figured that for
my type of intended use, the 24 was a more appropriate extension of my lens line-up. Actually I want both, but I'll first start to earn some money with the 24, and stitch when I need wider.
The movements will be very useful. In general, one will use the shift more with wider angle lenses, and use tilt more with the longer 45 and 90mm lenses. It is very important to control perspective with the (ultra)wide FOV angles, and the shift will allow to do that (e.g. avoid keystoning).
I've seen some results of the 17mm TS-E (e.g. on DPReview), but it can quickly lead to exaggerated stretched results when e.g. shooting tall buildings from street level when fully corrected for keystoning. The reason is that with such short focal lengths at relatively close shooting distances, perspective ditortion becomes too obvious when we look at the images from too far away. In theory, one needs to look at a proportionally shorter viewing distance to maintain the same perspective as the lens.
When looking at a 5x7in or an 8x10in image at a normal viewing distance, a 50mm lens on a 36x24mm sensor gives an approximately normal (same as lens projection) perspective. It figures, a 50mm lens captures a HFOV of 40 degrees, and a VFOV of 27 degrees. At 30cm (approx. 8 inches) viewing distance those angles correspond to a surface of 216 x 114 mm. A 17mm lens would require an output size of 635 x 424 mm viewed from 30cm to maintain the 'proper' perspective, but that's not a pleasant experience, so people move away more to view the whole scene, and thus distort/disconnect the 'proper' perspective of the scene.
The simple rule to maintain 'proper' perspective (which we may not
want to do from a creative point-of-view) is to keep the output size and viewing distance in the same proportion as the sensor size and the focal length, IOW output magnification of both distance and size is a constant.
When we cannot shoot with a longer focal length, e.g. due to shooting distance restrictions but we need the vertical FOV, it is often better to shoot from a higher vantage point because that will reduce the apparent exaggeration of perspective. For shooting interiors, one needs to take care of objects placed in the corners of the image (circles become sort of elliptical, squares become trapezoids). One can use software to couter-act some of the unwanted effects, but not all (depth perspective remains, projection distortion can be reduced).
Just some thoughts,
Bart
