Canon 8-15mm zoom for macro?

[DQE]

I was just reading some specs about the new Canon 8-15mm zoom lens and noticed that it has a maximum magnification of 0.39X, and a minimum focus distance of 6 inches (15cm). Since the lens is about 3 inches long, would its working distance be about 2-3 inches?

http://www.bhphotovideo.com/c/product/7 ... sheye.html

Would this lens be technically able to do macro work with extension tubes? If so, what would its magnification be with the usual assortment of tube lengths? Would it lose its circular image format with tubes?

I realize that this lens would likely be unsuitable for normal macro work for many reasons, but perhaps it's technically entertaining to predict what would happen if it were used for macro work.

I don't recall seeing fisheye macro photographs...

[rjlittlefield]

Sorry, but I'm not optimistic.

I have two lines of concerns.

The first involves published specs. The lens is spec'd as minimum focus distance of 15.75 cm. Normally that's from the film plane. The lens length is spec'd as 9.40 cm. Then you have to add the 4.4 cm flange distance. The result is 13.8 cm, which suggests that the lens only has about 2 cm of working distance at its specified close focus. I assume the rated maximum magnification of 0.39X happens at 15 mm FL, simply because that's good specsmanship. Putting all this together implies that the front principal plane is about 3 cm deep inside the lens. If you extend the lens so as to focus closer, you'll reach the limit at about 0.8X when the plane of focus hits the front of the lens. The needed extension to do this is only about 6 mm, so if the calculations are correct it'll take some pretty thin extension tubes to confirm them.

The second is by experimental analogy with a different fisheye that I have at hand -- a Sigma 8 mm. The Sigma is not a zoom lens, but at the short end its specifications are not wildly different from the Canon's -- 20 cm close focus distance. Sure enough, observation says that the front principal plane is buried deep behind the front surface, and putting on my thinnest extension tube makes the lens unable to focus at any distance.

I haven't seen many fisheye macros either, except of course for endoscopic exams.

--Rik

[Harold Gough]

I don't recall seeing fisheye macro photographs...

I have peered through ultra-wide lenses to see potential for macro. Without recalling the detail, I seem to remember that getting the insect to form a significant part of the image is very diificult to impossible. Also, to get the fisheye effect the front of the lens would have to be within mm of the insect.

Some of the fibreoptic lenses, as used for filming inside termite nests and suchlike may offer more potential.

The other route might be macro 'panoramic' stitching.

Harold