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View Full Version : Marco Solorio on the Canon 8-15mm fisheye and the BMCC



Andrew
04-28-2012, 03:43 PM
http://magazine.creativecow.net/article/is-the-new-blackmagic-cinema-camera-the-hdslr-killer

Scroll down near the end of this article and read what he writes about the 8-15mm lens. He's saying that the crop factor will actually be less at 8mm than at 15mm. So the lens' effective (35mm equiv.) focal length will be something like a 10-37mm zoom.

I would love for this to be true, but I just don't fully understand how he is getting this and think he might not be calculating it right. I get that an 8mm fisheye is actually wider than an 8mm rectilinear lens because of the extreme compression of the scene around the edges of the frame. But with the 2.3x crop factor the distortion/compression of the scene into the image seems to hardly matter. It does seem like an 8mm fisheye will be a bit wider (with more distortion) than an 8mm rectilinear on the bmcc, but I don't get how he concludes that it will be a 10mm FF equivalent.

Anybody out there who can break this down for me?

Thanks!

Andrew
04-28-2012, 03:55 PM
Right now I'm planning on purchasing the Sigma 8-16mm lens to cover WA on my bmcc, but if an 8mm fisheye is significantly wider on this camera then I might have to purchase one.

Phil
04-28-2012, 04:02 PM
http://magazine.creativecow.net/article/is-the-new-blackmagic-cinema-camera-the-hdslr-killer

Scroll down near the end of this article and read what he writes about the 8-15mm lens. He's saying that the crop factor will actually be less at 8mm than at 15mm. So the lens' effective (35mm equiv.) focal length will be something like a 10-37mm zoom.

I would love for this to be true, but I just don't fully understand how he is getting this and think he might not be calculating it right. I get that an 8mm fisheye is actually wider than an 8mm rectilinear lens because of the extreme compression of the scene around the edges of the frame. But with the 2.3x crop factor the distortion/compression of the scene into the image seems to hardly matter. It does seem like an 8mm fisheye will be a bit wider (with more distortion) than an 8mm rectilinear on the bmcc, but I don't get how he concludes that it will be a 10mm FF equivalent.

Anybody out there who can break this down for me?

Thanks!

I think he means that on a FF Camera like a MkII at 8mm you have black with a circle inside where there is an image....Now the image that you see inside the circle is the 8mm bit. Stick the lens on the Magic Cam & you zoom past almost all the black so the image almost fills the screen at a guess. The visible image bit will not be a lot different to the original as your zooming past the black frame prior to cutting the image...

Andrew
04-28-2012, 05:19 PM
Thanks for your reply! I get what you're saying and that does makes sense. I guess I still have doubts that the crop factor applies equally to a fisheye mapping of the lens as it does to a rectilinear one.

10mm FF equivalent just seems overly optimistic. I own a 5d with a Sigma 12-24 rectilinear lens, and I have doubts that 8mm fisheye cropped by the bmcc sensor is going to give a wider fov.