Patent: Canon RF 15-35mm f/4L

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The 16-35 f4L patent mentions a 10.35mm :oops: backfocus at max wide angle. Wow, that's sticking the lens edge half way past the mount towards the sensor. And you still have to have room for the 1st & 2nd mechanical shutter and housing mechanism! Sometimes I'm just amazed at what they can design & build.
 
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The 16-35 f4L patent mentions a 10.35mm :oops: backfocus at max wide angle. Wow, that's sticking the lens edge half way past the mount towards the sensor. And you still have to have room for the 1st & 2nd mechanical shutter and housing mechanism! Sometimes I'm just amazed at what they can design & build.

And an ND filter stack on the C70!
 
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What does 'focus by wire' mean, please?
Assuming this is one of those "lost in translation" issues: "Focus by wire" is just a rotating ring with high resolution encoders that the camera sense so that it can adjust the AF mechanism accordingly. It removes the complexity of a mechanical user focus mechanism which would interfere with the latest high-tech AF mechanisms. I think "focus by wire" is the best thing you can have, provided they can make it feel smooth with proper damping/resistance with the proper range of motion from near-to-far and making it as par-focal as possible when combined with the mechanical zoom often used. It's also best (IMHO) when it's a fixed (predictable) focus range instead of a continuously spinning +/- one, but I'm sure others will prefer the other.
 
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Why almost every mirrorless lens is focus by wire? Is there any technical limitation for mirrorless?
Focus by wire is usually cheaper and less mechanically complex. It also gives more freedom to use multiple focus groups in the lens without having to worry about mechanically linking them all to a single control ring. A bonus is that it (potentially) allows the user to customise how the focus ring behaves.
 
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15.45 and 16.48 are suspicious numbers. It seems Canon want to be able to round down and sell them as 15mm and 16mm. I always hate cheating like that. I am not a lens engenieer, but if you have a formula for a 15.45mm lens, it should be technically possible to tweak some parameters and make it exactly 15mm. The same is true at the long end of tele lenses, where Canon often rounds up.

It is good though that Canon brings slower versions of its very expensive lenses with f/2.8. With a powerful IBIS you do not need much light and I usually chose an aperture just below the diffraction limit of the camera to get as much depth of field as possible. That's f/11 at my 18 megapixel camera. So f/2.8 for me is just something that makes a lens twice as heavy and twice as expensive and I only need it for low light hand held shots.
 
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