Comments on: Canon Patents a New Live View Autofocus System

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By: Zac

Zac — Wed, 25 Feb 2009 05:20:57 +0000

Thank you. You’re statement is completely true, and hopefully will help all of us put our own technological desires in perspective.

By: Bear

Bear — Fri, 13 Feb 2009 08:35:43 +0000

I think, that different mirror assembly can allow mounting EF-S lenses on fullframe body.

By: Ed

Ed — Thu, 12 Feb 2009 22:27:29 +0000

The patent is pretty complex, and provides two different implementations defining movement of the mirrors. The net result is

1. conventional slr taking with mirror out of the way

2. Imaging thru the mirror with high speed autofocus available. This would allow autofocus while using liveview, taking movies, and allows ultra high speed photography for sports. Some light loss thru the mirror, and probably some image degradation due to imperfections in the resin mirror.

3. I noticed that a eyepiece shutter was also mentioned. That would be a nice feature, it may be that its required due to the mirror configuration.

By: Ed

Ed — Thu, 12 Feb 2009 21:19:23 +0000

I use live view for product photography, and it works great. The display is too dime to really make use of it outdoors.

The full text of the patent can be found at http://www.freepatentsonline.com/y2008/0316353.html

You can join (Free) and also view the 25 pages of diagrams.

It does read like a serious patent, and you get the feeling that it has been tested in the lab. How long it might take to get to production( if ever) depends on how much is already developed and designed.

By: 24-70 IS

24-70 IS — Thu, 12 Feb 2009 14:11:42 +0000

then live view mode, the coms will only get half of the light as well? new dslr’s iso performance will be damned

By: Photographer/Videographer

Photographer/Videographer — Thu, 12 Feb 2009 14:08:00 +0000

Despite of this (possible) new system, companies are working to improve contrast detection AF.

So, hopefully we could get both systems, and if contrast detection AF is the only choice for a specific situation, it might be faster than the actual one.

By: Nikkorian

Nikkorian — Thu, 12 Feb 2009 12:15:19 +0000

Oh, thanks for the info, Gusto. Didn’t know those details about the DxO measurements. So what you say is, the D90 is actually not as much better than the D300 as the DxO ISO sensitivity suggests? If I remember correctly, the dynamic range is better as well though?!

By: Gusto

Gusto — Thu, 12 Feb 2009 11:29:30 +0000

ISO sensitivity as measured by DXO has absolutely NO RELATION whatsoever to actual sensor sensitivity. DXO measures ISO by determining the point where highlights start to clip. The standard way is spot meter off an 18% gray area so that the image luminance level is set at 50% of the final image file. Andy Westlake has the explanation here:

http://forums.dpreview.com/forums/read.asp?forum=1032&message=30685499

In fact, DXO results have often been found to disagree with real world photos. For example, performance of Canon 5D2 vs 1Ds3 (latter in reality has better dynamic range) or performance of D90 vs D300 (noise level at high ISO). I won’t give a hoot about so-called scientific results if they have no bearing whatsoever on how real world photos turn out. Of course, you can always use your camera SOLELY to shoot brick walls, test charts, color charts etc etc. ;)

By: Bob

Bob — Thu, 12 Feb 2009 11:06:12 +0000

This is how AF works at present: a partially reflecting main mirror reflects light to the viewfinder and any light passing through reflects off a sub-mirror to the AF sensor. The change just seems to be that the light that was going to the viewfinder now goes to the AF sensor and the light that was passing through and going to the AF sensor now goes to the main sensor for live view. If we assume that the light was split evenly before (and that is a big assumption, I’ll admit) then there should be no real difference in AF performance. If it the viewfinder got the majority of the light, then the AF performance will improve, but the live view image might have a bit more noise. The mirror can still swing up when you take the shot, so the noise will not be present in the final image.

Of course, if you want to make videos in low light, then you can’t have the mirror clattering up and down and you’ll either want to use contrast detection AF or jack up your ISO and live with the noise.

By: Nigel

Nigel — Thu, 12 Feb 2009 10:17:59 +0000

> This improvement indeed will help a lot the Movie/Video mode in DSLRs, wich is also going to be improved and implemented in future DSLRs, despite some people like it or not.

But all the time DSLRs use CMOS sensors it’s a half-baked implementation. Unless they can figure some way to prevent image degradation on movement.

By: Nikkorian

Nikkorian — Thu, 12 Feb 2009 08:48:48 +0000

I doubt this will be a pro level camera option. Look at the DxO measures and how companies struggle for a few digits iso sensitivity. By using a partially reflecting mirror they would have to give up some good part of the light for the AF metering. And it does need light – as you know the AF becomes slow on slower lenses.

UNLESS of course the partially reflecting surface swings upwards when taking a picture, like the mirror does right now. That would be a nice solution. It could stay down for video I guess, losing some light in favor of a video AF.

Of course, I could not image for Nikon not to have such a patent?! :-p

By: Photographer/Videographer

Photographer/Videographer — Thu, 12 Feb 2009 08:39:49 +0000

well, would be TERRIBLE to have this feature only in an APS-C sensor camera and Not in a FF camera….

I think it wouldn’t make sense.
In case of the FF camera bodies, I supose Canon would make them a bit bigger to get enough space to put it inside.

Otherwhise it would be ridiculous to have faster LiveView AF in xxD than in xD DSLRs