Movie-mode DSLR patented

Author: Gareth Halfacree
Published: 19th February 2008
Comments (11) Stumble
The patent would allow video shooting on digital SLR cameras, much like compacts currently offer.

The patent would allow video shooting on digital SLR cameras, much like compacts currently offer.

Inventor Hiroshi Terada has filed a patent for what he describes as a “movie image shooting mode” for digital single-lens reflex (DSLR) cameras. The patent details a system whereby a 30FPS film mode could be added to consumer grade digital SLR cameras, bringing a feature more associated with point-and-shoots to a higher level.

The main reason DSLRs don't already have a movie mode – aside from the fact that the people likely to be lugging such a beast around with them aren't the ones who want a VGA resolution movie of their family waving from a boat – is due to the way the mirror works. The mirror reflects the light from the lens to the viewfinder and, more importantly, the auto-focus sensor. When you take a shot, the mirror hinges out of the way to allow the light to fall on the sensor and the image to be captured: it's this motion that makes the tell-tale 'clunk' of an SLR. In order to take movie footage, the mirror would have to move in and out of the path of the light thirty times a second – a recipe for a great deal of noise and a rapidly deflating battery.

The patent details a novel solution to this problem: a mirror which is partially translucent. The idea is that the mirror will allow 70% of the light to pass through it, and 30% to be bounced to the auto-focus sensor. This means the mirror can stay in place when the camera is in movie mode, and still hinge away when required for high-quality still shooting.

The patent also details solutions to other technical speedbumps such as a much faster auto-focus mode when shooting video, a wider field of focus, and a cropping system to prevent the field of view chancing during focussing.

It's not a function that you're likely to see on the professional – or even 'pro-sumer' – end of the spectrum, but if the technology works as well as detailed in the patent it's quite likely we'll see the system picked up by at least one of the camera manufacturers as a way to tempt people to DSLR from compact cameras – and thus into the market for lovely high-margin lenses.

Something you'd like to see on your next DSLR purchase, or is video shooting something best left to dedicated devices and toy point-'n-shoot cameras? Share your thoughts over in the forums.
Quote Bauul 19th February 2008, 09:21
To be honest, I can't really see many DSLR owners bothering with taking movies on their cameras. If they're serious enough about pictures to own an SLR, they're probably serious enough about video to own a proper video camera.
Quote The_Pope 19th February 2008, 09:25
It's just the next attempt at differentiation in a world when many dSLR models are essentially the same. I can't remember who was first with LivePreview (pointless rubbish) but that didn't stop everyone else from following them to restore the status quo of featuresets
Quote The_Pope 19th February 2008, 09:30
Incidentally, rather than a "semi translucent mirror" which sounds like ghetto window tinting, I wonder if they're also working on some sort of l33t electro-chromatic "mirror" - a bit like an electromagnet (on / off) but a mirror instead. The tech exists but not sure what it would take to run it on this sort of small scale.

I would assume you could flip that signal on & off at 30fps... :)
Quote DXR_13KE 19th February 2008, 10:00
how about feeding the viewfinder with the signal from the sensor?
Quote alastor 19th February 2008, 10:11
Quote:
Originally Posted by DXR_13KE
how about feeding the viewfinder with the signal from the sensor?
That kinda defeats the point of having an SLR system; being able to see exactly what's coming in through the lens.

Surely any DSLR with live view is capable of shooting video? Just through the use of contrast detection auto focus.
Quote chicorasia 19th February 2008, 12:50
A mirror with 70% transparency would make for a darker than usual viewfinder (a f/2 lens would look like a f/4 or f/5.6); it would also limit the amount of light hitting the CCD, so one would have to crank up the ISO settings in low light conditions - thusly increasing electronic noise.

One possible use for this tecnology is action photography in burst mode - a situation when every little bit of light matters, so losing 30% (about 1/2 f-stop!) of all the light hitting the sensor may not be the best way to go.

FYI: Movie cameras (real movie cameras, the likes of Arri and Panaflex) use a rotating mirror shutter to direct light to the viewfinder/video assist and the film, alternating at 24fps (tipically).
Quote TGImages 19th February 2008, 13:49
As a fairly long time digital SLR shooter (started with the D1H, currently on the EOS 20D) I, at first, would really like to get this feature that has been in the low end P&S for years now. However the more I think aout it the more I think I'd still rather just get a separate camera for shooting video. Incorporating continuous audio along with HD Video (anything less wouldn't be worth it) and the appropriate external lighting and mic connectors, plus accomodating more storage needs, etc. and I just don't think it's going to be practical. Most serious SLR shooters have a quality expectation that this method looks like it will compromise on too much.
Quote Phil Rhodes 19th February 2008, 14:34
Many DSLRs already have partially-silvered mirrors because they use the sensor data for focussing and at least several motion picture cameras (generally older types) use beamsplitters for both the video tap and viewfinder. I'm really not sure what the novelty of this is.
Quote Firehed 19th February 2008, 15:29
Quote:
Originally Posted by DXR_13KE
how about feeding the viewfinder with the signal from the sensor?
Viewfinders are just a window through the lens. You could do it to the monitor on the back I suppose, but that's going to suck down a lot of battery life.
Quote Cthippo 19th February 2008, 20:32
Actually, I could see this being a fairly useful feature. My dSLR gets a LOT of use and once in a while I would like to be able to get a little video, but not so much that I'm going to lug around another piece of kit.

Yeah, it may be a gimmick, but for me at least it's a more useful gimmick than say a 10 Mp sensor.
Quote outlawaol 20th February 2008, 03:01
*sigh*

This sounds like another brilliant idea to make a point-n-shoot out of a DSLR. LIke the titanic screen on the new Xsi/XTi that effectively removes the info LCD for the sake of a bigger preview screen (the only way that is acceptable is if the info remains)

This is like buying a 4 cylinder mustang....
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