A new tool has entered the digital photographer’s arsenal: “Single-Lens Reflex” (SLR) still cameras with video-recording capabilities.

The idea of adding video to these new DSLRs did not form in a vacuum. Simple video capability has existed for years in the “Point and Shoot” category of cameras. Almost all P&S cameras support either or both of the VGA (640x480) and QVGA (320x240) resolutions, at somewhere in the range from 10 to 30fps. A few have odd resolutions and frame rates. Their most common video encoding format is Motion JPEG, though various forms of MPEG 1 and MPEG 4 are also found. All of them have built-in microphones and none of them support external audio input. A more detailed review of video capabilities on P&S camera is beyond the scope of this article, though. It will be the subject of a later companion article.

This article examines the current crop of video-enabled digital SLRs, comparing them to each other, to similar products soon to be introduced, and also, as a reality check, to a dedicated video camera. Some aspects of sensor design (comparing CCD vs. CMOS sensors) will be discussed, as they affect video. While the major still-image capabilities of the cameras will be mentioned, the emphasis here will be on the video capabilities.

Just as SLRs raise the bar for still pictures, they offer unique capabilities in some areas of video as well. (But their performance depends on design tradeoffs made in the imaging sensor, so SLRs are not always better in every respect.)

First of all, just what is an SLR? “Single Lens Reflex” describes a camera that uses a mirror and pentaprism to redirect light from the main lens to the viewfinder. Thus, the photographer sees pretty much what the lens sees. There is no “parallax” (viewing from a slightly different angle, as can happen with simple second-lens or “rangefinder” style viewfinders) to throw off the composition when focusing close. Usually, an SLR also has a system of interchangeable lenses (there are exceptions, but they are rare).

While it’s possible for a P&S camera to have an SLR-type viewfinder, this is not typical. Most P&S cameras either dispense with the viewfinder entirely (and rely upon “Live View” on the display screen), or they go with simple auxiliary-lens viewfinders (that suffer from parallax at close range), or they have an EVF (an “electronic viewfinder”), which may look like an SLR’s “pentaprism bump” but instead houses a miniature LCD screen.

It’s also possible for “SLR-like” system cameras with interchangeable lenses to use an EVF, and dispense with the noisy mirror and bulky pentaprism. This is a recent trend, with Olympus and Panasonic / Lumix, in particular, pushing this approach in their “Micro Four-Thirds” system. (While there are no such cameras on the market yet with video capabilities, Lumix has announced it will introduce one, the “Lumix G HD”, in the spring of 2009.)

Overview 

At the moment there are only two products available in this new video-capable DSLR category. One is the Nikon D90, the other is the Canon EOS 5D Mark II.

Nikon got to market first. As of November 2008, the D90 was already shipping and in the hands of users. Its capabilities and limitations are becoming well known through firsthand use.

Canon began shipping the EOS 5D Mark II in early December of 2008. Until very recently, only a few lucky people had been able to try prototypes. Firsthand experience was rather limited, but a few quirks and capabilities had already become apparent. While clearly no panacea for all uses, this is still one awesome camera.