Canon EOS 1Ds Mark III Viewfinder

The optical viewfinder on the Canon 1Ds Mark III offers a true 100 percent field of view, a relative rarity, even among high-end SLRs. Magnification is 0.76x, which may seem low compared to other DSLRs, but keep in mind this is a full-frame model. The optical viewfinder has a glass pentaprism design, using a mirror to reflect the view from the lens, just as in a traditional SLR viewfinder design.

On the left side of the viewfinder eyepiece, hidden by the eyecup, is a diopter adjustment dial, which corrects the viewfinder display from -3.0 to +1.0 diopter units to accommodate eyeglass wearers. The viewfinder has a moderately high eye point of 20mm, meaning that the view should be reasonably clear, even with fairly thick eyeglasses. (In addition to the rather wide range of diopter adjustments available on-camera, Canon also offers dioptric correction lenses for the viewfinder ranging from -4 to +3 diopters in 10 steps. These clip on externally, and act in addition to the built-in diopter adjustment, for a total range of -7 to +4 diopters. If you can see well enough to pick up the camera, you should be able to see through the viewfinder!) Eleven interchangeable focusing screens are available for the 1Ds Mark III. On the right side of the viewfinder eyepiece is a small lever that opens and closes a shutter behind the eyepiece. This prevents any additional light from filtering into the camera through the viewfinder eyepiece during long exposures on a tripod. The 1Ds Mark III also features a removable eyecup that fits over the viewfinder eyepiece, handy for high ambient light environments.

A full information overlay along the bottom and right of the viewfinder window reports the current exposure settings, including shutter speed, aperture, exposure compensation, and ISO, among other information. A circular black outline at the center of the viewfinder window indicates the central spot-metering area, (although as I'll explain later, the Mark III is capable of spot metering at a number of locations within the field of view). A large, black elliptical outline marks the boundaries of the autofocus area. A total of 45 discrete autofocus sensors are distributed within this ellipse, and may be used singly or in combination. Active AF points are normally invisible, illuminating red when the Shutter button is half-pressed and focus is achieved at one or more of the points.

The amount of information conveyed by the 1Ds Mark III's viewfinder readout is quite impressive, all the more so because the display is actually quite uncluttered and easy to understand. The illustration below (courtesy Canon USA) shows all the internal viewfinder displays and their functions. (Readers familiar with the EOS-1v film SLR or the previous EOS-1Ds Mark II will immediately recognize this display as being very similar to the one used on those cameras.)


Viewfinder Test Results

Very good accuracy with the optical viewfinder, though tilted somewhat; excellent accuracy from the LCD monitor's Live View mode.

70mm, Optical 70mm, Live View LCD

The Canon EOS 1Ds Mark III's optical viewfinder was quite accurate at about 99% coverage when measured with our Sigma 70mm f/2.8 macro test lens, however it was tilted off axis by about one degree. That might not seem like much, but it sure is noticeable and should be sent in for adjustment. Live View LCD mode proved extremely accurate, with 100% coverage. As expected, it has no tilt, since the sensor image itself is used to frame the target.


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