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The Canon Digital Rebel XT

Type  Digital SLR
Shutter Range 1/4000 to 30 seconds
Shutter Type Vertical Travel, Electronically Timed Focal Plane
Meter Type Silicon 35 zone (capable of 9 % semi spot)
Meter Range EV 1 to EV 20
Exposure System Multimode AE, and manual
Lens Mount Canon EF Autofocus S-compatable
Battery NB-2LH
Digital Specs
Sensor Type CMOS  
LCD Display 1.8" color 144K pixels
Sensor Size 22.2 x14.8 mm Recording Media Compact Flash
Sensor Resolution 8 MP (3456x2304)
File Size 3.3 mb
Focal Length Compensation 1.6 Film Speed Equiv. ASA 100-ASA1600

     The Rebel series, is Canon's offering to the amateur or casual photographer, as opposed to it's pro oriented D, and DCS series. The Rebel has a plastic body, is a bit more plain, and may be somewhat less feature laden, than the more advanced pro versions of the Canon digital line up. This is in no way meant to slight the Rebel. These are all great cameras, and would have been unobtainable, at any price, just ten years ago. So far, there have been three versions of the Digital Rebel. The original had the 6.3 MP imager, and is no longer in production. The current models, have improved features, more advances autofocus and processing systems, and have higher resolution, than the original.
     This is my fourth digital camera, and my second digital SLR. It was purchased for a trip to Alaska, specifically to permit the use of the new S series of lenses, offered by Canon for it's digital cameras. This new series of lenses addresses one of the big drawbacks of the new generation of digital SLR. This is the focal length compensation factor, required by the small size of the average digital imager unit. For most cameras, this is a factor of 1.6 to 1.
     Focal length compensation can come in handy, for the nature photographer, or sports photographer. It can make a 200mm lens, act like a 320mm lens.. Unfortunately, for most photographers, wide coverage will be required far more often than extreme close up. The same focal length compensation that does such wonderful things for telephotos, will also turn your 28mm wide angle, into a normal lens, equal to a 42 mm. To get anything like a good wide angle coverage, with this type of camera, you will need to go with an 18mm, or even smaller. the problem here, is that lenses in this range are really expensive, and tend to be rather slow, as well as quite large. There are reasons for this, that I will cover in my section on the EF series of lenses.
        The S series of lenses is designed specifically for the smaller imager, rather than the larger area of the standard 35 mm film camera. This means that it produces a smaller image circle. This in turn means that less glass can be used, fewer elements, and a smaller housing, making for a far less expensive lens. These new lenses emphasize the domination of digital cameras, and their ultimate replacement of the film camera. Initially, the ability to use standard 35 mm lenses on the new generation of digital SLR cameras was a big selling point. Now they are being replaced by a new series of digital only lenses, that will not mount on a standard 35mm film camera.
The Effect of Film Speed on Image Quality of the Digital Rebel
ASA 400
(cropped down from a much larger photo)
A shot of a section of my pool table, in average room lighting. Note that the ASA 1600 photo lacks the resolution, and color rendition of the ASA 400.
ASA 1600
(cropped down from a much larger photo)
    If there is any real handicap to using a digital camera, it is the constraint placed upon the digital photographer of always using the same imager, no matter what the conditions or effect desired. The film photographer has a distinct advantage here, because of the film camera's capability of being loaded with any of a multitude of films being produced. Film photographers have bulk loaded everything from commercial movie film to 35 mm microfilm into their cameras. There is also a selection of special purpose films such as Infra Red, High Contrast, and false color films.
    One of the ways that digital cameras can fight back, and get more versatility, is by the use of film speed settings, and quality settings (parameters can also be used, but I do not use them, or know enough about them to really comment). This gives the user a bit of versatility, though not to the degree of that enjoyed by the film photographer. Still, the technology is moving along, and who can say what types of imagers might be a few years down the road. Of course, film and chemical technology are not standing still either. It will be interesting to see what developments lie ahead in both areas.
     Film speed can be selected from a range of between ASA 100 and 1600. As with a classic film camera, at higher speeds, grain increases, color accuracy lessens, and sharpness decreases. Still, the low light photo you can get at ASA 1600, will be better than the missed photo at ASA 100. In practice, I keep the camera set at ASA 400, which seems to offer good speed, as well as good looking photos. The camera also allows selection of three different resolutions - 3456 x 2304, 2496 x 1664, or 1728 x 1152. Though I almost never use pictures at full size, I keep the camera set to the highest resolution.
     Image quality can also be switched, between normal and high. In practice, with the large memory cards available today, I see little reason to shoot at anything other than high quality; but the option is there. The quality setting is different from the resolution, in the at it does not effect how the photo is taken. It affects how the photo is stored. Photos are stored in JPEG format, which is a compressed image format. At lower quality settings, the compression is increased. During compression, details are thrown away, intentionally, using certain pattern finding algorithms. During viewing, the same algorithms are used to reconstruct the original picture, and put back the missing details. The problem is that these details are gone, and have to be filled back in by the algorithm, which essentially "guesses" at what was thrown away during recording. The higher the compression, the more the detail that is discarded, increasing the amount of guessing that will have to be done by the algorithm during reconstruction.
The Effect of Image Quality Settings on the Canon Digital Rebel

High Quality
These two photos are taken of the exact same subject, with the exact same exposure, under the exact same conditions. Only the quality level has been changed. Some added detail loss can be seen in the cross hatch pattern (this is a photo of a Fresnel lens) in the average quality image. The difference here is not quite so striking, as in the photos above; but will still be noticeable. With the huge size of modern memory cards, there seems little point in shooting at anything but the highest quality levels.

Average Quality
     As with all of the EOS series cameras, including the D30 and D60, the Rebel has a number of different modes to which it can be set. There are the automatic and programmed modes, as well as the following series of AE settings collectively referred to as the Easy Shooting Zone. Each member of the series is pre programmed to give good results taking the following types of shots:
  • Portrait (Low Aperture, center spot metering)
  • Landscape (High Aperture, averaging metering)
  • Close up
  • Sports (high shutter speed)
  • Night scenes (Auto flash, combined with slow shutter speed)
     For those who are traditionalists, or want a bit more than snapshots, the EOS series also offers what Canon calls the Creative Zone modes. They are:
  • Manual exposure
  • Aperture Priority
  • Shutter Priority
  • Automatic Depth of Field
     The memory cache of the Rebel permits shooting at up to three frames per second, for a total of up to 14 frames. Size at best resolution and quality is 3.3 MB, giving approximately 300 pictures per Gigabyte. At the smallest resolution, and lowest quality, file size is 0.6 MB, giving 1650 pictures per GB. The camera is able to handle CF cards of up to 32 GB, giving a theoretical total of  9600 photos at highest resolution and quality. I have never used such a large drive, and there may be a lower true capacity, due to cluster size issues with the cameras FAT 32 file system. Wouldn't it be great if someone would develop a camera that uses NTFS? Oh well.

               This page is a work in progress; but should be finished by March - 2009.
semi spot
focus points