Canon EOS Digital Rebel XT Hands-on Review (EOS 350D)

White Balance

The image below shows the white balance under tungsten and fluorescent lighting for both the EOS 20D and Digital Rebel XT. These are crops of a shot of a Kodak 18% gray card. Canon EOS Digital Rebel XT (350D) Review

Canon EOS Digital Rebel XT (350D) Review

The bar below the images shows what a theoretical 18% grey patch should look like. The small numbers in white are the Red, Green and Blue (RGB) intensity values. As you can see neither camera gets it quite right under any of the white balance settings! All Canon cameras seem to bias towards red/yellow for tungsten in both AWB and Tungsten modes. Some have suggested that this is because people expect indoor shots under Tungsten lighting to be a little red/yellow, so Canon built in that bias. The best neutral performance is shown by the 20D using AWB under fluorescent lighting.

The images below show the same gray card shot under daylight illumination from a cloudy sky.

Again there are differences, but they are not so noticeable. In both cases, Auto WB does a slightly better job than selecting Cloudy white balance. The aim is for all three numbers to be the same (which is what makes a neutral gray). It's noticeable that the Digital Rebel XT images in all these tests are slightly lighter than those from the 20D. In theory, a shot of an 18% gray card in sRGB color space (gamma=1.8) should be RGB 117:117:117.

Note that in all cases and under any given lighting, if you use the custom white balance function you will get a neutral color balance, by definition. You shoot a gray (or white) card under the desired lighting and use that as a reference. This results in similar shots of the gray (or white) card being exactly neutral.

The next two shots are the exact same scene shot with the Digital Rebel XT and the EOS 20D so you can see what a somewhat neglected lawn looks like in the rain! White balance was set to auto.

As you can see, on a real world image (rather than a gray card), color balance looks similar (I'd say slightly magenta). The 20D shot is still a little darker. If you convert both images to grayscale, then average the whole image, the average RGB value of the XT image is 108, that of the 20D image is 98 so in this case both meter slightly darker than 18% gray (117) on this scene.

Both look better with slight level and color tweaks though, as shown below:

In these and other "real world" exposure tests I saw the 20D give, on average, about 1/3 stop less exposure than the Digital Rebel XT. This is with both cameras using exactly the same lens at the same aperture and the same parameter sets and other settings, and it was independent of metering mode (evaluative, partial etc.). This appears to be due to metering differences, not ISO differences, since at a given aperture the 20D seems to select a shutter speed about 1/3 stop slower. Whether you regard this as a defect or a feature could, I guess, depend on your point of view. The 20D images are a little darker - on the other hand they give you 1/3 stop more "headroom" for highlights under default conditions. Whether this difference is intrinsic to the camera metering algorithms and was designed that way by Canon or simply represents sample to sample variation in these two particular cameras, I don't know since I only have one sample of each to test.

Infrared Capability

While no DSLR is specified for IR use, many people are using them for IR work. Sensitivity isn't high and exposures are long, but I have seen some pretty good examples shot with cameras like the 20D and Digital Rebel.

Below is a comparison of shots taken with the EOS 20D and Digital Rebel XT using a Hoya R72 filter. This blocks most visible light and allows most IR over 720nm to pass. There wasn't a lot of IR around for these shots. Conditions were overcast.

There are a couple of things worthy of comment. First, to get roughly comparable image brightness the Digital Rebel XT needed an exposure of 2.5s when the EOS 20D needed 15s, so the Digital Rebel XT seems more sensitive to IR. However this may not be as good as it seems. As you can see from the histograms, the Digital Rebel XT's blue and red pixels seem to respond to whatever gets through the R72 filter, while in the EOS 20D most response seems to come from the red pixels. Whether this results in lower contrast is hard to say, but the XT's image is lower in contrast than that of the 20D. Note these histograms are for images taken using Auto White Balance. However the same general conclusions hold true for the various fixed white balance options. Using custom white balance is a better option, but since it uses an image shot with the camera as a reference, channel response differences cancel out, so it's not the best option if you want to know what's going on!

Of course IR images are usually converted into black and white (as shown above), and with enough manipulation both image can be made to look similar, though the XT's image needs stronger corrections Note the central "hotspot" in the XT's image. This is a phenomenon which has been observed with many DLSRs and which depends on the lens in use. Some "hotspot" much more than others. It appears to be due to some sort of back reflection from the surface of the sensor or sensor filters interacting with the lens. Whatever the cause, it seems to be significantly worse for the XT than for the 20D. So from these tests it seems that though the sensitivity of the XT to IR is higher (and exposure times therefore shorter), the intrinsic image quality (contrast) is lower and the hotspot sensitivity is higher.

Conclusion

The Digital Rebel XT is a very capable camera indeed. The image quality equals that of the EOS 20D. It does have a few less bells and whistles than the 20D, but you save a signifcant amount of money and many photographers may not need the added features of the 20D. The XT has pretty much everything the average amateur photographer could want and I can certainly recommend it to the photographer on a budget. I think the EOS 20D is a better camera, but currently (03/06) it sells for about $400 more then the Digital Rebel XT

If you don't have another wideangle lens (like a 16-35 or 17-40), then get the XT with the EF-S 18-55 kit lens. It's inexpensive and it's not too bad. A better lens is the EF-S 17-85/3.5-5.6 IS USM. In fact for many photographers that may be the only lens they need. It's not cheap, but it covers a lot of popular focal lengths (equal to 28-135mm on a full frame camera) and it has Image Stabilization as well.

You can now get the Digital Rebel XT body for under $500, or you can get the XT kit with the 18-55 lens for around $590

[Visit the HOME PAGE to see what else is new on the site]

Canon EOS Digital Rebel XT Hands-on Review (EOS 350D)

White Balance

Infrared Capability

Further Reading

Conclusion