I was interested in finding a compact, relatively light telephoto zoom lens in the 75-300mm range to put in a light kit with wide-angle zoom that I could travel easily with and use for grab and shoot purposes with my Canon APS-C camera (20D / D60). Ideally, it would yield reasonable quality prints that I could enlarge well above an 8x10 inch print size if needed. I compared two compact Canon zoom telephoto lenses with other larger, heavier lenses. This review focuses on comparisons between Canon's relatively expensive EF 70-300mm f/4.5-5.6 DO IS lens based on diffractive optics against the inexpensive EF 75-300mm f/4-5.6 III USM.

Canon EF 70-300mm f/4.5-5.6 DO IS USM Lens

Lenses Used in Tests Which of these 300mm lenses would you want to carry all day on your shoulder, back or around your neck, and how much lens performance are you willing to sacrifice? Click here for lens specification on size and weight.

Resolution and Modulation Transfer Function

Resolution

Resolution of the EF 70-300mm f/4.5-5.6 DO IS lens was found to be comparable to other Canon zoom telephoto lenses tested in the range from 70mm through 200mm. Resolution of greater than 60 line pairs per mm was achieved at all focal lengths tested except at 300mm. Images produced by the lens were free of significant chromatic aberration at all focal lengths tested. At 300mm, the EF 70-300mm f/4.5-5.6 DO IS lens was only able to achieve resolution ranging from low 40's to high 50's line pairs per mm. Photographs of birds and other wildlife taken at 300mm and enlarged beyond 8x10 inch print levels noticeably lacked the sharpness and contrast that were achievable with a 300mm prime lens.

Method for Lens Resolution Measurement with Kodak Technical Pan

Digital Camera 50% MTF at 200mm and 300mm

What the EF 70-300mm f/4.5-5.6 DO lens lacks in resolution at 300mm, it appears to make up for with higher contrast and higher MTF scores. 50% MTF was calculated at 200mm and 300mm using this method.

Comparison of Image Sharpness at 300mm Comparison of Image Sharpness among 300mm lenses using a life size taxidermy specimen	Comparison of Image Sharpness Various Focal Lengths Comparison of images produced under ambient lighting
Bokeh of the EF 70-300mm f/4.5-5.6 Click here for comparison of diffuse out of focus background examples.	Lense Flare of the EF 70-300mm f/4.5-5.6 Comparison of images produced at 300mm under constant studio lighting (The DO lens flares badly under bright background lighting)
Out of focus background highlights with diffraction grid pattern and aperture diaphragm pattern. The hexagonal pattern of the aperture diaphragm is notable in the background. In this photo of a white-eared catbird in the San Diego Zoo, I stopped the lens down to f/10 to try to squeeze depth of field out of the image. This is shot hand-held in the shade at ISO 800, 1/100th sec at 185mm with a 20D. The image-stabilization saved the day.

Other comments on performance characteristics of the EF 70-300mm f/4.5-5.6 DO IS USM lens

• Image stabilization: This feature works well and is highly valuable for shooting at slow shutter speeds in low ambient light or medium lighting with low ISO settings.
• Autofocus speed: Autofocus is very fast with cameras ranging from the D-60 to the EOS-1D Mark II and much faster than that for the EF 75-300mm f/4-5.6 III USM.
• Backround blur / bokeh: Softly blurred out of focus background was comparable to other quality Canon telephoto zoom lenses at the same aperture.
• Construction: Finish and overall construction appears to be very good and at a level comparable to the EF 28-135mm f/3.5-5.6 IS USM lens.
• Zoom-lock switch: The lock on the zoom control will fix the lens at the 70mm setting. I looked at two samples of the lens. One of the lenses would extend to the 300mm setting when you carry it around on a camera strap or otherwise point the lens down. This zoom creep can be annoying.
• Stealthy: This lens is compact, black and more readily overlook when you are carrying it than a longer, white 70-200 L-zoom.
• NOT quite a 300mm lens (at times): Official Canon lens specifications from Canon USA state that the 70-300 DO lens has a diagonal field of view of 8° 15' (the same as their 300mm prime lenses). When focused at less than infinity at the 300mm setting, the 70-300 DO has a wider field of view than a 300mm prime lens. A simple examination of image fields produced with a full frame camera on a tripod with a set focus point and constant working distance shows that the 70-300 has a wider field of view than a 300mm prime lens.

Using Polarizing and UV filters with the EF 70-300mm f/4.5-5.6 DO IS USM lens
A lens tip page by Xavier Henri pointed out benefits and disadvantages of using filters with the lens:

• UV filters can decrease image contrast and color saturation under some lighting conditions. If you use a protective filter, it should be a clear filter, not a UV filter for best performance results. See examples
• Circular polarizing filters work well to enhance sky-cloud contrast and to reduce reflections. See examples

Conclusions:

The Canon EF 70-300mm f/4.5-5.6 DO IS USM is a compact, very fast-focusing zoom telephoto lens that provides generally excellent imaging function including excellent image stabilization at a high price. It is a weak performer at 300mm. It generally provides noticeably better performance than the cheaper consumer 75-300mm lens. Under some lighting conditions (e.g., backlighting of subject into the lens), the lens flares and renders images unusable. Because of its compactness and generally excellent performance with image stabilization, the lens is very useful for travel or other applications where you don't want to carry a heavy, long and easily noticed lens.

Gallery of images taken with the EF 70-300mm f/4.5-5.6 DO IS USM and Canon D60

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© 2004, William L. Castleman
Posted 07 August 2004; last revised 06 June 2007