Spoli58, a FredMiranda forum member, posted an extensive report on Canon EF 70-300mm f/4.0-5.6 IS USM and wrote:
“- Overall impression: good quality optics, better than EF 55-200, probably not L grade but not too far if you consider the price and the class of this lens.
– In the range 70 to 85mm @ F8…F11 the results look similar to my EF-S 17-85mm IS USM, surprisingly sharp at the corners (hard to see real differences in terms of sharpness and geometrical distortions) — great outdoor lens in good light conditions.
– At F8 the image is sharp for almost the entire focal range — at the long end (between 200-300mm) the image looks a bit soft without affecting the resolution — maybe it’s just the fact that I’m using a cheap tripod and IS turned on rather than a rock solid tripod, mirror lock and no IS.
– Wide open the softness at the long end is present, however not annoying; corner softness is also more obvious, especially at short focal length, but nothing to worry about in real situations.
– Stopped down to F16 or more this lens is soft but usable — you can turn this into an advantage in portraits or other situations where softness is desired.
– Using a 1.6x FOVCF camera, I cannot complain about vignetting or geometrical distortions (I would be curious to run some tests on a full frame camera) — barrel distortions are minimal at 70mm and disappear around 100mm, pincushion at 300mm is also minimal. I guess that on a full frame camera the distortions may be more pronounced.
– CA (Chromatic Aberration) is very well controlled — it is much better than my EF-S 17-85mm IS USM or EF 55-200mm USM.
– Canon EF 70-300mm IS USM Lens has an 8-blade circular aperture that give a very good defocused image quality (bokeh), better than EF-S 17-85mm IS USM or EF 55-200mm USM.
– With a maximum magnification of .26x, Canon EF 70-300mm IS USM can be used for macro (minimum distance 1.5 m) with good results. At 300mm the depth of field is very shallow and focusing is critical – AF single spot seems to work in many cases, but sometimes manual focusing and a good tripod may be critical. Here is where I miss the MTF of a real ring USM lens.”
Bruce Gilling has posted some samples on Canon 70-300mm F/4.0-F/5.6 IS USM with Canon EOS 350D and commented:
“Well first thing is the weight it’s light and inconspicuous compared to my 70-200 L with its black finish, it feels very nice and it’s fast to focus, image stabilizion is excellent and the range is great 112mm to 480 mm on my xt rebel. Colours and sharpnesss are a not nice as my 70-200 f4 L but image stabilization and weight and extra range make it very attractive I am happy with it”