OVERVIEW

Perhaps “compact telephoto” is over-statement, but in the world of the big-white Canon L lenses, the Canon 70-300mm F4-5.6 L IS is compact. On our past vacations the Canon 70-200mm F4 L IS had been the de-facto telephoto zoom lens. The 70-200L F4 L IS is an outstanding lens, producing sharp images, nice contrast and rich colors. Though, the F4 aperture is a bit slow, and producing highly blurred bokeh is tricky. With the 70-300mm F4-5.6 L IS, I had hoped that Canon re-used the 70-200mm F4 design and just added some extra reach at the tele end - in other words, the Volume Knob goes to ’11’.

Technically, the 70-200mm F4 L IS is a bit more exotic in its element composition than its 70-300mm F4-5.6 L IS cousin. The 70-200mm F4 L IS combines 1 artificial fluorite element with 2 UD (Ultra-low Dispersion) elements to help achieve images free of secondary spectrum aberrations. The 70-200mm F4 L IS’ aperture diaphragm is circular, to help create very natural out-of-focus background highlights. The 70-300mm F4-5.6 L IS has much of the same DNA. But surprisingly it was one LESS element than the 70-200mm F4 L IS; the 70-300L has 19 elements, while the 70-200L F4 IS has 20 elements. Sadly, the 70-300L also lost the artificial fluorite element.

According to Canon, the use of two “ultra low dispersion” (UD) glass elements provides the same benefit as using one fluorite element. Fluorite elements are used to reduce (or eliminate) chromatic aberrations. Fluorite glass is expensive to manufacture, so UD elements are used in its place. UD glass provides the same benefits, but is cheaper to manufacture. The 70-300mm F4-5.6 L IS has two UD elements, which is one more than 70-300mm F4-5.6 IS (non-L) consumer-grade lens. That is a complicated way to say that the 70-300mm F4-5.6L IS is probably not quite as good of the 70-200mm F4 L IS, but better than the 70-300mm F4-5.6 IS. 

The Canon 70-300L does have a couple other tricks up it sleeves, such as 3 aspherical elements and floating element system and circular aperture blades.

BUILD QUALITY

The first thing I noticed was the 70-300L’s girth - it is clearly fatter than the 70-200mm F4 L IS. The 70-200mm F4 L IS is a long, skinny lens. The 70-200L F4 IS looks out of proportion with the 1Ds Mark III. Whereas the 70-300L is a manly looking lens and its proportions balance nicely with the 1Ds Mark III size. Aesthetics really should not matter, but if spending $1500, I want to know that I bought something substantial - and the 70-300L is a substantial lens. The lens is bigger than expected. For some reason I had it stuck in my head that the lens was about the same as the Canon 24-105mm F4 L IS. The 70-300L is about 1 inch longer, so similar, but noticeably longer. But the 70-300L is indeed compact. Compared to the 70-200mm F2.8 L IS II, the 70-300L is about an inch shorter and almost half the weight. The 70-300L is a tad heavy as a travel lens, but compared to the 70-200L F2.8 L IS II, the 70-300L is a big, big improvement (in terms of weight). The 70-200mm F4. L IS is the lightest of the bunch, but its lack of reach always left me wanting for more during vacations.

The lens barrel construction is a mix of metal and durable plastic - presumably some type of polycarbonate. The barrel appears to be mostly metal and the focus ring sections are plastic. The lens feel solid with no wobble or play in its construction. The lens barrel is finished with Canon’s standard off-white paint with a slightly dimpled texture. In my experience this finish holds up well and resists scratches and marks. Canon uses white paint to reduce heat absorption when used in sunlight.