I’m in the market for a replacement for my Nikon 300mm f2.8 and the Canon 300mm f4 IS is one option - yes it’s a stop slower but Canon claim the image stabilisation gives a two stop advantage, and the big plus is that the Canon 300mm f4 IS weighs 1165g, a full 1800g less than my Nikon 300mm f2.8. If you’ve read that review you may well think I’m obsessed with the weight of these lenses - To an extent that’s true, but with good cause. In my world of travelling by air, and especially by helicopter, there are very strict limits on the weight of equipment you are allowed to carry and a 3KG lens uses a big chunk of that allowance, so any weight saving for the same performance would be great news. The Canon 300mm f4L IS is also very reasonably priced for it’s performance - it’s about a third of the cost of the Canon 300mm f2.8 IS.

In terms of finish and handling this is exactly what you would expect from a Canon L series lens - it’s a professional tool and is built to last, so absolutely no worries there. Optically the two questions that mattered to me were - how good is it at full aperture,  and how good is the IS - Long lenses tend to get used wide open far more than mid range lenses simply because, unless you can tripod mount them all the time, you need high shutter speeds to get a sharp image so unless the light is good enough to allow 1/2000th or better, shutter speed has more effect on image quality than aperture - most of the time I work from helicopters so tripod mounting isn’t an option.

Optical quality - This simply isn’t an issue with any Canon L series lens I’ve used and the Canon 300mm f4L IS is no exception - In fact both sharpness and resolution at full aperture are stunning. This is a very sharp lens with no sign of vignetting or CA - color fringing - even wide open.  In purely optical terms, whether or not to buy this lens is a real no brainer. That takes us on to the next part of the test which is how good is the image stabilisation system? This has two modes - one to stabilise all shake and one to allow panning in the horizontal plane. Canon claim a two stop gain in stability using this lens - in effect that means that instead of my normal limit of 1/500th of a second with this long a lens, I should be able to hand hold at 1/125 second and get the same 90-95% sharp hit rate. Based on the tests I shot at Photokina I’d say that the advantage is a little over a stop.

Results at 1/400 and 1/200 were all absolutely sharp but by 1/100 the edge had gone and I wouldn’t rate any of my test frames at 1/50 second as useable. Still the ability to hand hold a 300mm lens at 1/200 of a second and virtually guarantee sharp results is a very worthwhile gain. That coupled with a superb optical performance make the Canon EF 300mm f4L IS USM high on my shopping list and yes the image stabilisation system really does help turn this lens into a viable  300mm f2.8 equivalent in normal use.

Now, what I want to know next is - does it work with the intense high frequency vibration found in helicopters? Guess I’ll have to buy one to find out.

Update:  Since making this test I have indeed bought a Canon 300mm f4 L IS and although optically it is superb, the image stabilisation is no help at all shooting from helicopters, and in normal hand held situations is only good for about 1 stop. More modern Canon lenses seem to have more effective systems, giving in some cases up to 3 stops of an advantage. The Canon 300mm f4L is still a great lens though.

photo courtesy of Canon