Is 200% the same as twofold and 300% the same as threefold?

Canon 70-200 or 70-300 ?

• Im considering either the Canon 70-200 F4 L lens or the Canon 70-300 F4-5.6 IS USM. The 70-200 is £500. The 70-300 is £350. I am leaning towards the 70-300 because of the USM and IS, the USM would be really handy on a shoot, and the IS would come in handy just to help steady the shot abit, But the downside is that at the 300 end the max aperture i could use is f5.6. This lens also has 3 stop IS, so it'll be good in low light. And the 70-200, would be good because, well, basically it's an L lens. And i'm not sure if the 70-200 L lens would outweigh the features on the 70-300. I would mainly use the lens for portraiture, but could and would, use it for many other things like sports and airshows. But, again, with sports you need a low aperture to be able to give a good bokeh effect and a low aperture means higher shutter speed, better for sports .. I'm using a 550D. Thanks in advance, just like some of your opinions.

• Answer:

  I'd say the 70-200mm would be more suitable for portraiture where you're more likely to be working at around 80-100mm. It'll offer better quality too, as you say, and it has a faster aperture. But for sports and airshows, you really need a longer reach in my opinion. I've shot various sports with a 70-300mm and often found that I want a longer focal length. Not to mention that using a zoom lens at either of its extremes usually won't offer maximum quality. So now I have a 400mm prime which is significantly better than the 70-300mm at 300mm. The fast aperture isn't necessarily a must for sport use. If you are shooting outdoor sports in daylight, you can get away with it easily, and in fact I often stop down to f/8 or more so secure a deeper depth of field, so you are more likely to get sharp pictures. If you're wanting to use this for indoor or winter sports, you might need the faster aperture. I would start with the 70-200mm because you can't go wrong with L glass. If you find you need more reach, you could get a 1.4x or 2x teleconverter. A 70-200mm with a teleconverter would almost certainly still be better than the 70-300mm. Have fun!