Extenders (or Teleconverters!) Tips
As you probably realise by now, I’m a Canon user. A personal choice of course ( I’m not bashing their competitors here) - but once you’ve made a decision and invested in the kit then it’s not exactly an easy change. Anyway, I read a lot online where people give their views of Canon vs Sony vs Nikon etc etc and one area that seems to comes up often in the forums is people having mixed results with teleconverters/extenders - so I really wanted to give my own view here because this is an area which can of course be quite fraught with high expectation and poor results, often not the fault of the magical extender itself. Can a modest investment of a couple of hundred pounds really enable you to extend the focal range of your lens without a loss of quality? I picked up both of my extenders second hand with virtually no sign of use at all so clearly some people either buy them and don't use them, or they're unhappy with the result. The truth is, matched to good glass the results can be perfectly usable. Interestingly enough years ago Canon would package a matched 1.4x extender with their legendary 300mm 2.8fd mount lens (shame they don’t do it now) so that’s a good indication in itself as to how acceptable extenders actually are when matched with high quality glass - and in professional or capable hands extenders can and do help to get great images. So a few tips and myths busted as follows. These are just my views of course and just so you know my experience I use Canon’s 1.4x and 2x extenders quite regularly on 200 f2, 300 2.8, 400 2.8 and 24 TS-E (tilt shift) lenses and occasionally on others. Just because I'm hanging them on L series lens doesn't mean that they can't get good results on other ones though, it's really about your expectation of the results.
- A lot of the time it’s going to be better than digitally cropping your image (within reason). Don’t think that pulling a section from an image will ever be better, you’ll probably get more degradation by doing that. Compared side by side a slightly stopped down lens with an extender will produce a better result, but bear in mind the quality of your lens.
- Remember when you extend the focal length you need to increase your shutter speed because the longer reach will increase camera shake. I look at images where a photographer is unhappy with the result from an extender and I can see that camera shake is perhaps to blame.
- Remember to stop down at least a little bit. Even the best prime lenses aren’t as sharp wide open as when they’re stopped down. My 400 2.8l with a 1.4x extender has a minimum aperture of f4 so if sharpness is important I shoot it at f5.6. Experiment to find what works best.
- A 1.4x extender will have marginally less degradation than a 2x and only lose one stop. Remember if you’re photographing action that you’ll also find that the autofocus performance slows down a little.
- Some extenders need to be attached to the lens first, then the whole assembly goes onto the camera. Check the manufacturers instructions because it can make a difference to how the camera body autofocus and metering functions work.
- If you’re using good quality, fast lenses you’ll get some interference with the bokeh which I must admit I don’t always like. I try not to have a complex out of focus area behind my subject to avoid this.
The main point I’ll make is that if you’re a pixel peeper then you probably won’t be very happy. But if it’s about getting the shot and sharpness isn’t the number one priority then they’re good to have in the bag (or rattling around somewhere in the boot of the car). Don’t expect miracles if you’re using an extender with a consumer grade lens though (like the kit lens for example), even if it fits. You’re perhaps better off putting the money towards another, better lens in my opinion. Invest in good quality, fast glass and add the extenders later if you think you still need them. I'll post sometime about my favourite mid range lenses.
So those are my thoughts - they’re a handy thing to have in the bag and I’ve been glad I had at least one to hand on a few occasions (Amusingly and annoyingly Canon's 400 2.8 hard case has a couple of recesses for 1.4 and 2x extenders, which makes it stupidly long. I use one as a cup holder).
My usage is in a couple of areas - with the 400 2.8 I don’t always know where I’m going to be positioned for an equestrian event and if I can’t get close enough I’ll use it. With the 300 2.8 I’ll leave the 400 at home and just use the 300 with a 1.4x and the results are absolutely fine (same with the 200 f2 which does actually become a very respectable 280mm f2.8 with the 1.4x and is even sharp enough wide open). The 24mm TS-E is an interesting one, I don’t own a 45mm tilt shift so on the occasions where I need something to fill the gap then it works but it’s not brilliant and to be honest the mark 1 24mm TS-E isn’t exactly a stellar lens for sharpness anyway so it's a gap filler at best.
In summary - think of them as something that will get you closer to your subject once in a while with a trade off (depending on your main lens) of a tiny bit of sharpness. rather than relying on them all the time and expecting the same performance as your prime or main lens.
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