Tuesday 10 March 2009

Gear we use and abuse-Extenders

To get a little closer to our subjects and to give some flexibility when using primes i use extenders, I use the Nikon 1.4x and 1.7x, They do make a 2x but i havent read many good things about them, Like the Canon 2x you either get on with it or you dont, All extenders will affect image quality as you are putting extra glass for the light to get through, 1.4x extenders have little effect on IQ and used correctly the 2x can give very good results,Firstly lets get something straight-They are not a cheap alternative to getting a cheap long lens so dont rush out and buy one for your budget 75-300 thinking you will get a good cheap 600mm lens,They are designed for top end lenses-Fast primes in particular but will also work very well on fast zooms like the Nikon 200-400, They do have an effect on your shutter speed, A 1.4x will take 1 stop of light away so instead of getting 1/250 you will get 1/125, A 2x will take 2 stops so instead of 1/250 you will get 1/60-a big difference,The Nikon 1.7x takes 1.5 stops of light, If you think you need good long lens technique with a 500mm lens then it needs to be doubly good when used with a 2x-only the biggest best tripod or ideally a beanbag will give good results with extreme focal lengths,Another thing to think about when using one is that the view finder will get slightly darker as the light fights its way through the extra glass and that 2 stops of light from the 2x will make your F4 lens an F8 lens and the 1.4x will make the F4 lens a F5.6 lens,This means that you will need good light and may need to increase your ISO to compensate for the slower shutter speed, To get the best IQ i would advise not to shoot wide open,This is not such a problem with the 1.4x but a 2x needs at least an extra stop down to bring good results,On my old 500mm F4 lens when using a 2x i would set the aperture to F11, This i found gave very good results in good light, Most people i know don't like the 2x and complain that results from it are rubbish-its all down to set up and technique, I would advise to only use an extender when you need to and only on the best lenses,
To show the difference they make here are 3 images-The first with a 600 only, To its right is a 600+1.4x and below the 600+1.7x,The good thing about extenders is that they do not affect the minimum focusing distance


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