Monday 20 July 2009

Focus Assist Points

Cameras these days are getting more advanced AF systems and along with that more and more AF points to allow you to compose your image without moving the camera-brilliant, But why use just the 1 AF point when you can use more, I don't mean having them all alight so that the camera grabs what it thinks you want, I mean use the AF assist points, My Nikon D3 and D300 have AF 51 points and i can choose to have 9,21 or 51 assist points to help the main AF point incase the main subject drifts off of the point of focus, I currently have my bird in flight set up using 21 assist points,What does this mean-well the centre focus point tends to be the most accurate and fastest so this grabs the subject first and tracks the subject,if you track a bird and the bird moves off of the centre AF point then the assist points jump in to help keep it in focus, On the Nikon this works very well even with a busy background, I didnt have the same confidence in the Canon 1D3 which grabbed the background at every available oppotunity, I think the last couple of firmware updates have helped with this, Whilst talking of the Canon 1D3/S bodies i feel Canon took a big step backwards when moving from the 45 points of the 1D2 to the 1D3 where they disabled the photographers ability to use all 45, Although there are 45 points some can only be used as assist points-come on Canon give the photographer the right to choose and not be told,I am sure it could be fixed with a firmware upgrade, Anyway back to Nikon-The D300 and D3 bodies have a 51 point 3D tracking where as the centre point works first and then ALL the points automatically track the subject where the AF points dances around the screen whilst keeping the subject in focus-very clever and great for birds in flight against a plain background but i am not sure about a buy one, Have a play with the assist points and find what one works for you, All i can say id that they have saved my bacon on many occasion and allow you to move the subject off of centre giving a better composition, The images below are all taken using the assist points where the main point is the centre one-all are full frame-not the best images in the world but show how without using assist points i would have ended up with an out of focus main subject


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