24 December 2008

Stop the blurred pictures when manual focussing

You've bought a great new EOS camera, and it's got a great autofocus system, though sometimes you just need to focus manually. With the advent of Digital EOS the viewfinders of the cameras were shrunk since the sensors and mirrors also were downsized. This can make it harder to see the correct focus point when you have taken the plunge and 'gone on manual'.

EOS dioptre correctionIf you pictures look blurred in the viewfinder normally, but the camera seems to focus fine then most likely the viewfinder is not set correctly for your eyesight. You need to adjust the viewfinder dioptre correction. It's a bit like the camera needs to be tailored for you, just like glasses or contact lenses are optimised for you. you can find the dioptre correction knob next to the viewfinder. Normally the cameras have a range of +1 to -3 dioptre but you can get additional correction lenses if you need a bigger or smaller correction.

EOS dioptre correctionOn most models the dioptre is easy to locate, but some models, EOS-1D series in particular, it's necessary to remove the eyecup to get at the adjustment. This tends to make it less likely that the adjustment gets changed by accident, and also follows that most pros use the same camera all the time. Your EOS 450D - pictured - may get passed from one family member to the next and need regular changes of dioptre setting.
The dioptre adjustment control is the one circled in yellow.

How do you adjust this viewfinder dioptre setting?
One of the most sensible ways is to remove the lens and simply look through the viewfinder, you are looking at the focussing screen that the images are seen on. If this focussing screen and the various marks, AF points etc look sharp to you then that is a good starting place. You may find it necessary ot point the camera at a brightly lit area or subject to judge this all critically. Once set you could even gaffer tape the control in place if you like - and some do!

It's Christmas eve and no amount of dipotre correction can fix alcohol base focussing - have a good one.


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