5DIII+24mmL+135mmL for wedding : seems good ! (and a question)

risbac,

my 2c FWIW. If you think you are having focus trouble with the 5d3 (which supposedly has an excellent indoor AF system at low EV). And you are charging someone to shoot their wedding images you have really no option but to use an additional light source / flash.

At minimum you should use the flash on your camera, using the AF assist beam, but disabling the flash head. This should improve your keeper rate.

Although you comment that you don't like flash for personal taste, and that your customers are happy. As other posters have pointed out, the art of using flash well is to make not obvious to the viewer of the image that it was used. That is not always easy to do for sure. In some cases it is better to get a correctly exposed image that is focussed correctly, than one that is not correctly exposed or out of focus.

By all means use natural light where possible (my preference also), but there comes a point when additional light is needed - and bouncing flash / off camera hand held etc etc can work nicely. In receptions i've shot, I still like to think that I can capture interesting images that clients are very happy with while using a flash - have a look at some of the sets at the link below if you want.

Good luck, and a bit of practice before the day with a flash may convert you.

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Cheers, Forbaz
http://www.flickr.com/photos/markforbes/collections/