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I'm looking into upgrading to a full format camera (mostly for pleasure and maybe some money on the side shooting weddings) and 5d seems to have the best price to performance ratio.

However, I see that a lot of reviewers mention that they use the L series lenses. For an amateur photographer the prices seem a bit steep as the fast ones go for well over $1000.

So my question is, is it even worth buying a 5d (or any other full frame camera for that matter) if i'm not willing to shell out thousands of dollars for the best lenses?
If you buy a body to do weddings you're planning on skimping on lenses, don't do weddings. This may sound mean, but I'm serious. If you want to shoot weddings you should have ATLEAST two bodies (you don't need 2 5Ds but atleast have a second Canon body), a wide angle, a telephoto, and a standard lens, all f/2.8 or faster, as well as a lighting kit (flashes, triggers, light stands, umbrellas). The one thing to remember about weddings is it's a once in a lifetime event (usually) and there are no redos.

There are some nice non-L lenses and third party lenses out there, but I sure hope you're not planning on showing up at a wedding with a 70-300 f/4-5.6 because a lens like that would be wholly inadequate to shoot your -victims'- customers' wedding. If you want to shoot weddings, you absolutely unequivocally need lenses that are f/2.8 or faster if you don't you will be unable to catch the important low light moments, it will be difficult to shoot candids during the reception, and you will not be able to use low depth of field to separate your subjects from the background effectively.

As far as the great non-L lenses are concerned:

The 50 f/1.4 is a great lens, the 85 f/1.8 is a great lens, the 35 f/2 is good and the Sigma 70-200 f/2.8 is good but not quite as good as the Canon version of this lens. If you decide to get just one L lens, a good one for a wedding shooter would be the 24-70 f/2.8.

The other thing I'll mention is EF-S lenses are incompatible with the full frame bodies.