I am Canon Fan/ user since 1954, My First Canon Camera = FT-QL, and until 1999, I have 6 more Canon Camera Bodies, And 7 Canon FD Lenses.
The Question that = The FD Lenses are worth to use with my EOS system with the Cheap Adapter( $ 35 US Dollars ) ?.
Yes, I have 24 Canon/ Sigma/ Tamron Lenses ( include 8 Canon " L " Lenses).
Thanks you, Sir.
Even though you got some answers, the no was not made quite obvious:
The FD lenses have a mount flange distance of 42mm, which is shorter than the mount distance of EOS with 44mm. That means, in order to put an FD lens on an EOS body, you need an adapter with a glass element in it so that infinity focus can be maintained. This adapter works a little like a teleconverter. These are the cheap adapters you can find on ebay. They are not high quality, if you use your FD lenses with them, an 50mm F1.4 wide open will have very poor quality. A link to a test by bob atkins is found here:http://photonius.wikispaces.com/Canon+FD+and+EF-S+adaptations
1) As pointed out, you can use an adapter without glass, which works fine for macro etc, so it's like using your macro lens in the good old all manual focus days.
2) Ed Mika: He makes adapters for some long FD lenses, which can focus past infinity, so it works. Ed Mika also makes conversion kits, i.e. you take your lens, remove the the FD mount, and put on an EOS mount. It works only with a select set of lenses. Links to Ed mika are found in the above link, but he posted also here.
3) EOS-M. The mirror less cameras have much shorter flange distance. The EOS-M for example is only 18mm. That means it's easy to make a glass-less tube adapter for FD lenses. So you can use them with no problem.
Consumer FD glass is hardly worth using, since inexpensive modern kit lenses, e.g. 18-55 IS etc., are probably better. But anything you can use with a simple glass-less adapter should work like in the old days. The more expensive lenses (L), macros, even the 50mm f1.4 should be fine.