Pick any one but not all three.

Assuming ownership of a 20d and a pretty good range of lenses and accessories... (and ignoring price differentials)

Which would you part with your pennies for?

Used Canon 1ds body

New Canon 1d MKII

500 or 600mm f4 IS _L_en$

New Canon 1d MKII thank you very much.

YiKeS

That's easy... a used 1Ds body!

Definitely the lens

It depends purely on what kind of photography you intend to do.

---Bob Gross---

3 more 20Ds

1D II, the 1Ds is like a really slow 1D II with a big sensor.

Then sell the 20D and buy a long peice of Glass. That is if you do sports, the 1D blows the 20D away, and the 1Ds is awsome in the studio.

If the 20D does what you need it for, then lens for sure.

I'd take the lens and trade it for a 400 2.8.

One for each eye

"Really slow"?!

Now come on. Must you always have to say something negative about everything I say?

Have you ever even seen, touched, or used a 1Ds before? I have, and it's anything but slow. Speed isn't everything.

Used 1Ds

Unless you need a backup, sell the 20D for the down-payment on the glass

Totally depends on what your needs are.

Do you find yourself needing longer glass much of the time?

Do you shoot relatively slow subjects but need to make huge prints?

Do you need a faster camera to capture fast objects or sports?

If you are happy with your 20D but are constantly wishing you could get closer to the action, go for the glass.

If you think your glass is sufficiently long and you want a faster pro level camera go for the MkII.

If you think your glass is sufficient but you constantly need those extra 4 mp, go for the 1Ds.

For me it would be between the mkII and the glass as I cannot see where the extra few mp would make the 1Ds worth it. But that is just me and I have been working with a regular 1D and find that 4mp can do an awful lot.

The reason I would take the 1Ds is NOT for the 11MPs, but because of the full frame sensor and the excellent BMW type build quality.

One of the big lenses!! The 20D is an excellent camera, and glass is where you should invest your money ... particularly if you intend to photograph wildlife. Now if sports is your interest, or if you need something that can handle extreme elements ... then I might recommend one of the 1D's.

I'll take a lens anyday, bodies upgrade and go...but good glass is always good glass.