How do I get the 300d to constantly autofocus in Tv mode?

I think what you're experiencing is exactly the reason a lot of people find the Drebel unacceptable for fast action sports shots. It doesn't have AI Servo funcationality outside of the sports mode, so you can't use it in any other mode.

So basically, if you want to have that functionality, go back to sports mode... otherwise just try to focus on something at a similar distance or use some manual focusing.

Let me ask the obvious rhetorical question.

What is wrong with sports mode for a sports subject?

---Bob Gross---

Sports mode.... so that is what I should have used....

ok, will try it next time on a sports even.... or just point my camera on the highway, taking shots of fast moving cagers....

Nothing, except if BikerFox wants raw instead of jpg files or wants a higher ISO than 400.

the AI Servo which is in 10D can be enabled for 300D series, what you have to do is just upgrade your firmware (unofficial one) and it'll activate lots of hidden features.
I can't give you the link but you can find it easily by entering Canon 300D firmware on Google.
Enjoy.

The problem with sports mode on the 300D is it tends to choose very fast shutter speeds. It's no good for if you are panning and want to show some movement in a car's wheels for example. I use Tv mode for motorsport but have to put up with the auto focussing limitations. My friend shoots with a 10D using the same settings but using AI servo and I think we end up with the same amount of badly focussed rejects.

I have the firmware hack for the 300D , but i can't actually make the photo when shooting in A1 Servo mode. He does focus , but does'nt make the photo .....

300D heck

Here you go.

Do so at your own risk.

http://satinfo.narod.r​u/en/index.html

I have not upgraded mine yet....

BikerFox wrote:
OH MY! I had no idea. that really SUCKS!

The reason I don't use sports mode is it's too "automatic." I'll be shooting a boxing match this weekend which requires a VERY fast shutter speed (at least 1250) and iso of 800 or so. I just bought the 50mm 1.4 for this purpose. I can't believe there's no way to continually autofocus on the 300d. I plan on upgrading to the 20d soon, does it have that feature?

I'll check into the firmware, thanks.

Yes, the 20D has this feature. It also has a feature called AI Focus that I usually keep mine in for general purposes- basically what this does it uses the standard focus for still subjects, but once it notices the subject start moving, it starts automatically refocusing like in AI Servo.
For your purpose, I'd probably stay in AI Servo since things are moving fairly constantly.
The 20D also has a faster frame rate than the 300D, so you can get more shots in when you're shooting. It's a great camera, and I've really seen the 300D's limitations when comparing my friend's Drebel with my 20D

"Obvious rhetorical question" = sarcastic

Yeah, I totally understand- I don't use sports mode on my 20D very much myself for similar reasons. With the 20D you can use AI Servo in any of the Creative Modes, I think... I don't have my 20D with me at the moment to verify that, though.

No problem, good luck getting some good shots with the 300D, though.. I'd be interested to see what you get.

Edit:
I'll leave it to the 300D owners to answer your edited in question.... I don't own one so I don't know about the hacks available for it or how they work.