So even though I have some good prime lenses, it's true that sometimes you just need a good Robert-Altman-pleasing zoom lens that maintains a constant aperture while zooming. I'm open to older manual lenses, so what's the best zoom lens that doesn't cost an arm and a leg but is the best combination of

-fast
-inexpensive
-sharp
-good zoom range

?

And while I'm at it, one that has an auto-focus fast enough to compete with video camera autofocusing? This is not essential since I'm used to doing everything manually, but I'm curious. All my prime lenses are useless for autofocusing while shooting video.

thanks!

You can't have all attributes, so pick the important ones. My son has the EF-S 15-85 IS, which is an excellent zoom lens (particularly when compared to the various kit zooms) with good IS and has a useful zoom range, but it is not fast.

I have the EF-S 17-55 f/2.8 IS, which is optically excellent, and fast, but it is not cheap. The build quality is so-so.

as always it depends, 15-85mm is good outdoors, indoors my choice is 17-55mm, or 70-200mm 2.8 IS it's really hard to find fast and inexpensive, but I'd love to :)

Though not quite what I'd consider fast, one of my favorite lenses is the 70-200 F4 L non-is. But it does meet your other requirements.
It's about $650. It's constant aperture so zooming during shooting works. It's got enough range to cover a wide variety of shots. It's very sharp. And it's light. Outdoors it's perfect and indoors, natural light requires a bump up of ISO but not to where it starts to affect quality. It can still get great bokeh at f4

The autofocus works great providing there's enough light. You can't do constant AF like a video camera so that's moot.
I have several L glass lenses and this is the one that seems to go on the camera much more than the others. The price and weight make it somewhat a hidden gem amongst all the IS lenses. I haven't missed the IS at all since when it gets called for video duty, it's on a tripod which means it should be shut off anyway.
My 2 cents!

Other than a pretty substantial difference in autofocus, which is worth nothing when shooting video, the differences in image quality and build quality between the canon 17-55 2.8 IS and the Tamron 17-50 2.8 IS are SO far from the difference in price. Ever since I got my Tamron it pretty much hasn't come off my camera. Occasionally when I need a lot of light I will use my 50 1.8 but its just so inconvenient using it indoors.

That Tamron actually sounds pretty much like what I was looking for, if the image quality is as good as you say it is... only thing, when I look it up on line, I find a huge price range from 600 bucks down to $350. Is this the correct lens:

Tamron | SP AF 17-50/2.8 Di II LD Aspherical IF Macro WidEAngle Telephoto Zoom Lens For Digital SLR Cameras (67mm) *FREE SHIPPING* | AF016P700 | Tri-State Camera, Video, and Computer (http://www.tristatecamera.com/lookat.php?refid=279&sku=TAMAF1750XRP*)

if so, i might just have to go down and grab it! thanks!

thank you for the other lens recommendations, everyone. I'd say the 70-200 F4 gives me more zoom than I'll ever need with less speed, and the other suggestions don't seem to offer that much more to make the price tag worth it. I think. I'm open to criticism of the Tamron...

The huge price range for Tamron 17-50 is due to two versions of the lens, one with VC (vibration control) one without. If you are filming a lot handheld, then VC is a must have. I think Tamron's VC is at least as effective as Canon's IS in non-L lenses, it makes image look like on a tripod.
One drawback of this lens is that both zoom and focus are opposite to Canon's directions.

What about the Canon EF-S 18-135mm IS? This lens came with my Canon 550D kit. I don't know but I find that it delivers an impressive image quality.

http://www.cameralabs.com/reviews/Canon_EF-S_18-135mm_IS/index.shtml

Stelios

There's nothing wrong with the Canon EF-S 18-135mm, but it isn't
what you'd call a fast lens. My suggestion would be the constant
aperture Canon EF-S 17-55mm f/2.8 -- it's just about the best lens
in the EF-S line in terms of quality vs. cost.

Chris
What is a "constant aperture" lens and where do you use it. Does it mean that you cannot change the aperture?

Stelios

Just means that during zooms the aperture remains where you set it. It is still adjustable. This is critical for video applications where you might zoom. If it's not, you will end up with flickering and odd fluctuations in light during the zoom.
Most camcorders don't have constant aperture lenses but they are designed to deal with zooms smoothly. The dslrs don't have that ability.

Thanks Robert for your prompt reply.

Gotta do something while i wait on renders! Ha ha!