What is the difference between...

A 70-200 f/2.8 IS lens and a 70-200 f/4 L USM lens?

1 stop?

airfrogusmc wrote in post #6045445
1 stop?

Huh? I'm new to photography... so you're going to have to explain this like you would to a first grader.

And the f/2.8 version has "IS" = Image Stabilization whch allows you to shoot at lower shutter speeds than might otherwise be attainable.

The 70-200 f/2.8 IS has a larger lens opening, so lets in more light (which is measured in f/stops). f/2.8 is 1 stop faster (larger) than f/4. It's also got Image Stabilization, essentially gyro stabilization so you can hand-hold it at slower shutter speeds with less problem from your shakiness.

BoxandJamaica wrote in post #6045429
A 70-200 f/2.8 IS lens and a 70-200 f/4 L USM lens?

About US$900

FlyingPhotog wrote in post #6045456
And the f/2.8 version has "IS" = Image Stabilization whch allows you to shoot at lower shutter speeds than might otherwise be attainable.

... shoot handheld...

Also, you can get the f/2.8 version without IS, or the f/4 version WITH IS. The IS in the f/4 version is better than the IS in the f/2.8 version, and it's slightly better optically, though you probably wouldn't see much of a difference in day to day use.

The 2.8 version is heavier but gives you a shutter speed twice as fast as the f/4 version.

One stop means that, with the 70-200 2.8, you could shoot a low-light photo at f2.8 and 1/200th of a second. With the 70-200 f4 you'd have to shoot at f4 and 1/100th of a second shutter speed...and run the risk of blurring your photos because of camera shake.

The Image Stabilization on the 2.8 helps eliminate some camera shake when you're hand-holding the camera (and aren't using a monopod or tripod). IS, however, does not stop motion on the subject (a running person for example). That's still up to a combination of shutter speed and aperature, and proper handling of the camera and lens.

The 70-200 2.8 is a heavier lens than the 70-200 f4, and the 2.8 lens is quite a bit more expensive than the f4 ($1625 for the 2.8 and $600 for the f4).

I bought a used 70-200 f4 recently and will be seeing how it performs along the sideline for High School football this Fall. The field is very well lit, so I don't anticipate any real issues. For Winter sports (basketball, wrestling, and volleyball) I'm going to try the F4, but figure, even with a well lit gymnasium, I may be stretching the F4's capabilities.

If that's the case, I'll just revert back to my 85 1.8, a darn near perfect lens for basketball.

BTW, I'm shooting with a Canon XT with a battery grip, so I'm limited to 1600 ASA (another adjustment you need to consider when comparing the 2.8 and 4.0 70-200 lenses).