What is a "Full Frame Lens"?

I have seen lenses described as full frame, why?

Isn't full frame determined by the sensor size of the camera body?

For example "Tamron Announces Development of Full Frame 15-30mm f/2.8 VC

As long as it is an EF mount couldn't I use the above lens on my crop body 50D?

tekin112000 wrote in post #17149953
I have seen lenses described as full frame, why?

Isn't full frame determined by the sensor size of the camera body?

For example "Tamron Announces Development of Full Frame 15-30mm f/2.8 VC
As long as it is an EF mount couldn't I use this lens on my crop body 50D?

The point in specifying that it is a "full frame lens" is so people know that it will indeed work on a full frame camera. IIRC APS-C lenses from third party manufacturers use the EF mount rather than the EF-S mount, which could explain why they feel the need to spell it out.

tekin112000 wrote in post #17149953
As long as it is an EF mount couldn't I use the above lens on my crop body 50D?

Yes, but the other way, an EF-S lens on a full frame camera body can create issues, some even major damage. So you have to be careful in that regard. Generally speaking, most 3rd party lenses for cropped format bodies will physically mount on a full frame body but you can experience issues like vignetting under some circumstances.

I think a lot of it has to do with 15-30 being an odd focal range. They just wanted to clarify that the lens will work on both formats.