HELP! Is the "image stabilizer" canon lens really necessary?

tripod for your telephoto shots, it's probably not worth it. If you aren't, it probably is. The problem is camera shake. It's simply not possible to hold a camera without a slight shake. This is not noticed at short distances, but, at telephoto distances, it tends to blur the shot. One way to avoid seeing this blur is to use a faster shutter speed, but that means you need more light. If you don't have the light, you can't use the faster speed. Thus, the measurement that it's worth 1 - 2 f stops. It won't stop all of the blur, but it will reduce it.

To me, Image Stabilizer Lense will be helpful when I take the picture in the sport mode ( shooting fast action pictures that require high shutter priority). Only few occasions in a year is likely to happen. That kind of shooting are mostly for pros and require the lenses, perhaps, over 300mm focal length. In additions, I'd hug the camera up with my tripod to avoid the undesired outcomes when taking the photos at that speed. My collegues told me that some old Canon IS lenses don't last long despite some defect inside magnetic machanics. I'm not sure whether the manufacturer has corrected that. Canon IS lense is not necessary unless you want to turn pros. Good luck.