I have been looking at lenses - This lens does not have Image stablization. The Picures I have taken so far are pretty good. But seeing other lenses RF have IS. I see other lenses with f/4.has IS.
My question is the lens being f/2.8 not need IS becasue it is a faster lens when compared to the f/4 versioon?
Lens stabilization helps when you need to use a shutter speed that is low enough that camera shake becomes an issue. The general rule of thumb is that most people can hand hold a camera steady enough when the shutter speed is at or faster than the reciprocal of the focal length or around 1/30 second or faster shutter speed with a 16-35 lens.
If you are very steady you can hand hold it at a slower shutter speed and if you can steady it against something, then you can hand hold at a significantly slower shutter speed.
1/30 is slow enough that it isn't going to be useful for freezing animal or people motion so if you are mostly after action, camera shake blur without IS won't be a concern. BUT if you are shooting landscape or other stills where you can use slow shutter speed without fear of subject motion then IS can help. But in general, IS becomes more helpful when you start getting into the telephoto range and this is why IS is often found on those longer focal lengths. For example the popular 70-200 would need somewhere around a minimum 1/200 shutter speed at the tele end for the average person to avoid blur from camera shake.
With a f2.8 lens you can achieve the same exposure level at twice the shutter speed of a f4 lens so it does become more useful for narrow aperture lens also.
If you are primarily shooting action, you won't find as much use for IS. All of my long Canon primes have IS but I almost never use that capability because the shutter speed I am using to freeze action makes blur from camera shake a non-issue.
And one additional bit of info: the old 1/focal length rule of thumb works less well as camera resolution increases. I can generally get away with slightly violating this rule with my 20 MP 1DX series bodies but with my 5DS and 5DS R I have found that blur due to camera shake seems much more evident with these high MP sensors. And it isn't just from the smaller body size compared to a 1 series because I added the battery grip to the 5DS R and it really makes no difference in the blur/shutter speed issue although it does make the camera far more comfortable to me when using big glass.
IS is not cheap, so price is certainly an issue. I suspect it is also a matter of the limited benefit IS would bring to a WA or UWA lens. It also adds weight to a lens. It's cheaper to build IS in the camera body and it seems that is becoming more common.