I owned 17-40 F4 L, Should I get 35mm or 50mm?

PaanJr wrote:

wow, now you got me thinking about 28mm F1.8... but it dont have the IS, does it makes a big different?

Remember, the 17-40 does not have image stabilization. In fact, IS is a bit more rare and a lot less necessary on wide angle lenses in general. If you follow the often-observed advise that, in order to avoid camera operator motion blur,  your minimum shutter speed should be 1/focal_length, then you can easily see why stabilization is more effective for longer lenses and less so for wide. For example, following this rule, a 200mm lens would require a minimum shutter speed of 1/200, while the 28mm would require only 1/30. In practical terms, just about any focal length under 50mm really doesn't benefit too greatly from stabilization. After all, stabilization is designed to counter the magnification of operator movement that comes with the magnification of the telephoto image.

In addition, the 28mm f1.8 is already about 2 1/2 stops or so brighter that your 17-40 f4. so you already have LOTS more light coming in. If you needed, for example, 1/30 second to shoot something at your zoom's maximum f4 aperture, the 28mm f1.8 would allow you to shoot the same thing at 1/180 or so. That's a pretty big difference!

I enjoy using the 85mm f1.8 sometimes. Beautiful bokeh, and wow, what a small, compact, lightweight, but solid-feeling lens! Although spoiled by image stabilization on my telephoto zooms, the much brighter aperture of the prime makes it a virtually a non-issue by comparison. And it's even LESS of an issue with 28mm.

Best of luck