They're a bit past due for a refresh. Namely the 24 f/2.8 and the 35 f/2. What would be prefered USM versions positioned between the current models and the L ala the 50 f/1.8, 1.4, 1.2 options. That way there's still a small, light $200-350 option for those who want it. Improvements to the 20 and 28 USM and AFD versions are also welcome.
While we're at it I wouldn't mind a 20mm L in the f/1.4-1.8 range. With that on a 5D Mk II or 1Ds Mk III I could crop the images to a 16MP square and it would be like shooting 6x6 with the old Hassy 50.
Tangentially related something along the lines of Nikons 35mm DX lens would also make sense. I'm not an APS-C shooter myself, but if I was I'd really want a 30-35mm prime on par with the 50f/1.4 It's a bit much to pay for the 35L (and carry the extra weight) when a quality lens with reasonably fast aperture could be made lighter for cheaper if it was only throwing an image circle for an APS-C sensor. My guess is Canon is watching to see how well Nikon's 35mm DX sells to see if it would be worth the investment in R&D and manufacturing setup costs.
-300 f/2.8 is golden doesn't need to be touched.
-The 4 70-200 lenses are amazing, no refresh needed.
-24-70 f/2.8L would be nice with IS and some minor optical improvements, but I'd hate to see them stretch the lens on either size of range if it costs IQ.
-The 85L weighs enough and is large enough as is without IS.
-IS on anything 50mm or wider is not nearly as beneficial as it is on long lenses so I really don't want it on wide to normal lenses as I can hand hold pretty slow shutter speeds.
-The current 50mm line up is pretty good with the 50 Macro being the worst of the bunch, which isn't that bad.
-Love the 85 f/1.8 optically, just put a proper bayonet on it to fix the hood.
-I'd love to see Canon bring back the 50 f/1.0L (or even a 0.95) but I'll be honest and say it wouldn't be the first thing on my list to buy, but it would be nice to know it was there if I wanted to rent it for something (especially for video uses)
-For some strange psychological reason I never liked the 28mm length, so I really don't care about the possibility of a 28mm L.
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~Kurt