Upload & Sell: On
Jason Lang wrote:
Shoot with 7D, 50 1.4, 70-200 2.8, and 100-400. Looking for an ultra wide and am stuck between these two. 17-40 is about half the price... But my, albeit infrequent, night landscapes and star work may require faster glass. Opinions?
You bring up several considerations here: the question of the 17-40 versus the 16-35, the night photography question, and the issue of shooting cropped sensor with a plan to eventually move to full frame.
Regarding the two lenses you mention...
Both the 17-40 and the 16-35 are very fine lenses that are used to produce a lot of excellent photography. Either could be the better choice depending upon your needs. (Some make the false assumption that the 16-35 must be able to serve them better simply because it carries a higher price and has a larger maximum aperture. Maybe and maybe not.)
On full frame cameras, the 16-35mm f/2.8 can be an excellent choice if your main need is for an ultra-wide zoom for hand held shooting in low light at the largest apertures. Its chief virtues relate to the fact that it has f/2.8 and that it is better in the corners at f/4 than the 17-40. However, stopped down it provides no advantage over the 17-40.
On full frame cameras, the 17-40 is a great choice if you are most interested in a lens for ultra-wide shooting at smaller apertures and likely from the tripod - in other words, it is a fine lens for landscape and similar work. Stopped down it is the equal of the 16-35 and some suggest that it could be marginally (but, in reality, insignificantly) sharper stopped down and a bit less subject to flare.
About night photography...
If your approach to night photography is about the high ISO, biggest-possible-aperture, stop the stars and show the milky way thing, I can see why you might be interested in aperture. On the other hand, most night photography is not done that way, but instead simply lengthens the exposure time, uses apertures and ISOs similar to those used for daytime work, and relies on the tripod... and patience from the photographer as long exposures complete. Here, neither of these lenses has a significant advantage over the other. In fact, if you are pushing things to the point that you need to maximize aperture for this sort of thing, you might be wise to invest in a few inexpensive, large aperture primes. The difference between f/4 and f/2.8 isn't nearly as significant as getting, say, f/1.4.
On the idea that you will eventually get a full frame camera...
This comes up a lot when those who own cropped sensor cameras start looking at lenses. It is a tricky question. It brings up the question of whether there are lenses that will actually perform better for you than the L alternatives (and L lenses are not always the best choice), how soon you will really "switch," whether or not you will keep the cropped sensor body when you do, and how particular focal length ranges function on crop and full frame.
Neither 16mm or 17mm is "ultra-wide" on your cropped sensor camera. If you need ultra-wide, you will not have that if you buy either of these lenses for your fine 7D. What you will have is a wide to normal or short telephoto lens. If you don't need that and you do "need" ultra-wide, I wonder if it really makes sense to spend a lot of money right now for a lens that will not provide what you need.
True ultra-wide lenses are available for your 7D, including the highly regarded EFS 10-22 and third-party options. They [i[will give you the coverage that is your primary reason for your lens shopping.
If you don't really need ultra-wide, but are actually looking for a lens that goes no wider than about 17mm, then there are better options for your current camera than either of the L lenses. On virtually every count the Canon EFS 17-55mm f/2.8 IS lens provides better functionality and image quality on a cropped sensor camera than either of the L zooms. It provides a large focal length range, it gives you f/2.8, image quality is as good or arguably better, and it includes image stabilization. If you put red rings and the letter L on the 17-40, the 16-35, and the 17-55 and asked unbiased shooters to choose based purely on performance, the cropped sensor shooters would have to choose the EFS lens. (There is an argument that it doesn't have the "L build," but it is a very well built lens.)
This gets to that question of "buying gear for the camera I don't have." This can be a good idea in certain situations. For example, if a lens provides excellent functionality on both crop and FF, it is almost a no brainer as long as that functionality is what you need. Or, if you are certain that you will get a full frame camera very soon (say in a few months) and are in the process of getting the lenses it could make sense. However, it doesn't make sense if your intent is more of a deadline free hope, and you might find yourself shooting with the present camera for, say, a year or more. In that case it usually makes more sense to get the lens that is best for the camera that you do (and with which you'll be making photographs for the foreseeable future) than to get a lens that might be great for a camera you don't have and may not have for a long time.
I understand the economic argument for not investing in lenses that you might not use for a long time, but that may not be quite what it seems either. What will happen when and if you do get the full frame camera? Will you keep the cropped sensor body as a second/backup camera? If so, you'll still want your lenses for it, won't you? Or will you sell the 7D? If so, you can sell the lenses that you don't need along with the body or separately. Since everything in photography depreciates over time, you will get back less money than you spent - that is unavoidable. However, imagine that you "lost" $180 of the value of the lens over the course of a year - if you think of that as "rent," it cost you $15/month to use the lens. Is it worth $15/month to you to have the optimal lens for the camera you use to make your photographs - e.g. the equivalent of a few stops at Starbucks or a third of a tank of gas?
Good luck with your decisions.