Should I Buy A 17-40 L Lens For My 70d

What is the best day-to-day walk-around lens for a Canon crop body?

I find that I switch between several options, based on where I am and what my goals are.  When travelling, I use and 18mm-200mm.  I use Nikon, but Canon, Tamron, etc. all have lenses in that range, often now up to 300mm.  This allows me to capture the widest variety of shots as quickly and quietly as possible.  I don't hold up my fellow travelers (much), I get to spend most of my time being a tourist and I can carve out a reasonable travel log when I'm done.But when I'm at home, I do almost the opposite, most often carrying the 105mm macro lens.  The Nikon version has stunning clarity and I expect the same from the Canon version.  It is long enough to sneak portraits of people, but short enough that you can usual back up far enough in an enclosed space.  It can do 1-1 macro, so you can capture that bug or bee just by setting the camera down, holding up a handkerchief as a diffuser, maybe a piece of foil to redirect some sunlight for fill.  It lets me photograph nature inside suburbia.  It's not a zoom, but at home, on walks, I have the time to let my feet do the work.  I don't need a shot of this flower, that hummingbird, I see something happen, then I watch for it to happen again, finding the patterns, then I look for the right time/place to get the shot I want.  This works because nobody's paying me to shoot and I'm not trying to get particular shots.  I'm foraging for things that are new and interesting, previously overlooked by myself and others.

Is anyone using a Sigma 18-35 F1.8 lens for a Canon? How is it performing?

It’s a fantastic lens, beautifull colors, creamy bokeh, sharp…when you can get the thing to focus properly.The only downside to this lens is that autofocus misses quite often. Like others have said, you can get the sigma usb calibration dock and do some focus adjustments on the lens. But even with that it will miss focus. As a result this is not a good lens for shooing fast moving subjects. It is great for landscapes, street photography and for shooting video.Also, the lens is heavy compared to other lenses of similar focal length, you may want to hit the gym and build some upper body strength before purchasing the lens.

Which is the best lens for a Canon camera for a perfect sunset picture?

I guess the ideal upgrade lens for a Canon camera is the Sigma 18-35mm f/1.8 DC HSM. At 18mm it's wide enough for beautiful landscapes: The Top Canon Lenses You Need in Your BagIt is the f/1.8 aperture far superior to what most kit lenses offer, but this lens can essentially take the place of four prime lenses - an 18mm, a 24mm, a 35mm, and a 50mm. it has an internal zoom and focus design, there's no barrel extension, so this lens is compact for easy carrying.

Should I get Canon 16-35mm F4 or the F2.8 II? Or Sigma 18-35mm ART?

I normally only use wide angle lenses for outdoor landscape photographs, at which point you don't really need a fast lens like the 1.8 or 2.8, since you're probably on a tripod, and shooting in optimal lighting conditions. Also when shooting landscape, you don't want a shallow depth of field, so you're going to boot up the aperture to around 8, 11, 16, etc.Also the F4 comes with image stabilization, so you can compensate by having a slower shutter speed to get the same result as the F2.8 at a faster shutter speed.I may be biased to the F4, since its the only one of the 3 I've owned, but that was the justification in my head when i bought it. The F4 was about 400$ cheaper than the F2.8 II, and I know I could achieve the same results with it for what I needed.With that being said, if you choose to shoot things that are not in the ideal lighting conditions, than by all means go for the F2.8 or F1.8.

What is a decent low light lens (Canon DSLR) that is efficient for on-the-go handheld shots? I’d love a video lens recommendation as well.

The 50mm f/1.8 is notoriously noisy when autofocusing, it’s not just you. It shouldn’t be blurry though as long as you shoot stopped down a couple of notches (say f/4 or so). You don’t say what you are shooting but I’m going to guess it’s general purpose walking about shots. I’d suggest the following options:A new nifty-fifty. Your current one sounds like it might need adjusting, but the lens is so cheap, it’s probably a better bet to just buy a new one.A Sigma 17–50mm f/2.8. I love this lens. Love, love, love. It has a consistent aperture throughout the zoom range which makes it great for video and it’s relatively sharp when stopped down while producing some lovely creamy bokeh wide open. The lens is practically welded to my 70D. f/2.8 isn’t super fast but it’s usually enough unless it’s very dark. Autofocus can be a bit slow, especially on moving subjects but otherwise this is a very solid lens.Canon 50mm f/1.4. This is a lot better quality than the f/1.8. The money isn’t just going towards that extra half a stop. It’s exceptionally sharp even wide open and focuses like a dream.