You don't mention your experience level nor the type of photography that you want to do. So my response is based on the following assumptions:
1. You don't currently own a DSLR or you would already have strong opinions.
2. You only mention travel so I assume you want to include scenery, city landscapes, people and possibly wildlife.
3. Occasional low light photography (evening, night, indoor...)
Hello,
I am hoping to buy a body and 1 or 2 (max) lenses. I don't want anything heavy or big because i travel a lot.
If weight is important to you, the items at the top of the list many would consider to be heavy. The 5D and 7D are significantly heavier than the 60D or T3i. Heavy is subjective and you should go to a camera shop and pick them up. It is the only way to know what is heavy for you. Also the L glass takes beautiful pictures and are built to take the abuse of heavy duty use. Because of that it is heavier.
Which of these would make the best combination in terms of image quality and general usability?
Image quality: 5D and L glass is going to be hard to beat.
General usability: Hard to beat the versatility of a zoom lens.
I want to carry the body and lenses around as i travel.
While outside in the elements, I try to minimize the number of lens changes that I make to avoid introducing dust to the internals of the camera. A light weight camera and Lens and a wide range zoom make for a good walk about system.
Canon 5D Mark II + Canon 50mm f/1.4 = $2,888
Canon 7D + Canon 35mm f/1.4L = $3,078
Great for portrait work. I like a wider lens for indoor and landscapes.
Canon 7D + Sigma 30mm f/1.4 + Canon 17-55mm f/2.8 IS USM = $3,187
The 17-55 is such a good lens, the 30mm 1.4 is going to give you shallower dof but only slight increase in IQ.
Canon 60D + Sigma 30mm f/1.4 + Canon 17-55mm f/2.8 IS USM = $2,587
Canon T3i (600D) + Canon 17-55mm f/2.8 IS + Sigma 30mm f/1.4 = $2,312
These have the same sensor as the 7D but are both lighter. The differences between these cameras are in features (e.g. Focus, Processor, FPS, LCD....). The light body and heavy lens might not be a good balance. You need to pick one up in the store and judge for yourself.
Also, how does the Sigma 30mm f/1.4 perform on a Full Frame camera? Would it be a viable alternative to 50mm f/1.4 on FF, 35mm f/1.4 on Crop?
Here is a handy site to compare lenses.
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=398&Sample=0&FLI=0&API=0&LensComp=678&CameraComp=474&SampleComp=0&FLIComp=2&APIComp=1
Any help and suggestions much appreciated (alternate combinations also). $ is USD.
For travel and versatility I would go lighter. The 60D or T3i. For the very slight increase in price, I would pick the 60D over the T3i. Better shutter and more features.
The lenses you list will all work with the 60D. If, as I have assumed, you are relatively inexperienced with DSLRs, you might want to consider the 18-135 kit lens. Now, before too many forum regulars go ballistic this lens, it is a good walkabout lens, well matched to the 60D body. Also, as a kit lens, you get a $500 lens for a $300 increase in price over the body only. Last I checked you can get this kit for $1,200. I recommend adding a good external flash to the mix especially since the 60D can control the external flash remotely.
Once you get comfortable with the camera and the type of pictures you take the most, you can choose a lens. The picture meta-data will record the focal length and you can determine if a fixed 35 or 50 mm will be a good match for you.
If you are confident that the 17-55 f2.8 will fill your needs, and the increase in price doesn't phase you, go for it. consider the external flash before buying the prime lens.
