Not all of sigmas lenses are made with a 4/3 mount - but some are - http://www.4-3system.com/modules/lenses/
Well, There are some producers of digital camera lenses in the world. But the most popular are: Tamron, Sigma, Canon, Nikkor (Nikon lenses), Pentax and Kenko.
Depending on your camera, lenses are available or not available. Nikon, Canon, Olympus etc., all have very good zoom lenses for their cameras. You will also find good lenses from Tamron, Sigma, and Tokina, that would suite your requirement. However, I am assuming that you have an SLR camera...
One of the fancier lenses in the world of SLR and digital SLR (DSLR)
canon and olympus are leaders in digital slr cameras and they have very wide range of lens options.
NO Nikkor lenses are compatible with all nikon slr's the DX lenses are for the digital camera's other wise there for the 35 mm NO Nikkor lenses are compatible with all nikon slr's the DX lenses are for the digital camera's other wise there for the 35 mm
The answer is no! Digital SLR cameras do not take videos.
Personally i say Olympus, some people may disagree but Olympus make great digital and SLR cameras
It depends on the model of the Olympus camera you are talking about. Olympus has its own versions of waterproof, point and shoot and Digital SLR cameras.
Generally, no. Each manufacturer has proprietary mounts for their lenses and, for example, Nikon lenses will not fit a Canon and so on. There are aftermarket lenses made to fit various cameras, but you need to specify the make and even sometimes the model of the camera in order to get a mount that fits.
The best brands for digital SLR cameras are: Epson, Canon, Casio, Axis, JVC, Java, Lenovo, Panasonic, Olympus, Medion, Nikon, Samsung, Sony, and Sanyo.
The best quality cases for a digital SLR camera are made by Loewepro, Case Logic and Olympus. These companies offer cases in a variety of sizes and fabrics.
Digital SLR referes to "digital single-lens reflex." This terminology is often used when speaking about cameras. Such cameras can allow the photographer to change lenses as he or she sees fit.