I want to buy a professional camera like Nikon D300. I googled a lot but did not overcome the following dubs. 1) I want a high optical zooming camera. In DSRL specification no zooming is specified. My question is is there no zooming in DSLR?
2) Probably for better zooming I need to buy lenses. Is it right? Because the lens which comes which the camera (kit) is of low zooming capability.
As noted by @mattdm, part of your question is answered before:
But it seems that you don't have a good understanding of the whole concept. An advantage of a DSLR is that you can use it with many different lenses, there are lenses with high zoom ratio.
Photo: Photozone.de
Picture above is NIKKOR AF-S DX 18-300mm f/3.5-5.6G ED VR, it has the highest zoom ratio in Nikon lenses, that is 16.7x (300 / 18)
But there are other lenses, with more magnification and smaller zoom ratio. for example, NIKKOR AF-S NIKKOR 200-400mm f/4G ED VR II with only 2x zoom ratio is much longer than NIKKOR 18-300 (above) and more expensive.
Also some lenses come with a fixed focal lengths, such as the Nikkor 14mm f/2.8D AF ED which is wide lens on DX cameras or the recently announced NIKKOR 800mm f/5.6E AF-S FL ED VR which is the longest lens in the NIKKOR lineup. a prime lens has a fixed focal length and angle of view, and there is no zoom to play with.
To have a better understanding of different focal lengths, I suggest you to check this NIKKOR Lenses Simulator, there you can choose different lenses and bodies. as you may know, D300 is a DX camera, which means it has a cropped sensor, on the simulator you should choose DX body with either DX or FX lenses.
If you need a camera with high zoom ratio at an affordable price, take a look at Nikon COOLPIX P510 or its newer version, Nikon COOLPIX P520, they both offer 42x optical zoom, their lens is similar to a 24-1000mm lens in 35mm (FX) format cameras.
The camera just records images, it does not offer any sort of optical zoom, all of that is handled by the lens. This is actually good news as it means you can get the camera and choose different lenses for different situations.
The kit lens will offer approximately 3x zoom, starting at a fairly wide image, ending up zoomed in to a comfortable portrait field of view.
If you want more than this then you can get a super zoom lenses with up to 16x optical zoom.
For example: a 20-50mm lens can zoom 50/20 = 2.5X (equivalent of compact digital cameras)
It means that at 50mm, the image will be magnified 2.5 times comparing its size at 20mm.
A DSLR does not specify an optical zoom because it makes no sense to do so. The zoom is a property of the lens and not of the camera. There is an explanation on my blog.
Even though you can measure DSLR lenses in terms of optical zoom, this is rarely done because it says nothing of the field of view of the camera. A typical 18-55mm lens can be considered a 3X zoom but so can a 70-200mm lens and they give you very different views.
