Sony alpha DSLR-A100 10.2 Mega with Sony 18-200mm lens
I want to know how to judge a camera based on mm. I need a camera with a really good zoom. a decent all in one zoom lens ..... i'm planning to get one for myself .... the mm means millimeter .....and it's the unit used in measuring lenses focal length.
Many digital SLRs have sensors smaller than the sensitive area of 35mm film. Typically the sensor diagonal is 1.5 times smaller than the diagonal of 35mm film.
As a consequence, a sensor smaller than a 35mm film frame captures only the middle portion of the information projected by the lens into the 35mm film frame area, resulting in a "cropped field of view". A 35mm film camera would require a lens with a longer focal length to achieve the same field of view. Hence the term Focal Length Multiplier (FLM).
so.... depend on the above ur lens is ((18x1.5)-(200x1.5))=27-300 mm((35mm equiv.)).
if u want to know the zooming strength of the lens simply ((200/18=11.1x)) ...but this equation is used with the compact digicams with fixed lens not with digital SLRs...
anyway .... ur lens is very good and it will be ur all the time basic shooting lens ((no need for changing the lenses and cosequently exposing ur camera to dust and dirts)) and also u will feel the freedom of carrying one lens rather than an extra lens or 2 in ur bag.
but if u r planning to be a serious photographer u will need another more dedicated and may be faster lens for the category u r planning to start shooting in .
but for starting it's a decent choice. The 18-200 lens is a pretty good range. In a 35 mm equivalent, it would be 27-300 mm. 300 mm would be called a 6-power telescope. (Do not confuse this with "6X zoom" as used in point and shoot cameras.) You will be able to take pretty good sized pictures without getting really close to your subject.
I have just uploaded a sample picture to my Flickr site to show the difference in some common focal lengths.
See "Focal Lengths"
This is NOT a lens test or a camera test! It is merely intended to show the difference between various focal lengths. The camera was a Nikon D200 and the lens was the Nikon 18-200 VR lens. There is further explanation on the image itself. It would help is you click on "All Sizes" above the image.
http://www.flickr.com/photos/7189769@N04... It would be the same as 27-300mm on a 35mm film camera. Check out this website for samples.
http://www.paragon-press.com/lens/lencha... The mm (milimeter) rating of a lens is it's focal length. That is, the distance from the the image sensor (or film) that is the point of focus. With a little reading about lens optics and physics, you'll see what it means when a lens has a focal length of 18mm or 200mm.
As a photographer wanting to make pictures, you're likely more interested in what the lens can do for you than what all the numbers mean.
You say you need a camera "with a really good zoom." That leaves a lot to interpretation. Are you making pictures of people at a party, birds in trees, sports in a stadium, exotic wildlife in Africa? Do you need wide angles, telephotos, or both?
You can't really judge a camera based on the focal length of the lens. A lens for one purpose could be useless for another purpose. A 100mm lens with a f/2 aperture could be considered much better than a 200mm lens with a f/5.6 aperture. There's more to lenses than just milimeters.
You can imagine the focal length of a lens using the following trick. Make a circle with your finger and thumb. Hold your hand18mm from your eye. That's roughly the field-of-view from an 18mm lens. Now hold your hand 200mm from your eye. The field of view you can see through your finger and thumb is a lot narrower. Imagine taking a picture that is of everything inside that narrow field of view. That's roughly what the picture would be with a 200mm lens.
If you are unsure if a camera or lens is right for you, I recommend renting one for a week and giving it a try.
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Disclosure: I am the owner of www.lenslenders.com lens rentals in Canada. | 