Digital cameras 101

[timinator]

Hi, SLR newbie here, trying to understand lens sizes. I see all these sizes: 24-70, 28-105, 55-200, 28-80 etc.
Can someone explain these dimensions or poin me to a link ?

Thanks
Tim

[Mike54]

Hi Tim,

The "dimensions" your asking about are actually the zoom range(s) of various lenses. In other words they are an indicator of the minimum and maximum focal length of the lens, usually designated in milimeters (mm).

[bdery]

Hi timinator,

just a few more notes. Just like with a point-and-shoot camera, you sometimes have to convert the focal length value of a lens to the standard "35 mm equivalent" . There is only one reason for this, and it's historical. But it does allow a convenient frame of reference to compare lenses.

For instance, my S2 has a 35mm equivalent of 36-432mm, but in fact the lens is a 6-72mm (6x correction factor). That's quite different. The Nikon D50 has a 1,5x conversion factor. That means that a 50-200mm lens will actually be a 75-300mm lens. Note also that some lenses are made specifically for digital cameras, and that sometimes there is no need for a conversion.

[Deb]

Hi, just thought I'd add .............

If you are doing telephoto work and your lens is standard (not DX or EF-S), then the conversion factor found with some digital SLRs is quite an advantage. In effect, you get more telephoto capability without having to invest in a more powerful lens.

If, however, you mostly do wide-angle work (deep landscapes, etc.), then the conversion factor is disadvantageous and you either would want to get a wider angle lens or a DX/EF-S version to achieve the same effect you would have gotten using the same lens on a standard SLR.

Whether or not to invest in DX or EF-S lenses or non-DX/EF-S lenses is the question. For example, in my case, I don't invest in DX lenses because I use my lenses on a variety of bodies both digital and film (with and without a conversion factor). Others really love their DX or EF-S lenses and get fantastic results on their digital SLR bodies.  

PS: "DX" is Nikon's designation for those lenses which are specially designed to compensate for certain digital SLRs with magnifaction factors (ie. DX format digital SLRs). Canon uses the designation "EF-S" for their lenses which fit their non-full frame digital SLRs (Digital Rebel).

[timinator]

I saw some great pictures of close ups of animals. The exif info said, focal length: 400mm. How do I know what type of lens that is?

Thanks

[Deb]

Unfortunately, this doesn't identify if it's a prime lens or a zoom lens. "400mm" is the focal length the image was shot at. Could be either type of lens.

You could try contacting the photographer and ask her/him.