Lens Specifiaction - Quick Questions

[aby]

Normally a lens has its specs written as
35-80mm f/4.0-5.6 or
50mm f/2.0 Lens
How does this translate in terms of Focus, Zoom, Aperture etc.

Also, in the digital world, we get 3x, 4x zoom. How do we convert from 'mm' zoom to 'x' zoom.

Thanks.

 

[Soulreaver]

35-80mm f/4.0-5.6
X zoom 80/35 = 2.2X ( about)
Minimum aperture is 4.0 at 35mm and 5-6 at 80mm ( dark lens)
No relation to focus

50mm f/2.0
X zomm - Not a zoom lens, this one is fixed length.
minimum aperture 2.0 .50mm generally are 1.4 or 1.8

 

[Big Mike]

The "#X" is a measure of the zoom range. 20mm to 60mm would be 3x zoom. 20mm-80mm would be 4x zoom.

Also, in the digital world, we get 3x, 4x zoom. How do we convert from 'mm' zoom to 'x' zoom.

It's different for each camera. Check www.dpreview.com for specs on most digital cameras. They will list the zoom of a camera and give you what the equivalent would be on a 35mm camera.

 

[Unimaxium]

35-80mm f/4.0-5.6
X zoom 80/35 = 2.2X ( about)
Minimum aperture is 4.0 at 35mm and 5-6 at 80mm ( dark lens)
No relation to focus

50mm f/2.0
X zomm - Not a zoom lens, this one is fixed length.
minimum aperture 2.0 .50mm generally are 1.4 or 1.8

You mean maximum aperture...the smaller the number, the larger the aperture. Just a small correction

And for the original subject... in terms of x zoom,that's not a digital thing, that's a point-and-shoot thing. When you get into cameras with interchangable lenses (digital or film), the focal lengths (mm) of the lenses become important because that tells you how wide the field of view is (when you talk about zoom all that tells you is the comparison of the widest field of view of the lens to the narrowest field of view... for example a 2x zoom means the widest FOV is 2x wider than the narrowest FOV). But if you have a prime (fixed focal length) lens, the zoom would be 0x, since it doesn't zoom, but still a 100mm prime will have a narrower FOV than a 50mm.