how come compact cameras offer large aperture?

Started Mar 12, 2013 | Discussions thread
MarkInSF Senior Member • Posts: 2,237
Re: It's a relative aperture

ARShutterbug wrote:

The part that you're missing is that the pocketable cameras have a lens that is very small, and usually a recording sensor that is small and returns lots of noise. A 6 mm f/2.8 lens is smaller than a 50 mm f/3.5 lens. It's the physical size of the aperture that matters.

Yes, if you look at apertures they are of the form f/x where f = the focal length.   An f/2 aperture on a lens with a smaller focal length is proportionally smaller than an f/2 aperture on a lens with a larger focal length.  Those apertures on small lenses that look larger are usually smaller, just not as much smaller as the focal length is.

An example.   A traditional standard prime for a full frame camera is 50mm.   An f/2. 8aperture is actually 50/2.8 or 17.8.   A standard lens on Micro 4/3, with the same fov as the 50mm we just looked at, has a focal length of 25.   Now let's say this lens has a much faster f/1.8 aperture.   The aperture is really 25/1.8 or 13.9.  Much smaller than 17.8, though f/1.8 looks much faster than f/2.8.

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