F2.0 on G3/G5 Lens - How?

[partialresponse]

Could someone explain how smaller digicams like the Canon Powershot G series are able to achieve f-stops down to F2 with their tiny lenses, and yet at the same focal lengths, lenses for SLRs cannot do that unless they weigh 28 lbs.

Puzzled.

Kofi

[daveh]

Because they also have tiny sensors. Where you pay is in the noise from those tiny sensors.

[CyberDyneSystems]

It is true,. these lenses seem miraculous.

It is because the CCD is so much smaller than a 35 mm film back, you do not need to have as much diameter to get to the same ratio of light to film/CCD,.
Well this is misleading because it is really a matter of the actual focal length of the lenses that makes the difference. Althought the focal length in the G3 may be "equivilent to" a 35-105mm lens,... it is actually more like 8mm - 24mm. Thus a smaller relative opening is needed to acheive the given f stop in camparison to a lens that needs to cover a larger surface area.

[Stoneh]

is it also true that a F8 on a digicam is like a F16 on normal lense? i.e F4 is like F8 etc..

The reason I ask is that I am sure I read this in a magazine and my own tests prove this is the case.... On normal lenses the optimum sharpness is usually between F8-F11, on my G2 I get much sharper pictures using F4 than F8. Try it........