The Canon G1X Mark III: Neither fish nor fowl

spider-mario wrote:

Twitchly wrote:

It has a large, capable sensor but to take full advantage of it in low light you need to avoid zooming.

Actually, that’s a common misconception. If you do not move closer to the subject (which would change the perspective and may not be desirable or possible), then it is better to zoom than to crop, assuming that the f-ratio does not grow faster than the focal length.

That is true because the crop is taking a wider view but through what is a smaller aperture despite the flattering f number at short focal lengths. The idea that the f number and aperture are exactly the same thing is so ingrained for many in DPR that it is difficult to really make the point.

I think calling f number aperture as though it is exactly the same thing is very poor practice and leads to confusion but many reviewers and commentators who should know better do it.

That is, in the case of the G1 X III, 45mm (72mm equivalent) at f/5.6 will receive more light from the subject than 15mm (24mm equivalent) at f/2.8. Maybe less light in total, but why should we care about the light outside of the crop.

For more information about this: http://www.clarkvision.com/articles/exposure/

Understanding Etendue is key to understanding recording of light and getting the best performance from your camera system in different situations. The implications, for example, include:

[…]

For low light photography, use the largest aperture diameter lens you have as long as your subject fits in your frame as you desire.

For example, given a 20 mm f/2.8 lens and a 50 mm f/4 lens, both of which frames your subject adequately (e.g. you would crop the image from the 20 mm lens), the 50 mm lens will give a better low light image. The 20 mm f/2.8 lens has an aperture of only 7.1 mm diameter, whereas the 50 mm f/4 lens has an aperture of 12.5 mm so collects 3 times more light on the subject.