RX100M3 lens hits f/2.8 at around 30mm - ouch!!!

Started May 16, 2014 | Discussions thread
falconeyes Senior Member • Posts: 1,454
Re: 24mm and 70mm rule the game

dpr4bb wrote:

falconeyes wrote:

dpr4bb wrote:

Cropping a 24mm capture to 28mm will give you a 15 megapixel image which is not too shabby. If I really needed that extra stop, I'd shoot at 24mm f/1.8 and crop.

As not everybody seems to understand. Cropping changes the equivalent aperture too.

Normalized to a 1" sensor, cropping a 24mm/1.8 image to 28mm yields an 28mm/2.1 image. Better than F2.8, but who knows how exact those DPR figures really are ... Following a cropping law, the 24/1.8 would hit F2.8 at 37mm.

I understand how cropping affects DOF and noise, but if you wanted the perspective and framing of a 28mm eq. lens, isn't what I suggested a reasonable approach? Perhaps I misunderstood your first comment. Did you mean that the lens is best used only at the 24mm eq. or 70mm eq. ends with no cropping? I'd genuinely love to learn more details on how you would use this lens to achieve your photographic goals.

I have been kindly asked by PM to answer to this question. So, here we go:

There is nothing wrong in cropping 24mm to a 28mm FoV. I actually do it all the time as I prefer to decide for 24/40/70 when shooting rather than to finetune my focal length in the field (I rather try to catch the decisive moment than the exact focal length). The keepers then get cropped more carefully in post. But it is still a reason why one shouldn't care what the aperture is at 28mm.

My earlier comment only wanted to make sure that everybody understands that cropping 24mm F1.8 to 28mm yields a 28/2.1 image rather than a 28/1.8 one. But cropping by small amounts is ok, nothing wrong with that. And it is the reason why you need to use the long end rather than just crop to the inner third (besides resolution).

And don't listen to the ones who can't understand the equivalence theoreme (a proven law of physics), rather google my name and equivalence if you need know more.

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Falk Lumo

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