Fast lenses, and High ISO

Started Jul 18, 2014 | Discussions thread
Albert Silver Veteran Member • Posts: 3,313
Re: "fast" is relative

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

A F0.95 lens on M43rds is equal in performance to a F2.0 lens on FF, which (for a prime on FF) is pretty slow.

We won't even talk about how slow the superzooms are in FF terms.

Chris R-UK wrote:

Fast lenses are clearly less important on MF and FF cameras because the larger sensor allow for higher ISO settings and better DoF control.

However, as sensors get smaller, fast lenses as measured by the f-number became much more important because high ISO performance is worse and depth of field control is more difficult.

That is why Voigtlander has a range of f/0.95 lenses for M4/3 and there are superzooms like the Panasonic FZ200 with f/2.8 over the entire 24x zoom focal length range.

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Chris R

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professional cynic and contrarian: don't take it personally

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