f/1.8 on m4/3, ASP-C, FF; are they the same?

Started Nov 1, 2010 | Discussions thread
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Joesiv Veteran Member • Posts: 5,497
Re: f/1.8 on m4/3, ASP-C, FF; are they the same?

SLOtographer wrote:

If it were the case that f values changed with sensor size, then compact cameras would all be f/20 or f/30 and they'd need high ISO to take daylight photos.

They don't "need" higher ISO values, but the noise at the same ISO "setting" is roughly "equivalent" to that scale.

so f/20 at the ISO that is needed to get the same exposure on the larger sensor, will end up looking very similar to the lower ISO but wider open lens' on the smaller sensor.

EG:
ISO100 on LX3 @ f/2.8 1/100th
ISO1600 on D700 @ f/11 1/100th

These images will be generally on par for depth of field along with noise.

This is the general way the "equivalence" theory goes, some may argue for or against it, but I've found it to be pretty reasonable in practice.

To answer the original OP's question, yeah f/1.8 is the same on all those formats, however, the smaller formats will be have deeper depth of field (for better or for worse) at those settings. And the smaller sensor will struggle more for noise. however, the difference between m43 and APS-C is pretty minor, and differences in technology can make or break the difference.

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