Possibly moving to full-frame mirrorless from m4/3’s

Started 10 months ago | Discussions thread
abera Regular Member • Posts: 103
Re: Two quick and easy reasons

ZapperVT wrote:

avalvo wrote:

- Yes, lenses on FF are getting smaller. But, that is only if you are comparing the slower FF lenses, say a 50mm 1.8 to say a 25mm Oly 1.2. They are about the same size, but the Oly is still a faster lens and can be shot at 1.2.

f/1.2 in M43 is equivalent to f/2.4 on FF. Or, f/1.8 on FF is equivalent to f/0.9 on M43. Functionally, the FF f/1.8 has a one stop advantage over the M43 f/1.2.

If you shoot with at 25mm f/1.2 on M43 FF and 50mm f/2.4 , with the same shutter speed and two stops faster ISO on FF, you will have images that are very close in field of view, depth of field, motion blur, and image quality. This is because for the same f number, the diameter of the entrance pupil scales with the crop factor. It is twice as big for full frame, letting in 4 times as much light at the same f number. If you go to f/1.8 on FF, you have an image with a depth of field one stop smaller and an IQ potentially one stop higher than possible with f/1.2 on M43.

You may object that in terms of exposure, f/1.2 is still f/1.2, and you would have to use a slower shutter speed or higher ISO on the FF f/1.8 lens to get the same exposure wide open.

ISO is not an exposure parameter - it's actually defined by using the exposure parameters so it would be a circular definition. In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a frame of photographic film or the surface of an electronic image sensor, as determined by shutter speed, lens aperture, and scene luminance.

Also, if one shoots raw, there isn't really need to use higher ISO - they can be be benefits (less read noise), but also drawbacks (lower saturation point).

Other than this, you're correct.

That is part of the equivalency. If you shoot at the same shutter speed and wide open with both lenses, you will have to increase the ISO by 1 stop on FF to get the correct exposure.

Nope, ISO is not an exposure parameter - it influences the lightness of the output image if one shoots JPEGs, as well as usually has influence in noise and max signal capacity.

But a FF sensor has a two stop advantage in noise vs IQ, so you still end up with a 1 stop advantage in IQ on the FF system.

Noise advantage is (almost entirely) a function of collecting more light - either by using a larger aperture diameter, longer exposure, or changing the ambien light (e.g. flash light). In practise this means that FF has more potential, but in some cases it can't be used - for example limited available light situation with deep DoF and fast exposure requirement.

Source: Here's an article on equivalency by one expert.

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