Comparing Olympus 4/3lenses to FX "Full Frame" offerings

Started Jan 25, 2014 | Discussions thread
bobn2 Forum Pro • Posts: 55,712
Re: Wrong

JiminDenver wrote:

The same amount of light is being delivered to either the 4/3s sensor or the same space it would result in on a full frame sensor. Otherwise the shutter speed would change in a like situation.

The extra light is from the larger image circle delivering the larger scene onto a full frame sensor. 4/3s sensor can not see or use this extra light because it can not see the rest of the scene that the full frame can.

Lets try and concentrate on what we are comparing. We are comparing a Four Thirds lens projecting its image onto a 13x17.3mm sensor with a FF focal length with 'equivalent' focal length (2x the FL of the FT lens) projecting its image onto a 24x36mm sensor. The FT lens has a FT sensor behind it, the FF lens has a FF sensor behind it. The FF lens does not have a FT sensor behind it, so what that sensor can and cannot collect is irrelevant. At the same f-number the FF lens projects four times the number of photons onto its sensor as does the FT lens onto its sensor.

The same is true if you could adapt a medium format lens to a full frame sensor. Is there more light, yes. Does it make a difference to the full frame sensor, no because it too can not see the whole scene being delivered by the medium format image circle. However it will still require the same f stop to get the same luminance as a medium format rig would in the same conditions as well as if you used the equal full frame lens.

Again, we are not talking about an MF lens in front of a FF sensor. If we wanted to continue the discussion to MF we would be talking about an MF lens in front of an MF sensor.

Maybe a easier way for you to understand is a king sized sheet covers more area than a queen, that's a given. Put that king sized sheet on a queen bed and the extra fabric falls to the side. It doesn't make the fabric on the bed any thicker does it? No, it is wasted without the king sized bed it is intended for. So there is extra light but without the sensor big enough for it to fall on, it is wasted and effects nothing.

I 'understand' perfectly well. What you should understand is that the OP is comparing FF lenses used with FF sensors and FT lenses used with FT sensors.

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