I finally 'get' equivalence

Started May 22, 2012 | Discussions thread
azazel1024 Senior Member • Posts: 1,133
Re: I finally 'get' equivalence

Not really. The light level, lux, of the sensor is exactly the same so long as all the intervening filters over the sensor are the same between the micro 4/3rds camera and the full frame camera. The difference is that the 35mm camera is receiving 4x the light, spread over 4x there area. Exposure on each square millimeter is EXACTLY the same between the two cameras. The difference is that the full frame camera, with the same number of pixels is going to have much larger photosites. If that is the case, say a 12mp 35mm camera versus a 12mm m4/3rds camera, each photosite on the 35mm camera, because they are larger, WILL gather more light. However, if it is a 12mp m4/3rds camera versus a 48mp 35mm camera, the photosites will be the same size and would thus gather exactly as much light as each other.

THAT is the difference. The light circle produced by a full frame 50mm lens at f/2.8 and a m4/3rds 50mm lens at f/2.8 have the same lux (luminance per unit of area) as each other, the full frame lens is just projecting it over a larger area.

Dorus wrote:

it has taken me long time to get to this insight, and looking at the discussions, I am not the only one

What has always mystified me (don't ask me why, as it is so obvious) is the importance of seeing this concept ONLY in the context of the final product. So let's say that I am going to print an 18x24 picture. If I printed that picture from a 35 mm equivalent Full Frame sensor, at an f-stop of 2.8, that picture will have incorporated 4x more light than if it was taken on a 4/3 or m4/3 sensor at the same f-stop of 2.8. Thus, with identical sensor technologies, the FF picture should have better noise performance and better DR (at least if the media of the final product allows to see the difference between the 2, but that is a separate discussion), since 4x more light was used to generate the picture.

So apologies for bringing the equivalency discussion to this forum. But maybe it can help a simple soul or two who like me never reached that final insight.

Btw, I personally think that the recent improvements in sensor technology as well as the continuning limitations of the output media have rendered the whole concept much less relevant than it was just a few months ago.


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