I finally 'get' equivalence

Started May 22, 2012 | Discussions thread
mh2000 Senior Member • Posts: 2,813
light gathering

Exposure is based on light/area, but pixels provide the actual light gathering area. Tiny pixels spread across a large sensor do not capture anymore light than the same number of pixels spread across a smaller sensor.

Macx wrote:

No, you really do need to consider the sensor size and not the individual pixels.

Consider an image at any size you like. However you divide up this final image, a full-frame 135 format sensor will give you four times as much light on this part of the image compared to a 4:3.

If you look at base ISO shots and have a hard time spotting this, it's because noise performance is getting to a point where it's plenty good enough most of us and where it's hard to distinguish between shots taken at ISO 100 and ISO 400. Also, advances in sensor technology improves noise performance as well and a new E-M5 compares very well to full-frame 135 systems released four or five years ago. As such, this becomes much less of an issue for us in everyday photography.

So when you crop the 135 format to get it to the same size of the 4:3, you end up with less light and as a consequence more noise and less dynamic range, just as if the image had been made with a 4:3 sensor.

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