Something I don't understand about crop factor Locked

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Alex Ethridge
Alex Ethridge Veteran Member • Posts: 4,013
Something I don't understand about crop factor

There are several things about crop factor I do understand, such as the m43 sensor is one quarter the size of full frame, it doesn't work as well for low light because for a given number of pixels on a sensor each photo cell has to be smaller, and maybe another thing or two.

Perhaps I don't understand this already as I know it won't affect what I make pictures of or how I make them.  This is more a curiosity question as I doubt the answer(s) will affect the format I use or the lenses I select so here goes.

I have heard it said by much more knowledgeable people than I that considering crop factor, I should also apply the crop factor to aperture as well.  I don't care about depth of field as I can get milky smooth backgrounds with any lens if I want.  What I don't understand is why that would affect light-gathering ability as it applies to what reaches the sensor.  Yes, the full-frame lens gathers more light; but, it also spreads that light over four times the area.

So, given the same mathematically-computed aperture in an m43 lens, why should I apply crop factor to the aperture?

Please bear in mind that depth of field is not a concern in my question.

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