SURVEY - Do FT / mFT users know the difference from "full frame"? Replies wanted!!

Started Apr 26, 2013 | Discussions thread
AndyGM Contributing Member • Posts: 698
Re: SURVEY - Do FT / mFT users know the difference from "full frame"? Replies wanted!!

Kewee wrote:

Great Bustard wrote:

It's a shame that you can't understand that f/2.8 on mFT puts the same amount of light on the sensor as f/5.6 on FF for a given shutter speed, which, in turn, results in the same noise for equally efficient sensors.

I'm assuming you believe f/2.8 allows twice as much light to pass through the lens as f/5.6, if so your wrong, as are many others who calculate f-stops but multiplying by two. Aperture values are quite different. Each full f-stop either doubles or halves the light passing through a lens depending on whether your opening the aperture or stopping down. F/4 lets twice as much light through the lens than f5.6, f2.8 lets four times as much light through the lens as f5.6, it doesn't just double the light transmission as many appear to believe.

GB didn't use "twice" or "double" anywhere.

"Full Frame" 135 format sensors are 4 times the area of Four Thirds sensors (roughly). The f stop is an artificial construct to have a means of describing aperture in a way that is useful of working out exposure, universally, across all camera formats, so that the same "light per unit area" falls on the recording medium no matter what camera.

So an FF lens at f/2.8 and an m43 lens at f/2.8 are projecting the same "light per unit area", but since the FF lens image circle has 4 times the area, there is 4 times as much light entering that camera. To equalize the total light entering the two cameras, you have to reduce the aperture on the FF lens by a factor of four... and then I am kinda back to what you said.

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