G3 heralds the end of APS-C DSLRs

Started May 13, 2011 | Discussions thread
MichaelJP
Regular MemberPosts: 128
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Re: For DOF purposes,
In reply to nick_webster, May 13, 2011

nick_webster wrote:

f1.4 is not equivalent to f1.4 on different sensor sizes.

Nick

sorry , but it is the same. Lens speed is defined light per square mm on the sensor.

For any lens the size of the image on the sensor does not change, but for 4/3s the crop factor is 2x 35mm - so the picture in hand has the objects twice the size relative to the size of the image.

To fill a larger sensor with as much light as a 4/3 the lens, the FF must be bigger in diameter than a 4/3 designed lens to capture enough light to spread around the sensor.

If you put a 4/3 lens on a larger format camera the light intensity per square mm will be the same, but the image will not fill the sensors and visa versa,

a full frame lens on a 4/3 the image will overflow the sensor ( ie the crop factor)
but the light intensity over the sensor is the same.

What you are trying to say is the light intensity in the center of the lens will be more than that at the edges, for an object of uniform intensity... and vignetting is not appreciated by most of the photography community.

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