Contituation of the Versatility thread

Started Apr 5, 2013 | Discussions thread
FoolyCooly
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Re: Advice for the thread starter
In reply to Martin.au, Apr 7, 2013

Mjankor wrote:

FoolyCooly wrote:

Mjankor wrote:

FoolyCooly wrote:

olliess wrote:

FoolyCooly wrote:

Correct my if I am wrong but a f1.4 lens still lets the same amount of light in regardless of the sensor size.

As pointed out already in several threads on equivalence in these forums, a 25mm f/1.4 lens is going to project the same light per area onto the sensor regardless of the format. However, a larger sensor is collecting light from a bigger area.

Think about it this way: to take the same picture as a 25 mm lens on m4/3, you need a 50 mm lens on FF. The entrance pupil on the m4/3 lens is 25 mm/1.4 = 18 mm, while 50 mm/1.4 = 36 mm, or exactly twice as big, meaning 4 times the area to admit light.

OK now I am confused. Shooting from the same position with the same lens, what will my exposures be?

FF Body 50mm f1.8 @ 1.8, ISO 400 1/30th Second

MFT Body 50mm f1.8 @ 1.8, ISO ??? 1/30th second

For equivalent pictures

FF - 50mm , f3.6, iso400 1/30

m4/3 - 25mm, f1.8, iso100, 1/30.

But if the MFT user is shooting 2x tighter then everything is equal.

Nope, focal length doesn't change exposure. It would be non equivalent, but for same exposure 50mm, iso100 f1.8, 1/30

Wait, I'm going to take a picture of the sky with the same fixed 50mm lens. I'm pretty sure the ISO, Aperture and Shutter speed are going to be the exact same regardless if it is FF, DX or MFT. The only thing that changes is the FL of that lens 50mm, 75mm and 100mm.

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