why not f/1.2 by Sony?

Started May 14, 2013 | Discussions thread
TiagoReil
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Re: why not f/1.2 by Sony?
In reply to GaryW, May 18, 2013

GaryW wrote:

franzel wrote:

Great Bustard wrote:

They are related in that, for equally efficient sensors, the same total amount of light falling on the sensor results in the same image noise.

The reason larger sensor systems are less noisy than smaller sensor systems is because more light falls on the sensor for a given exposure.

Negative - it's pixel density; or enlargement factor , if the sensors only differ in size but havethe same resolution.
In real life, it is more complex, but not by much .

There is no such thing as measuring any 'total' amount of light, based on the area it covers .
The "amount of light" - which isn't exactly proper terminology - is the exposure any object of a predetermined brightness creates on any given part of a sensor, no matter its size .
It's physically impossible to collect more light from a lit object or scene (aka light source) by increasing the area it is projected on .

You don't collect more light per unit area, but since the area is larger, then more photons were collected (assuming the same shutter speed, obviously).  So, you can think of it in those terms if you really want to (collecting more light), but that's not how the f ratio works -- it works as you describe, per unit area.

TiagoReil wrote:

Also, a lens is considered fast cause you can get a very fast shutter speed with it, not because the DoF is shallow. Those people that say that a fast lens is not fast on an aps-c camera have it wrong. It is still a fast lens (ignoring the sensor problem) it has less shallow depth of field than the same lens on a FF camera, but it is as fast in terms of light.

Amen .

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Gary W.

Exactly. Some people think that you will actually get more speed with a FF lens on FF than on a crop sensor, and it will give you the same (more or less) shutter speed. So, if you receive more light, how is it that you have the same shutter speed value?

IF you receive more light, why a photometer doesnt have sensor size as a parameter? why you use the same photometer for a P&S, for a crop sensor, for a FF or for a medium format camera?

Of course when you compare cameras there are more difficult things, for instance, different manufacturers grade ISO numbers differently, or even different technologies from same manufacturer. There are many factors, but when you compare with an Ideal sensor, that you could consider the same, a lens is not more bright in a FF camera than in an aps-c camera. IT is the same actually. You dont get a faster shutter speed. You get the same (approximately, again, depending on other things)

If not, lets through all our photometers and lets get one (imaginary) that besides ISO, you have to enter the sensor size. Where do I get one?

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