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You'll have to set ISO higher to get the same image at f/3.4 as you would at f/1.7 on a smaller sensor because the intensity of the light is reduced. I'm inter

by Zak 5y ago

You'll have to set ISO higher to get the same image at f/3.4 as you would at f/1.7 on a smaller sensor because the intensity of the light is reduced. I'm interested to learn more about the effect of light angle on noise. Do you have a source that talks about this? I didn't find anything useful in 2 minutes of searching the web.

sudosysgen 5y ago
No, the intensity of light is not reduced. ISO is not gain. In other words, ISO 200 on full frame is the same as ISO 100 on M4/3 in terms of what actually happens inside the sensor. This is because of how the ISO standard is written. As for light angle, it's a consequence of the second law of thermodynamics, that translates in optics as the conservation of étendue. Basically what this means it that the amount of light captured from a light source is equivalent to the solid angle of light from that light source onto the entrance pupil - whose size is the focal length divided by the f number. So basically, what determines in the same scene how much light is received by the sensor depends on the size of the aperture in milimiters. So on a sensor of the same efficiency, it's the physical size of the aperture that determines how much light is captured.
- Zak 5y ago
  The intensity of the light is reduced because the aperture is the same diameter (50/3.4 = 25/1.7), but the light has to cover four times the area. To get the same exposure with double the f number and the same shutter speed will require four times the ISO. > what determines in the same scene how much light is received by the sensor depends on the size of the aperture in milimiters That's true, but the amount of light is not the intensity of light.
  - sudosysgen 5y ago
    It's the amount of light that decides the amount of noise. Yes, you will need four times the ISO. But you will get exactly the same amount of noise.

by Zak 5y ago

sudosysgen 5y ago

No, the intensity of light is not reduced. ISO is not gain. In other words, ISO 200 on full frame is the same as ISO 100 on M4/3 in terms of what actually happens inside the sensor. This is because of how the ISO standard is written. As for light angle, it's a consequence of the second law of thermodynamics, that translates in optics as the conservation of étendue. Basically what this means it that the amount of light captured from a light source is equivalent to the solid angle of light from that light source onto the entrance pupil - whose size is the focal length divided by the f number. So basically, what determines in the same scene how much light is received by the sensor depends on the size of the aperture in milimiters. So on a sensor of the same efficiency, it's the physical size of the aperture that determines how much light is captured.

Zak 5y ago
The intensity of the light is reduced because the aperture is the same diameter (50/3.4 = 25/1.7), but the light has to cover four times the area. To get the same exposure with double the f number and the same shutter speed will require four times the ISO. > what determines in the same scene how much light is received by the sensor depends on the size of the aperture in milimiters That's true, but the amount of light is not the intensity of light.
- sudosysgen 5y ago
  It's the amount of light that decides the amount of noise. Yes, you will need four times the ISO. But you will get exactly the same amount of noise.