3 ms·

At the risk of sounding pedantic - the f-stop* roughly equates to "light per area" or brightness, so if you're using crop factor, you need to apply it to the f-

At the risk of sounding pedantic - the f-stop* roughly equates to "light per area" or brightness, so if you're using crop factor, you need to apply it to the f-stop as well as the focal length. So for a given full-frame lens at a given f-stop, if you drop down to an APS-C sensor, you're reducing the amount of light gathered by about one stop (half). On an m43, you're obviously losing 75% of the light gathering capacity (two stops). Putting a 300mm f/2 lens on a micro 4/3rds body should result in images similar to a full-frame camera with a 600mm f/4 lens. *Obviously t-stop would be better, since it's an actual measurement of brightness.

deleted 7y ago
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rodgerd 7y ago
Except you're not. This is a popular talking point in 35mm circles, but the amount of light on a given area on the sensor remains unchanged, which is what actually matters. The smaller sensors are challenged to keep their noise down, given they typically have a smaller pixel pitch to keep up the megapickel count.
- ip26 7y ago
  Noise is the key, as far as I can tell a FF sensor usually has at least 1 stop more usable ISO compared to a crop of the same generation. So to get a comparable shutter speed, assuming 1 stop less ISO, you still need that 400mm f/2.8 on crop to match the 600mm f/4 on FF. Humorously, they have the same front element size.
- falcrist 7y ago
  > the amount of light on a given area on the sensor remains unchanged This isn't the only thing that matters. It also matters that you're amplifying the noise more by enlarging it 4x as much as you would have on the larger sensor. It's analogous to film in that a larger format will exhibit less obtrusive grain than a smaller one despite using the exact same film speed. You're using the same exposure over a larger area, and thus gathering more light to drown out the noise. You can either think of it in terms of total light gathered compared with the underlying noise of the sensor (signal to noise ratio) or in terms of enlargement of the image. The result is the same, smaller sensors have "more noise" simply because they're gathering less total light and amplifying everything more. And don't be fooled by the old "higher megapixel = more noise" fallacy. All else being equal, it's the same amount of noise. However each pixel is gathering less light (signal) to offset the noise, so the signal to noise ratio is worse when comparing pixel for pixel. However, if you were to downscale the output of the higher res sensor to match the lower resolution sensor, you'd find roughly the same amount of noise in both images.
brudgers 7y ago
John Hess has a good explanation of these trade offs. https://youtu.be/MytCfECfqWc https://youtu.be/MytCfECfqWc

deleted 7y ago

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rodgerd 7y ago

Except you're not. This is a popular talking point in 35mm circles, but the amount of light on a given area on the sensor remains unchanged, which is what actually matters. The smaller sensors are challenged to keep their noise down, given they typically have a smaller pixel pitch to keep up the megapickel count.

ip26 7y ago
Noise is the key, as far as I can tell a FF sensor usually has at least 1 stop more usable ISO compared to a crop of the same generation. So to get a comparable shutter speed, assuming 1 stop less ISO, you still need that 400mm f/2.8 on crop to match the 600mm f/4 on FF. Humorously, they have the same front element size.
falcrist 7y ago
> the amount of light on a given area on the sensor remains unchanged This isn't the only thing that matters. It also matters that you're amplifying the noise more by enlarging it 4x as much as you would have on the larger sensor. It's analogous to film in that a larger format will exhibit less obtrusive grain than a smaller one despite using the exact same film speed. You're using the same exposure over a larger area, and thus gathering more light to drown out the noise. You can either think of it in terms of total light gathered compared with the underlying noise of the sensor (signal to noise ratio) or in terms of enlargement of the image. The result is the same, smaller sensors have "more noise" simply because they're gathering less total light and amplifying everything more. And don't be fooled by the old "higher megapixel = more noise" fallacy. All else being equal, it's the same amount of noise. However each pixel is gathering less light (signal) to offset the noise, so the signal to noise ratio is worse when comparing pixel for pixel. However, if you were to downscale the output of the higher res sensor to match the lower resolution sensor, you'd find roughly the same amount of noise in both images.

brudgers 7y ago

John Hess has a good explanation of these trade offs. https://youtu.be/MytCfECfqWc https://youtu.be/MytCfECfqWc