Think of it like this: The effective aperture (called right) admission students) is the diameternot the area of the aperture, seen through the front of the lens. This means:
- Doubling the diameter of the aperture increases the amount of light that can be transmitted fourfold, But all this light still falls on the same image circle. This means that each point on the image circle receives four times the illuminance.
- As the focal length of a lens increases, the minimum diameter of the front element must increase to maintain the same f-number. For a 100mm lens, a 1: 2 aperture is 50mm wide, so the front of a 100mm (2: 2) bezel must be at least 50mm wide. Otherwise, you will not be able to measure the aperture through the front of the 50mm wide lens. A 200 mm 1: 2 lens must have a front element with a width of at least 100 mm.
- If we refer to apertures by total area and not the f-number, we would need different combinations of Tv / Av / ISO for the same amount of light at each different focal length! By using the f ratio, the correct exposure values for an object with a certain brightness can remain the same regardless of the focal length.
More about why the exposure is determined by the amount of light per unit areaand not the total amount of light collected, see lens aperture number and speed for custom lenses
I have opened this link and will be reading it, but I wanted to say quickly that I understand and agree with the reasons for measuring the aperture in f-numbers, not the entire area. In this case, however, I find that it is rather unclear than that I can understand what is going on. The FF sensor only works better because it receives more light and not because it is more sensitive.
It only receives more light because the sensor is larger. The amount of light per cm² of a 50 mm aperture 2 corresponds exactly to the amount of light per cm² of a 100 mm aperture 2 (provided that both see the same scene).
Does not the noise depend on the total amount of light entering the sensor, not on the light per unit area? If the latter were the case, you would find that a FF sensor with a 1: 2.8 lens is not better than an APS-C sensor with a 1: 2.8 lens, right?
NO. The picture noise depends on the signal-to-noise ratio. Since the noise at each pixel is fairly constant, the stronger the signal at each pixel, the lower the noise level, the lower the overall level of the pixel. Therefore, larger pixels are inherently less noisy: each pixel can collect more light / photons /.signal No more reading noise is generated than with a smaller pixel.
Larger sensors allow either: larger pixels for the same resolution / number of pixels or higher resolution / number of pixels for the same pixel size or a combination of both (moderately larger pixels and moderately more of them).
If the pixels are the same size in both the FF and APS-C sensors (and are identical in terms of other technological issues), then at the pixel-accurate 100% display level you are correct that the noise level in the FF and APS C cameras would be the same. BUT: If you then display the images of the different size sensors with the same display size (eg 8×10 or 16×20, even 36×24 or even larger), the higher magnification is required to get the 10 MP APS-C sensor in place Compared to the lower one The magnification required to display the 22MP FF image would also increase the perceived noise.
If both sensors have the same pixel size, the APS-C image would be less than half the total area of the FF image at a display size of 100% on your monitor.
On the other hand, if both the APS-C and FF sensors have the same number of pixels, each pixel on the FF sensor is 2.25 times the area of each pixel on the APS-C sensor. This means that the FF camera collects 2.25 times more light / photons / for the same scene through the same lens.signal Pixels per pixel as the APS-C camera, which means that the SNR is twice as large at each pixel (one stop) as that of the APS-C camera.
I totally agree with your last five comments, Michael. I do not think that we actually have a difference of opinion here. To be clear, I view the photos on a computer monitor of fixed size, as I wrote in my updated question, rather than 100%. Since with this setting the noise depends on all the light falling on the sensor (not per unit area), it is not wrong to say that it is not the sensor itself but the larger entrance pupil of the lens that is responsible for the better Picture quality. Right?
If you are viewing the output from two different sized sensors on the same sized monitor, the magnification difference (between the size of each sensor and the size of your screen) will be related to the noise.
"For this setup, the noise is dependent on the total light falling on the sensor (not per unit area) …
Just because you keep repeating yourself is not the correct way to do it the first time.
They also ignore the elephant in the room because they made it clear that this is not a comparison of FF and APS-C using exactly the same technology, but rather a Sony APS-C and a μ4 / 3 from Olympus. The difference in how each manufacturer designed the sensor and how it processed the output of this sensor is probably more related to the relative performance of each sensor.
No matter what sensor size I have, a lens with an entrance pupil of 20 mm² gives me photos with less noise in low light than a lens with an entrance pupil of 10 mm². Even if these two lenses are mounted on different sized sensors. As long as the FF equivalent focal length of these two lenses is the same and we do not have a mismatched system (such as attaching an FF lens to APS-C without Speed Booster, which wastes light, or an APS-C) lens on FF housing).
They still ignore the effects of the different magnification factors on the noise. Depending on the difference between the two sensors, it can be very important when comparing photos taken in low light.
If all other factors are equal, a frame sensor outperforms a 1.5X APS-C sensor with respect to SNR by a factor of 2.25 (approximately 1.15 stops). A 50mm APS-C camera lens offers the same FoV as a 75mm FF camera lens. The 26.8 mm wide e.p. On the 75mm f / 2.8, the 50mm lens is placed in a 1: 1.9 aperture. That's about 1.15 stops. But here ends the "all other things same". The smaller sensor requires as many circuits per pixel on the sensor chip as the FF sensor, which means that the smaller sensor with less total area actually collects light.
Let's assume the same size of the sensor. I explain since the problem came up. In this context, one can use two APS-C sensors with different megapixel number and thus different sensor sizes. Let's not use that other factor.
This "other factor" is the real world versus the purely theoretical.