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 p.4 #19 · Fuji's marketing concept? | |
gdanmitchell wrote:
The “larger sensor collects more light” business always intrigues me.
On one level, it is true. More photons fall on a larger area.
On the other hand, consider an analogy. Let’s say my garden occupies a half acre and my next door neighbor’s garden occupies a full acre. It is true that twice as much rain falls on my neighbors garden, but if my neighbor gets one inch of rain, so do I. A plant in my garden that needs and inch or rain does just as well as a plant in his that needs an inch or rain, and plants that require two incenses are rain fail in both.
Unless…
… each plant collects water from an area twice as large in his garden.
So the potential benefit of the larger garden accrues in two says:
1. You can fit twice as many plants requiring an inch of water into the larger garden, OR
2. You can can reduce the number of plants in the larger garden and grow plants that require more water.
The analogy here, as far as I can tell, is that a larger sensor can:
1. Allow more photo sites and those record more detail, OR…
2. Allow images to be made in somewhat lower light.
(Or some balance of the two.)
So, the business about “more light on the larger sensor” providing better low light performance would not see to work if we compare sensors with the same pixel pitch. (Which I think is the case when we compare the high resolution Sony sensors of different sizes used in APS-C, full-frame, and mniMF cameras these days.) Each “plant” (e.g. photo sites) gets the same number of photons in all three cases.
There are a couple of “complexifying” issues:
1. The “noise grain” will be finer with the larger sensor, given that each photo site is a smaller percentage of the frame size. So if the size of the grain is an issue, the larger sensor with the same pixel pitch will produce a slightly “smoother” (subjectively) image.
2. There are obviously different DOF and aperture choice (relative to diffraction) imperatives with different size sensors.
...Show more →
Dan, I did NOT write “larger sensor collects more light” - this exact statement is literally meaningless.
A sensor collects only as much light as is allowed to reach the sensor through the attached lens, and up to a certain limit.
This amount of light is decided exclusively by the shutter speed and the physical size of the lens' iris.
In general, the size of a sensor does not directly correlate with the amount of light that falls on it. The same can be said about the pixel pitch.
What I said was very specific, about "the largest(!) amounts of light they can collect (at base ISO)" - with reference to the sensors of the GFX100, FF, and Fuji APS-C cameras. This is easy to tell by invoking the photographic equivalence, specifically that the ISO on sensors of different sizes relates via the square of the crop factor (which is also the ratio of the surface areas of the sensors).
For example, the square of the crop factor 0.79 is 0.62; thus, the base ISO 80 of the GFX100S II and GFX100 II is equivalent to ISO 80 x 0.62 = 50 on a FF sensor. ISO 50 is different from the base ISO of FF cameras (100) by a stop. Thus, the largest amount of light that a GFX100 sensor can collect (at ISO 80) is twice the largest amount of light that a FF sensor can possibly collect at the FF base ISO.
The same consideration can be used to show that a FF sensor can collect very close to 1.5 more stops of light compared to a Fuji APS-C camera, with both at base ISO (100 vs 125).
Regarding "different DOF and aperture choice (relative to diffraction) imperatives with different size sensors" - once again, these factors relate via the crop factor. For example, if the very first, barely noticeable signs of diffraction softening can be seen when pixel-peeping images from a FF camera at f/8, so the GFX images are expected to show this at 8/0.79 = f/10.
At the equivalent f-numbers, the DOF is also the same for sensors of different sizes.
I believe that the pixel pitch is practically irrelevant, while the relevant practical parameter in photography is the size of CoC (circle of confusion). To the best of my knowledge, several (6 - 13) photo sites are within a typical CoC. Something related to this is that a 24MP FF camera isn't in practice significantly different from a 60MP FF camera in terms of the dynamic range, despite the significant difference in the pixel pitch of the two.
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