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Let's say I have a full-frame camera A with pixel pitch 4 microns and a full-frame camera B with pixel pitch 6 microns. Will using same camera lens at same exposure f/2.0 and same ISO allow me to operate camera B at faster shutter speed e.g. 1/160s when in camera A i would have to resort to slower shutter speed of 1/60s?

In other words camera with sensor that has larger pixel size (e.g. 4 vs 6 microns) will see more light so can be set to lower shutter speed for the same photo?

EDIT: This is for shooting in very low light conditions i.e. street lights only.

in my understanding if yo have tiny window versus much larger window, bigger one allows more light in. and if we measure at same time limit i.e. set exposure to say 1/160s then smaller window lets less light in compared to bigger one?

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ISO should mean the amount of light that must be received by the sensor to provide a proper exposure. As such, it is independent of pixel size. The 6 micron pitch sensels will receive 36/16 times more light each than the 4 micron sensels. If the sensors are of similar technology you could expect lower noise with the 6 micron sensels or to use a higher ISO with the same noise.

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  • \$\begingroup\$ I wish there were a side by side comparison somewhere because its difficult to believe especially in very low light conditions that smaller pixels catch same amount of light. \$\endgroup\$
    – LilBro
    Jan 24, 2022 at 9:02
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    \$\begingroup\$ Each pixel catches less light, but there's more of them. The amount of light falling on the sensor is exactly the same. \$\endgroup\$
    – Philip Kendall
    Jan 24, 2022 at 10:34
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    \$\begingroup\$ Image noise will be essentially the same regardless of the pixel size. The difference in light/pixel (and thus noise/pixel) is only relevant if you are comparing pixels, and not images. \$\endgroup\$ Jan 24, 2022 at 14:00
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    \$\begingroup\$ @PhilipKendall: that is correct. More light per pixel means less statistical noise in the number of electrons per pixel. In theory you could achieve the same result by binning the smaller pixels together, sacrificing resolution to get lower noise. \$\endgroup\$ Jan 24, 2022 at 14:52
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Sensors with large pixels are one possible way to make a camera usable at higher ISO settings without suffering from too much noise (this is the way eg the Sony A7s series and Nikon D3s/D4 do it). Other possible ways are: Using BSI and other improvements in sensor technology, averaging multiple smaller pixels into one each (can implicitly happen when displaying the image on a lower resolution display, or even visually on a very high resolution display with tiny pixels). So the idea is that eg a typical APS-C camera will be able to be set to ISO 3200 as a maximum before results get unusably noisy, a large pixel fullframe might be comparable at ISO 12800.

Generally, same object and illumination, same exposure triangle values (ISO included here), same brightness.

It is debated how precisely ISO values are actually matched between different camera vendors and models, but this is independent of the aforementioned matters.

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  • \$\begingroup\$ "APS-C camera will be able to be set to ISO 3200... a large pixel fullframe might be comparable at ISO 12800" – If you're going based on pixel size alone, it should be about ISO 6400 for the full frame because the size difference is (a little more than) a stop. \$\endgroup\$
    – xiota
    Jan 24, 2022 at 21:07
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    \$\begingroup\$ With "large pixel fullframe" I was referring to D3s like cameras, which are lower resolution than typical APS-C cameras. \$\endgroup\$ Jan 24, 2022 at 21:40
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The lens' aperture diameter (entrance pupil) determines how much light passes through the lens, and the lens' magnification (focal length) determines how spread out that light is; those two factors combine as the f#. Aperture (f#) alone determines the intensity/density (luminous flux) of the light at the image plane.

SS then determines for how long the image plane is illuminated with that intensity, and ISO adjusts the output brightness of the resulting exposure... exposure is size/area independent.

In your big window/little window analogy, the correct "window" is the size of the image plane/sensor, not the size of the pixels "behind" it. In your house you can stand behind a large window or a small window and it will make no difference; if you place your hand (small pixel) in the opening, or your face (larger pixel) in the opening, both will receive the same illumination (exposure/area); and that's *all that matters. But a larger window does pass more light overall; and similarly a larger image area/sensor receives more light as well. That last bit is often confused as "larger pixels" when discussing different sized sensors of the same resolution; but that is the wrong correlation.

DP review has a **good comparison tool. This is set for four Nikon cameras, low light, and the same output size. The top row is the 16MP D4 (7.3um) and the 46MP D850 (4.3um), both are FF sensors. The bottom row is of two smaller sensors.

![enter image description here

The D4 image is a little out of focus which helps it a bit, but otherwise the noise in the top row is nearly the same (it will never be identical because it is random). The 1.5x crop factor D7500 image is noticeably noisier even though its' pixels are the same size as the D850 (4.2um); and the 2.7x V3 is much worse.


*at the extremes there can be notable differences in fill efficiencies that would make the larger pixels more effective; but that is essentially a non-factor in any realistic comparison.

** The comparisons reduce the exposure by changing the SS, so the ISO noise results may differ from reduced exposure due to lower light levels.

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    \$\begingroup\$ "The D4 image is a little out of focus which helps it a bit, but otherwise the noise in the top row is nearly the same" Are you sure it is out of focus rather than simply being lower resolution? ... Also, I would consider the D4 image to be visually better (especially color wise!) by a stop or or two, even if the theoretical noise level might be the same. \$\endgroup\$ Jan 24, 2022 at 21:44
  • \$\begingroup\$ @rackandboneman, Did you follow the link and view the original samples? They look a little different than the screen sample posted here. And the D4 image is definitely somewhat OOF comparatively, which will blur/blend the noise some (it could be a lack of resolution). \$\endgroup\$ Jan 25, 2022 at 0:41
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    \$\begingroup\$ Yes, I compared also with the a7s series which show the same apparent blur - appears to be a resolution based effect. Also, it seems, all things combined, the D5 (relatively low resolution, combined with more modern tech) rules everything supreme when it comes to visual palatability of the end result :) \$\endgroup\$ Jan 25, 2022 at 1:23
  • \$\begingroup\$ @rackandboneman, if the D4/D5 image is becoming soft/lacking detail then it can't be used/output at the same size. Or, if all of the samples/images were downsized until the lower resolution images appear sharp; the noise in the larger resolution D850 image would be equally reduced. In contrast, if anything the lower resolution D4/D5 image would initially appear noisier with downsizing due to becoming sharper. \$\endgroup\$ Jan 25, 2022 at 14:36
  • \$\begingroup\$ noise shouldn't care about the focus on solid-color planes. \$\endgroup\$
    – dandavis
    Jan 29, 2022 at 10:10

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