<p>If I have an object of some size and spectral radiance, and it's some distance R from a camera, how would I calculate its digital count value in an image? I'm sure there's an equation out there, but I don't know what to search for. It would be a function of integration time, aperture, focal length, gain, quantum efficiency, point-spread function, spatial resolution, etc. For simplicity, I'd assume the noise is Gaussian, and that atmospheric transmission is perfect.</p>
<p>Can someone please help?</p>

CC BY-SA 4.0
2021-02-11T15:56:25.290Z
What do you mean by "pixel intensity" and "digital count?"
WarpPrime
CC BY-SA 4.0
2021-02-11T16:31:33.703Z
I mean the intensity of the pixel when I take a picture with a digital camera and view the picture electronically.
user3433489
<observational-astronomy><telescope><angular-resolution>
Convert Object Intensity to Pixel Intensity
user3433489
# Convert Object Intensity to Pixel Intensity

(Asked by: username_0 on 2021-02-11)

If I have an object of some size and spectral radiance, and it's some distance R from a camera, how would I calculate its digital count value in an image? I'm sure there's an equation out there, but I don't know what to search for. It would be a function of integration time, aperture, focal length, gain, quantum efficiency, point-spread function, spatial resolution, etc. For simplicity, I'd assume the noise is Gaussian, and that atmospheric transmission is perfect.

Can someone please help?

**Tags:** observational-astronomy, telescope, angular-resolution

> **Comments:**
> **username_1**: What do you mean by "pixel intensity" and "digital count?"  
> **username_0**: I mean the intensity of the pixel when I take a picture with a digital camera and view the picture electronically.  

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