Luminous emittance vs value recorded on image sensor

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SUMMARY

The discussion focuses on calculating the gray level of a gray wall in relation to a light bulb's luminous emittance when captured in an image. The light bulb has a luminous emittance of 160,000 lux (16 EV), while the gray wall has an emittance of 300 lux (7 EV). Given that the exposure is set for the bulb, the wall appears very dark in the image. The ratio of emittance between the bulb and the wall is 533:1, which exceeds the 255 levels of an 8-bit grayscale A/D conversion, indicating that the wall's gray level will be significantly lower than the maximum value.

PREREQUISITES
  • Understanding of luminous emittance and its measurement in lux
  • Knowledge of exposure settings in photography
  • Familiarity with 8-bit grayscale imaging and A/D conversion
  • Basic principles of light ratios and their effects on image capture
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  • Research the effects of exposure settings on image brightness and contrast
  • Learn about the principles of dynamic range in digital imaging
  • Explore formulas for calculating light ratios in photography
  • Investigate advanced topics in image processing and histogram analysis
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Photographers, image processing specialists, and anyone interested in understanding the relationship between light emittance and digital image representation.

jamesdo
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Assume that I have a light bulb with luminous emittance of 160000lux (16ev), and a gray wall with luminous emittance of 300lux (7ev). I take the photo of this bulb and this background. Is there any approximate formula to estimate the gray level or RGB value of the bulb and the background in the image. In this case, I assume that the exposure is set for the light bulb (so the background should be very dark). Let's say the grayscale is 8 bits. If the gray level of the bulb is 255, what would be the gray level of the wall.

Thanks!
 
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jamesdo said:
Assume that I have a light bulb with luminous emittance of 160000lux (16ev), and a gray wall with luminous emittance of 300lux (7ev). I take the photo of this bulb and this background. Is there any approximate formula to estimate the gray level or RGB value of the bulb and the background in the image. In this case, I assume that the exposure is set for the light bulb (so the background should be very dark). Let's say the grayscale is 8 bits. If the gray level of the bulb is 255, what would be the gray level of the wall.

Thanks!
The lamp and the wall have a ratio of emittance of 533. If you use an eight bit A to D conversion it can only handle a ratio up to 255.
 

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