How to compare camera film ISO number to quantum efficiency?

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SUMMARY

The discussion centers on comparing the ISO ratings of digital cameras to the quantum efficiency (QE) of scientific cameras, specifically the Princeton Instruments PROEM and Canon cameras with high ISO ratings. Participants conclude that while ISO provides a user-friendly metric for sensitivity, it does not directly correlate with quantum efficiency, which measures the physical conversion of photons to electrons. The conversation highlights that increasing ISO through ADC gain amplifies both signal and noise, potentially misleading users regarding image quality. Ultimately, the consensus is that ISO ratings can be influenced by marketing and do not always reflect true sensor performance.

PREREQUISITES
  • Understanding of quantum efficiency in imaging sensors
  • Familiarity with ISO ratings and their implications in photography
  • Knowledge of analog-to-digital conversion (ADC) processes
  • Basic principles of signal-to-noise ratio (SNR) in imaging
NEXT STEPS
  • Research the quantum efficiency curves of various camera sensors
  • Learn about the relationship between ISO settings and signal-to-noise ratio
  • Explore the impact of ADC gain on image quality in digital cameras
  • Investigate the differences in sensor technology between CMOS and CCD cameras
USEFUL FOR

Photographers, astrophotographers, and imaging professionals seeking to understand the nuances of camera sensitivity and performance metrics, particularly in low-light conditions and scientific applications.

  • #31
how Iso connect to potential barier??
 
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  • #32
Andy Resnick said:
Interesting... I never thought of that. I figured it was field-of-view related, like the bright sky tended to get included in the metering if I used my wide angle...
Most cameras provide Spot Metering so that you can avoid that problem but it is hard to use it any better than just using the auto setting and compensating later. It's something else to learn about and can be avoided if you are prepared to use bracketing shots. Also, if you shoot with Raw, you have a fair amount more tolerance than when using JPEG files. (But I now see I have made a similar point before on this rather elderly thread)
 
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  • #33
parinaz said:
how ISO connect to potential barrier??

that was a bit difficult to understand what you are referring to ?? I will assume you are referring to the individual pixels on the sensor

The ISO setting doesn't affect that. All the ISO setting is, is an amplifier that takes the signal from the sensor and increases/decreases the signal level by changing the gain setting electronically.
Increasing the ISO = increasing the gain ... it amplifies signal + noise. This is why, particularly on lower end cameras, greatly increasing the ISO is pointless as the noise level becomes unacceptable even at moderate ISO settings 800 - 1600. High end DSLR cameras, like
the Canon 5D Mk3, 6D, Nikon D810 and the like have much higher quality sensors and amplifier electronics to reduce the noise level so that the ISO (gain) can be increased higher before noise become so much of a problem.Dave
 

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