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  1. Doug Kerr

    "Luminous exposure" vs. "photometric exposure"

    Some while ago I adopted the term "photometric exposure" to mean the phenomenon (H) to which film and digital sensors respond, the product of the illuminance on the film/sensor and the time that it persists. I more or less "made up" this term. I have recently realized that all this time there...
  2. Doug Kerr

    Light Painting tonight in Stratford, Ontario

    Rob, Exquisite! Best regards, Doug
  3. Doug Kerr

    Dynamic Range versus Bit Depth?

    Hi, Ted, I think to do a "kitchen table" assessment of the dynamic range of a camera we would want to do this: 1. Take a large number of shots with the camera observing a test target such that (considering the luminance of the test target and the photographic exposure used) the expected...
  4. Doug Kerr

    Dynamic Range versus Bit Depth?

    Hi, Ted, Thanks. Interesting and not surprising. I understand. Best regards, Doug
  5. Doug Kerr

    More on the measurement of dynamic range per the ISO standard

    Here is the background behind the above posts. The basic concept of the dynamic range of a camera is the ratio of: a. The largest phtometric exposure (H) the camera can "deal with", to b. The smallest phtometric exposure the camera can "deal with". It is reasonable to consider (a) to be the...
  6. Doug Kerr

    More on the measurement of dynamic range per the ISO standard

    More contemplating of the confusing language of the various issues of ISO 15739 leads me to conclude that the prescribed phtometric saturation at which the noise is to measured for determination of the dynamic range is indeed 0.01 Hsat, as I had originally reported. I think. Best regards, Doug
  7. Doug Kerr

    More on the measurement of dynamic range per the ISO standard

    Well, Maybe not. The interpretation in my prior post was based on an interpretation of the tortured language of the 2003 issues of ISO 14739. In the 2023 issue, that matter is described even more vaguely. So there is even more uncertainty as to the phtometric exposure value to be used for the...
  8. Doug Kerr

    More on the measurement of dynamic range per the ISO standard

    Mea culpa. In my various writings on the ISO 15739 definition of dynamic range, I have repeatedly said that this is based on an assessment of the noise at a test exposure that resulted in a phtometric exposure of 0.01 Hsat. I just now perused that standard, and it turns out that the prescribed...
  9. Doug Kerr

    More on the measurement of dynamic range per the ISO standard

    As can perhaps be seen from some of my recent essays here, if we have a fixed and highly stable phtometric exposure (perhaps during testing of a camera), and the photodetector system exhibits some certain degree of read noise, the quantization that occurs during the initial digitization of the...
  10. Doug Kerr

    On the interaction of quantizing with read noise and the like

    Hi, Ted, Thanks so much. Best regards, Doug
  11. Doug Kerr

    Dynamic Range versus Bit Depth?

    Hi, Ted, Oh, I suspect this means the precision with which GIMP makes its various calculations when manipulating images, and/or perhaps the format it uses for internal storage of images. This may or may not be relatable to the matter of the way that a digital camera initially digitizes the...
  12. Doug Kerr

    Dynamic Range versus Bit Depth?

    Hi, Ted, Sounds as if it could be interesting. What might be discerned by such an examination? I am not really familiar with GIMP, although I have often seen it referred to. I'm not sure of the significance of its operating with those various precision models. Is uses those when doing what...
  13. Doug Kerr

    On the interaction of quantizing with read noise and the like

    The quantization of photodetector output voltages (as the voltages are digitized) itself is the cause of "errors" in the representation of the voltages. But quantization also has an effect on the various sources of random noise (read noise, photon shot noise, dark current noise - but for...
  14. Doug Kerr

    Dynamic Range versus Bit Depth?

    Hi, Will, Could you be so kind as to tell what dynamic range Canon quotes for typical cameras with14-bit an 16-bit raw files. Thanks. Best regards, Doug
  15. Doug Kerr

    Dynamic Range versus Bit Depth?

    dpr member Jim Kasson has done a lot of work on the matter of noise and dynamic range. He points out that if the σ of the photon shot noise and read noise is greater than about Q/2, further increase in bit depth does not produce further significant increase in dynamic range. I am a little...
  16. Doug Kerr

    Dynamic Range versus Bit Depth?

    [i think I started here with an erroneous value. This has been revised to be based on what i hope is the correct value. I will be looking into this further to be certain as to the numbers involved.] It is straightforward to determine the amount of "quantizing noise". In what follows, it is...
  17. Doug Kerr

    About quantizing "noise"

    The effect of quantization on the observed (in digital form) noise from a photodetector is interesting. Suppose that the width of a quantizing band is Q, and the centers of those bands fall at (N+0.5)Q, where N is an integer. Suppose that in a noise test, the actual value of H produces an mean...
  18. Doug Kerr

    About quantizing "noise"

    Quantizing error is the discrepancy between a value as represented in quantized form (typically in a digital representation) and the actual value. As this applies to the basic digital representation of an audio waveform, and especially in the telephone industry, it became common to speak of...
  19. Doug Kerr

    Dynamic Range versus Bit Depth?

    Just for the sake of thoroughness, I note that there is a further component in the overall noise observed in the "output" of a sensel photodetector exposed to a certain illuminance for a certain time. That is dark current noise. It is a time-random quantity. Its name includes "dark" since it...
  20. Doug Kerr

    Dynamic Range versus Bit Depth?

    A complication comes from the fact that the noise seen in the ISO test (at H=0.01Hsat) comprises both shot noise (from the randomness of arrival of photons) and read noise (typically thermal noise in the analog amplifiers involved in reading the sensor. Typically the read noise is in fact...
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