What I doubt is the usefulness of such inclusion without allowing for exceptions, that is without a possibility / option to describe particular exposure conditions.
May 31, 2023
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And, in the case of the 1931 2 degree SO, not completely representative of the population. Collectively, that group was somewhat blue-deficient.
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You'll need to define sensor for this definition to have precision. Are you talking about the silicon? The CFA? The microlenses? The top of the sensor stack?
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In your way of thinking, does the CFA spectral response affect the exposure? Does the hot mirror affect the exposure?
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Depending on definition, orthochromatic film is already a problem, X-Ray is another problem, including "actinic light" into the definition is a partial solution.
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With X-ray plates, you can have density without light (measured in lux) hitting the sensor.
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What does exposure mean for a sensor with a IR-pass, VIS-rejecting stack, and a 950 nm low-pass (for frequency) filter on the lens?
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Absolutely.
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That is a great pity because most, if not all, light meters (external or in-camera) are calibrated to that curve as I am sure you know!
I don't understand what an exception might be. Is it possible that I have missed such an exception in this thread?
With a spot meter going around a scene it would give different exposure recommendations for evenly-lit, equally reflective, equally distant objects if they are, for example, red, green and blue.
If the blue is 450nm and the green is 550nm then the perfect spot meter would recommend about 5 EV more than the green. But if someone exposed for the green then the blue would be rendered pretty dark - which could naïvely be called "under-exposed".
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Trying to find a continuous wave model for something that is a quantum phenomenon is always going to be problematic. Remember that exposure was formalised before the development of QM. More interestingly, studying the effect of very low light levels on photographic plates was part of the process that settled that QM applies to light.
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So light meters can not be calibrated to the CIE luminous efficacy curve, it would appear.
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They certainly can. The problem is, how do they react to sources that don't conform the the CIE efficacy curve. There's no reason that all meters calibrated to the curve will behave the same under different conditions. Most problematic, you can devise light sources that would provide the same set of colours to the standard observer, but would meter quite differently.
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How about they certainly are?
No, there's no reason that they should. Don't make me insult you by claiming that a source of blue light, nay UV light, would make the light meter recommend more exposure or make a lux-meter say "nope, not much light there" ...
That is a Straw Man, sorry!
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As Danno says, "hitting the sensor", so I'll agree with him and say that different CFAs and different hot mirrors will cause different exposuires all else being equal.
It comes as no surprise to me that when I remove the UV/IR filter from a Sigma SD1/14/15, the metering lies horribly ...
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So you're saying that the sensor in the definition is only the silicon part? Does that mean that for the purpose of exposure calculation, you would like to apply the CIE Y spectral sensitivity curve to the energy that passes through the CFA and hot mirror? How then would you measure the exposure for an IR-only camera? It would have response with zero exposure. That doesn't make a lot of sense.
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No.
For the average punter, there is no such thing. But if we are talking about a camera with a permanent IR filter and only for use with IR it makes sense to me that the metering method would be for IR, i.e. not photometric.
I know of no radiation measurement device that "would have response with zero exposure". Please don't explain, it should make no sense to anyone
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If light is measured in lux, then you can get finite sensor response with zero light, if the camera's spectral sensitivity is sufficiently different from CIE Y. Consider a camera with the hot mirror removed in the presence of narrowband 1000 nm radiation.
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Then what do you mean?
