Take the rainfall analogy: light energy is like rainfall; more intense rain, higher the rainfall but does not matter how large the aperture of the gauge is, all would indicate the same rainfall (within reason) over time.
It really depends what you want to measure. If you're a meteorologist, you'd only care about the height to which the gauge is filled over a standard [24h] period of time.
Indeed, and I had hoped that by now, it would be obvious that I am not saying 5 gallon bucket would collect the same amount of rain water as a gallon bucket.
But if you want to store the rainwater for your fields, the size of the water basin becomes very relevant: a basin of 36m * 24m has a surface of 864m2, one of 17.3m * 13m has a surface of 225m2. That means the bigger basin can receive almost 4 times as much water as the smaller one, given the same depth.
Sounds almost like the E word
The conversation is if "total light energy" as defined in the Manual of Photography to be the "photographic exposure", is a good definition or not good or completely wrong.
I've been trying to explain why I think it is a good definition. However, I realize, it depends what "light energy" means. To me, it simply the intensity or the amplitude of light energy. Bobn2 says, it's intensity, time and area. I beg to differ as "joules" is a scalar quantity, measured only in "amplitude". However, he knows a heck of lot more than I do and can say that way better than I ever can.
Another way to understand "light energy" is the amplitude of the EM field. Does it mean an EM field with higher amplitude more intense light? How does that compare with light with more photons per unit volume?
I think I see where bobn2 is coming from that without clear understanding of Quantum Exposure, it may be difficult to answer/understand and I am not sure if I have enough years left in me to get into that rut ;-)
I'm reading this article:
QUANTUM THEORY OF PHOTOGRAPLIICEXPOSURE
Hey, mbp! How are you making out with
Dr. Silberstein? It has been 4 days since you posted the above. Anything to report?
Well, not very far; however, somewhat tangentially I 've thinking what is the difference between heat and temperature ;-)
Have you read the link you offered us yet? If so did you learn what Silberstein uses as Exposure of a sensitive halide film?
The difference between heat and temperature is a very common misconception in the popular literature including in the minds of elementary school teachers. They plant seeds of misunderstanding because they, themselves, do not understand the difference, mainly because they are often memorizing definitions without understanding the physics/thermodynamics behind the definitions. Too bad for their students.
Heat is an
extensive property of a system, being the
energy that passes spontaneously from a hotter system to a colder body, without work being performed, if there is a
heat transfer pathway. It is measured in calories, Joules and other units depending on the application.
Temperature is an
intensive property of a system, or body which measure the relative hotness or coldness of a system or body. It is measured using a temperature scale, commonly, C, F, and K. It can be considered from the point of view of the
Kinetic Theory of particles in a fluid, or more generally from a
Thermodynamics point of view.
Since the link you provided did not include Papers I, II, III which made reading the summary paper a little difficult, I took the liberty of finding
his work in the BHL, starting at Page 257.
http://www.biodiversitylibrary.org/item/121877#page/269/mode/1up
In
the link you provided above , Silberstein develops (page 129) his Equation (1) which is preceded by this:
- "But the knowledge of the type is required only in order to derive the integral law, concerning the photographic “density" as a whole, from the elementary law of exposure concerning each size-class of grains separately. To begin with the latter, let there be, per unit area of the plate, N grains or targets each of size (area) a, which can be measured, and let n be the number of light-darts, again per unit area, impinging upon the plate. Let e be the fraction* of the area of each target vulnerable to light, i.e., such that on being hit by at least one light-dart of sufficiently small wave-length, it becomes itself and therefore also makes the whole target or grain developable. Then the total number k of grains affected or made developable by this shower of n darts will be, statistically (cf. Paper I),
(1) k =N(l-e^-ean)." [ the “e” in "ean” represents epsilon in Silberstein’s Equation (1)]
Please note Silberstein's use of "per unit area" in the definition of both N and n. That was back in 1922. Nothing has changed. A mark of a good model is that the fundamental definitions don't change.
I am no expert on sensitometry and I have no particular interest in learning more about it. But it is clear to me that Silberstein, way back in 1922, used the usual scientific definition of
Exposure (photography) , namely:
The bolding of
amount of light per unit area is mine. ( It is the result of integrating the area power density [with respect to time] to give the area energy density.)
"
amount of light per unit area" is measure of unit of "light power"
Wrong. Please re-read the sentence in the brackets.
as opposed to what is "light power".
Amount of light per unit area is the energy density, not the power density.
It kinda makes me ask what "is" is...
I'd advise you to read what is written before traipsing off into your personal wilderness.
As I said earlier, "amount of light per unit area" can be expressed as a distance from a light source.
Nope. "a distance from a light source" is measured in meters etc. "amount of light per unit area" is measured in lux seconds. Re-read the work that Tony Field did for you.
The predilection for lumen/m^2 is to multiply with a sensor area and derive "total amount of light".
Of course!
Do you know what linear density is? Give an example please.
Do you know what surface or area density is? Give an example please.
Do you know what volume density is? Give and example please.
Are the above densities intensive or extensive variables?
However, "more light" over wider area is not same as "more light" over a same area; former does not affect "exposure" and the latter does. Of course, I realize you know this.
No I don't as it is an incomprehensible statement.
imho, "more light (energy)" should mean higher EM amplitude or higher photon density.
What??? I thought you said you were an EE! JC Maxwell would roll over in his grave. (So would Max Planck.)
I always had a difficult time when telling my undergraduate students, "The textbook is wrong." It was a lot easier with grad students as they were a bit more mature.
I then always wondered, "why did you choose this text book..."; I realize probably you did not pick the book. ;-)
I usually did pick the text.
But since most texts have errata, one of my responsibilities as a teacher is to point or errors in textbooks, the literature, manuals etc.
I suggest that you consider the above possibility when you continually quote an incorrect definition from the Manual of Photography.
What is exposure is "total light energy".
Wrong.
I can now say that with 92% confidence level.
Why not say it correctly and go for 100%?
Exposure (photography) is the amount of light per unit area, measured in lux-sec.
What is the exposure for your next gig is:
"Let's see, light power density of 10, 500W bulbs over 50m^2 area is 1018 lux; and EV15 is 4096 lux-second, so use EV11 for "exposure", or use an incident meter :-D
As you know, internet articles and the consumer photography press is filled with incorrect definitions. You could latch onto a wide variety of definitions of Exposure, ISO, Exposure Triangles etc if you wish. It gets quite difficult to learn more advanced topics, though, if you insist on using incorrect vocabulary.
MoP, however, is not every other Tom, **** and Harry web article.
Is this an appeal to authority? So you not have the ability to understand and to rationally criticize a sentence that you say is in the MoP.
So I expended little more time trying to understand what they meant.
Better spend a little more time.
Just for the fun of it, try using Silberstein's "light-darts" instead of "quanta" and see how far it gets you on this forum.
Thanks for the reference to Silberstein. I haven't heard of him since my days as an undergraduate engineer when I had a lab instructor who couldn't understand A.E. and therefore dismissed his theories, including the PE Effect. His lack of understanding, in that case, was caused by a false understanding of
"stopping potential" when dealing with Photoelectrons.
BTW, I have not dismissed any theory.
Have you learned which theories are applicable to the Exposure (photography) yet?
The false understanding was based on confusion between of the "Intensity of light" and the "energy of quanta", a confusion that still existed to this day with undergraduates who have been improperly taught, by teachers who weren't "pedantic" enough (when defining such terminology.)
A fighter pilot/professor is rather powerful combination, if I may say so.
Both help me to make
the occasional nice photo.
Of course no properly trained Solid State EE would endure that confusion.
Indeed, a properly trained Solid State EE would never endure that confusion; OTOH, like myself, confusion is what keeps me going :-( ;-)
Most of the rest of us try to minimize confusion by correcting false definitions and concepts so that they don't contaminate the minds of folks who want to learn useful stuff, not play around with
non-sequiturs .
By the way, have you ever considered an exposure with varying scene Luminance with monochromatic light? That is, where the area density of light is high resulting in a dark portion of the developed emulsion or a bright portion of the digital jpeg? Something to think about.
Indeed, a photo of non-varying scene Luminance would be as interesting as a photo of gray card, which, incidentally, is loved by the DPR forumites, so it seems. ;-)
Think about a scene with varying
reflectance illuminated by monochromatic light. Does the Exposure (photographic) vary from region to region on the surface of the sensor at the end of the open shutter interval?
I suggest that you at least try to answer the questions posed above. That will give us some feedback to determine where your misunderstandings are.
The pleasure is all mine and to keep this on topic -
Do you see the difference in "what is sensitivity" vs. "what is the sensitivity of camera"?
Yes. As you read in my answers to both bobn2 and Iliah Borg, I have a background in both electronics where, in the receiver world, sensitivity refers to the minimum detectable signal and in transducers, where sensitivity refers to the derivative of a transfer function. I am aware of the difficulty of relating exposure (photography) to output brightness. While exposure (photography) is very well defined, output brightness is not, leading to a very vague transfer function.
I see the parallel with what is "exposure" and what is the exposure (or heat and temperature, another example). YMMV.
Oh. Try using Exposure (photography) and you'll see the errors that you are propagating.
BTW, it's mostly semantics, as usual...
No it is not. There is a discipline and rigor to scientific and engineering discourse. Yes, the context has a lot to do with the discussion but in this case it is a sloppy use of terminology by a correspondent who has little respect for discipline and rigor in his utterances.
