I'm not sure but I think hell has just frozen over 😀
If I understand your concession correctly, does that mean you finally accept that exposure can be defined in layman's terms as the amount of light that struck the sensor per unit area while the shutter was open?
And that only
affect the exposure as defined above?
Im a practical man. i have to see things . i cant see photons ,luminance ect. but i can see a histogram. my brain is not as advanced and my daughters brain where she can see the concepts as if they were in front of her. its why i could never study biology and science like her, its like defining where does the universe end it pickles my brain. 😁
Yes 😁😀😎
Where did you find those values? I can not see them in Exifs of my pictures. ( Sony and Canon)
me neither, but it did lead me on a search to find out what LV was.
Quote: A histogram is simply a graphic representation of the exposure levels within an image.
It depends on what type of histogram you are looking at - RGB or luminosity
So, 7.2 foot-candles, eh?
My references are:
The concept became known as the Light Value System (LVS) in Europe; it was generally known as the Exposure Value System (EVS) when the features became available on cameras in the United States (Desfor 1957).
en.wikipedia.org/wiki/Exposure_value
This is a Composite tag calculated by ExifTool using the formula:
LV = 2 * log2(Aperture) - log2(ShutterSpeed) - log2(ISO/100)
exiftool.org/forum/index.php?topic=7195.0
Your references are?
A pity that the ISO setting is not shown, so no way to check ...
Download Phil Harvey's ExifToolGUI.
There are many, many, many EXIF tags, apps do not show them all.
The histogram is computed using ISO, WB, etc settings (JPEG), none of them being part of exposure.
again:
Phil Harvey says:
This is a Composite tag calculated by ExifTool using the formula:
LV = 2 * log2(Aperture) - log2(ShutterSpeed) - log2(ISO/100)
exiftool.org/forum/index.php?topic=7195.0
Time this whole insane thread was moved elsewhere, IMHO.
That is not applicable to this. That is a description of 'Exposure Value' otherwise known as EV, given by the formula
EV = log_2 * N^2 / t
I think that's definitive with respects to how ExifTool calculates it - that is, it's not a value passed through by the camera. But we should think why that is done. The APEX system says
Ev = Av + Tv = Bv + Sv
Here, EV is Exposure Value, as above. Av is 'Aperture Value', 2*log_2 N. Tv is Time value, Log_2 1/T, Bv is Luminance Value (sometimes written as Lv) - i.e. the meter reading. SV is the logarithmic exposure index, scaled by an appropriate value.
So we can reform the second two clauses as Lv = Av + Tv - Sv, which, when you arrange for 'shutter speed' rather than exposure time, comes down to the formula that Phil used there. The idea is that the exposure meter reading provides for a combination of aperture, shutter speed and ISO - so if you want to know what the meter was reading, you can calculate from those. What it's missing is that it should take into account the EC control - otherwise what you get is the meter reading as corrected by EC.
See my reply to your earlier post
I was hoping for a reference that supports your opinion that "Light Value" is scene luminance derived somehow from in-camera metering.
Without a credible reference, the opinion carries little weight, sad to say.
You can try following the reasoning. I gave you a link to the Wikipedia article, that explains the Bv is Luminance Value or LV. I showed how the APEX equation comes down to the same thing as EXIFtool uses, and that it would give the luminance value, on the assumption that EV was zero.
Just levels, Donald, not "exposure levels".
