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-   -   What is the Percentage Range? (https://forums.steves-digicams.com/general-discussion-11/what-percentage-range-168336/)

Bynx Mar 30, 2010 7:56 AM

What is the Percentage Range?
 
If you consider the sun as being 100% white, and a totally black area as 0%, what is the % range that a camera can capture as (1) a jpeg, and (2) a Raw file. For arguments sake, lets say the camera is a 10 Megapixel. Are there any factors which would change the percentages? Like the sensor size or the size of lens. It seems when bracketing a shot to create an HDR image the percentage range is increased from the optimal single jpeg or Raw file.

Mark1616 Mar 30, 2010 8:40 AM

Not a clue but interested to find out the answers..... although I'm guessing the Sun is not pure white, but we can use the assumption it is for this process (I could be wrong).

Bynx Mar 30, 2010 8:51 AM

I guess what we are talking here is brilliance rather than color. Or are we talking temperature? Anyway the sun is the brightest and the shadiest is the darkest.

pbjunkiee Mar 30, 2010 10:29 AM

well if you think about it, when you look at levels in photoshop, the left side is white and the right side is black, so you can get a true black,and a true white in an image, im guessing it can pick up the entire range?

TCav Mar 30, 2010 12:15 PM

The Sun isn't 100% white. That's why the sky is blue and sunsets are red. Magnesium Oxide is 100% white (well, 99.996% white, actually), even if it's in a dark room.

Digital cameras are capable of recording images that range in brightness of from 2 to 20 EV, but not all at the same time. They have a dynamic range of from 9 to 11 EV (from dimmest to brightest), but a good deal of that dynamic range is lost during processing and the conversion of 12 or 14 bit data to 10 or 8 bit data in JPEG images.

Bynx Mar 30, 2010 5:20 PM

Ya Im not talking about color when I mentioned the sun. I just figure its the brightest thing to shoot. And absolute darkness would be the darkest thing. So if one is 100% and the other is 0% then the range of a single jpeg should be say from 15% to 80%. A Raw file might go 10% to 90%. No single file can go from 0 to 100. Now TCav you talk about EV. So that can translate to percentages right? It doesnt seem the dynamic range of any shot is very much compared to how much there is in a single full range scene with the sun shining and lots of deep shadows. The reason I ask this is that when I take shots for HDR use if I underexpose a lot for the sun and overexposure a lot for the shadows, then the range has to be a lot more than any file, jpeg or Raw. If this is true then HDR has to be an improvement in any shot with a long range.

Mark R. Mar 31, 2010 3:47 AM

Quote:

Originally Posted by TCav (Post 1072665)
The Sun isn't 100% white.

This is, in itself, true. The sun's light is a mixture of emission spectra of hydrogen, helium, carbon, etc. But it's almost white, i.e. it contains almost all visible wavelengths. If you look at a spectrum of the sun's light, there are only a few wavelengths missing. (These are absorbed by gases in the sun.)

Quote:

Originally Posted by TCav (Post 1072665)
That's why the sky is blue and sunsets are red.

With all due respect - this is nonsense. Even if the sun were a perfect white (containing all visible wavelengths in its spectrum), the sky would still be blue, and sunsets still be red. These sky colorations have nothing to do with the "whiteness" or spectral make-up of the sun, but rather they are atmospheric effects, having to do with the stronger scattering of short wavelengths. Blue light is scattered sideways, by the air molecules and dust - hence the sky is blue. In the evening, the sunlight travels a long distance through the atmosphere, hence most of the blue and green light is scattered away. What remains, is yellow, orange and red.

Quote:

Originally Posted by TCav (Post 1072665)
Magnesium Oxide is 100% white (well, 99.996% white, actually), even if it's in a dark room.

Magnesium oxide, a white powder, is not a light source. It is a light reflector. It can only reflect what it receives. If you put it in sunlight, it will reflect sunlight. To my knowledge, the best white reflector is Titanium dioxide.

However, what you may be referring to, is magnesium that is actually burning. Because the flame is so hot, the material emits black-body-radiation across pretty much the whole visible spectrum, making it a near-perfect white.

Regards,
Mark

TCav Mar 31, 2010 5:48 AM

The earth's atmosphere scatters short-wavelength light more than long-wavelength light. When the sun is high in the sky, violet and blue light is scattered over the entire sky, making it blue, and the wavelengths of light that are not scattered make the sun appear yellowish. When the sun is lower in the sky, it's light travels through more of the atmosphere so more of it's light is scattered, making the sun, and the sky around it, orange and red.

Magnesium Oxide, along with Magnesium Carbonate and Barium Sulphate, is a frequently use standard for white because of it's near perfect reflectance factor. Titanium dioxide is commonly used as a pigment in paint and food, but it has an absorption band around 400nm, so it's "warm" and isn't used as a standard for 'White'.

Bynx Mar 31, 2010 6:28 AM

Well, two pretty smart guys duking it out over the sun and the sky. How about answering the question. I think its an important one and should be easy enough to answer. Its a technical question and should apply to all cameras.

Mark1616 Mar 31, 2010 6:49 AM

Well I think the thing we need to know is what is the difference in EV between the sun and the inside of a closed box..... would that give the scale?


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