Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Mar 30, 2010, 7:56 AM   #1
Senior Member
 
Bynx's Avatar
 
Join Date: Jun 2007
Posts: 8,585
Default 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.
Bynx is offline   Reply With Quote
Sponsored Links
Old Mar 30, 2010, 8:40 AM   #2
Super Moderator
 
Mark1616's Avatar
 
Join Date: Oct 2005
Posts: 7,397
Default

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).
Mark1616 is offline   Reply With Quote
Old Mar 30, 2010, 8:51 AM   #3
Senior Member
 
Bynx's Avatar
 
Join Date: Jun 2007
Posts: 8,585
Default

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.
Bynx is offline   Reply With Quote
Old Mar 30, 2010, 10:29 AM   #4
Senior Member
 
pbjunkiee's Avatar
 
Join Date: Nov 2009
Location: Pensacola Fl
Posts: 914
Default

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?
pbjunkiee is offline   Reply With Quote
Old Mar 30, 2010, 12:15 PM   #5
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,544
Default

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.
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.

Last edited by TCav; Mar 30, 2010 at 2:05 PM.
TCav is offline   Reply With Quote
Old Mar 30, 2010, 5:20 PM   #6
Senior Member
 
Bynx's Avatar
 
Join Date: Jun 2007
Posts: 8,585
Default

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.
Bynx is offline   Reply With Quote
Old Mar 31, 2010, 3:47 AM   #7
Member
 
Join Date: Mar 2010
Location: Pretoria, South Africa
Posts: 72
Default

Quote:
Originally Posted by TCav View Post
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 View Post
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 View Post
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
__________________
A good photo starts with a good lens.

Last edited by Mark R.; Mar 31, 2010 at 3:51 AM. Reason: Typo
Mark R. is offline   Reply With Quote
Old Mar 31, 2010, 5:48 AM   #8
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,544
Default

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'.
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.

Last edited by TCav; Mar 31, 2010 at 6:32 AM.
TCav is offline   Reply With Quote
Old Mar 31, 2010, 6:28 AM   #9
Senior Member
 
Bynx's Avatar
 
Join Date: Jun 2007
Posts: 8,585
Default

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.
Bynx is offline   Reply With Quote
Old Mar 31, 2010, 6:49 AM   #10
Super Moderator
 
Mark1616's Avatar
 
Join Date: Oct 2005
Posts: 7,397
Default

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?
Mark1616 is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 2:40 PM.