If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
Photographing Ultraluminous LED-lit Art Projects
I wrote:
I tested my Canon 30D with the 100 mm f/2.8 macro lens with monochromatic (2nm wide) light. And what color is violet? Well, it is not violet, not blue, in fact it is BLACK, dead BLACK. At 420 nm the camera is rather weak in response, and produces blue. At 410 nm and below it is dead as a doornail. I don't have any other lens with me, so I don't know whether it is the lens or sensor. I should have realized that I saw into the UV (398 nm) with my eyes, through the viewfinder. That means that the sensor has a cutoff filter on it. Not unexpected, of course. I should add that no real reflective objects depend on reflectivity in the 380-415 nm region for color. That is because the eye's sensitivity is too low there. You really need an actual spectrum to see that violet color. The spectrum from a CD looking at the sun or a fluorescent light will do. Doug McDonald |
#12
|
|||
|
|||
Photographing Ultraluminous LED-lit Art Projects
[A complimentary Cc of this posting was sent to
Chris Malcolm ], who wrote in article : The problem with violet is that while it's theoretically possible to mix up an undetectable different equivalnce to any colour using three primary colours Wrong. You assume that *physically possible* colors (those obtained by mixing pure spectral colors in the range about 400..700nm) form a triangle in the "linear" color space (more precisely, in the "projective" color space). They do not. In particular, any triangle with vertices in the "real color" space does not cover the "real color" space. (In addition, no triangle "comes close" to covering all the space.) Hope this helps, Ilya |
#13
|
|||
|
|||
Photographing Ultraluminous LED-lit Art Projects
On 2008-03-19 21:39:39 -0700, Pooua said:
http://web.mit.edu/neltnerb/www/artwork/index.html features artwork illuminated by super-bright LEDs, but the photos do not accurately reflect the colors of the lighting. The artist says that his camera has trouble picking up the purple lighting, instead showing it washed out, apparently because it is outside the normal color space of the imaging sensor. Does that sound likely? What might a photographer do to take better photos of these tricky lighting situations? There is a device called an Expo/Disc. You hold it over the lens and point the camera at the light source, take a shot and measure the white balance. You set the white balance for whatever the Expo/Disc saw. But the artist is not all wet. You can easily get outside the color space of the sensor in situations like this. Sometimes it helps to switch to Adobe RGB in these situations. Sometimes it makes it worse. -- Waddling Eagle World Famous Flight Instructor |
#14
|
|||
|
|||
Photographing Ultraluminous LED-lit Art Projects
On 2008-03-20 21:35:48 -0700, Pooua said:
On Mar 20, 9:02*am, Don Stauffer in Minnesota wrote: On Mar 19, 11:39 pm, Pooua wrote: http://web.mit.edu/neltnerb/www/artw...eaturesartwork illuminated by super-bright LEDs, but the photos do not accurately reflect the colors of the lighting. The artist says that his camera has trouble picking up the purple lighting, instead showing it washed out, apparently because it is outside the normal color space of the imaging sensor. Does that sound likely? What might a photographer do to take better photos of these tricky lighting situations? Here is yet another problem. *We frequently do not perceive with our eyes the true color of LED or laser light sources if we view them directly. *Some of the cones can saturate, really throwing off our eyeball calibration. I suppose I could adjust hue in Photoshop. I've just never been very accurate with that thing. Any other ideas? You have to get it right when you take the picture. Photoshop cannot put back what was never there. -- Waddling Eagle World Famous Flight Instructor |
#15
|
|||
|
|||
Photographing Ultraluminous LED-lit Art Projects
"C J Campbell" wrote in message news:200803221855388930-christophercampbell@hotmailcom... You have to get it right when you take the picture. Photoshop cannot put back what was never there. What? In terms of hue and intensity? Wanna bet? -- Jeff R. |
#16
|
|||
|
|||
Photographing Ultraluminous LED-lit Art Projects
Ilya Zakharevich wrote:
[A complimentary Cc of this posting was sent to Chris Malcolm ], who wrote in article : The problem with violet is that while it's theoretically possible to mix up an undetectable different equivalnce to any colour using three primary colours Wrong. You assume that *physically possible* colors (those obtained by mixing pure spectral colors in the range about 400..700nm) form a triangle in the "linear" color space (more precisely, in the "projective" color space). They do not. In particular, any triangle with vertices in the "real color" space does not cover the "real color" space. (In addition, no triangle "comes close" to covering all the space.) Interesting point. I wasn't aware of that. Are you referring to the need to use negative primary values to get to the intensity of saturation of pure spectral colours outside the triangle? -- Chris Malcolm DoD #205 IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK [http://www.dai.ed.ac.uk/homes/cam/] |
#17
|
|||
|
|||
Photographing Ultraluminous LED-lit Art Projects
[A complimentary Cc of this posting was sent to
Chris Malcolm ], who wrote in article : Wrong. You assume that *physically possible* colors (those obtained by mixing pure spectral colors in the range about 400..700nm) form a triangle in the "linear" color space (more precisely, in the "projective" color space). They do not. In particular, any triangle with vertices in the "real color" space does not cover the "real color" space. (In addition, no triangle "comes close" to covering all the space.) Interesting point. I wasn't aware of that. Are you referring to the need to use negative primary values to get to the intensity of saturation of pure spectral colours outside the triangle? Yes, this is one of the manifestations. [Since the pure colors form a convex curve in the projective color space, ANY pure color which is not a primary will REQUIRE negative coefficients to express it via the primaries.] Yours, Ilya |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Free plans and projects to share. | The Hurdy Gurdy Man | Digital Photography | 1 | February 9th 05 01:43 AM |
Free plans and projects to share. | The Hurdy Gurdy Man | 35mm Photo Equipment | 1 | February 9th 05 01:43 AM |
Free plans and projects to share. | Intrepid | Digital Photography | 4 | February 9th 05 12:05 AM |
Free plans and projects to share. | Intrepid | 35mm Photo Equipment | 2 | February 9th 05 12:05 AM |
Free plans and projects to share. | Randy Replogle | 35mm Photo Equipment | 1 | February 8th 05 02:14 PM |