JoeV
Thin Air, Bright Sun
I don't presume to be "more knowledgeable", but here goes. The spectral sensitivity of B/W film varies between specific brands and types, but it theoretically could contain all the tonal information of your original color scene, but expressed as a gray scale rather than as color information.
The place where using channel mixer is very powerful is being able to alter the spectral sensitivity of the original color image, to achieve whatever B/W effect is required. Of course, the digital camera's sensor also has a limited spectral response, as does film, so using channel mixer is really like using a continuously variable color filter over the lens, but after the fact, rather than in front of the lens. BTW, you can also use color filters on the digital camera's lens to achieve a similar effect.
To respond to the OP's question, the color spectrum chart is a diagram of wavelength (i.e. color) versus intensity (we see this type of chart when discussing the spectral response of film, for instance), whereas monochrome images map light intensity over a band of wavelengths that have been normalized to a range of gray tones.
So various shades of gray aren't mapped to specific colors; rather, objects in the image field are mapped to various shades of gray by the spectral senstivity of the sensor or film. And this isn't a unique mapping, where a particular shade of gray equates to a specific wavelength; rather, you could have the case where various colors in the image field all map to the same shade of gray, like light green and dark green as an example. It all depends on the specific sensitivity of the media being used.
Theoretically you could have a B/W medium that has a linear response across a continuous band of wavelengths; in that case your original supposition would be correct; but I know of no real-world sensor system with those properties.
~Joe
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antiquark
Derek Ross
Yes, if you just shoot plain B&W film.
If you use lens filters, you can achieve the similar effects as channel mixing. However you would need a huge number of filters to get all the minor variations that photoshop gives you.
For example, if you took a B&W pic and used a blue filter in front of the lens, the red objects would look black.
Wiyum
Established
This thread has called to mind a story of the old days of cinema that has quite a bit of relevance to many of the questions at hand.
James Wong Howe (pioneering cinematographer responsible for Hud, The Thin Man, Sweet Smell of Success, Picnic, and countless others) rose to prominence in Hollywood despite his race and the prejudices of the times (he was Chinese, and began working as a cinematographer in the silent era) because he solved what was then a problem with shooting certain actors.
When Howe began working, he was an on-set photographer. Because panchromatic film hadn't been invented yet, actors with blue eyes ran into problems with orthochromatic film. The film's overwhelming blue sensitivity rendered blue eyes as white, and as a result, blue-eyed actors appeared ghostly, their eyes reduced to near-white. When shooting stills of an actress, Howe hit upon the idea of surrounding his lens with a frame black velvet, cutting the light that hit the blue eyes of the actress and rendering her eyes a normal-looking grey. She was so impressed that she insisted he be hired on as a cinematographer for one of her future films (if memory serves, he shot only her closeups on that first film). His ability to innovate in similar ways brought him to prominence as a cinematographer, and he remained very nearly the only non-white person working in prominent positions on Hollywood sets for decades. His work is really something too, if you haven't seen any of his films.
Anyhow, like I said: the topic at hand reminded me of the story.
Will
James Wong Howe (pioneering cinematographer responsible for Hud, The Thin Man, Sweet Smell of Success, Picnic, and countless others) rose to prominence in Hollywood despite his race and the prejudices of the times (he was Chinese, and began working as a cinematographer in the silent era) because he solved what was then a problem with shooting certain actors.
When Howe began working, he was an on-set photographer. Because panchromatic film hadn't been invented yet, actors with blue eyes ran into problems with orthochromatic film. The film's overwhelming blue sensitivity rendered blue eyes as white, and as a result, blue-eyed actors appeared ghostly, their eyes reduced to near-white. When shooting stills of an actress, Howe hit upon the idea of surrounding his lens with a frame black velvet, cutting the light that hit the blue eyes of the actress and rendering her eyes a normal-looking grey. She was so impressed that she insisted he be hired on as a cinematographer for one of her future films (if memory serves, he shot only her closeups on that first film). His ability to innovate in similar ways brought him to prominence as a cinematographer, and he remained very nearly the only non-white person working in prominent positions on Hollywood sets for decades. His work is really something too, if you haven't seen any of his films.
Anyhow, like I said: the topic at hand reminded me of the story.
Will
JeremyLangford
I'd really Leica Leica
So what makes shooting B&W film better than shooting color where you can either keep the colors or using an advanced program to convert to B&W?
There is the obvious ability to process and enlarge yourself which could be cheaper. The only other thing I can think of is push/pulling, higher dynamic range and maybe better sharpness.
Whenever I shoot B&W film, I'm afraid of wanting to shoot something that has really good color and not being able to capture the colors at all. With color film, I can always take away the hue/saturation if I feel like it would be better in B&W.
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antiquark
Derek Ross
It changes your frame of mind.
Exactly! It forces you to compose your pictures without relying on color.
JeremyLangford
I'd really Leica Leica
It changes your frame of mind.
Exactly! It forces you to compose your pictures without relying on color.
I honestly don't think I will ever be so into B&W film as most people on this forum. It is a fact that I can shoot with color film and choose the final image to have color or no color. It is also a fact that I won't ever get the colors I saw if I shoot on B&W film.
I understand that your frame of mind is better when you're not relying on colors and only relying on light. But I think I can shoot color film and switch my frame of mind to not rely on color and instead imagine the final B&W image after I convert it. However, I can never deny the ability and ease of push processing a roll of B&W film for shooting in an extremely low light situation.
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