December 19, 2014, 09:09:06 AM

Author Topic: More colors  (Read 3542 times)

Jettatore

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Re: More colors
« Reply #15 on: April 20, 2012, 03:18:34 PM »
Semi-related to the topic.  I wrote a macro script that separates the color layer from the underlying value layer of any image for Photoshop to it's own layer, isolated from the underlying values.  It's really useful for studying images and how colors work, and I also find it useful for my photo-retouching and digital painting workflows.  You can get it free here:  http://forums.cgsociety.org/showthread.php?p=6313023#post6313023

This is a slightly more complicated version of the above that also seperates out the high and low frequency details to separate layers.  http://forums.cgsociety.org/showthread.php?p=7088384#post7088384

You have to register to download the files posted in those threads but that's free.
« Last Edit: April 20, 2012, 03:21:06 PM by Jettatore »

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Re: More colors
« Reply #15 on: April 20, 2012, 03:18:34 PM »

LetTheRightLensIn

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Re: More colors
« Reply #16 on: April 20, 2012, 03:19:38 PM »
Silicon is naturally less sensitive to blue and violet wavelengths of light than it is to green, and it is most sensitive to red. I am not really sure that adding additional pixel types with, say, a violet filter, will really improve the quality of violet in digital photos taken with such a sensor. Current bayer CFA's use fairly broad filter ranges for blue, green, and red pixels. Blue filters allow in light down to around 380nm (very violet), while red filters allow in light up to and beyond 700nm. Green overlaps both just a tad.

Assuming you did actually involve say violet, blue, cyan, green, yellow, orange, red, deep red CFA pixels in some "advanced" sensor design. One way or another, you still need to "coalesce" that greater variety of colors into RGB image pixels in the end anyway. You would have to do some weighted mathematical averaging of blue with violet and cyan, green with cyan and yellow, and red with deep red, orange and yellow. There are a few drawbacks to such an approach, and potentially no real benefits:

 - You need to be extremely careful about how you lay each color out in the CFA to ensure that color distribution is effective to capture enough luminance per pixel and still be capable of interpolating an output pixel (today most interpolation is based on 2x2 quads of bayer pixels with slightly weighted algorithms to eliminate color artifacts, zippering, etc.) Fuji's mew X Pro-1 uses 6x6 blocks of pixels to produce an output pixel, and it still only uses RGB albeit with less pattern repetition.
 - You need a more complex RAW file format to acomodate the increase in various CFA pixel color types.
 - You need considerably more complex interpolation algorithms to convert larger blocks of input CFA pixels into output RGB pixels.
 - You need more advanced logic to convert multiple input colors into fewer output channels per output pixel with appropriate color accuracy.
 - When working RAW, you need to reprocess the bayer pixels and send them through your entire pipeline of edits to render the image on screen, so more complex interpolation and color conversion will impact the performance of post-process workflows

I think more can be done by moving to a Foveon X-3 style sensor, where each color channel is stacked at a single photosite. Silicon is naturally sensitive to most of the visible wavelengths of light, and considerably more sensitive to near infrared than it is to UV. As such, it also naturally filters light the deeper it penetrates into a silicon well, making it pretty easy to capture blue at the surface, green in the middle, and red deep into the well (which is exactly what Foveon sensors do.) By eliminating an alternating pattern of RGB pixels, you improve a LOT of the characteristics of the sensor directly, and since you have full color data at every single pixel, you also have full color fidelity. Foveon sensors are fairly well known for having richer blues than bayer-type sensors, without the need for a lot of complexity. You also eliminate color moire, minimize monochrome moire, reduce noise in the blue channel, etc.

I think I'd have to generally agree with much this.
Anyway it's complicated stuff.
« Last Edit: April 20, 2012, 03:23:26 PM by LetTheRightLensIn »

Jettatore

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Re: More colors
« Reply #17 on: April 20, 2012, 05:38:00 PM »
I think for an idea along these lines to have a practical impact, there might need to be serious upgrades to the sensor and resolution (phase 1 Medium format++) to even begin to get to a level where there is a shift in hue/saturation that isn't at least recorded along with the value data already.  Even if the hue and saturation are 'off' (aka don't match what your eye's see) that's a simple slider shift in editing.  However if there are subtle variations in the hue/saturation that are not being picked up by current sensor technology there would be missing data that would not be shift-able via a slider.  I'm not sure that there is any missing data capture for hue/sat, that would show up to the human eye, current HD monitors and or high-end printers.  I took a test shot of a pillow with a detailed semi-photo realistic embroidery on it with my 7D and then compared it zoomed in on the back of the camera to the pillow, and my eye could not see hue or saturation shifts that were not being captured by the camera accurately.  Zoomed in that far I could see each individual thread and the shading and colors were all captured so far as my eye could see.

TrumpetPower!

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Re: More colors
« Reply #18 on: April 20, 2012, 06:06:54 PM »
I took a test shot of a pillow with a detailed semi-photo realistic embroidery on it with my 7D and then compared it zoomed in on the back of the camera to the pillow, and my eye could not see hue or saturation shifts that were not being captured by the camera accurately.

If you want to know what all the fuss is about, compare the pillow to a print of the photo of the pillow instead of the back-of-the-camera preview. I guarantee you you'll see differences.

If you were doing portrait photography and your model had posed with the pillow, I can all but guarantee you that you wouldn't give a damn about those differences, so long as the model's skin looked good.

And if you took a picture of the pillow to sell it on Ebay or to email to your family, it'd also be just fine.

If you took the picture to include in a product catalog, depending on the client, it might matter or it might be "good enough."

If it were an oil painting instead of a pillow and you were making giclee prints to sell at a hundred bucks a pop for an 8" x 10", it would not be "good enough," though there're those who'll still try to pass it off as such.

And if it were an oil painting that you were recording as part of a preservation effort for a major museum, you'd be laughed out of the room.

For the overwhelming number of users for the overwhelming number of situations, modern DSLRs have unimaginably fantastic color reproduction just as they are. For the overwhelming number of the remainder of users for the overwhelming number of remaining situations, modern DSLRs can be made to function to superlative standards, if you know what you're doing. And, for a very tiny fraction of a percent of the population, modern DSLRs are a toy when it comes to color reproduction.

Me? Most of the time I'm in the first camp, but I spend a significant amount of my photographic time in the second camp. And I'm positively thrilled with my 5DII and I'm in the process of getting my 5DIII all dialed in and anxious to see how well it does. I'm pretty sure that the 5DIII, more importantly combined with some enhancements to my workflow that I'm working on at the same time, will let me actually get some results that might start to rival the stuff they do in major museums -- maybe even good enough for minor museums, which could open up some really interesting possibilities for some really fun gigs.

Cheers,

b&

AJ

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Re: More colors
« Reply #19 on: April 20, 2012, 06:40:07 PM »
I took a test shot of a pillow with a detailed semi-photo realistic embroidery on it with my 7D and then compared it zoomed in on the back of the camera to the pillow, and my eye could not see hue or saturation shifts that were not being captured by the camera accurately.

If you want to know what all the fuss is about, compare the pillow to a print of the photo of the pillow instead of the back-of-the-camera preview. I guarantee you you'll see differences.

If you were doing portrait photography and your model had posed with the pillow, I can all but guarantee you that you wouldn't give a damn about those differences, so long as the model's skin looked good.

And if you took a picture of the pillow to sell it on Ebay or to email to your family, it'd also be just fine.

If you took the picture to include in a product catalog, depending on the client, it might matter or it might be "good enough."

If it were an oil painting instead of a pillow and you were making giclee prints to sell at a hundred bucks a pop for an 8" x 10", it would not be "good enough," though there're those who'll still try to pass it off as such.

And if it were an oil painting that you were recording as part of a preservation effort for a major museum, you'd be laughed out of the room.

For the overwhelming number of users for the overwhelming number of situations, modern DSLRs have unimaginably fantastic color reproduction just as they are. For the overwhelming number of the remainder of users for the overwhelming number of remaining situations, modern DSLRs can be made to function to superlative standards, if you know what you're doing. And, for a very tiny fraction of a percent of the population, modern DSLRs are a toy when it comes to color reproduction.

Me? Most of the time I'm in the first camp, but I spend a significant amount of my photographic time in the second camp. And I'm positively thrilled with my 5DII and I'm in the process of getting my 5DIII all dialed in and anxious to see how well it does. I'm pretty sure that the 5DIII, more importantly combined with some enhancements to my workflow that I'm working on at the same time, will let me actually get some results that might start to rival the stuff they do in major museums -- maybe even good enough for minor museums, which could open up some really interesting possibilities for some really fun gigs.

Cheers,

b&
I'm satisfied with the color response most of the time, but there are times when I'd like deeper reds, and more details in those reds (blows out so easily on a DSLR).  Ditto for deep violets and blues when shooting sunsets.  Greens on the other hand are really well represented with RGB.

I can get close to the colors I want by shifting hues and color-balance.  Contrast and saturation doesn't get you into that part of the gamut, it just tends to blow things out.  That said, it's a past-processing fix of something I'd like my camera to capture in the first place.


Jettatore

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Re: More colors
« Reply #20 on: April 20, 2012, 06:57:32 PM »
Sounds possible that your lighting or camera settings are off if you feel you are missing the fine shifts in hue contrast and saturation contrast.  Think if you set up a gorgeous studio still life or product photography shot, do you feel that taking a picture of a really controlled and well lit environment would still be missing these aforementioned shifts?  1 to 1 on my 7D, I cannot see any missing shifts perceivable to my eyes.  One thing you might want to play with is the Vibrance adjustments in something like Photoshop (if thats not it, sorry, just brainstorming possibilities).  PS should have Vibrance an option both a fixed adjustment and an adjustment layer.  That might get you where you want to be?  For something further, please post an image you want improved so the whole thread can have something tangible to focus on and figure out if simple edits or adjustments in shooting might help.

jrista

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Re: More colors
« Reply #21 on: April 20, 2012, 09:45:17 PM »
Silicon is naturally less sensitive to blue and violet wavelengths of light than it is to green, and it is most sensitive to red. I am not really sure that adding additional pixel types with, say, a violet filter, will really improve the quality of violet in digital photos taken with such a sensor. Current bayer CFA's use fairly broad filter ranges for blue, green, and red pixels. Blue filters allow in light down to around 380nm (very violet), while red filters allow in light up to and beyond 700nm. Green overlaps both just a tad.

Assuming you did actually involve say violet, blue, cyan, green, yellow, orange, red, deep red CFA pixels in some "advanced" sensor design. One way or another, you still need to "coalesce" that greater variety of colors into RGB image pixels in the end anyway. You would have to do some weighted mathematical averaging of blue with violet and cyan, green with cyan and yellow, and red with deep red, orange and yellow. There are a few drawbacks to such an approach, and potentially no real benefits:

 - You need to be extremely careful about how you lay each color out in the CFA to ensure that color distribution is effective to capture enough luminance per pixel and still be capable of interpolating an output pixel (today most interpolation is based on 2x2 quads of bayer pixels with slightly weighted algorithms to eliminate color artifacts, zippering, etc.) Fuji's mew X Pro-1 uses 6x6 blocks of pixels to produce an output pixel, and it still only uses RGB albeit with less pattern repetition.
 - You need a more complex RAW file format to acomodate the increase in various CFA pixel color types.
 - You need considerably more complex interpolation algorithms to convert larger blocks of input CFA pixels into output RGB pixels.
 - You need more advanced logic to convert multiple input colors into fewer output channels per output pixel with appropriate color accuracy.
 - When working RAW, you need to reprocess the bayer pixels and send them through your entire pipeline of edits to render the image on screen, so more complex interpolation and color conversion will impact the performance of post-process workflows

I think more can be done by moving to a Foveon X-3 style sensor, where each color channel is stacked at a single photosite. Silicon is naturally sensitive to most of the visible wavelengths of light, and considerably more sensitive to near infrared than it is to UV. As such, it also naturally filters light the deeper it penetrates into a silicon well, making it pretty easy to capture blue at the surface, green in the middle, and red deep into the well (which is exactly what Foveon sensors do.) By eliminating an alternating pattern of RGB pixels, you improve a LOT of the characteristics of the sensor directly, and since you have full color data at every single pixel, you also have full color fidelity. Foveon sensors are fairly well known for having richer blues than bayer-type sensors, without the need for a lot of complexity. You also eliminate color moire, minimize monochrome moire, reduce noise in the blue channel, etc.

I think I'd have to generally agree with much this.
Anyway it's complicated stuff.

I'm glad we can agree on something. :)

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Re: More colors
« Reply #21 on: April 20, 2012, 09:45:17 PM »

Jettatore

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Re: More colors
« Reply #22 on: April 22, 2012, 04:27:15 PM »
Someone told me the downloads I put above weren't working well.  Alternate links below:

Color Extractor Script (Photoshop)
http://www.mediafire.com/?jww7dp5m8u303jb

Custom Split Script (Photoshop)
http://www.mediafire.com/?mee40136455tri3

Descriptions of what they do are several posts above in the links, and they both come with a simple instructions file.  Hope you like them.

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Re: More colors
« Reply #22 on: April 22, 2012, 04:27:15 PM »