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Author Topic: Turning layers into channels  (Read 9332 times)

Jeremy Payne

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Turning layers into channels
« on: September 16, 2009, 10:49:50 AM »

Let's say I have three aligned monochrome layers that I would like to transform into the Blue, Red and Green channels of a single image.

Is there an easy way to do that?
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Mark D Segal

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Turning layers into channels
« Reply #1 on: September 16, 2009, 11:12:21 AM »

You can make Alpha channels from Layers using Calculations, but I don't know that exactly what you are asking to do is possible. Why do you want to do this?
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Mark D Segal (formerly MarkDS)
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Panopeeper

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Turning layers into channels
« Reply #2 on: September 16, 2009, 11:33:01 AM »

Quote from: Jeremy Payne
Let's say I have three aligned monochrome layers that I would like to transform into the Blue, Red and Green channels of a single image.

Is there an easy way to do that?
You can copy a channel and paste it over another channel. This way you can even swap the color channels. (The monochrom layer has a single channel.)
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Jeremy Payne

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Turning layers into channels
« Reply #3 on: September 16, 2009, 11:52:39 AM »

Quote from: MarkDS
Why do you want to do this?

I'm fascinated by the work of Prokudin-Gorskii and I'd like to make my own color image files from scans of his raw negatives ...

http://www.loc.gov/exhibits/empire/making.html

I have been having a lot of fun playing with the fully rendered and color versions doing my own retouching and color correction and then printing them ... they look terrific.

I'd now like to try and create my own color images from the positive scans of his filtered original captures.

Here's an example of the scanned negatives:


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Mark D Segal

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Turning layers into channels
« Reply #4 on: September 16, 2009, 05:46:47 PM »

Fascinating but not clear to me what gymnastics would be needed to get each greyscale image representing one of the primaries into a channel reflecting that primary.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml

new_haven

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Turning layers into channels
« Reply #5 on: September 16, 2009, 09:16:18 PM »

You should use the Image>Apply image command. Set the destination layer or channel by making it the working layer or channel. Select the source from the Apply image dialog. The source can be either an entire layer or just a channel from the current document or another loaded document. So you could create a new layer and copy your source layers to individual channels. -R
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Jeremy Payne

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Turning layers into channels
« Reply #6 on: September 16, 2009, 09:21:38 PM »

Quote from: new_haven
You should use the Image>Apply image command. Set the destination layer or channel by making it the working layer or channel. Select the source from the Apply image dialog. The source can be either an entire layer or just a channel from the current document or another loaded document. So you could create a new layer and copy your source layers to individual channels. -R
Sweet - thank you!  I will give it a go.
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Misirlou

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Turning layers into channels
« Reply #7 on: September 16, 2009, 09:36:34 PM »

Cool idea. I was living near DC when that exhibit opened, and I got all caught up in it myself. Not sure I ever really understood how he fired off all three shots quickly enough for that to work. At the time, the images with moving water made me think that he had some method whereby he passed a single holder through the camera back almost in one motion. I suppose the curators have a very good idea of the exact method. It's a shame other photographers didn't try the same thing elsewhere.
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Gary Brown

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Turning layers into channels
« Reply #8 on: September 16, 2009, 09:59:43 PM »

Quote from: Misirlou
At the time, the images with moving water made me think that he had some method whereby he passed a single holder through the camera back almost in one motion. I suppose the curators have a very good idea of the exact method. It's a shame other photographers didn't try the same thing elsewhere.
The Wikipedia article says,

Any stray movement within the camera's field of view showed up in the prints as multiple "ghosted" images, since the red, green and blue images were taken of the subject at slightly different times.

The exposure time of the frames is likely to have varied, even if the developed negatives were later on similar glass plates. In a letter to Leo Tolstoy requesting a photo session, Prokudin-Gorsky described each photo as taking one to three seconds, but when recollecting his time with Tolstoy, he described a six-second exposure on a sunny day. Blaise AgŁera y Arcas estimated the exposure of a 1909 photo taken in broad daylight to have had combined exposures of over a minute, using the movement of the moon as comparison.


(It includes references for that info, but I haven't looked at them.)
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Mark D Segal

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Turning layers into channels
« Reply #9 on: September 16, 2009, 10:37:49 PM »

Quote from: new_haven
You should use the Image>Apply image command. Set the destination layer or channel by making it the working layer or channel. Select the source from the Apply image dialog. The source can be either an entire layer or just a channel from the current document or another loaded document. So you could create a new layer and copy your source layers to individual channels. -R

I don't think this procedure would transform the monochrome layers representing R, G and B information into R, G and B channels separating that information accordingly.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml

rovanpera

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Turning layers into channels
« Reply #10 on: September 16, 2009, 11:25:43 PM »

heres one way how to do it...

[attachment=16618:Prokudin...i_layers.jpg][attachment=16617:Prokudin_Gorskii.jpg
]
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new_haven

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Turning layers into channels
« Reply #11 on: September 17, 2009, 12:41:44 AM »

This is the result after loading the different images into RGB channels and experimenting with a curves adjustment layer.

In the scanned images which is the red, green, and blue channel?

« Last Edit: September 17, 2009, 01:01:29 AM by new_haven »
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Jeremy Payne

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Turning layers into channels
« Reply #12 on: September 17, 2009, 06:49:09 AM »

Quote from: new_haven
This is the result after loading the different images into RGB channels and experimenting with a curves adjustment layer.

In the scanned images which is the red, green, and blue channel?

Very cool ... didn't have time last night to play around - was printing up a storm ...

They are Blue, Green & Red from top to bottom.
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Mark D Segal

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Turning layers into channels
« Reply #13 on: September 17, 2009, 07:58:54 AM »

Quote from: new_haven
This is the result after loading the different images into RGB channels and experimenting with a curves adjustment layer.

In the scanned images which is the red, green, and blue channel?


Nice try, but not successful. There must be a way to do this, and I thought of some similar approach to what you are displaying here, but these layers are not really substitutes for channels.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml

Mark D Segal

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Turning layers into channels
« Reply #14 on: September 17, 2009, 08:17:22 AM »

Jeremy, I went back to the L.o.C website and re-read their process description. What's missing is exactly how they filter the individual grayscale images in a digital process to produce colours amenable to fine-tuning for producing a correct-looking result. Why not send a request to the L.o.C for more detailed technical information on how they did it? It's *probably* not a secret.
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Mark D Segal (formerly MarkDS)
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papa v2.0

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Turning layers into channels
« Reply #15 on: September 17, 2009, 08:39:34 AM »

Hi jeremy

If you do contact L.o.C. they may be able to tell you the colour of the filters used and try to work out the x y values of the dominant primaries.

These then could be loaded in custom rgb working space and saved as a profile in photoshop.

You would in effect be working the the filter colour space which was used to make the separations and the resulting projections.

This might help in colour adjustments.
Ill play around and see what I get.
[attachment=16622:custom.jpg]

[attachment=16623:profile.jpg]
« Last Edit: September 17, 2009, 09:10:05 AM by papa v2.0 »
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papa v2.0

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Turning layers into channels
« Reply #16 on: September 17, 2009, 03:11:03 PM »

hi eaiest way to assemble image is to open the three image file ( blue green red plate from top to bottom)

use marquee tool to select top image (blue)
copy
open new file (rgb untagged)

select blue channel and paste.

save file

repeat for other two plates

then select move tool and align red and blue to green plate



asign a rgb profile of your choice
colour adjust to taste.
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new_haven

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Turning layers into channels
« Reply #17 on: September 17, 2009, 10:31:09 PM »

Here's what I get using apply image loading the aligned gray scale scans into the appropriate rgb channels.




Same image with white and black points set and mild s curve.

« Last Edit: September 17, 2009, 10:48:31 PM by new_haven »
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papa v2.0

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Turning layers into channels
« Reply #18 on: September 18, 2009, 09:11:30 PM »

hi


just did this today from the 68mb file
(aside from the matlab exercise in image registration, im more interested in colour rebuilding methods)

i think i need to contact the LoC as to the method of digital capture. this is an intriguing experiment.

can we reproduce the capture effect from glass plate negatives?
can we determine the filtration used based on the unknown bgr separations?
can we determine the white source of the projections of the tri negatives?
if i could get any of this info i might be able to try run it thru ciecam02

 i think  basically we have a camera raw file from c1900

any ideas any one?




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Jeremy Payne

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Turning layers into channels
« Reply #19 on: September 23, 2009, 06:55:57 AM »

Here's my first pass ... this is fun!

[attachment=16764:1_3.jpg]
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