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Channel Swap - Photoshop vs NX2

NanoMeter

US
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NanoMeter Silver Member Nikonian since 17th May 2012
Wed 27-Mar-13 03:22 AM

I have tried several methods of channel swapping using NX2, but so far I have not been able to duplicate the result I get with Photoshop.
If anyone knows of a better way to channel swap using NX2 I would welcome your input.

Top photo: The RAW file.
Middle photo: Red/blue channel swap using Photoshop.
Bottom photo: Red/blue channel swap using Capture NX2.

The NX2 channel swap that I show below is the method outlined in the sticky here:
https://www.nikonians.org/forums/dcboard.php?az=show_topic&forum=214&topic_id=370&mesg_id=370&page=

Click on image to view larger version

ericbowles

Atlanta, US
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#1. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 0

ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2015 Nikonian since 25th Nov 2005
Wed 13-Mar-13 03:50 PM

Did you correct WB in CNX2 before the channel swap? The image from Capture looks a little blue. PS ignores the WB and creates a new WB to your specifications. What is your WB technique in each?

I've found a lot of variation in my edits in CNX2.

Eric Bowles
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NanoMeter

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#2. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 1

NanoMeter Silver Member Nikonian since 17th May 2012
Wed 13-Mar-13 08:29 PM | edited Fri 15-Mar-13 07:56 PM by NanoMeter

Eric, Photoshop is not ignoring the WB and making a new WB.
I am not sure what you are referring to when you say that.

The top image is WB using NX2 Margee. The other two images are swapped from that image.

The middle image is the top image swapped in Photoshop.

The bottom image is the top image swapped in NX2.
(as described in the sticky)

Photoshop is not doing anything to the WB, it is just swapping the R/B channels.

The middle image is a more true swapped version of the top image.



ericbowles

Atlanta, US
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#3. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 2

ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2015 Nikonian since 25th Nov 2005
Wed 13-Mar-13 08:58 PM

So you're shooting RAW, using Capture NX2 to set WB, and then exporting a TIF or JPEG for PS? And you are not making any other correction in PS? I misunderstood your workflow for this example.

My reference was that PS does not read a WB set in the camera and would need a WB to be set in PS - or brought in as an image with WB corrected. There are also auto levels that can impact an image if they are used.

Eric Bowles
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NanoMeter

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#4. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 3

NanoMeter Silver Member Nikonian since 17th May 2012
Fri 15-Mar-13 07:59 PM | edited Fri 15-Mar-13 07:59 PM by NanoMeter

Yes, I am shooting RAW, using Capture NX2 to set WB, and then exporting a TIF for PS?

Here is another example. I adjusted the LCH-Hue-180 side slider as close as possible to match the colors of the Photoshop swap.

Top image is the RAW image Marguee WB in NX2.
Bottom image is the top image channel swapped in NX2.
Middle image is the top image channel swapped in Photoshop.

These are 590nm. I have also tried this with 665nm, and 720nm.
Basically, the NX2 swaps loose color intensity compared to the non-swapped version. The Photoshop swaps keep the same color intensity (saturation) as the original image.

Click on image to view larger version




domer2760

Ann Arbor, US
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#5. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 0

domer2760 Moderator Fellow Ribbon awarded for his frequent assistance to other members by sharing his perspective, skills and expertise, especially with infrared and macro photography. Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014 Awarded for his expertise in IR & Macro photography Donor Ribbon awarded for his generous support to the Fundraising Campaign 2015 Nikonian since 23rd Oct 2010
Sat 16-Mar-13 06:26 PM

Hi Steve,
I use some of the information in the Nikonians thread you referenced. There are a few exceptions. First, I shoot with the camera Picture Control set to Vivid with Sharpening at 9 (2 clicks to the right of the midpont) and the Contrast set 1 click to the right of the midpoint. CNX2 recognizes these settings. These picture control settings will add noise to some photos so I have to address noise issues very early in the post-processing workflow. Doing a channel swap on a noisy photo causes all kinds of problems.

I follow the other steps in the channel-swap thread except for Step 3. I do not crank up the saturation to 9. I leave the saturation alone. CNX2 works exceptionally well for some conversions and not so well for others. I don't know why.

When I make Photoshop channel swaps, I generally have to make adjustments in the red, blue, and green sliders to get the color to where I want it. I don't worry whether everyting adds up to 100%. The traditional photoshop channel swap (100% red swapped to 100% blue and 100% blue swapped to 100% red) often leaves a blue color cast in the photo that I don't like.

I don't know if this helps, but it is what I do.

Best,


Dan
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NanoMeter

US
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#6. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 5

NanoMeter Silver Member Nikonian since 17th May 2012
Sun 17-Mar-13 07:29 PM

Dan, Thanks for that info, very well written.
I didn't change the saturation either.
What color space are you using?
I use sRGB.

NX2 is handy because those settings like Vivid, and Sharpening that were set in the camera can be changed to whatever we want out of camera.
In my examples above, those settings are the same for both the Photoshop and NX2 swaps.
Those setting will adjust how the picture looks, but the resulting image is then swapped in either program.

I am beginning to thnk that NX2 is not really capable of a pure red for blue and blue for red channel swap, as can be performed easily in Photoshop.


domer2760

Ann Arbor, US
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#7. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 0

domer2760 Moderator Fellow Ribbon awarded for his frequent assistance to other members by sharing his perspective, skills and expertise, especially with infrared and macro photography. Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014 Awarded for his expertise in IR & Macro photography Donor Ribbon awarded for his generous support to the Fundraising Campaign 2015 Nikonian since 23rd Oct 2010
Sun 17-Mar-13 10:51 PM

Steve,
What you get at the end really depends upon where you start the process. Picture controls make a difference to CNX2 but they are not read by Adobe Camera Raw. Therefore, the image you get after channel swaps are often difficult to compare directly. The following images show what happens if you use start with a Photoshop WB and a CNX2 WB. These are from the same image with no additional processing.

The original image was taken with a LifePixel converted D90 (590 nm SuperColor filter). To establish a WB in PhotoShop, I used the white balance picker in CS5 Camera Raw and chose a point that was a medium grey. The resulting photo was used for channel swapping in Photoshop and Nikon CNX2.

Click on image to view larger version


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Starting from the same NEF image, I used the Nikon CNX2 grey point picker to set the white balance. I chose the same area for this WB as I did for the PhotoShot WB. I normally use the Marquee tool but I wanted to make things comparable for this demonstration. You can readily see the effect of the Camera Control settings in the first image below. Also, this program gives a broader color spread that can be used for BW and other adjustments.

Click on image to view larger version


Click on image to view larger version


Click on image to view larger version


Here are the take home messages.
1. Nikon CNX2 white balancing will give you a broader color range and more options for post processing. LifePixel says the same thig.

2. CNX2 can be used for channel swapping but you will have less control of the final output during the swap.

3. CNX2 and PS produce different images when they perform what appears to be identical tasks. You can take this into consideration to achieve a certain effect or you can stick with one workflow and create the effect by other methods.

I hope this makes sense.
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Dan
Ann Arbor, Michigan

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domer2760

Ann Arbor, US
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#8. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 6

domer2760 Moderator Fellow Ribbon awarded for his frequent assistance to other members by sharing his perspective, skills and expertise, especially with infrared and macro photography. Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014 Awarded for his expertise in IR & Macro photography Donor Ribbon awarded for his generous support to the Fundraising Campaign 2015 Nikonian since 23rd Oct 2010
Sun 17-Mar-13 10:57 PM

Steve,
I use the Adobe RGB color space because every image has to be manipulated in post.

Dan
Ann Arbor, Michigan

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NanoMeter

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#9. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 7

NanoMeter Silver Member Nikonian since 17th May 2012
Sat 23-Mar-13 01:39 AM | edited Sat 23-Mar-13 01:39 AM by NanoMeter

Dan, I appreciate your excellent comparison examples of white balance using ACR vs NX2, and I completely agree that NX2 performs the best white balance, however neither white balance nor picture controls are at issue here.
I am not using ACR. The question is about swapping the red and blue channels using NX2.
Any white balance or picture controls are set prior to LCH - Hue 'swap', and are set prior to exporting as a TIF to PS for a red/blue channel swap.

If you want to test that, load a RAW file into NX2 (adjust WB if you like), then save as a TIF file.
Load the TIF into both NX2 and PH (white balance and picture controls are already set and no where to be found in the TIF).
Now do the LCH 'swap' in NX2 and do the red/blue swap in PS.
(all you really need to do is export the image from NX2 to PS (File > Open with) prior to LCH, which works the same way)

> 2. CNX2 can be used for channel swapping but you will have
> less control of the final output during the swap.


NX2's LCH - Hue adjustment is not a red/blue channel swap.
It adjusts all three color channels at the same time (more like PS's Hue/Saturation adjustment), rather than swapping the red and blue channels alone.
I have not even been able to come close when using Anchor Points.

The NX2 'channel swapping' process outlined in the sticky link is not a red/blue swap, it is a hue adjustment which changes red, blue, and green simultaneously.
https://www.nikonians.org/forums/dcboard.php?az=show_topic&forum=214&topic_id=370&mesg_id=370&page=

Here is an NX2 "channel swap" as outlined in the sticky:

Click on image to view larger version


Here is a true red/blue channel swap using Photoshop:
Photoshop>Image>Adjustments>Channel Mixer
Red channel: Red = 0%, Green = 0%, Blue = +100%
Green channel: Red = 0%, Green = +100%, Blue = 0%
Blue channel: Red = +100%, Green = 0%, Blue = 0%
Click on image to view larger version


If anyone can process the image below using NX2 to match a red/blue channel swap using Photoshop please let me know.
Click on image to view larger version



NanoMeter

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#10. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 9

NanoMeter Silver Member Nikonian since 17th May 2012
Sun 24-Mar-13 01:48 AM | edited Sun 24-Mar-13 01:48 AM by NanoMeter

Using multiple anchor points comes closer to a true red/blue channel swap, but I had a hard time getting blue and yellow as pure as the Photoshop version.
However, I have not had success applying this method to photos yet.

NX2 > LCH > Hue > 180° > add points and adjust lower slider for each point. It's a bit tedious.

Click on image to view larger version


lastdaylight

Dallas, US
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#11. "RE: Channel Swap - Photoshop vs NX2" | In response to Reply # 10

lastdaylight Gold Member Laureate Ribbon awarded for winning in the Best of Nikonians 2013 images Photo Contest Nikonian since 09th Dec 2007
Wed 27-Mar-13 02:22 AM

Steve,

I realize that you are looking for the channel swapping solution in NX2, and I don't have that. But, just in case you (or others) are interested...

I've been playing with the "Imager" Perl module for creating and manipulating images using the Perl scripting language. It allows for very easy operations on the channels. Swapping the channels in an image is only a couple of lines of code.

So, if you are willing to load Strawberry Perl (free) onto a Windows machine or have Perl running on a Linux platform, I can provide a Perl script that will swap the red and blue channels on a JPEG file by entering a command like "RBSwap.pl RGB_test.jpg" at a command prompt.

Again, not in NX2, and it doesn't read .nef files, but might still be interesting to someone who wants to do the "pure" channel swap on a JPEG image. Let me know if there is any interest...



Click on image to view larger version




Mark Smith
Just like I previsualized it, more or less...

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