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Photoshop Channel concepts: The Power of Ten

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  #61  
Old 05-25-2011, 02:48 PM
creativeretouch creativeretouch is offline
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Re: Photoshop Channel concepts: The Power of Ten

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Originally Posted by Chain View Post
Yeah, but you can add raw images as smart objects. That's pretty close at least.
(Doubleclick to edit the settings (camera raw pops up)).
I have my flat (low contrast) 16bit LAB/ProPhotoRGB export from RAW file technique
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  #62  
Old 05-25-2011, 02:53 PM
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Re: Photoshop Channel concepts: The Power of Ten

Going to LAB just to get the L-channel? A grey/desaturating layer with color blending mode will give you just as nice luminosity info without having to do any color space conversion.

Ps: 16 bit is nice, if you have the processing power and ram
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  #63  
Old 05-25-2011, 02:57 PM
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Re: Photoshop Channel concepts: The Power of Ten

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Going to LAB just to get the L-channel?
No, not just for this. I do many magics here it depends on the image and the result I wish to end up with ...
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  #64  
Old 05-25-2011, 04:09 PM
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Re: Photoshop Channel concepts: The Power of Ten

I just know of a bunch of limitations in LAB, no real advantages...

I remember discussing it in a thread a while back, and one guy did it to be able to work on luminosity and color separately (he did not seem to be aware of luminosity and color blend modes), and it was also suggested that you needed lab to do a frequency separation that separates the color information as a separate layer. We ended up demonstrating that all this could be done in RGB with minimal need to flatten layers and converting color spaces back and forth. I've also seen LAB recommended for sharpening (sharpen L-channel only), but that as well can be achieved by blending the sharpening using Luminosity (or desaturating the HP-layer if that is the sharpening method)...

I would be interested in what magic you do in LAB (that cannot be done in RGB).
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  #65  
Old 05-25-2011, 04:23 PM
creativeretouch creativeretouch is offline
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Re: Photoshop Channel concepts: The Power of Ten

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Originally Posted by Chain View Post
I just know of a bunch of limitations in LAB, no real advantages...

I remember discussing it in a thread a while back, and one guy did it to be able to work on luminosity and color separately (he did not seem to be aware of luminosity and color blend modes), and it was also suggested that you needed lab to do a frequency separation that separates the color information as a separate layer. We ended up demonstrating that all this could be done in RGB with minimal need to flatten layers and converting color spaces back and forth. I've also seen LAB recommended for sharpening (sharpen L-channel only), but that as well can be achieved by blending the sharpening using Luminosity (or desaturating the HP-layer if that is the sharpening method)...

I would be interested in what magic you do in LAB (that cannot be done in RGB).
OK. The most important magic is to make colors more rich. you can adjust curves in a and b channel so color will get more "deeper." You can deal with noise much better in LAB. In really bad cases you can combine noise reduction in LAB and RGB. Hue/Saturation tool is also much precise in LAB than in RGB. Sharpening. Yes, you can sharpen in RGB using Luminosity blend mode, or you can sharpen HP layer in frequency separation or you can sharpen L channel in the LAB - depends on the final desired result. Color corrections are slightly different in LAB mode and again, depends on the image, sometimes I prefer color correct images in LAB or combine color correction in LAB/RGB.
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  #66  
Old 05-25-2011, 04:38 PM
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Re: Photoshop Channel concepts: The Power of Ten

Color correction in LAB will work slightly different since it's separated differently. But all in all you have a lot more tools available in RGB for changing colors in pretty much any way - and you can keep most as non-destructive adjustment layers that you would loose when jumping between color spaces (unless you start nesting smart objects).
Do you have an example of a before/after with the "richness" that the curves on a/b-channels produces? I'd love to try and see if I can get similar results in RGB.

I agree that the Hue/Saturation-adjustment is not that good in RGB unless you set blending to color. Then it works well.

You say that sharpening in LAB or RGB depends on the final desired result. Any example of what makes the sharpening in LAB look different from sharpening done in RGB (preferrably an example where the sharpening in LAB would be preferrable for what you want to achieve)?
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  #67  
Old 05-25-2011, 04:47 PM
creativeretouch creativeretouch is offline
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Re: Photoshop Channel concepts: The Power of Ten

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Originally Posted by Chain View Post
Color correction in LAB will be slightly different since it's separated differently. But all in all you have a lot more tools available in RGB for changing colors in pretty much any way - and you can keep most as adjustment layers that you would loose when jumping between color spaces (unless you start nesting smart objects).
Do you have an example of a before/after with the "richness" that the curves on a/b-channels produces? I'd love to try and see if I can get similar results in RGB.

I agree that the Hue/Saturation-adjustment is not that good in RGB unless you set blending to color. Then it works well.

You say that sharpening in LAB or RGB depends on the final desired result. Any example of what makes the sharpening in LAB look different from sharpening done in RGB?
Here you can get all answers:

http://www.amazon.com/Photoshop-LAB-.../dp/0321356780

Yes, I agree. Sharpening in LAB & RGB is very similar, but in LAB is slightly better.

I keep files with adjustments layers in different color spaces if necessary.
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  #68  
Old 05-25-2011, 05:27 PM
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Re: Photoshop Channel concepts: The Power of Ten

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Originally Posted by creativeretouch View Post
You can deal with noise much better in LAB.
That may be true if all you have is an RGB doc but I think if the original is raw data, in a good converter, you’ll remove a great deal before you even render the data. Remember too that the noise is usually all in shadows. Raw is linear data and by the time its gamma encoded, a lot of damage is done. And if most shoot with noise in mind, exposing the data for ideal raw, not a JPEG, the noise would be far less (certainly when shooting at low/native ISO).
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  #69  
Old 05-25-2011, 06:28 PM
RobertAsh RobertAsh is offline
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Re: Photoshop Channel concepts: The Power of Ten

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Originally Posted by Chain View Post
I just know of a bunch of limitations in LAB, no real advantages...
....
I would be interested in what magic you do in LAB (that cannot be done in RGB).
For me it's not whether it can or can't be done. For me personally, I can do certain color and lightness adjustments a lot faster and easier in Lab than in RGB. And I don't have a lot of time to learn multiple ways of doing things, esp. when one way is really easy and another way is more involved.

When I first got Margulis' book and started working in Lab I could do things I just couldn't do in RGB. That doesn't mean you or someone else couldn't do them, but I personally couldn't. Plus conceptually Lab's color model makes more sense to me than either RGB's or CMYK's. It's much more intuitive overall.

Over time I now mainly use RGB for portraits and Lab for landscapes/travel. Sometimes I use CMYK, mostly to extract some extra shadow detail or to fix skin colors.

Ideally, of course, I'd prefer one color space for everything. And it's really inconvenient losing all adjustment layers when I do Convert To Profile. But given the limitations of technology and of my current skill set it is what it is, and I don't get caught up too much in color space wars (or camera brand wars or the like), I just use what works for me, wherever it works best. And that balance changes as I learn more.

Last edited by RobertAsh; 05-25-2011 at 06:33 PM.
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  #70  
Old 05-25-2011, 06:59 PM
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Re: Photoshop Channel concepts: The Power of Ten

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Originally Posted by RobertAsh View Post
For me it's not whether it can or can't be done. For me personally, I can do certain color and lightness adjustments a lot faster and easier in Lab than in RGB. And I don't have a lot of time to learn multiple ways of doing things, esp. when one way is really easy and another way is more involved.
If you (or others) could provide how to do the more involved moves in RGB, I’d be most appreciative (I’d prefer to stay in high bit, wide gamut RGB all the time and the extra work is worthwhile).

As I alluded to earlier, the Calibration pane in LR/ACR provides some interesting options in terms of what I guess we could call “channel blending” for subsequent work in Photoshop. I don’t want to say its Lab or even Lab-like but the sliders and where they apply color is interesting, hopefully useful.
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