DSLR Photography Forum

Hi all...

Uli asked the other day, if I could talk a bit about lab colors, this is not meant to be a tutorial, but just to show the way I use Lab color to retouch my images. There are most probably lots of different ways to do the same or probably using some shortcuts. If someone would like to share some tips and enrich this thread would be great.


So we start...

Make a copy of your background layer. (optional, if your program runs slow with this extra layer you can do it at the end, before you convert your image in RGB again.)

go to image>mode>Lab color

click don't flatten (when you change your image between these modes you cannot preserved adjustment layers, they must be merged before you change modes, but you can preserve (image) layers.

There are some adjustments like selective color, channel mixer or exposure that you cannot work in this mode. The same goes for the blend modes and filters.

Start working in all colors.
I work with curves because this was the way I learned, but you can also work with levels.

So, open curves in an adjustment layer, in the menu you will have lightness, a and b.

- b will work the blue in the lower left part of the diag. and yellow in the upper right part.

- a will work green in the lower left part of the diag. and red in the upper right part.

- Lightness to work contrast.





So we work first with blue and yellow.
In the curves menue click b, and shift the left dot to the right, and the right dot to the left in the same
proportion as we want to work in the whole image.

Do the same with a (green and red).

Work lightness at the end so leave it for now.


Working the sky...
In this image I wanted the sky really blue... so

Go to color range and click in the sky.... click in different places to get the more of the sky no problem if you get
a bit of the house or tree you will refine that later. When you are happy with the selection click ok.

Go to curves and open a new layer adjustment and click in b (blue and yellow remember?)
then shift the left dot a bit to the right, and the sky will turn bluer, click ok. If you want to correct any imperfection in the sky take a soft
brush with opacity 50% and paint with white the places that you want to have blue and with black if you want to
remove the blue effect.

Now you have a selection of the sky, you may apply some other adjustments like saturation, leves or again curves but this time working with lightness.

To call the sellection to work again with another adjestment layer go to the layers palette, right click in the mask
that has the selection you want to call again. Click in the option Intersect layer Mask with Selection. You will have
the selection ready to work again.




As I worked with the sky I did with the dry grass near the lake. I enhanced the yellow and with the selection I

applyed levels.

I always leave my contrast at the end so...

As I don't want to mess with my sky because it is perfect now... Let's work only with the mid and dark tones here...

so

Go to your layer palette and click channels select lightness only and hold down your control key and click in the
mask.




A selection in your picture will appear, click again in lab to sellect all channels and then layers to come back to

work with this selection in your image...

This selection works only in the light and highlights in your image, but as I want to work with the mid and dark
tones go to selection and inverse the selection and now work with contrast and brightness, levels, or curves what you think work best.
You will see in the diagrama that only you are working in the left part so you are working the darks.

Here is the image with all layers I worked in this image before merging.




When you are happy with your image, merge visible all your layers with the copy of the background,
always leave the original intact so you can see the improvement in colors.

Go back to image>mode> and change it back to RGB.


So here is the before and after...







At the beginning and reading all this one might think it is a lot of work, but it isn't really. Specially if you work with little actions. You can have an action to duplicate background layer>change to lab color and open curves.

With the time you can make a preset in curves for lab colors and then include it in the action so your work will be
done with one click. You also can make another action to select highlights and lights and another one with the
selection inverted to work the darks too.


There is a lab color treatment for bw pictures I found interesting. Here is the link to the post processing
explanation. I have my action and works really well for certain pictures. Here is the link, the technique is at the end of the writing.

http://www.designbyfire.com/000100.html


So, this is the way I work with lab colors..

If someone has already a before and after and wants to show it, or wants to try and show the result,
post it here to see the effect in other images.

I really hope I wrote it well, and it is understandable and useful....

Irma, thanks for your interesting post.

I have a question: what advantages does working in Lab mode provide? Is it basically a larger colorspace than RGB? Ultimately one does not output (print or web display) in Lab color, so wouldn't any advantages disappear when one converts to an output colorspace like RGB?

Thanks a lot for this elaboration Irma!!! I will try this on some pictures, like I said I never worked in lab so far.

Happy Easter!!

Uli

Excellent, thank you Irma; yes, perfectly well explained and very useful. Lovely job and it makes a real difference...not only added more zing but kept the mid-tones too, which I find difficult to do if trying to to get this effect by other means. Thank you very much for this.

You are very welcome and I am very happy you found this writing useful...

Slehjamer
Mitch... I always thought that using this color space you lose a bit of detail in your picture, I really don't know. I thought so because of the brighthess of colors. And also because of the diagrams you have in a and b channels they go to the top as a bar. What I can say for sure is that you work so nicely with light. Up to now I haven't seen any change in the colors when you convert your picture again to RGB.

Reading to answer your questions (because I don't know much, if I am honest... ) I found a very interesting site. It is kind of a reading group of a book that appears to be very good, and talks about lab color and compares this color space with RGB and CMYK. I think it is much better if I share the link with you all....

http://www.dgrin.com/showthread.php?t=18203

I am sure this will give more information than my writing....

Just to add, I have seen that my bw pictures are much better when I work my colors first in lab color. Maybe because the color are purer?
I really don't know.

Thanks for that link, Irma; I'll take a look.

Thank you Irma - This is a wealth of information.
I've previously ignored LABcolour previously (mostly because I didn't understand it).
Time to get my head around it....

Irma, once again you've sent me on a whole new course; thank you for the link to yet another world(and one I know jack about..but seems a wealth of possibilities.)
slej: from what I understand, it's the huge width of the gamut that gives one the breadth...and we've now got Luminosity too....and then presumably the effect of a RGB conversion would be like "downsampling" from something exteremely high in "resolution", allowing a width of tone and contrast that otherwise a straight or uninformed raw conversion wouldn't allow on 3 discreet channels. And I'm guessing that the unbridled power of it(when tapped into by eventually getting an understanding: some late nights ahead, I feel!) is in how one visualises what one is doing.
I had thought that, because I'm from the "old school" of undertanding camera-to-pic, my digital life would be merely an analogy of that...yet am becoming aware that a raw file is a collection of data that is quite different to film emulsion(a truism, but one I need more personal revelation about). It would seem that LAB is very powerful tool for maximising the manipulation of that data, perhaps more than RGB. All I know is that the good LAB work I've seen seems to have a lovely placement of contrast and tones...and I wonder if this too is why Irma has said that she gets better monochrome output from LAB work too, as this has maximised the dynamic range that is already within the raw file. Fascinating, captain, as Spock would say.

Great tutorial, Irma. In the past, the only use I have made of LAB mode is to reduce color noise.

If you see noise (speckles) in the a or the b channels, you can use Gaussian blur on those channels until the noise goes away without blurring the photo as a whole. This is true because the a & b channels contain only color information - all the actual sharpness is in the lightness channel.

I can see now that there is a lot more that can be done with this tool.

Thanks for posting that Irma. I shoot mostly in RAW and do all my major adjustment in Lightroom these days but have a backlog of JPGs from before I started using RAW. This works very nicely on them.

ADK Jim

Your are welcome... I am so happy you all found it useful...

Smarti, I was sure you use lab color in your pictures. They have beautiful colors...
Your comment surprised me.

Zig, you are right there is so much to learn about it. I would be interested in your comment about LAB color and bw conversion when you have the chance to try it....

Toad, Thanks a lot for the advice. What I just did with a bw picture was to reduce noise in lightness, but it killed a lot of detail in the sharp areas, I had to mask my subject. I have to try your technique...

Jim, I think you will like it. I just worked on a jpg I took long ago from Toscana and the colors were really nice...

I would like to buy the book but it is 53euro.... ouch! I am afraid that it could be too technical and not so practical...

Basically, I've understood that Lab works best with images that have little contrast and flat colors, not so well with vivid and rich colors. It helps to make some color corrections as with Lab you can see easily if there's a color cast. Maybe you can see it with other color modes too but I can't think of them now.