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Sharpening in LAB color mode – Photoshop Tutorial

Sharpening in LAB color mode – Photoshop Tutorial

We all want to have a sharpen photo or manipulation,don’t we? In some cases the classic way of sharpening might not be the best idea. After applying it in RGB mode those might look artificial or over-shapened. We all been there. So we need the best way to keep the quality of the photo after sharpening it.

Shapening in LAB color mode might be a good choice for this. It might sound hard but is easier than you might think.But first let’s see what is LAB and where you can find it in the menu. The LAB color mode is structured in three channels:

-         The L channel contains luminance information. Luminance is another way of referring to the black and white data in a photo.

-         The A channel  provides information about greens and magentas.

-         The B channel provides information about yellows and blues.

In this way of sharpening the important point is that the black and white information is completely separate from the color information. The advantage of this is that you can sharpen the black and white pixels without any impact on the color pixels. The pluses are:

-Many shapes are outlined in black, so black is what you want to sharpen.

-Color pixels tend to get unattractive and just plain and sometimes creates nasty halos and color artifacts when sharpening ,since sharpening the LAB luminance channel doesn’t touch the color channels and that effect is avoided.

Once you’ve converted an image to LAB mode, if you open the Channels palette ,you’ll see the three channels: Lightness, or L, containing the black and white data; and the A and B channels for the color information.

Before we apply the Unsharp Mask let’s have a little introduction about it. An “unsharp mask” is actually used to sharpen an image, contrary to what its name might lead you to believe. Sharpening can help you emphasize texture and detail, and is critical when post-processing most digital images.

To use the Unsharp Mask on the L channel, open the Channels palette and select the Lightness channel .You should also make sure that all three LAB channels are visible—this is indicated by the “eyeball” icons shown in the left-hand column of the Channels palette.

The Unsharp Mask window has settings, Amount, Radius, and Threshold. Setting Amount higher, and Radius higher, each give you more sharpening. Threshold works in the opposite direction: the lower the Threshold the more sharpening, and the higher the Threshold the less sharpening.

Here are the three settings that i found most useful:

1. For people: Amount 150%, Radius 1, Threshold 10

2. For cityscapes, urban photography, or travel: Amount 65%, Radius 3, Threshold 2

3. For general everyday use: Amount 85%, Radius 1, Threshold 4

But of course you can play with those settings to find the best way for your photo.

You can apply the Unsharp Mask filter again, using the same settings. If your photo appears too sharp, before you do anything else, go under the Edit menu and choose Fade Unsharp Mask(Shift+Ctrl+F). In the Fade dialog, lower the Opacity slider to 50%, so you only get halfstrength on the second application of the filter.

 

After you are satisfied with your LAB sharpening, Flatten Image and convert it back to the RGB color space

So this is the LAB sharpening technique that i hope you’ll find useful for your work.Have fun.

 

 

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  • Andrew Tomlinson

    Nice tutorial. I have a quick question. would you save the image between 1st and second sharpening pass?

    • AdrianK

      You don’t have to save it,only if you want and your photoshop version is not very stable.

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  • Turrican

    For smaller images (internet) i use the normal unsharp mask in rgb with 300-500% strength and a radius of 0,2px.

  • Dennis Clark

    Thanks for the reasoning on sharpening in LAB and the easy steps to do so. I tried it on a few images and like the results!

  • http://www.mindstormphoto.com/ Burt

    MUCH Better! :)

    I was really hoping you put up the wrong image the first time, as that really did look like a “what not to do” example…

    One last recommendation. You now only show the “good LAB” result. It might be useful to show the RGB version also, and then say it is an example of why LAB works better than RGB for images like this.

  • http://www.mindstormphoto.com/ Burt

    The description of the technique was excellent, and I was all ready to bookmark this so I could try it later. Then I got to the final example picture… huh???

    Unfortunately, that final image is a good example of what NOT to do. It would get a scathing review if I were to put it up in our local camera club competition. The extreme halos around all the branches stand out and scream ‘sloppy!’

    Comes down to — I don’t see where there was any improvement using LAB. I could make halos like that much faster in RGB, and thus find out faster that it didn’t work and I should move on to a different image.

    You have an excellent style of writing and explaining. Please be sure that the images you choose to illustrate your tutorial actually show the technique working well though.

    • Adrian K

      My mistake Burt.The AFTER image had to be the sharpening in RGB color mode( i renounced to put it in the tutorial) but i messed up the imges.I updated the image and i hope now you can see better the result.