Does anyone use High Pass for Shapening?

[Kristy]

I was reading a tutorial about sharpening using the high pass filter. I gave it a try and it seemed to work, but I'm wondeirng if anyone uses it, swears by it or totally think it's a poor method... Opinions welcome.

The thing that benefits is that you don't get the grain that you get with USM.. otherwise, I'm not sure of pro's or con's.... Just curious what everyone else is doing. I'm sure USM is the norm, but anyone else doing something different?

[EOS_JD]

Kirsty it works fairly well and there are a lot of people use it to sharpen. Each to his own method. I prefer (at the moment) to use the LAB sharpening method but sometimes I'll try high pass too. They both do a decent job.

[Kristy]

thanks JD... :) I have so much to learn on the computer end of things.. what is Lab shapening?

[EOS_JD]

Firstly sharpening should be the last thing you do in your digital workflow. (just in case you were not aware).

Now open an image you want to sharpen. Go to Image>Mode>LAB. LAB is an image mode like RGB or CMYK.

In Photoshop, the Lab mode consists of three color channels. The first channel is Lightness (L). The Lightness component, also called luminance, can range from 0 to 100. A Lightness value of 0 equals black and a value of 100 equals white. The higher the value, the more vivid the color. The other two channels, a and b, represent color ranges. The a channel contains colors ranging from green to red and the b channel contains colors ranging from blue to yellow. (You don't really need to know all this though)

Once you have converted your image to LAB Mode, go to the channels pallete and click on the lightness channel. (You can use this method to convert to B&W if you like as it's a better way than desaturate - although not ase useful as channel mixer - anyway i digress again).

With the lightness channel selected go to Filter>Sharpen>Unsharpen Mask and select an appropriate amount of sharpening. For a high res image I go for amount 150, radius 1 and threshhold 0. Others will have their own figures but I play around and decide mostly image by image unless I'm batch processing.

Once you have sharpened go to Image>Mode>RGB (to convert back to RGB mode) and that's it.

The advantage to LAB is you are sharpening only the lightness channel which will sharpen without any colour artifacts so should provide superior results.

There's loads on google if you look.

Regards
Jim

[Kristy]

Awesome! Thanks for the tip and the lesson about LAB mode and lightness channel. I think I'll play around with it when I have some free time today. Can't wait to see how it works! :)

Thank you, thank you, thank you! :)

[DavidW]

Another thing you can try is conventional USM sharpening (without the move to Lab), then Edit -> Fade Unsharp Mask. Leave the opacity at 100%, set the blending mode to Luminosity.

I'm not convinced that gives the same results as sharpening in Lab mode, but you can give it a try. The big advantage of doing this is that it's less disruptive in my workflow. I tend to work on the image, then stamp visible to a layer, then sharpen that layer. That way I have sharpened and unsharpened images in the same file.

If I convert to Lab, then I lose the adjustment layers.



David

[Kristy]

That's a good idea too David... Sometimes I forget if I've sharpened something or not... if were on it's own layer then I'd be sure.... :)

[EOS_JD]

Another thing you can try is conventional USM sharpening (without the move to Lab), then Edit -> Fade Unsharp Mask. Leave the opacity at 100%, set the blending mode to Luminosity.

I'm not convinced that gives the same results as sharpening in Lab mode, but you can give it a try. The big advantage of doing this is that it's less disruptive in my workflow. I tend to work on the image, then stamp visible to a layer, then sharpen that layer. That way I have sharpened and unsharpened images in the same file.

If I convert to Lab, then I lose the adjustment layers.



David

Hi David

I don't often save my files with adjustment layers attached but you could save the file before you sharpen so your Adj Layers are intact?

At the end when I'm happy I flatten then run an action - coverts to LAB, sharpens - I just select the amount - and then converts back.

You can also use the Action in a batch process if you have a lot of images to sharpen. I appreciate once you have a workflow you are happy with it's best to keep that consistency but always worth a look :-)

Cheers
Jim.

[DavidW]

There's almost invariably two ways to do things in Photoshop. Another variant would be Image -> Duplicate, then, in the duplicate, flatten, convert to Lab, do whatever you wanted in Lab, convert back to RGB. Finally, shift-drag the layer back into the original document.

Does anyone know whether there's a difference between sharpening the L channel in Lab, and sharpening in RGB followed by fading 100% Luminosity?



David

[EOS_JD]

I think when you sharpen in RGB you are still amending colour pixels. RGB only has red green and blue pixels.

In Lab the lightness (luminosity) channel is a greyscale channel and therefor is independant of the colour information.

The best way to check I suppose is try it and see what looks best. :-)

[EOS_JD]

David
Just arrived back home from work and had a look at Scott Kelby's book. You'll probably see that my comments re using the Luminosity blending mode are wrong! Was an interesting read noting pro's use both methods.

I suppose my last comment is still right though. Try both and see what's best!

[Kristy]

This has been an interesting read. So is summarizing, both of you would prefer LAB mode or USM over using the High Pass mode? I've yet to try the lab mode, but perhaps later today. :)

[maderito]

Does anyone know whether there's a difference between sharpening the L channel in Lab, and sharpening in RGB followed by fading 100% Luminosity?
David From the LAB professor himself, Dan Margulis:
Aficionados of both sharpening and blending modes may say that even if you like the LAB version better, there really wasn't any reason to go to LAB to get it. They will say, we could have sharpened in RGB as shown above, and then used Edit: Fade>Luminosity, or we could have done the sharpening on a duplicate layer, to which we would change the mode to Luminosity.

Either method is supposed to hold the original colors and change only the detail, just as sharpening only the L channel does (you remember, of course, what the L stands for). And from this, several authorities have postulated that either method gives essentially identical results to sharpening the L.

I would call such people nincompoops or something worse, except it might be somewhat embarrassing. Here is the link (http://ep.pennnet.com/Articles/Article_Display.cfm?Section=Articles&Subsection=Display&ARTICLE_ID=193938) to the full article.


It boils down to the fact that the RGB luminosity blend mode is related to a different grayscale image than the L(uminosity) channel of Lab color space. (Apply the luminosity blend on a RGB layer with a white base layer to see the grayscale). Per Margulis, the L channel contains no color info - thus no possibility of color shifts with sharpening. Also, the L channel is lighter (higher gamma) than a desaturated RGB image, resulting in different effects of sharpening over the tonal ranges.

He argues that L channel sharpening in Lab color space is usually, but not alway better than sharpening with Luminosity blend mode in RGB.

Personally - RGB luminosity is good enough for me.

[EOS_JD]

This has been an interesting read. So is summarizing, both of you would prefer LAB mode or USM over using the High Pass mode? I've yet to try the lab mode, but perhaps later today. :)

USM using a luminosity blend mode so that only the lightness of the image is amended. To be honest try them all and go with what one you like. Apparently with the LAB or luminosity layer, you can sharpen more than you can in other ways....... Not sure how much you would want to sharpen though.

Trial and error works for me.

[sando]

I've been a fan of high pass sharpening for awhile now. I do tend to layer mask it it though and just apply it to the main subject.

I will try this LAB method though, heard good things about it recently.

each to his own though, if you liek your own method then that's cool! :)

[enigma]

Great thread!

I was wondering about LAB sharpening, though -- and I am surprised no one has mentioned this --- what about loss of information (or numerical precision) due to the two color space transformations?

Any info on this?

[René Damkot]

Shouldn't be any loss of information, as long as you untick the 'Use Dither' box.