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Sharpening in Photoshop

Posted 16/12/2012 - 22:59 Link
Carrying on from a point in another thread, a discussion of sharpening.

As little as needed avoids haloes and other artifacts, and Unsharp Mask is my tool of choice. I have used this from Photoshop 7 through to CS5, which I currently use.

Unsharp Mask, Threshold 3, Radius and amount depending upon size of final image and image factors. In terms of amount, web images are usually 1000 pixels on the longest side, which fits in with EPZ requirements. It is convenient to make just this one size wherever possible. Radius is around 1.1 to 1.4 pixels and amount about 50% for a K20D or K-5 and ambout 75% for a Q. Different types of sensor behave differently and cameras themselves have different characteristics of JPEG sharpening. For DSLRs +1 sharpening in camera is already set by me.

For A3 prints, a larger radius of pixels as there are so many more pixels in any dimension of the image, so usually 2.2 or therabouts. Sharpening for print needs to be slightly higher, so 100% to 125% is the norm. For other sizes, we can make something in between these two sets of values.

Hopefully my web images look sharp but not over sharp, and likewise my prints.

The technique of converting to LAB mode and just sharpening the luminance (black and white) channel is useful for architectural subjects as the colour information is not affected at all, so we end up with an underlying very sharp image with no artefacts in the colour channels. We convert back to RGB before saving for print.

In recent times, using LAB colour as an intermediate step has not seemed so necessary so I can only presume that the algorithms have been improved in each upgrade of Photoshop.

Comments and questions most welcome.
Best regards, John
Posted 16/12/2012 - 23:03 Link
Just to add to the OP, it is of course possible to make selections of specific areas of the image and sharpen these individually. For example, we can leave skin unsharpened but sharpen eyes, lips, jewellery, etc. This can be done on separate layers and the skin blurred slightly to mask imperfections.

Another example might be sky, where a larger threshold might leave sky unsharpened and prevent JPEG artefacts intruding.

Sharpening can be very complex when we wish it to be.
Best regards, John
Posted 16/12/2012 - 23:07 Link
I regularly use selective sharpening in Lightroom using the adjustment brushes. Selective sharpening, as well as avoiding artifiacts on areas which don't need sharpening, also helps to give a photo 'some depth'
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Posted 16/12/2012 - 23:31 Link
In lightroom if using the sharpening module press the 'ALT' key in windows or mac key on mac and the image turns black and white and shows exactly what is being sharpened.

If you then choose the mask slide and again click and hold teh 'ALT' key as you slide less becomes sharpened until just the in focus edges are sharpened.
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Posted 17/12/2012 - 08:35 Link
My prefered method is to duplecate the image use Fliter>other> highpass
set radius to 10
then change layer blending mode to hardlight or softlight and then low layer opcity to taste usualy find around 20% ish works you can also do selectively same as any other by using a mask.
This is in PS i didnt say. I made an action to speed process up.
I think as mentioned before not to over do it less is sometimes more.
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Edited by annieogg: 17/12/2012 - 08:36
Posted 17/12/2012 - 08:39 Link
Sue uses High Pass some of the time at least and she feels happy with the technique. It doesn't really suit me, at least for my images, but Sue's pictures look fine.

It just shows that there are many ways to achieve the same thing, thanks for mentioning High Pass.
Best regards, John
Posted 17/12/2012 - 08:58 Link
The technique of converting to LAB mode and just sharpening the luminance (black and white) channel is useful for architectural subjects as the colour information is not affected at all, so we end up with an underlying very sharp image with no artefacts in the colour channels. We convert back to RGB before saving for print.

A much simpler approach (and compatible with Photoshop Elements too) is to:

• duplicate the image onto a new layer
• apply the sharpening to the layer (which will include colour artifacts)
• change the layer blend mode from Normal to Luminosity

If you want to visualise it in the same way as Lab you can B&W the top layer before applying sharpening.

Luminosity blend mode is (99.9%) the L channel of the Lab mode.

Of course, one nice feature of this is the ability to fade the layer opacity and/or apply a layer mask to locally apply.

(But for me, all my sharpening is now done in LR)

(For gallery, tips and links)
Posted 17/12/2012 - 09:09 Link
Matt, what happened to Sharpen-o-Matic, was it overtaken by improvements in software and cameras?
Best regards, John
Posted 17/12/2012 - 13:28 Link
Maybe the kernels of this should be a stickie, I've learned a lot.
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Posted 17/12/2012 - 14:41 Link
Thank Ken, I've made it a Sticky.
Posted 17/12/2012 - 14:53 Link
Going to put the camera back to default and forget about the magic of manipultion, to much grey matter overload.
Photoshops heading for the recycle bin.
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Posted 17/12/2012 - 15:08 Link
Matt, what happened to Sharpen-o-Matic, was it overtaken by improvements in software and cameras?

Good point. It's still available from my website

In the early days of sharpening, I did find that the green channel required less sharpening (since there are twice as many green pixels). But, yes, these days the sharpening in LR is excellent.

Also worth mentioning is that the lens correction in LR4.1 makes a HUGE difference to perceived sharpness too. For example, the DA12-24 gives a great images, but when corrected (for CA & distortion) the sharpness goes up by a mile - especially on the corners. Likewise, the other day I had to process an image for inclusion in a book (hooray). It's taken two years to approve, and revisiting a K7 image taken with the DA17-70 and processed in Silkypix DS Pro I found that again, the sharpness increases substantially when handled in LR with the lens correction. 'Twas a very pleasant surprise!

(For gallery, tips and links)
Posted 17/12/2012 - 15:48 Link
Actually, this is getting good. Thanks John.

Now, I have more questions than you can poke a stick at, so I may as well get started.

I don't use Photoshop, but there are some general questions and some Lightroom questions that immediately spring to mind.

General - what different sharpening would you employ for different sized images? I have seen the Radius adjustment in Lr but have never moved it. I suppose I should just to see what happens, but what is it used for?

Lightroom - I know the use of the Alt key as Cabstar described. I also use it to show up any dust in the sky, as that shows up when using the unsharpen mask!! However, I have never used the Adjustment Brush in Lr for anything at all. I'm going to look it up now (as I've now just realised it is there in Lr 3.6), but smeggy said that he uses it for selective sharpening, is that right, smeggy?
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Posted 17/12/2012 - 16:15 Link
Can we start new threads for different subjects please - otherwise the theme of a thread becomes jumbled.

Radius has been mentioned above, but to see what happens just zoom into an image until you can see the individual pixels. Then adjust the radius and see the effect. You will then understand what is happening so much better than a lot of words can convey.

This is really a thread on Photoshop sharpening, so why not start another on the other question you pose?
Best regards, John
Posted 17/12/2012 - 16:30 Link
OK, John. But I did think you were going to start a thread on sharpening, not just Photoshop sharpening.

Most of the knowledge required is the same but not exactly how to execute it.
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