Sharpening

[MarkBarbieri]

How do you sharpen?

For those unfamiliar with the concept, sharpening is something that you do to pictures to make them look, well, sharper. One of the problems with translating the real world into a bunch of dots (which is all a picture is), is that the process blurs everything a bit. Most digital cameras make the problem even worse by using a filter to intentionally blurr things a bit. That helps prevent some other weird problems. There are also problems when you print. The dots on ink jet printers run a bit together and that has the effect of blurring things a bit.

The traditional method for sharpening in Photoshop is the "unsharp mask" filter. It seems like an odd name for a filter designed to sharpen things, but it's named for the process used in film processing in which used an unsharp (slightly out-of-focus) copy of the picture to help sharpen it. The technique works by finding places in the picture with lots of contrast (abrupt changes from light to dark) and increasing the contrast a little more (making the light side a little lighter and the dark side a little darker).

There are three adjustments you can make with the unsharp mask filter. The first is the amount. It controls how much the filter darkens the dark side and lightens the light side of high contrast areas.

The next adjustment is the radius. The radius controls how far from the high contrast area the adjustment will cover. A high radius will lighten and darken pixels farther from the edges than a low radius does.

The final adjustment is the threshold. This setting determines how much of a difference between light and dark areas there must be before the filter will work on them.

There isn't an optimal setting for these values. It all depends on the picture and the purpose for sharpening. I would recommend starting with something like 100%, 1.0, and 25 as your base values and play with them to see how they work for you. When you do that, always, always, always make the adjustments while looking at 100% magnification of your picture. If you don't, you won't really be able to see what is happening because the rescaling that occurs to show your picture at magnifications other than 100% makes it impossible to see the true effects of your sharpening.

As a general rule, use smaller radius values for pictures with more detail and larger radius values for pictures with less detail.

If you are going to do any noise reduction, it is important to do that before you sharpen your photo. Otherwise, the filter will confuse the noise with detail and enhance it. That makes the noise even worse.

I actually do three rounds of sharpening on important photos. When I first bring the photo into the computer, I perform an initial, fairly minimal round of sharpening called "capture sharpening." That helps remove the effect of the anti-aliasing filter.

For the second round of sharpening, I sharpen more aggressively, but only in the areas that I want sharpened. Using a mask, I sharpen only the detail that I want sharp. There isn't much point in sharpening out-of-focus areas. You'll also find that your photography budget goes down dramatically if you sharpen your spouse's skin. No one really needs to see every detail of their pores, blemishes, and wrinkles. Sharpen the eyes, mouth, and hair and leave the skin alone. Heck, you can actually boost your budget by applying a very subtle blur to skin.

If you want, you can even use different sharpening parameters for different parts of the photo you want sharpened. Perhaps you want the texture of your subjects shirt to really stand out, but you don't want their hair to look to crunchy. In that case, you could sharpen them both on different layers with different parameters. That's a bit more work than I'm willing to perform, but I'm sure your standards are higher than mine so I thought I'd suggest it.

After those two rounds, I'll save my photo. The final round of sharpening is something that I do differently for every different version of the photo. This round, called output sharpening, is something that is done after the final resizing. If I'm posting an 800 x 600 photo for some Internet contest, I'll use one set of parameters. If I'm printing a 3,000 x 2,400 pixel photo on my 300 dpi printer, I'll use a different set of parameters.

Sharpening for display on the computer is easy because you can see the affects of your adjustment. Sharpening for printing is a little harder because you have to guess at how much your printer is going to undo the effects of your sharpening when it prints. Every printer and driver is different, so you'll have to learn by trail and error.

Real World Image Sharpening with Adobe Photoshop CS2 by the late Bruce Fraser is the best book that I know of on the subject. There are innumerable tutorials all over the web that also explain the subject in much more detail than I've provided.

There are also numerous Photoshop plug-ins to help you with your sharpening. Avoid any that do a one-size fits all sharpening because the optimal amount of sharpening is different for different subjects, different resolutions, and different output devices. I really like PhotoKit Sharpener. At $99, it is a bit pricey, especially considering that it doesn't do anything that you can't do in Photoshop without it. I find, however, that it makes sharpening much easier and I get better results than when I do it myself.

So how do you sharpen?

 

[extreme8]

I'm a photokit sharpener guy myself.
It was based on Frasers sharpening techniques, and in fact, he had a hand in the development.
Nik's sharpeners are OK as well, especially in the "creative sharpen" phase.

 

[deletedpenguin]

I use, I feel with great success, the "Manyk" photoshop sharpening action. You can read more about it here:

http://news.deviantart.com/article/20250/

 

[alan]

Another use for the "unsharp mask" filter is to boost contrast - this is called Local Contrast Enhancement. By setting a small amount (eg 15%) and a large radius (I typically us 50 pixels in a 2100-pixel image) you can achieve a significant increase in contrast, often giving a "pop" to your pictures.

A more detailed explanation can be found at http://www.cambridgeincolour.com/tutorials/local-contrast-enhancement.htm

regards,
/alan

 

[SharonLowe]

The more current versions of PS have smart sharpen now which is much nicer but more complex than unsharp mask. I only sharpen when I am going to print something since my stock agencies say no sharpening at all, period. I use a variety of methods - the NIk sharpeners are pretty good for my Epson 2400 but I have been using the high pass technique more and more because it only sharpens edges, not things like skin.

To do this, you make a duplicate of your image (or duplicate all the underlying layers if you have multiple layers - set your cursor on the top layer and press option/alt/shift-e on a Mac; control/alt/shift- e on a PC). Set the mode of that layer to "overlay" - will look really nasty for a bit. Then, select filter/other/high pass and adjust the pixels to your liking - will depend on the image size. The nice bit about this method is that if you overdid it, you can just reduce the layer opacity to tone it down. Also, you can mask out parts if it sharpens something you don't want over sharp.

 

[Geoff_M]

I guess I'm a USM whimp... I mainly stick to using the "Sharpen Edges" filter. It seems like the USM always interjects noise into the non-edge areas of the images for me.

 

[mabas9395]

Assuming you wanted to use Photoshop's USM, I guess my question would be how do you learn which settings are best for the subject/size you want to print?

I've read some suggested settings for landscapes vs portraits and have heard that the larger your print size the stronger your sharpening needs to be. What is it about landscapes that makes the settings different from portraits? And how much stronger does it need to be for an 11x14 vs a 4x6? And can you tell by looking at your screen if something is sharpened enough or is printing it out the only way? And how much does your choice of printers impact things? I thought I did a pretty good job of sharpening some shots but when they got back from Wal-marts 1-hour I wanted to throw them away. How much of that was my fault vs the cheap print process?

And when the heck will Lightroom get decent output sharpening???

I've just added Fraser's book to my Amazon wishlist. Maybe Santa will take a look at the photos on my wall and have pity on me.

 

[Anewman]

Assuming you wanted to use Photoshop's USM, I guess my question would be how do you learn which settings are best for the subject/size you want to print?

It is very subjective, there is no such thing as BEST SETTINGS. What looks good to one person might look over or under sharpened to someone else.

What I do...
Sharpening is always last step(b4 uploading/saving)
I keep threshhold at 3 and Radius is dependent on IMAGE SIZE(not print size), for 8.2mp images I keep it at around 1.1 and then adjust amount depending on the image.

What is it about landscapes that makes the settings different from portraits?

There is typically so much more detail in landscapes that one would want to sharpen, and even within landscapes it varies. While with portraits most would generally want sharp eyes but a soft look in general.

And how much stronger does it need to be for an 11x14 vs a 4x6?

Again subjective, but IMO when one says that it depends on size they are not talking about PRINT size, they are talking about IMAGE SIZE so a 12 mp image needs a larger radius for the sharpening to be visible versus a 3mp image and that is regardless of what size the print will be.

And can you tell by looking at your screen if something is sharpened enough or is printing it out the only way?

In photoshop under the USM popup window you can click and hold the mouse on the preview window to get the before 100% view, and then release to see the after USM preview.

And how much does your choice of printers impact things?

Obviously a good printer is needed to be able to resolve as much detail as possible.

I thought I did a pretty good job of sharpening some shots but when they got back from Wal-marts 1-hour I wanted to throw them away. How much of that was my fault vs the cheap print process?

Not sure, but if you are going to use Walmart or other labs that automatically adjust your photos, you might want to try sending the photos as is and let them adjust(including sharpening). You can spend hours adjusting color, contrast and sharpening only to have them do it over and in many cases canceling out your work. If you want to do your own adjustments and see your photos printed as is, you need to send images to a lab that can turn off any and all auto adjustments.

I do not even allow the lab to resize, I send images in the exact dimensions printed and already sharpened. Not that they can not resize as well or better, it is just that I want to see the final results b4 not after. When the lab resizes, it will then need to REsharpen, which then gives me what they want not what I want.

 

[matthew_hull]

One thing that I have learned for Photoshop is the judicious use of the History-Brush. After sharpening, or noise-reduction, or other across-the image adjustment, I'll use the History-Brush at 50% (or 80%) to go over the human faces, or textured clothing, or whatever I judge needs it. The History-Brush reduces the effects of a recent adjustment in the area beneath the brush. I find this easier and quicker than using masks.

 

[SharonLowe]

One thing that I have learned for Photoshop is the judicious use of the History-Brush. After sharpening, or noise-reduction, or other across-the image adjustment, I'll use the History-Brush at 50% (or 80%) to go over the human faces, or textured clothing, or whatever I judge needs it. The History-Brush reduces the effects of a recent adjustment in the area beneath the brush. I find this easier and quicker than using masks.

It might be easier and quicker but it is "destructive" meaning you can't go back later and change what you have done. I recently fixed up a portrait for a client that someone else had taken. When I showed her the first proof, she wanted me to tweak it a bit. It took about 1 minute to do the tweaks because I had used masks. I would have had to redo the whole thing, taking about an hour, if I had not used masks.