Sharpening In Photoshop CS2

Sharpening In Photoshop CS2

(Backwards comapatible to PhotoshopCS and Photoshop 7 except for smart sharpen)

No matter how good your camera or photographic skills you will on some photos need to sharpen them. Digital photographers have never had it so good as some of the newer models have built in sharpening. There also exists many software products that will sharpen your photograph for you, This writing is using Photoshop CS2, and contains as much info that I know about various methods of sharpening a photograph.

First of all, what is sharpening? Well its really about contrasts where two edges, colours or even different hues meet. The software finds these areas of differing pixels and changes the colours of these meeting points, to ensure there is a definable difference between the two areas. Look at these simple grey blocks below they are all zoomed in to 1200% but show the affect sharpening has. The first is just shades of grey, the second has had a sharpen filter run on it (Filter/Sharpen/Sharpen) and the third image has had the shapen filter run on it twice.



You can see how in the second image, after the sharpen filter has been used there are clearly two extra lines of pixels and that the colour has changed in those, on the dark grey side the line is darker and on the lighter grey side the line is lighter, the contrast between the two is easier to see, therefore it is sharper. In the third image, where the sharpen filter was used twice, these darker and lighter lines are now more so, the contrast is greater, so the effect is a little bit more sharp. You could at this point say that the third image has gone too far, and it probably has, but remember that these images are zoomed to 1200%. One more thing we can learn from these images is that the extra lines in the 2nd and 3rd images are referred to as a "Halo" or "Haloing" which I'm sure you will have heard before, or if you have not you will at some point.

Sharpening Filters in Photoshop CS2

If you click on Filter/Sharpen you will see a sub-menu containing the following Photoshop Filters:

Sharpen
Sharpen Edges
Sharpen More
Smart Sharpen
Unsharp Mask

With one of these filters, you can sharpen the contrast on your photograph so that details appear to become clearer, you can even clean up slight camera shake too. But lets first look at each of the filters and what they where designed to do.

Sharpen (Filter/Sharpen/Sharpen)

The Sharpen filter does just that, it will sharpen the whole photograph without allowing you to change any of the settings.

Sharpen Edges (Filter/Sharpen/Sharpen Edges)

The Sharpen Edges filter looks for areas of significant colour change, ie edges..and sharpens those.

Smart Sharpen (Filter/Sharpen/Smart Sharpen)

Smart sharpen goes a little bit further and allows you to choose how much sharpening you want in both the shadows and highlights, it also allows you to choose the type of blur you want to remove, ie, Gaussion, lens or motion blur. The latter being that of camera shake, and you can also set the angle or direction of the shake to be removed.

Unsharp mask (Filter/Sharpen/Unsharp Mask)

Probably the most used of all the sharpening methods, and the least understood in its use is the "Unsharp Mask". Google unsharp mask and every piece of writing you see on the subject will give you a start point for the three settings contained there, the settings are "Ammount, Radius and Threshold" Well its hokum Pokum that the settings have a start point, if you understand what each of the three settings do, you'll no longer need to use the same settings as a start everytime you sharpen with the unsharp mask. Its using start point settings that contributes to so many over processed images online.

Threshold

Lets start with the setting at the bottom "Threshold", this controls how much definition there needs to be for the software to find edges or how much difference there is between one pixel and it neighbour. The software will analyse the threshold, then assess the radius you want and apply the ammount. If its set at zero, the threshold will find many differences in the photoraph to sharpen, however if its raised to 2 or 4 it will find less and less details to sharpen. Do be cautious of taking this number too high as you will end up sharpening in some areas whilst ignoring others.

Radius

This controls how far "spread out" you want your sharpening to be, for example if you had a photograph of a match and you sharpen it with a radius of 1 or 2, the width of the sharpened area would be about the size of a thread of cotton or thinner. If you increased the radius to around 30 the sharpening would blur slightly but also increase to around a couple of matches width, thus "spreading out". The bigger the number here the larger the sharpening area becomes, and blurred too. We can see how radius affects the actual sharpening by zooming into pixels and changing the setting below. This will help you see that at web size or full resolution these sizes will be different, hence why I have said there is no magic starting point for USM settings.




Ammount

This controls how strong the sharpening is that your applying, the higher the number, the stronger it will be. This should be your final adjustment before hitting the OK button to finally apply your unsharp mask settings to your photograph This can go all the way upto 500%, but if you use all the settings correctly you wont need to go that high. You can see an example of ammount in use below, to my mind the iamge on the left is about right whilst the image on the right is overdone. You'll see many photographs online like the one on the right, with that harsh almost prickly feeling to it, it just looks too sharp to be realistic. Notice how the stone bottom right has had its colour changed by oversharpening in the second picture.



How I sharpen using the unsharp mask

First of all, I make ALL of the other adjustments that I want to make first, sharpening is the last thing I want to do before I click save as. If I want diferent sizes of image, ie for printing, web viewing and/or thumnails I will before sharpening copy the whole document (Image/Duplicate) and resize each one for each of the uses I need them for. Then I save the document as a ".psd" (photoshop) file....only now am I ready to sharpen!

I click Filter/Sharpen/Unsharp Mask and first of all I make sure there is a tick in the preview box, (a small window is in the unsharp mask that you can zoom in and out of to view as you make changes to the settings and by left clicking and dragging you can move the previewed photo around I always use this!) Now to adjust the first setting, threshold, by default its set to zero so I use this to start with and move on to "Radius", now using the knowledge written above I know that there will be differences in the radius between photos that are resized diferently thats why we are sharpening last and for each different sized one. Between photos that are sized 3072 x 2048 and 800 x 533 a radius of lets say 2 will make a huge difference on one and none at all on the other.

So with the threshold set at zero I set the radius at one and then move to ammount and start pushing the slider up in chunks to see how its looking, I'll probably jump about a bit say 100%, 200% then move the preview photo around to see how the changes take effect, (incidently clicking on the preview image will temporarily remove the previewed sharpen effect) If the effect is too harsh I will move the radius to two and then continue to ammount again and go through it as described above, 100%, 200% previewing again. If its still too harsh a look I'll continue raising the radius untill either the effect is spreading too much or I have a good sharp image. There does come a point though, especially in web size photos (800 x 533px for example) that the radius will start to merge with the effect with the next part of the image, so we return to the start and raise the threshold to 1, then go to radius, start at one again and raise your ammount by 100%, 200% etc etc...previewing all the time, moving the preview around. If necessary, if its too harsh still raise the radius again and continue onto ammount etc etc.

Here is a numerical explanation of the last paragraph; Threshold = T, Radius = R Ammount = A:

T= 0
R= 1
A= 100%, 200%, 300% (If the effect is too harsh, move to the next set)

T= 0
R= 2
A= 100%, 200%, 300% (If the effect is too harsh, continue to increase the radius, testing the different amounts. If that does not yield results then move to the next example below)

T= 1
R= 1
A= 100%, 200%, 300% (If the effect is too harsh, move to the next set)

T= 1
R= 2
A= 100%, 200%, 300%

This is the best way to determine the settings for unsharp mask, there are no start points, aside from starting at zero and working up.

Oh, Ow or Wow?

By now you should have an understanding of what each of the settings in the unsharp mask do, and how to apply them for the best results for the different sizes of photographs your likely to want to edit. I can sharpen an photo in less than 30 seconds, if its your first time using unsharp mask it may take you five minutes, so what who cares how long it takes to sharpen when you consider that sharpening will make the difference between "Oh" (its just a photograph) "Ow" (that hurts my eyes - oversharpened) and "Wow" (Would you look at that, what a fantastic photo, its the best one I have seen all year!!!) So what do you want it to be, Oh, Ow or Wow?

Sharpening using the "High Pass Filter"

Nice and simple this one and worth a try, again have every thing done to the photo that your likely to want doing and save a copy of the file before continuing.

1. In the layes pallete, duplicate your layer.



2. Click Filter/Other/High Pass and your photo will now turn grey as the high pass filter box opens Ensure the preview box is ticked.



3. Move the slider up or down untill all of the picture is grey but not flat grey, you want it just grey so that no colour from your photo is showing. Click ok when done.



4. Go to your layers pallete and select either Soft Light/Hard Light/Overlay from the blending modes dropdown box.





5. When your happy, flatten your image (Layer/Flatten Image) and save using "Save as".



All done, quite a striking difference!!



Sometimes when you sharpen a photograph you can suffer from "colour noise" this will show as multicoloured speckles on you photograph and it can become a trade off to add sharpness at the cost of adding noise, or removing noise and also removing sharpness. However there is a little known way of sharpening that addresses this issue, read on.

Sharpening in Lab Mode

This is sharpening of the details held within the lightness channel of your image, this avoids sharpening the colours which are held in the a & b channels. Normally we work in RGB mode in photoshop as photographers, now we are going to break that and swap to "Lab Color" (this article is long enough so I'll spare you a Lab color description - Google it!) This method is best suited to full resolution photos. Lets get started: For this part I'll be working on a photograph 3072 x 2048 but zoomed out to keep the screenshots small for here.

Make all your adjustments to your photograph, save a copy.

1. Click on Image/Mode then click on "Lab Color"



2. Hold down the "Ctrl" and "Alt" keys and press the "1" key, this loads the lightness channel as a selection.



3. Now click Select/Inverse to inverse your selection then hold "Ctrl" and press "h" to hide the selection border.
4. Now go to your channels pallete and select the lightness channel, (this is the one we will sharpen and because this channel does not hold the colour we are avoiding colour noise artifacts) Your photo will turn Black and white.



5. Now click Filter/Unsharp Mask and try ammount 400%, radius 1 and threshold 2 and click okay
6. Click again on Filter/Unsharp Mask and leave ammount set at 400% and threshhold at 2, but now bring the Radius all the way to the left (zero) and start moving it to the right untill shape appears to come back to the photo, that should be somewhere between 10-30, (dont worry about the overall look here) once shape has returned to the photo lower the ammount to around 50 or what looks good to you and click okay.
7. Now hold the "Ctrl" key again and press the "d" key to cancel the selection.
8. And back in the channels pallete click the "Lab" channel to reveal your nicely sharpened photo.



9. To finish off click on Image/Mode/RGB Colour and you can then save your finished sharpened image.





Remember in all Photograph editing that "Less is more"


Steve...

 

Steve . This is great. I for one will go through it tonight to see if I came gain any more tips.
Many thanks for spending the time producing it.
robert

 

Nice one Steve.

 

Many thanks Steve. That must have taken you ages to write. It's by far the most comprehensive exposition of sharpening methods I've come across.

 

Thanks for the information, I have saved it out as a .pdf file for future reference. Although I don't use PS, I do have unsharp mask in The Gimp along with many other facilities (especially the perspective tool which straightens converging verticals).

 

Steve, I've at last saved and printed your tutorial and it's brilliant. I spent a good while this evening playing about with Lab Mode sharpening but need a few more hours with a variety of images to get anywhere near good at it.

You really ought to think about submitting your tutorial to one of the digital camera magazines.