Thursday, April 21, 2011

Cover Art: Photoshop Tutorial: Sharpening a Blurry Image

Cover art can be a pain when self-publishing. It can be hard enough to balance elements like genre and characters, and adding in all the technical issues and possibilities can make it feel totally overwhelming.

I can't tell you how to make your cover perfect, but I can show you how to use the different tools and techniques in photoshop to help you figure it out. So, I've decide to post some basic tutorials that can help you better use photoshop. To those who don't use photoshop, I'm sorry. I don't have any other program to hand. If there are GIMP users out there who want tutorials, comment here and if there are enough of you, I'll try to add GIMP instructions to the tutorials. However, I guarantee nothing.

To keep these posts from getting too long, I'll be covering just one tool or technique at a time. This tutorial will cover sharpening a blurry image.

Standard Filters

When using photoshop, you have several options for sharpening. There are filters just labeled "sharpen," "sharpen more," etc., but these don't give you any control over how much sharpening is applied or to what areas. And it's important to be able to apply sharpening to some areas and not others, because not every area needs sharpening, let alone the same amounts.

Unsharp mask is another filter that photoshop offers (Filter---> Sharpen ---> Unsharp Mask) and it has options. Using unsharp mask you adjust the amount, radius and threshold of your sharpening, but what does that mean? The simplest answers are that "amount" is the strength of the sharpen, "radius" is distance from the edge that the sharpening will effect (getting lighter as it moves outward), and "threshold" sets how much difference there has to be between one pixel and another before it sharpens them.

When applying these settings, remember that each picture is individual, some will do well with very little sharpening and other need a lot. Use a setting of .5 on the radius option and it will effect about a pixel away from the edge that's being sharpened. Any more than that and you'll start to get visible outlines. You can use threshold to sharpening only parts of an image, but it doesn't give you a lot of control and it may increase the graininess of the picture. Also, remember that you're apply the filter directly to the layer you've got selected. The only way to undo it is to hit undo, and that will undo all of it. This makes tweaking it difficult. (There are ways around that, similar to what I describe below with the high pass filter.)

High Pass Sharpening

Another method of sharpening requires a little more work, but will produce a second layer on which the sharpening is done. This means that you can add a mask to that layer. (More on that later.)

To use this sharpening method, first duplicate the image you want to sharpen by clicking on it in the layer menu and selecting "duplicate image." A little box will come up, and you can name the layer if you want to, then click OK.

Side Note: If you're working with an image that is made up of several layers, go to Select ---> All (or hit CTRL + A) and then go to Edit ---> Copy Merged (SHFT + CTRL + C) and then Edit ---> Paste (CTRL +V) which will copy the image as a whole and paste it in as a new layer.

After you've got a duplicate of your layer, go to Filter ---> Other ---> High Pass. This will bring up an options window with a "radius" option and a preview. Adjust the radius to around 5 (you can play with the setting, but 5 is a good starting point.) Remember that you can always duplicate the high pass layer in order to increase the sharpness later. Click OK.

Now, if you've been following along, what you see is a grey image. If you set the radius high, it may look very similar to your image. Either way that's okay, you just need to change the high pass layer's blending mode. This is located at the top of the layer menu, to the left of the layer's opacity settings. Switch it to "overlay" for the high pass layer. Poof! Your image is sharpened.

Masking Layers

Now, if there are sections of the image to which you didn't want to apply sharpen, you'll want to create a mask. Select the high pass layer and then look for a white circle in a grey square at the bottom of the layer menu. Click that button or go to Layer ---> Layer Mask ---> Reveal All and you'll create a mask on the high pass layer.

Masks are a vital tool when manipulating images or working on an image that requires multiple layers. What they do is allow you to "cover up" part of an image by coloring over it (while the mask is selected) with a brush set to black. You will be able to see through it to the layer beneath.

This took me forever to wrap my head around, so here's an analogy. Imagine you have a stack of transparencies. The top transparency is entirely covered over with red marker, so you can't see what's on the lower layers. But, if you take a rag and rub off part of the red marker, you can see through it to the layers beneath and in this way bring two elements of different layers together. That's what a mask does, but it also goes one step better. Because it doesn't delete what you've covered over, you can switch to a white brush and "unerase" anything you've hidden.

Masking the high pass layer means that you can adjust the sharpness in specific areas of the image by reducing the opacity of a black brush (the brush's opacity is on a menu at the top of the program between "mode" and "flow") and using it on the mask. When you're drawing on the mask, any part of the image that you paint over will have reduced visibility. So, if you use a brush set to 100% opacity, you'll "erase" it, but if you use a brush set to 75% opacity, the image will still be visible, but 75% lighter than it used to be.

You can use this effect to lighten the high pass layer and so reduce its sharpening effect. This allows you a lot of flexibility because you can choose exactly how much sharpness is applied to any one part of the image.

To see the effect that the high pass filter has had, click the little eye beside it in the layer menu. This will make the high pass layer invisible, and by clicking between the two you can see what areas have been changed.

Questions? Comments? Would y'all be interested in more tutorials like this? Let me know!

2 comments:

Ryan Sullivan said...

Hey, Marion! I don't have photoshop but I can download GIMP for free. So if you could do tutorials for GIMP it would be useful. (Although I'm intending to hire a cover artist, so don't stress.)

Marion Sipe said...

Hey there! I'm probably not going to. You were the only one to comment, and if you already plan on going with a cover artist than it sounds like you've got it covered!