Sharpening images is one of the most fundamental elements of graphic design; however a lot of people struggle with this key process in their designs. Without proper sharpening, an image can look flat, dull and uninteresting, but if oversharpened, artifacts and grains will be introduced that will detract from the design.
In this tutorial, you’ll learn what a sharp image should look like and the many ways of sharpening one of your designs to achieve the maximum visual appeal.
Let’s get started.
What is a sharp image? Well below are two screen shots of one of my older pieces. The first image is the sharpened version while the second one is the unsharpened version. See if you can spot the key differences.
The first thing you would notice is the first image, when compared to the second, seems very blurry. The second image has crisp details, strong bold edges and sharper well… everything. While the first images edges are flat and dull, they seem to smudge into one another.
What is too sharp?
There is no real standard for over sharpening but I think we can all agree that any time a image has any noise like artifacts due to sharpening its been over sharpened.
So how do you sharpen an image? Well there’s a ton of ways actually but first we need to discuss what to sharpen!
In the above images I have made some circles in red and blue to show what areas will take to sharpening and what areas will potentionally suffer. The blue areas like the background and skin are all very easy to sharpen. They have a tendency to take much more sharpening then other parts of an image. The red spots however are your trouble spots. They look wonderful sharpened but just a tad too much and they will get grainy in a second. Examples of other red spots to spot in your images would include:
- Any geometric pattern that’s tightly knit
- Scan lines
- Star fields
- Grass
- Hair
- Feathers
- Splatters
- Patterns
- Text
- Etc…
Whilst blue areas would be:
- Skin and other ‘Flat’ areas
- Water
- Gradient
- Dull textures
- Thick lines
- Or any other areas that has minimal disruption and appears as I stated above, ‘Flat’.
So how do we effectively sharpen our images? There are numerous ways such as the sharpen filter, high pass filter etc… But now it’s time we discuss each process and which ones best for you. Let’s start with the sharpen filter. The sharpen filter is great for some images, but for images that have a variety of different shapes/textures and designs in them then it might not work as well as some of our other options. Take for instance the below image. It is our unsharpened image from before, with a scan line on it and 2 sharpen filters applied. Take note of our red and blue areas from earlier and how they look now.
Without the scan line the image itself would be fine. But my point is, it won’t always be fine, there will be instances when you have something in your design such as the above scan line. So what should you do? Well we will discuss that later on.
Next up is the sharpen more filter; we will not discuss much about it since the name says it all. However it’s usually about 2 and a half sharpen filters. I have yet to use it and I doubt I ever will.
Now we can discuss the sharpen edges filter.
This is another filter that I have not found a use for as of yet. What does it do? Well it sharpens the edges! But why would you want just the edges of your design sharpened? I haven’t a clue, this filter like the last, is a filter you should just over look when sharpening your images.
Now let’s discuss the unsharpen mask. This tool is a tad bit more complex that then last few and has more uses! However with its increase in uses comes the decline in flexibility.
This filter consists of 3 slides. The first one is the most important it’s your amount setting. This is the % of sharpening your image will receive. The next setting is radius, this setting is a little bit odd. If increased the sharpness % goes down and it applies an overlay like effect. This could be very useful in some scenes but it seems far too limited. The last slide is the threshold slide I have tried to figure out what its purpose is but I cannot, from what I can tell it decreases the sharpness when the threshold level is increased. Which seems somewhat pointless when you already have an amount %. An example of the outcome is shown below.
This has potential but what if you had a large number of red sections (see above) and very little blue areas? By the time the blue areas are sharpened the red areas will be destroyed!
Our next sharpen technique is one of my favorites. It’s the high pass filter. The high pass filter is often used to create HDRI like effects; however one of the key elements in a HDRI image is sharp details!
So how do you use it? When you apply a high pass filter your only setting is “Radius” now the more you increase this the less defined the result will be. Higher radius are used to create the moody color tones in HDRI images. We will use a lower setting like the above to create just the amount of detail we want. Next we need to fade the result, I choose a soft light blending mode because it affects the outcome the least. Once this is done you apply your favorite sharpening method, I chose to apply a sharpen filter followed by manually sharpening the image. An example of the outcome is below, but keep in mind you don’t have to fade this; you could duplicate your image, apply the effect, set the blending mode on the layer and then merge it.
Finally we are left with the best choice and the choice I always use. Manually sharpening gives you the same bang for your buck that the filters do but provides flexibility that the others just don’t have. How to use it? Well it’s easy; it’s just like a normal brush. My set up is as follows.
If you have a tablet now is the time to use it! The set up I have above applies more sharpen % based off how hard you press with the pen but if you don’t have a pen this is no problem. Why the low %? well the sharpen tool works like the burn tool and dodge tool; meaning the longer you leave it over one area without releasing the mouse button the sharper it becomes. I prefer the larger feathered brush because this way we aren’t applying a sharpen to one set area, we are slowly and methodically applying the sharpen to the entire image. This way, if you take your time and carefully sharpen the red areas and then move to the blues you could have a perfectly sharpened image in no time!
But let’s say you sharpened your image and now it’s time to submit it or present it to the world and you need to size it down. What will happen? Well it’s safe to say that the image will not retain its sharpness, but if you play with the image interpolation algorithms this may not be the case!
Photoshop offers 5 different ways of sizing your images up and down. Bicubic is the most common because it’s the most effective. It works by selecting a pixel and then referencing it to all of the pixels that are on its sides, and since a pixel is a square this means it references all the pixels on all four sides of the pixel. Photoshop offers 3 Bicubic settings they are:
Standard Bicubic – just a standard size down
Bicubic smoother – Its sizes the image down and tries to smooth the pixels down to prevent any artifacts
Bicubic sharpener – This method does the opposite of the above, it sharpens the images pixels as it sizes them
What’s left?
Bilinear – This method is very similar to Bicubic except for the fact that it rather than addressing all of the side’s of a pixel it only address the pixels to the left and right of a corresponding pixel.
Nearest neighbor – It addresses the closest pixel to the original pixel and should only be used when enlarging an image. When used to shrink an image it will appear over sharpened.
So what does all of this mean? Well not much to the average designer such as you or me. My recommendation for large scale images that need to be sized down for easier viewing? And what method should you use to sharpen an image? Sharpen your image manually and then size it down using the Bicubic algorithm. Once that is done re-sharpen it manually. It’s the best way to sharpen an image.
I hope after reading this that you will take it upon yourself to look at the way you sharpen your images. Do they look sharp enough? Could certain areas be sharper? And in turn, I hope you find a way to sharpen your images to your liking; providing you with a crisp image every time. Have any questions or suggestions? Drop a comment and I’ll be happy to help!
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