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| Digital Photography Sharpening 101 |
Introduction
When looking at a digital photograph, one of the first things most people notice is the sharpness of the photo and the focus of the primary subject. In fact, most photographers are quite hung up on the issue of sharpness. And though under many circumstances certain regions of the photo are desired to show a “blur” – for instance background that is supposed to be out of focus, or motion blur to convey the feeling of speed, or a soft blur to give the photo a more romantic feeling – in many cases the sharpness of the final image seems to lack when compared to photographs from “professionals”. At first glance this could be attributed to better (and more expensive) equipment or just the fact that the “professional photographer” has more experience. But quite often these are not the only reason…
Causes of Blur
Before we start improving the sharpness of our digital photos, we need to understand some of the two leading causes of blur.
1. Resolution Capabilities of the Camera Lens & Aperture
The first hurdle the light has to pass to become a digital image is the lens of your camera. To keep this tutorial from becoming too long, we will cover lenses and aperture in more detail in a future tutorial. Just know for now that this kind of blur is known as “Lens Blur”, and this is exactly what we will be able to “fix” in our post-processing steps.
2. Motion & Exposure Time
This is probably the most obvious cause of blur, and unfortunately also the most common cause for a blurry photo. Exposure time is the time the camera is “recording” the image. The shorter the exposure time, the less light comes in, but the less movement is recorded. And when we talk about movement we don’t necessarily mean movement of the subject – often it is you that moves. Because no matter how still you think you can hold your hand, you always shake a little bit. One rather common mean to defeat shake is to use a tripod. But since we want to talk about post-processing today, we’ll leave this for another day also.
3. Magnification
The last factor of blur we will talk about is magnification. This is a rather simple principle – just think of the printing of a billboard or magazine. From the right viewing distance a billboard looks perfectly sharp. But if you walk up close and take a look, you will see a million dots and the details and sharpness will be gone. The way we can use this in digital photography is by defining how much we crop and resize the image before the final display output. And in one of our next tutorials we will cover how you best resize images for digital on-screen viewing.
Post-Processing: Image Sharpening
Now that we understand some of the main causes of blur in digital images, let’s get right into how we can improve the sharpness of a digital photograph in our post-processing.
We will start with this photograph of a bird – the original image is a lot larger, but we cropped and resized part of the image here.
At first glance this image looks reasonably sharp. But when looking at the 100% crop (i.e. an area of the image in original size, cropped) you will notice that it isn’t quite perfectly sharp – at least not compared to what you see in “National Geographic”.
So next we load the photo in our favorite photo editing software. We will explain the steps for some of the several common editing programs. In case you don’t have any image editing software, scroll down a few sections, and take a look at the FotoFiltre solution, which is based on a program you can download for free (though we don’t endorse this product specifically, we have heard good things about it).
Commercial Solution: Adobe Photoshop CS2
Image sharpening in Photoshop CS2 has really been made easy by Adobe.
Just before resizing the image, but after we have made all other edits (but before adding borders!) we go to the Filter >> Sharpen >> Smart Sharpen menu item. Since this is the beginner tutorial, we choose the “Basic” radio button, and leave the Settings drop-down at “Default”. When dealing with regular “Lens Blur” (see above for explanation) we choose the “Lens Blur” option in the “Remove” drop-down. We also make sure that the “More Accurate” check-box is checked, as it will improve the final output by Photoshop.
That leaves us with two sliders to play with: Amount and Radius. For beginners, the best thing to do here is to play with the two sliders until the output looks too sharp (yes, we said “too sharp”). A good starting point usually is a Radius of 1.2 pixels, and an Amount over 100%.
For our example we will use an Amount of 175% and a Radius of 2.4 pixels. You will notice that the output in the window will look “over-sharpened” and shows significantly more noise. As long as we plan to resize the final image, this is actually good (think of the billboard again!).
Next we will resize the image. We choose Image >> Image Size from the menu, and resize the image to 50% of it’s original size (Change the “pixel” drop-down boxes to “percent”, and type 50 in one of them – the other one should change automatically, if “constrain proportions” is selected). On the bottom of the dialog you can see a drop-down called “Resample Image”. We will change that from the “Bicubic” setting to “Bicubic Sharper”. Then we click “OK”.
But before saving the image off, we will do one more pass of sharpening. So we go back to Filter >> Sharpen >> Smart Sharpen, and this time choose a setting below “1.0” for Pixels, and also a low setting for Amount. In our example we will use 25% and 0.8 Pixels. Now we save the Image using the File >> “Save For Web” function, and making sure we use Quality above 60%, while watching the final file size (bottom left of the window). And we end up with a much sharper image…see for yourself:
Commercial Solution: Adobe Photoshop 6.0, 7.0 & CS
The “Smart Sharpen” feature was just introduced this year by Adobe in is only available in the latest version of Photoshop. So, for older versions we will have to use a different technique for sharpening our images.
The most common of these is the use of “Unsharp Mask”. Now, I can already hear you saying – “That’s a weird name…why would that make an image sharper?”. Well we could explain to you where the name comes from, and it actually does make sense, but for the purpose of this tutorial, we will ask you to just believe us.
So, just before resizing the image, but after we have made all other edits (but before adding borders!) we go to the Filter >> Sharpen >> Unsharp Mask menu item. Usually we will set the Threshold slider close to “0”, the Amount slider around 100% and the Radius above 1.0. For our example we will use Amount “128%”, Radius “1.8 pixels” and Threshold of “1 level”.
Next we will resize the image. We choose Image >> Image Size from the menu, and resize the image to 50% of it’s original size (Change the “pixel” drop-down boxes to “percent”, and type 50 in one of them – the other one should change automatically, if “constrain proportions” is selected). On the bottom of the dialog you can see a drop-down called “Resample Image”. We will change that from the “Bicubic” setting to “Bicubic Sharper”. Then we click “OK”.
But before saving the image off, we will do one more pass of sharpening. So we go back to Filter >> Sharpen >> Unsharp Mask, and this time choose a setting below “1.0” for Pixels, and also a low setting for Amount. In our example we will use 25% and 0.8 Pixels. Now we save the Image using the File >> “Save For Web” function, and making sure we use Quality above 60%, while watching the final file size (bottom left of the window). And once again, we end up with a sharper image than the original:
Freeware Solution: PhotoFiltre
If you don’t have any image editing software that supports photo sharpening, one application you can download for free (for personal use only) is PhotoFiltre. While we don’t endorse any specific product, you can download the free version of PhotoFiltre from here: www.photofiltre.com. Click the “Downloads” link the left menu, pick your language, and off you go.
Once you have the software installed, open your image, and choose Filter >> Sharpen >> Sharpen More. While the sharpening quality here is not quite as good as in some commercial packages, it’s very usable considering that you didn’t have to pay a cent.
Once again, the image will look slightly over-sharpened. This is on purpose as long as we plan to resize the image (think of the billboard example again). Next, we will resize the digital photograph.
Go to Image >> Image Size… Change the middle drop down to “Percent” and type in “50” in either the “Height” or the “Width” box. As long as “Preserve Aspect Ratio” is selected, the other dimension will automatically change also. Keep the “optimize” checkbox checked, and hit “OK”.
Lastly, we will save the Image, by going to File >> Save As. We choose “JPEG” from the “Save as Type” drop-down, and save the image.
That’s it for now with the basic 101 introduction to Digital Photo Sharpening. We will be adding the next tutorial soon. Until then, look around on our site and enjoy the amazing photographs some of our members have submitted.
(c) Copyright 2005, EyeFetch.com. All rights reserved.
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