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Why Does Sharpening Help? What Does It Do?

Why Does Sharpening Help? What Does It Do?

Today’s digital photography tools have changed the profession in ways that nobody could have imagined. Photography has always been an art, but now it involves more than the use of the camera. Half, if not more than half, of the technique of photography is carried out in the post-processing phase. Sharpening has grown to become an important step in that process.

With so many amateur and professional photographers sharpening their photos, it’s only natural to stop and ask why they’re doing it. What does sharpening really accomplish, and to what degree is it necessary? Should you sharpen every image you take, or can you reserve it for a select few? I want to take a moment to consider that thought and look at some sample images that have been sharpened with photo editing tools.

Sharpen to improve contrast

That’s the main reason anyone applies a little extra sharpening to their images. It makes your subjects POP. Sharpening programs/filters really only do one thing. They make edges appear more defined by darkening the darker pixels and brightening the brighter pixels. This creates a crisp edge between light and dark portions of the image, giving it more contrast.

Have a look at the following image. It’s a nice looking bowl of fruit, perhaps a little too soft and bright, but otherwise fine.


An unsharpened picture of a bowl of fruit. Notice the softness in the matt and on the surface of the fruits.
Photo By Flickr User bogoni

Now here’s the same bowl of fruit after we’ve applied a little sharpening. Can you tell the difference?

Here’s one thing I notice right away. The shadows underneath the fruits are a lot darker. If you look even closer, the shadows in between the weave of the matt are a lot darker too. Because these edges are more apparent, the fruit takes a central role in the image. It stands out a lot more. I also see the spots on the apples are a lot more pronounced.

All of this should make sense. Remember, sharpening algorithms and filters work by darkening dark areas and brightening bright areas. If you think about it, that’s literally what it means to add contrast to something. More of the image clashes with itself, and that makes it more visually interesting.

How much is too much?

As with any of these tools, it’s pretty easy to get too carried away with it. You see how a bit of sharpening can improve an image, and then you want to sharpen it “just a little more” until you end up with something that no longer looks natural. Here’s a handy way to prevent yourself from doing this.

Photoshop include a preview feature with all of the filters you use. Unsharp Mask is one of the sharpening tools you’ll become familiar with as a photographer. I won’t give you all of the details here because I’ve already written a tutorial on it, but you’ll want to use the preview image to look for the key characteristic of oversharpening.


Too Much Sharpening

Do you see how there is almost no gradation in color? It’s more like one uniform mass. Contrast this with the more gradated pixels in the original image. Even after you apply a sharpening filter, most of your pixels should look like the original.

When you sharpen too much, everything starts to look like the amorphous yellow mass that has become the pear. If you zoom in to 200%, you can find the parts of your photo that might have this problem. The only solution is to sharpen less.

Should you sharpen every picture you take?

Unless you intend to convey softness (perhaps in baby pictures, etc.), you should sharpen most of your images as much as you can. Added contrast really does make an image more interesting, and as long as it doesn’t make your pictures appear unnatural or pixelated, you’ll end up with something that’s better than what you started with.

Also remember that most digital cameras sharpen your images as they are taken, and depending on the model, you may already have an image that’s sharp enough. As a general rule, point-and-shoot cameras sharpen more because their users tend not to edit their photos heavily. Digital SLRs, on the other hand, often sharpen a lot less because the camera manufacturers know that you’re more likely to do the job yourself. Creative control is the reason you would purchase a digital SLR, after all.

What sharpening doesn’t do

Some people are under the impression that sharpening will help them recover lost details in pictures that are otherwise too blurry, dark, or bright to be usable. Unfortunately, nothing could be further from the truth. Sharpening doesn’t give back details. It makes the details you already have appear to stand out a little more.

Let’s look at another example. This time, we’re going to look at a photo where the main subject is out of focus and thus blurry.

Can a sharpening program make this image less blurry? Can it give us back some of the detail lost on the child’s face? Let’s give it a try.

And this is the result. You’ll notice that we haven’t really recovered the lost detail we wanted to recover. The parts of the image that were out of focus are still blurry. After the sharpening, the background that’s in focus looks better, but our main subject is still very blurry.

When you think about it, the sharpening program did exactly what we would normally expect it to do. It brightened the bright pixels and darkened the dark pixels. The areas that were already in focus have a little more contrast, but the rest of the image remains mostly unaffected. Whenever you think about sharpening an image, you have to remember that this is what’s going on.

Sharpening programs are not intelligent. They aren’t like the detectives on Law and Order or CSI. They aren’t trying to uncover what’s beneath the blur. They’re more like robots. They only do one thing. They brighten the bright parts and darken the dark parts. No more. No less.

How do you use sharpening and post-production in your digital photography? Let me know by leaving a message below.

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About the Author ()

David Peterson is the creator of Digital Photo Secrets, and the Photography Dash and loves teaching photography to fellow photographers all around the world. You can follow him on Twitter at @dphotosecrets or on Google+.

Comments (12)

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  1. Christel says:

    Thanks for that Dave, now I know what I’m doing.

  2. Jerry Anderson says:

    I always start the sharping process only on my “Keepers”, sometimes the picture just doesn’t need it and I back off. I find sharpening an art along with adjusting exposure and color. I enjoy your tips and look forward to them daily. Thanks..

  3. NEVILLE says:

    FOR EVERY PHOTO, I USE THE HIGH PASS FILTER SET AT 4 AND IN LAB MODE. SCRUTINY HAS SHOWN ME THAT THIS WORKS AS GOOD AS YOU WILL EVER GET IT. THIS WORKS EVERY TIME ! THERE’S NO NEED TO CHANGE THE SETTING.

  4. Ron Sand says:

    Strange! I found the top picture of the fruit sharper than the picture below??

  5. Esther Runyan says:

    Thanks, Dave. I do sharpen my images quite often, but I’ve always felt it was somehow “cheating” and that I hadn’t done a good job taking the picture in the first place, although I’m very careful not to move the camera, and to use myself and something near me as a “tripod” if I can. This article has eased my conscience about sharpening my pictures. Thanks again.

  6. Although the poll asked whether I sharpen my images with ‘yes’ or ‘no’ I believe the question should be more specific ~~~ ?Do I sharpen ALL my images? and the answer would be NO!
    Some images need sharpening and others not at all.
    mike

  7. Maurice Mol says:

    More or less knew about sharpening. Your explanation is very clear.
    Now I know about unsharp mask.However, there are more and different sharpening tools.

  8. As well as unsharp mask, I use an action with the high pass filters from a tip I picked up somewhere.

  9. Rob Elliott says:

    Hi David,

    I use the unsharp mask but never in RGB mode. I always convert to LAB and then sharpen the lightness channel only, then convert back to RGB. This way, I can sharpen more without developing those annoying little coloured edge artifacts.

    Kind regards,

    Rob

  10. John Rocha says:

    Thanks David – there’s a lot of good advice here. It’s all true as far as digital cameras and post processing are concerned. However although it’s implied I feel a lot of emphasis should be put on taking sharp pictures in the first place. For all sorts of reasons photographers often don’t pay enough attention to this.
    I’ve written a series of articles on this if anyone is interested and they’re on my site (absolutely free of course)
    Looking forward to my next Digital Photo Secrets
    John

  11. Roving Jay says:

    Great tip. The photo’s you use illustrate your example perfectly. I’ve used the sharpen tool – but didn’t really understand what it was doing to my photo’s – so thanks for the education!

    Jay

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