Photo Sharpening Techniques
As a follow-up to my previous post “6 Tips for Controlling Sharpness“, we'll now focus on the post-processing side of things. Of course, you'll still want to do everything in your control to get a sharp image when you release the shutter, but almost all photos can use some amount of sharpening via software. Your camera has the ability to sharpen photos as part of the processing, but you'll be better off leaving the sharpening setting at zero in the camera — your computer can do a much better job. I'll be using Adobe Photoshop CS3 for the following techniques, but they're pretty generalized.
Sharpening should be the absolute last thing you do during post-processing. Any adjustments made after sharpening may accentuate the sharpening in a bad way, making the photo look over-sharpened or over-processed. So once you get the image looking the way you want it, here's what you do:
- Create a new layer on top of the layer stack and rename it to “Sharpen” (Layer >> New >> Layer…).
- Select the new empty layer and press Ctrl+Alt+Shift+E to merge the layers below into the new layer. If you're in a real hurry, skip to step 6 then jump to step 10.
- Now duplicate the layer into a new document so we can sharpen it (Right Click >> Duplicate Layer…).
- Switch to LAB color mode (Image >> Mode >> Lab Color).
- Go into your Channels Palette and select only the Lightness Channel. Your image should turn black & white now. We're going to just sharpen the Lightness Layer so we don't get artifacts from the color information.
- Now apply the Unsharp Mask to that selected channel (Filter >> Sharpen >> Unsharp Mask…).
- Set the Radius from 3 to 5 pixels and the Threshold to 2 or 3. These are just starting points.
- Raise the Amount to somewhere between 150% and 300%. You'll want to stop when you see very distinct halos in the image. I usually start off around 200%.
- Now adjust the Radius until it gives good sharpness with limited halo effects.
- Adjust the Threshold to account for any noise that may be produced from the sharpening.
- Now go back to the Amount and lower it until the halos disappear. I usually end up between 50% and 150% depending on the photo.
- Once you're happy, click OK. See the image below for examples of under-sharp, sharp, and over-sharp.
- Select the LAB Channel to reactivate all three channels, and go back to the Layers Palette.
- Switch back to RGB color mode (Image >> Mode >> RGB Color).
- Duplicate the layer back into the original document (Right Click >> Duplicate Layer…), delete the original Sharpen layer, and rename the new one to “Sharpen”.
- If you want to selectively sharpen some parts of the image less than others, you can apply a layer mask. If not, you're done!
- Click on the little “Add Layer Mask” button at the bottom of the Layers Palette (dark box with a white circle).
- If you want to un-sharpen a few parts of the image, select the layer mask, grab a soft brush, set it to black, lower the opacity of the brush to 5 or 10%, and start painting OUT the sharpness.
- If you want to only sharpen a few parts of the image, you'll first want to fill the mask with black, then you can grab the brush, set it to white, and do just like the previous step. But now you're painting IN the sharpness.
The image below shows examples of under-sharp, sharp, and over-sharp samples viewed at 100%. You want to avoid the halos shown in the over-sharp example, but you'll also want to be more aggressive than the under-sharp example.
These are all just general guidelines, and every image requires a different amount of sharpening. I only went over the Unsharp Mask in this example, but Photoshop offers several others in the Sharpen Filter menu. I use the Unsharp Mask because it offers good control and it's quick to apply. The other sharpening techniques may be substituted in the steps above for the Unsharp Mask Section. So go try it out, and you'll see how just a small amount of sharpening can make big improvements in your photos.
Photo of the Day…
Photo by Brian Auer
03/05/07 Neuchatel, Switzerland
Konica Minolta Maxxum 7D
Konica Minolta AF DT 18-200
27mm equiv * f/3.5 * 1/30s * ISO100
Brian AuerMay 14, 2007
Sharpening is a tough thing to get a handle on. Some people oversharpen badly without realizing it. I typically oversharpen just slightly, then go back and mask things out using a soft brush at 5% or 10% opacity. I often find that one level of sharpening does not work well for the entire image.
Christopher SchollMay 14, 2007
Great tutorial. While I use Photoshop for serious sharpening, and Adobe Lightroom for less serious stuff, I’m not big on either. Some of the plugins seem to do a better job.
And by the way, I particularly like your photo of the day.
soriJanuary 3, 2009
I agree that over sharpening can create an issue, expecially when using free or cheap programs like irfanview to perform the task. Though, I must say I like irfan for it is free, quick and good in a pinch.
AlJanuary 10, 2009
Thanks very much for the tips. Someone told me I was over-sharpening my photos, this tutorial has really helped me get back on track.
Brian AuerJanuary 10, 2009
It’s easy to go overboard with sharpening — you really have to watch out for halos at 100% zoom.
Sarah BolopskiFebruary 6, 2009
I found that doing one or two refinements of adjusting sharpness is more than enough. Good tips though.
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