What is a simple and effective method to sharpen for web output in Photoshop?

Question

In Photoshop, I've got a master PSD image file with all mask and adjustment layer treatments, but no sharpening at all. I save for web and create a JPG at 1200px. Now, I bring that file back into Photoshop for some sharpening.

What's a quick and effective way to sharpen? I've read that using Filter -> Sharpen twice is good, but to me the outcome looks a bit over-processed. Is Smart Sharpen a better tool than just Sharpen? What about Sharpen More, Unsharp Mask, and Sharpen Edges?

Asked by RaffiM

Answer

There are a number of different lines of thought on this issue, and it seems that each one vehemently defends itself as the "one true way" to sharpen your image. In my experience, it comes down to personal preference and the specific image that you're working. Keep in mind that "sharpness" is really just an area of high contrast along an edge or line in your image. There are three primary methods that people use, but each have the fundamental effect of increasing this contrast:

1. Unsharp Mask - As I understand it, this was the "old" method for sharpening photos. Without going into too much detail, this method creates a blurred copy of the image and compares it to the original to determine where the edges are that need to be sharpened. This method has three options, Amount, Radius, and Threshold. Amount controls the intensity of the sharpening, radius controls the distance from edges that will have the sharpening applied, and the threshold controls how "different" two pixels have to be to be considered for sharpening. The unsharp mask in my experience tends to have a stronger effect than other methods, which I prefer, but some people don't.
2. Smart Sharpen - This method is the newer method for sharpening photos, with a bunch of different options. The Gaussian Blur option behaves similarly to the unsharp mask, but it also has the option to remove lens blur and motion blur. It has similar options to the unsharp mask method. I use this when I want to try to remove lens or motion blur, but I find that its Gaussian Blur sharpening isn't quite as pronounced as the unsharp mask.
3. High pass filters - This method is different than the other methods; it actually creates a second layer, and uses blending options to get a sharp effect on the edges. I don't like the appearance that the high pass filter gives to images, but I know a lot of other people prefer them.

The other filters (Sharpen, Sharpen More, and Sharpen Edges) I find to be less useful, because you have much less control over how they are applied to your image. But in some circumstances they may be appropriate.

This website has a really nice comparison of the high pass filter to the unsharp mask, and Ron Bigelow has a really detailed series of articles on each of the different sharpening methods. But I think the best thing to do is open up a few different copies of an image, apply different sharpening methods to each, and see which ones you like best.

Answered by David

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Should I perform the final color space conversion before or after final sharpening of an image?

Question

When preparing an image for the web (or other media), the last two steps is usually to resize the image to the desired resolution and sharpen it at that resolution. However, when working in a larger/different color space than the final result is going to be exported in, when should I convert to the target color space relative to these two operations?

Answer

My last steps, in order, are resize, sharpen, convert color space from ProRGB to sRGB, convert to 8-bit.

The only really critical orders are sharpening after resizing and changing to 8-bit after changing the color space.

In fact, I was curious, so I just tried. One copy, I did my above steps. On the other copy, I converted color space, converted to 8-bit and then resized and sharpend. I put the images over each other and changed the blending mode to difference.

There was absolutely no pixel level difference between the two. I expect to see a few minor differences at 100% that would never show up on the print, but in the case of this one particular photo, there were absolutely no differences at all.

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Does the order of sharpening and noise reduction matter?

Question

I have been shooting for more than three years, but I never do too much in post-processing. I tend to be strict and keep in mind that PP can only do little to save an otherwise-great photo.

I was going to enter the "Photo of the week" thing, and I was doing sharpening and noise reduction in Photoshop.

NR makes your photo blurry, while sharpening amplifies noise.

I wonder, does the order of these operations matter at all?

Should I apply noise reduction and then unsharp mask, or the other way round?

Answer

Simple answer is YES!

Noise is an undesirable artifact, and many operations can enhance its appearance, not just sharpening. Tweaking curves, adjusting contrast, working exposure, etc. can all have some impact on the noise that is present in an image...although sharpening tends to have the greatest impact. It is important to handle the bulk of your noise reduction as one of the first steps of your development workflow. You should not necessarily aim to "eliminate" all noise...rather your goal should be to reduce the effect noise has on an image as much as possible without adversely affecting detail that you wish to keep. The tool you use to remove noise can have a HUGE impact on the results as well...Photoshop in particular is not really known these days as having the best noise reduction tools. Lightroom has some fairly excellent noise reduction, and there are other tools like Noise Ninja and Neat Image that also do an excellent job.

Keep in mind your final presentation format and size...a LOT of noise that may be present in an image at 100% is going to get "absorbed" (for lack of a better term) into the final presentation format. Prints can sometimes exhibit pronounced noise, particularly when the noise contrasts well with the base image. Usually a moderate amount of noise, particularly in smooth gradients, can be beneficial to final print output as it normalizes content and eliminates harsh transitions. Presentation on a computer screen is often best done at significantly lower resolution than the original image, and downscaling is a superb mechanism for eliminating noise. If you start out with a moderate amount of noise, or an even distribution of high amounts of noise, downscaling for display on a computer screen (i.e. via a web page) can be all the noise reduction you need.

Sharpening is a facet that is closely linked to the viewing medium of an image. Generally speaking, its best to save sharpening for last. Not only that, its best to keep sharpened images saved as separate files from your primary work image (which in turn should be separate from your original master image.) The amount of sharpening done, and the type of algorithm used and its settings, should be matched to the output medium for your photos. If you intend an image to be viewed onscreen, the kind of sharpening you do will be different than if you intend to print. The size of the final image for either medium will also affect how much sharpening you do, and how that sharpening is done. It's a good best practice to save resizing, cropping and sharpening for the very last two steps of your image editing. Duplicate, crop, resize, sharpen. If sharpening greatly enhances the remaining noise in your image, you may also want to do a final "light" pass of noise reduction to minimize it as much as you can without adversely affecting sharpness.

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What's the professional approach to removing noise from a cell phone pic?

Question

I have a cell phone photo that's a bit grainy and slightly blurry. It's not the out-of-focus type of blur, but the blur brought on when edges run together due to lack of sharpness.

I have Adobe Photoshop CS5 and have used Filters > Noise > Reduce Noise. After playing with the options, I finally got a decent look. The options I used are Strength:5, Preserve Details:0, Reduce Color Noise:0, Sharpen Details:100.

Are there other more effective ways to remove grain noise and blur from a cell phone pic? What would the pros do provided they use CS5?

Answer

These days, I would think pros use tools like Adobe Lightroom as much as Photoshop. Lightroom 3.x specifically is particularly well suited to removing noise as it uses a newer, more advanced algorithm to do so. It may also be the case that the latest version of ACR (Adobe Camera RAW) for photoshop has the same noise reduction tools if you happen to be using RAW. Lightroom will work with JPEG images as well as RAW, however, so its advanced noise reduction should still be viable for a cell phone photo. Lightroom is quite a bit cheaper than Photoshop as well, currently listing at $299.

I would say a moderate amount of luminance noise reduction, 60-80, would be sufficient to clear up a cell phone pic to reasonable levels. I would still throw back in some sharpening, to offset the effects of noise reduction and the blur (which is probably diffraction softening, given that it was a cell phone photo...they tend to have excessively small sensors with extremely high MP count, which when paired with the incredibly small apertures for the tiny lens, usually results in a fair amount of diffraction softening.) As far as sharpening tools, Lightroom's is ok, but not superb. Photoshops Smart Sharpen filter is probably one of the better sharpening tools. There are also a variety of other manual sharpening techniques that you can find around the web that involve various layer duplications, inversions, filtrations, and blending modes to achieve. Some algorithms and procedures are better for some types of photography, while others are better for different types of photography (i.e. how you sharpen a landscape would be different from how you sharpen a portrait.)

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Is it me or is the Lightroom's zoomed out preview inaccurate in displaying noise and color?

Question

I'm having some trouble with the Lightroom viewer (In develop mode) when zoomed out. Look at this picture:

See how the sky seems to have a lot of chroma noise

Now check the zoomed in version (Of the sky part)

I can't see any (significant) chroma noise here!

Finally, check this side by side comparison: Lightroom (RAW original file) and Windows image viewer (Exported JPG, 100 quality) (Click here for the full size version)

The windows image viewer shows a much better sky, without all the "blotches" of color and strong noise that the LR version shows. Do I have something wrongly configured? Do you suffer the same issue?

Answer

I don't use Lightroom but I regularly use Adobe Camera Raw which is pretty much the same thing but built into Photoshop, and have observed the same effect.

By default ACR applies chroma noise reduction to the raw image. The noise reduction only seems to be applied in the preview when you zoom in (perhaps Adobe figured the noise wouldn't be visible in the zoomed out view due to resampling), so what you're seeing in the zoomed out version is the actual noise level, and what you're seeing zoomed in is what it looks like after Lightroom has smoothed the noise.

You could confirm this by turning off noise reduction in Lightroom and seeing if you get the same result zoomed in as zoomed out.

As soon as you export to JPEG the noise reduction is applied to the whole image, which is why you don't see it in the Windows Photo Viewer.

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