Sharpening for the web

Lopseychops

Lopseychops

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Mark
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I was told some time ago that the best way to ensure good, crisp, sharp images to display on the web was as follows:

1. Open the image in Elements/PS.

2. Resize the image to 3 times the width that you will post it on the website. i.e. If I am going to post an image at 800px along the longest side I would resize to 2400px. (600 would be 1800 etc)

3. Then click on 'enhance' and the 'unsharp mask' Set the sharpening to 200% and then ok.

4. The image will then look oversharpened.

5. Resize the image to 800px

Does anybody else find that this or a similar process works for them?
 
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Never heard of that. I simply sharpen at full size as normal then resize to around 1000px on the long edge and use smart sharpen at 0.3 and around 35%.
 
Depends what you are sharpening. Different subjects need different amount and/or techniques. F'rinstance, many portraits are left a little soft for reasons of flattery. Architectural images tend to get a lot of sharpening to give the lines prominence. A car shot may be selectively sharpened to emphasise detail, as may a landscape.

Sharpening may also be added at different times; when you take the photo if shooting jpeg, selectively during editing, and pretty much any shot will benefit from some sharpening as the final bit of processing.

Think of it as being like any other aspect of photography. It's a skill, and the more you lean and practice it, the better your final results will look.
 
Any full size image that is down-sized for the web will need some sharpening. Images lose sharpness. Since what you see on your computer screen is what you will see on the web (same resolution) sharpen until it looks right.

Sharpening for print is a different matter. Even if your image will be 300dpi for print, it still only displays at 72ppi on your computer monitor. So over-sharpening (as it appears on your monitor) is permissible to get a sharp(er) image when printed.
 
The best method I have found is somewhat similar to what the OP describes, but my (and others) testing has shown it to give better overall results. Basically you want to shrink in gentle steps applying a little Unsharp Mask (USM) (or your preferred sharpening method) each time you shrink until you get to the final result. You start with medium strength USM on the original image then light USM for each shrink thereafter. Here is a rough table of the number of steps (times you apply USM) I recommend, counting starting image and final image each as a step. This is assuming the final goal is a 0.5-2mp image. You would need less steps for larger final images of course.

4-8mp = 2-3 steps
8-12mp = 3-4 steps
12-18mp = 4-5 steps
18-30mp = 5-6 steps
30-50mp = 6-7 steps

You would want to shrink each time by roughly (original image width-final image width)/(steps-1). You can of course use height instead of width if it makes the math easier.

Here is an example. Lets assume we are taking a 12mp image and 4 steps, starting image size 4000x3000, final image 800x600:

Apply medium USM to the original image.
Resize image smaller by 1/3rd the difference between starting image and final image size. In this case for mathematical simplicity I would shrink the width by 800 to 2933x2200.
Apply light USM.
Shrink by roughly the same amount again, in this case, down to 1867x1400.
Apply light USM.
Shrink to final size, 800x600.
Apply light USM (skip if your hosting site applies their own sharpening on upload).

If you are almost always working with the same file size you can create an action for this and get great results very quickly. My testing has shown it to make a visible improvement in final web images over any other method I have heard of. As to the amount of USM to apply at each step, I am at work and can't check the exact numbers I use (It is an action so I don't pay attention much anymore anyway), but it isn't anywhere near 200% at any step. I think closer to 80% on the first step and about 40% thereafter.
 
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Thanks all for taking the time to reply.

Special thanks to Mike for your very informative piece. I think I will trial your workflow seeing as it closely mirrors mine.

Cheers.
 
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