(Answer) (Category) Digital Photography FAQ's : (Category) Canon EOS-300D / Digital Rebel / KISS Digital FAQ : (Category) New User Questions :
What is USM and why do I need to sharpen my photos?
The 300D deliberately doesn't sharpen pictures as much as prosumer point-and-shoot cameras do. This is to allow you do more in post processing. (see (Xref) Why are my pictures soft compared to my .... ? )

In some cases, post processing is essential for pictures taken with the 300D, and especially the sharpening shouldn't be underestimated.

Downsizing pictures for web display does two things:

1. it makes them smaller
but 2. it makes them softer too

In order to compensate for this softness, you might want to apply a bit of sharpening to bring back that "zing".

USM (unsharp mask) is a sharpening technique used in Photoshop and other image processing programs. You might want to check out the sharpening section in this article to learn a bit more about it: http://www.seittipaja.fi/data/Photography_lessons/a_Photography_lessons.html

Personally I use two passes of USM on most pictures for web display:

1st pass: 30-60% / 0.7 pixels / threshold 0
2nd pass: 150-450% / 0.2 pixels / threshold 0

Just make sure you don't overdo sharpening or the pictures will look oversharpened. It takes a bit of practise and different pictures take different values, but after a couple of tries you should get the hang of it.

Oh, and sharpening should be applied as the *last* step in your workflow.

(nubui)

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