Sharpening images the pro way
When working with digital images an often overlooked final job is sharpening. This is especially true for images that have been resized down from large files (which should be incrementally sized and sharpened in stages if resizing down more than about 200%). Sharpening is also an important step for any image destined for lytho printing, as the process can sometimes introduce a slight bluring of images - in this case I’d actually slightly over-sharpen the image to compensate on this (but don’t go too far!).
Sharpening should always be the very last step in your image preparation - eg after you have completed all colour correction and composition work. It is advised you sharpen after all other steps as particularly colour correction can ehance unhealthy artifacts within your image.
Everyone is aware of the basic sharpening tools - these are all very well and good for beginners, but offer you no control (apart from fading the filter after). You should be using the unlikely named filter ‘Unsharp Mask’ Filter>Sharpen>Unsharp Mask - which, although the name suggests otherwise is the pro users sharpening tool.
You shouldn’t just apply Unsharp Mask straight to the image (which you should only do in a hurry!) as it can introduce unhealthy artifacts around high contrast edges. Instread we are going to use one of the most useful Photoshop Ninja ignored features - LAB colourspace:
1)First convert your image to LAB colour space - Image>Mode>LAB Colour.
2)Go to your channels palette, and select the ‘Lightness’ channel. This basically stores all the image information, the other two channels relate to colour.
3)Now apply Unsharp Mask to just this channel, I often think it’s best to start off with fairly low figures in the range of:
Amount: 50-75%
Radius: 0.5-1px
Threshold: 0
4)Try not to sharpen perfectly all in one run of the filter, I often think it’s better to apply this filter 2 or 3 times at lower settings. Always check the full composite image by clicking on the all channels view in the channels palette.
6)Once sharpened, remember to convert your image back to the desired colourspace for output (either CMYK or RGB).
The important thing here is to not oversharpen your image - you can compare your sharpening stages by stepping back through your history. Also, remember if you have areas that need more sharpening than others use your history brush to alter this for small areas, or use a composite layer and use a layer mask to brush in or out the higher sharpened areas. Sometimes just a little fade (Shift+Command+F) will do the trick to take that sharpness down just to the right level!
BONUS TIP
Just a quickie this week - remember that if you need to apply a filter with the same settings as just used, or bring up the settings again (eg Unsharp Mask in the example above) use the shortcuts below:
COMMAND+F - APPLY LAST FILTER
COMMAND+OPTION+F - BRING UP SETTING FOR LAST FILTER
COMMAND+SHIFT+F - FADE LAST FILTER APPLIED
April 28th, 2007 at 11:22 am
[...] another add on link using LAB mode Sharpening images the pro way ? Photoshop Ninja - Expert Photoshop tips and tricks HALF-LIME Photo / Video [...]
June 14th, 2007 at 9:14 am
This one makes sence “One’s first step in wisdom is to kuesstion everything - and one’s last is to come to terms with everything.”
October 3rd, 2007 at 7:06 pm
Lab sharpening is great, but as always there’s an easier way. Using more aggressive unsharp masking followed by a luminosity fade will give you the same result without mode changing or multible filter hits.
Great tip.