Sharpening - Monitor vs Result

[Claire]

I've realised that I tend to sharpen too little. On my screen it looks ok, not too soft and not too overdone. Then I save it and when I print it out or look on the web it seems it's still too soft at times.

How do I really know how much to do? Ok, it's a stupid question as it depends on the image and your taste, but still...am I the only one having this problem?

/Claire

[ejwebb]

You are not alone in struggling with this. I have found that sharpening is specific to the intended use. What looks great on the screen in the full size photo doesn't do once you have resized it smaller for the web - you must sharpen more. Additionally, printed photos can often handle (or need) more sharpening as well. I do not profess to undrstand the science behind it, but when I intend to print a photo I crop and resize as needed and then sharpen - more than I would for screen use. It is somewhat hit or miss at first but I am developing a feel for what will work and what will not given the print size and subject matter, etc.

Currently I use mostly simple USM at various settings but am investigating some other sharpening techniques. I would search for sharpening techniques - there are many to try and they all produce different results. So much to learn... :P Hope this helps.

[Scottes]

For web stuff, view at 100% and sharpen until it looks like it's too much. Back it off a little, look away from the screen, look back. Turn Preview off and on. When it looks good hit OK.

For printing, it's generally considered best to view at 50% and basically do the same thing, but you want it to look a bit over sharpened. You don't want sharpening artifacts - bright white spots and/or dark black spots caused by sharpening and generally found at or near edges. But you *do* want it to look a bit over-sharpened.


A general rule of thumb is to keep sharpening halos at 1/50 or 1/100 of the DPI of the final result. So for a 300 DPI print the halos should be about 3 to 6 pixels wide. So when the sharpening looks good, zoom in to 200% or 400% and check the halos. Are they too wide? Are they too contrasty? If one side of the halo is bright white and the other side is fairly dark then it's probably too much.

Following this 1/50-1/100 rule is easy by setting the Radius first. For a 300 DPI print try setting the Radius between 1.5 and 3 (half the halo size). For some reason I always seem to start with 2.1 - go figure. Now think look at the image and check how noisy it is, and how small the details are. For clean (not noisy) but high detailed images like fur you want a low Threshold, like 0 or 1. For softer images (portraits), or ones with a lot of noise, run the Threshold up to 4 or maybe even 5. Architecture-type images might be running at 1-3 depending on noise. Experiment to get used to it.

And if you have a high-detailed but noisy image you'll have to find a middle ground - noise and details are basically the same thing - small groups of pixels. Removing noise removes detail, and saving detail accentuates noise. It's tricky and you might not get a perfect image in the end.


Now that you have the Radius and Threshold set, the only thing left is Amount, so now it's easy. Run the Amount up the scale, view at the right percentage, turn Preview on and off, and zoom in from time to time to check halos. Don't worry about the number - sometimes "300%" scares people but if that's what makes it look good then use it.

OK, so now it looks OK, but is it perfect? Without touching the Amount go back and play with Threshold and keep an eye on noise and or details. You'll want to be at 100% for this. When the details and/or noise look OK, zoom back to 50% view and play with Amount again until it looks OK.

Then check Radius. At 50% view try changing Radius a little - no more that 0.5 at a time. Check the effect on the edges of your image - does this make an edge too contrasty? Or not sharp enough?

Once you have a Radius that looks good, change the Amount again until it looks good. When it really looks good, look away for a moment, and back again. If it still looks good then hit OK.


This sounds like a lot of work but it's quicker to do it than describe. And once you do it a few times you get *much* faster at knowing what numbers to plug in.

And it's not a bad idea to try 3 different settings and print them. That is, find one that looks good, and save it. Do the same thing but increase the amount by 30%. And once again but decrease the amount by 30% from the first one. Print and compare the three - it's a cheap way to see the differences.


To recap:
1) View at 50% or 25% - not 66% or 33% because PS does anti-aliasing at these views, and it *will* mess you up.
2) Halos at 1/50 to 1/100 of final output DPI
3) Set Radius first to match the halo size
4) Set Threshold next to match noise level and/or detail size.
5) Play with Amount.
6) NEVER try to tweak Radius and Threshold at the same time. Set one, then Amount, then the other, and Amount again.

[who10]

There is some really good information about sharpening (when, how and to what degree) on PixelGenius' web page describing their sharpening tool set... aside from being "yet another thing to buy", I've had truly excellent results especially with their output sharpener (target sharpening for image size to target output medium)....

http://www.pixelgenius.com/sharpener/index.html

For me it solved my tendency to "undersharpen" for printed output - and gave me better consistency with web sharpening (I use their product as a PSCS plugin).

Worth reading their white papers even if you choose not to buy their stuff...

As I was typing this Scottes finished his summary... the Pixelgenius page supplies some further explanation as to why his recommendations work so well (great information Scottes ! )

[ejwebb]

Great summary, Scottes. Very helpful information.

[Claire]

Thanks. I'll try to figure the process out with the help of your instructions Scottes.

/Claire

[Roger_Cavanagh]

One way to take the guesswork out is to use QImage (http://www.ddisoftware.com/qimage/) for printing. You feed it images that have only capture sharpening and creative sharpening (using the Pixel Genius terms). QI also takes care of resizing on the fly as well. The interface is very quirky and it does take some getting used to, but the results are excellent.

Regards,