Hi all!
Disclaimer: I am not claiming to be an expert on sharpening, but I do believe I have a firm grasp on it.
KPD Magic Sharp is a wonderful/powerful sharpening action. It is so great, because it boosts local contrast, as well as edge contrast or standard sharpness with a luminosity fade. The reason it is so great, is the values used.
I've been using Magic Sharp, since before I even had it. What I mean, is I've been using a similar sharpening action since before I even knew about Magic Sharp. I was one that would look at the images on [b]ecker's, Jessica Claire's, and Jasmine Star's blogs and not only love the color and great imagery, but the pop the images had/have. This is due to Magic Sharp and I'm pretty sure it's applied to images constrained to 900 pixels (or close to it) on the longest dimension. That's how I use it for my BLOG images. The same action applied on a 12MP image does not have the same effect, although it still really helps the image pop a bit.
Ideally, there are two types of sharpening to be applied to your images. Capture or input sharpening (I will refer to as capture) and output sharpening. The first step is a very mild sharpening adjustment; the second, is based on the intended output such as; print, web, press, etc.
Capture sharpening is performed to take away the softening done by the anti-aliasing or low pass filter in front of your sensor. This filter helps reduce moire and capture more wavelengths of light, but by doing so softens the image slightly.
ACR 4.x and Lightroom (same architecture) do the capture sharpening part for you by default with the values:
Amount: 25%
Radius: 1.0px
Detail: 25
Masking: 0
Those values usually do a great job sharpening the image enough to bring it to a 'neutral' point.
Output sharpening is like a whole other art form, that some master printers are well, masters at, but anyone can do a decent job by trial and error. Ouput sharpening is based on so many variables like; paper type, size, viewing distance, color, output device, and others. There are programs such as Nik Sharpener Pro 2.0 that can do a lot of the work for you with little direction that do a pretty great job. I used to sharpen that way, but since I'm not printing exhibition pieces and whatnot, I feel I don't need or want to spend the time taking the steps to get those results.
Local contrast enhancement or clarity (in Lightroom and Kubota Production Pack 1), is the first step in Magic Sharp as well as what I do. This is what really gives the image that in your face pop. This is done with USM with a low amount like 25% and a higher radius like 50px; threshold is adjusted based on image content (people versus landscape) I have this set to 6. Having a threshold of 0 will usually bring out too much texture in continuous tones such as sky's and skin.
Second step is a 'standard' sharpening adjustment with USM. A high amount like 250% and a low radius like 0.8px. Same thing with treshold...around 6. This will bring out lines such as eyes, teeth, and other edges.
The third step, is a 100% luminosity fade to help reduce halos from the second sharpening step. In photoshop, Edit>Fade or Shift, Command, F. Set the mode to luminosity and the opacity to 100%.
So, imagine you have an image of an open book with just text. Black text on white pages. The first sharpening pass, will make the words almost come forward and pop in your face. The second pass, will make the edges of the text separate more from the pages. The luminosity fade will help make the edges of the text sharp, but smooth.
Here's what the action I've been using for a couple years does:
Pass One:Unsharp Mask
Amount: 25%
Radius: 50px
Threshold: 6 levels
Pass Two:Unsharp Mask
Amount: 250%
Radius: 0.8px
Threshold: 6 levels
Pass Three:Edit>Fade
Opacity: 100%
Mode: Luminosity
I feel these values work well on my full resolution images (12MP). I don't think it perfectly mimics what Magic Sharp does on 900 pixel images though, but the intended output for the two is different and it comes close. All of Magic Sharp's values are lower than mine, but I will not tell you them, as that wouldn't be too ethical.
I use Lightroom to process my files and use the default sharpening values to do my capture sharpening and when I export my files, I have a droplet created from my sharpening action apply sharpening to the exported files...but what if you don't want to do two steps of sharpening and you only want to use Lightroom? Many people agree (I'm one of them) you don't NEED to do two sharpening steps and that fine, so in Lightroom or ACR 4.x for that matter, here is an option.
In Lightroom 1.1, the Clarity slider was added and that made me go WOO-HOO! Clarity is a local contrast enhancement like the first pass of sharpening in Magic Sharp and my sharpening action. A value between 25-50 can really help cut down on haze (hence the name clarity for the slider) and help make the image pop in a similar way. There's pass one right there. I have this as 35 in all my presets because I use the sharpening droplet, but if you want to do all your sharpening in Lightroom, 50 will probably give you great results.
Next, is the actual sharpening under the Detail portion in the Develop module. Here you will see four sliders; Amount, Radius, Detail, and Masking. Think of Detail and Masking as together making up Threshold and Amount and Radius as being very similar as USM in Photoshop.
To sharpen, it is always a good idea to view the image at 100% or actual pixels. Magic Sharp does this for you. In Lightroom, just click on the image to get there (with default settings) or go to the upper left in the Develop module in the Navigator window and click on the 1:1 view option. This will allow you to get a better idea of what you are doing as well as engage some options in Lightroom you can't get in full view. Note, images will usually look a little over sharp when viewing at 100%, but this is usually a good thing, as you are viewing them closer than you normally would.
The closer you are, the less sharpening that needs to be applied for the image to appear 'sharp' and the the further you are the more sharpening that needs to be applied for the image to appear 'sharp'. This goes the same for size. Smaller things need to be sharpened less (BLOG images) and larger things need to be sharpened more (prints).
In Lightroom, the Amount slider only goes up to 150%, not 500% like Photoshop. I find that between 100% and 150% works best if you like that Magic Sharp look (I like 150%). For Radius, I like the same value as my sharpening of 0.8 pixels. Now here's where it gets different. Basically, the Detail slider lets you choose what to sharpen and the Masking slider lets you choose what not to sharpen. It's hard to see this and this is why Adobe put in a easy viewing option.
First, put both Detail and Masking to 0. Then hold down the ALT key (on a Mac at least, you can do it on a PC as well, I just don't know what key it is) and click on the Detail slider. You will see the screen go a light grey and see dark areas where edge detail is in your image. (If you use the high pass sharpening method in Photoshop this will look similar) The goal here, is to bring your slider to the right and reveal (darker areas) what you want to be sharp. I think a value between 10-20 works best for people images...I like 20. Next, you will ALT click on the Masking slider and the view will turn all light grey. The goal here, is to bring the slider to the right and just like a layer mask in Photoshop, black conceals and white reveals. Anything in white will REMAIN sharp, and anything in black will no longer. A value of 75-90 works best for people images...I like 80. That's it. You can toggle the detail slider on and off to see the effect. For non-people images, a higher detail value and a lower masking value will be better. This would be for images like landscapes and whatnot, but now you know how to see what you are actually sharpening, you be the judge, afterall, they are your images/vision.
Boutwell Magic Glasses rocks and is a local contrast enhancement with edge masking, making it appear stronger and more sharp. Really, it's just a nice big pop to the image, not necessarily a true sharpening adjustment. This in conjunction with a USM adjustment like my second pass, would be similar to Magic Sharp.
Note: Boutwell Magic Glasses is very strong, but more sophisticated and adjustable to your liking, as it is on it's own layer. Doug did a great job developing this action as well as the rest of the killer Totally Rad action sets.To make this an even more powerful method for sharpening, open the action contents, click on the USM adjustment, then record, open USM, then input 250% for Amount, 0.8 pixels for the Radius, and 6 for Threshold (same values from my full res sharpening action) and you now have a full sharpening action that is adjustable on it's own layer. I've been using this method more and more as it leaves the skin smoother (due to some masking), but due to the sophistication of this action, it takes quite a bit longer than Magic Sharp or my sharpening action.
When should you sharpen?
First and last. Huh? If you do both capture sharpening and output sharpening, you will sharpen before you do any adjustments what-so-ever or with ACR 4.x the same time as RAW conversion. The last step is to sharpen based on output. But, you should always have sharpening (of the output kind, which is a much stronger adjustment then capture sharpening) be the last step in your workflow on an image before saving or printing.
Hopefully, this helps some of you, as that is my sole intention. Just trying to spread the love. Definitely play around with different values, as we all have different opinions on what 'good' sharpness is. Sorry if this was a little long as well, but like I said, I'm just trying to help. Feel free to ask any questions having to due with the above mentioned items.
Take Care~