Unsharp Mask

[leek]

For those of you (like me) who don't understand why something that sharpens your photo is called the unsharp mask and don't full understand the effect of the three settings in the unsharp mask - then this excellent article is for you.

There is one interesting tip in the article as well... Bob recommends applying the USM after resizing for the web... I always do it before saving as JPG... Any thoughts on this??? Does it make any difference?

[Manta]

That's a great article John - thanks for sharing it. I have certainly noticed a difference in final quality when USM has been used at different stages of processing, though I'm not technically savvy enough to know the ins and outs of it. I actually don't use USM that much - when I do, it's quite often to exaggerate edges and over-emphasise contrast.

[Frankenstein]

I actually don't use USM that much - when I do, it's quite often to exaggerate edges and over-emphasise contrast.

Manta,
if you don't use USM that much, what process do you use to sharpen images? I'm always on the lookout for alternative methods.

Frank

[sirhc55]

Hi John - yes it will make a difference. If you resize the longest edge of 3008 down to 800 for web placement and you have already used USM the mere fact of reduction will decrease the apparent effect of USM. If applied in the reduced form (i.e. 800 pixels) the eye will be accommodating the smaller size for USM - at least that is my theory

The best test is to try it and see if there is a difference.

[sirhc55]

Frank - the best sharpening procedure is USM as it uses the tried and tested method used by old time printers.

[Holden]

Just read the article , very interesting as I have just discovered usm
At least it gives me a bit more understanding of what I am doing

[Alex]

Thanks for the interesting article. Just out of interest what would be the most common settings people use for USM? I normally use 100 %, 0.4, 1. Scott Kelby's suggestions are very different though.

Alex

[Manta]

I actually don't use USM that much - when I do, it's quite often to exaggerate edges and over-emphasise contrast.

Manta,
if you don't use USM that much, what process do you use to sharpen images? I'm always on the lookout for alternative methods.

Frank

I'm not trying to be smart here, Frank, but I find the best sharpening tool is that metal cylinder locked on to the front of the camera body! Call me old-fashioned....

What I'm saying is that I rarely do any post-process sharpening. If you want an alternative method to USM, standy by and I'll dig up a post from (I think) Killerkoala about using a bas relief adjustment layer....

Give me a minute...

[beetleboy]

You'll find different settings have a different effect at different resolutions (too many "different's"!). I like to use high percentages but low pixel settings with 0 threshold; but it changes depending on the size of the image.

To answer your first question leek, Chris was spot on. When you reduce an images physical resolution (ie convert from 3008 to 800pix) Photoshop uses anti-aliasing (edge smoothing in layman's terms) which often slightly softens your image. If Photoshop didn't do this you'd get unsightly jagged edges..thus you must do your sharpening as a FINAL step. I even prefer to do it after all colour adjustments etc and if you find the sharpening is altering the colour in the image you're probably over-sharpening (also if you get halo's on egdes).

Hope this helps..

Liam =] PS - My girlfriend just read this and said I must add a disclaimer: I AM A GEEEEEEEK!

[beetleboy]

Manta..

Although your sentiment is spot on, digital images are inherently softer than their film counterparts as the CCD has a bayer interpolation pattern that tends to soften images and all professioinals use software sharpening to overcome this.

Liam =]

GEEEEEEEEEEEEEEEK!!!

[Frankenstein]

Frank[/quote]

I'm not trying to be smart here, Frank, but I find the best sharpening tool is that metal cylinder locked on to the front of the camera body! Call me old-fashioned.... [/quote]

What, your camera has a bullbar???

I agree, but as digital images are inherently slightly unsharp (due to the bandpass filter or some such thing), surely some degree of sharpening is required? I know I have to apply some sharpening to the shots I want to print.

Frank

[Manta]

I'm not trying to be smart here, Frank, but I find the best sharpening tool is that metal cylinder locked on to the front of the camera body! Call me old-fashioned....

What, your camera has a bullbar???

I agree, but as digital images are inherently slightly unsharp (due to the bandpass filter or some such thing), surely some degree of sharpening is required? I know I have to apply some sharpening to the shots I want to print.

Frank

I wish it had a bullbar sometimes!

In all seriousness - there are way too many excellent photographers who know a helluva lot more about the technical side of this subject than I ever will. Obvioulsy, I'm missing out on a lot without sharpening. I have slapped myself (quite hard I might add) and will endeavour to correct my error in the future. Keep an eye out for sharpened images from Manta in the future!

Here's that post I was talking about - it wasn't bas relief, it was high pass.

(Courtesy of Killerkoala in the "Shanghai Nights" thread)

Another way to sharpen using a High-Pass technique from Luminous Lanscapes.

On the Layer palette select your Background Layer and right click. Select Duplicate Layer.

* With this new layer highlighted select Filter / Other / High Pass. Set the Radius to 10 and click OK.
* Zoom into your image to Actual Pixels level so you can better see what you're going to do next.
* Go back to the Layer Palette and select Hard Light from the left drop down.
* Now go to the Opacity Slider and select a level of sharpening that seems best to you. Usually something between 20% and 70% will be best.

[the foto fanatic]

You can also sharpen by using a Luminosity rather than Normal layer when applying USM.
This just sharpens the lightness details, not the colour, and avoids halos.

[Killakoala]

USM is a beautiful thing. I use it quite often. I also use the high pass technique when USM doesn't do a good job.

[SoCal Steve]

You also have the option of sharpening in Photoshop Camera Raw under the Detail Tab if you have the Preferences set to affect the image as well as just the preview picture.

It is a variant of unsharp mask where the threshold value is automatically calculated based on the camera model, ISO and exposure compensation as recorded in the image metadata.

However, as Chris said, preforming the sharpening this early in the process (before resizing, format converting and stuff) probably isn't the most useful. But it's there to try out if you want to.

[Alex]

Thanks for the explanation, beetleboy.

Cheers
Alex

[Alex]

The problem I find with doing USM after resizing is that my workflow normally goes like this.

- I do all the adjustments including crops
- I run USM in PS CS
- I convert 16 bit to 8-bit if my starting point was a NEF
- I save it as a high quality JPG and this is my masterfile (or a file which I can later use to print)
- Then I go 'save for web' twice one 800 pixel and the other 200 as largest dimension.

If I do USM 2nd time during re-sizing then it is 2 USMs with one being on already saved JPG which might introduce artifacts.

Not sure how to go around this...
Alex

[dooda]

I use USM as apart of 99% of my photos as most are inherently soft and I personally like my photos to be as sharp as possible. I have done this to some photos and they looked fine on the screen but oversharpened when enlarged, so I scaled it back a little bit. I don't worry about it to much on the web versions though, just the versions I'm about to print and possibly sell.

[Matt. K]

John
It's called "unsharp mask" because it "masks" unsharpness. Must have been labelled by an academic.

[joolz]

If I understand it correctly, the term harks back to the "dark" ages.
In the darkroom, one used a blurred negative image masked over the original.
This "unsharp" mask increased edge contrast making the image look sharper.
In PS, USM similarly accentuates the differences in edges, making the image look sharper.

Joolz

[stormygirl]

Thankyou for posting the link, Leek. I now have a better understanding of it!

[SteveGriffin]

Thankyou so much for posting that link. I have been struggling with the whole notion for too long

[gstark]

I find that sharpening is best done with an oiled stone.