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 09/04/2004 12:59:18 AM · #1
Actually, I have PS Elements 2.0 but I don't think that affects these questions:

1) Why is it that while I'm editing my pictures they always look more grainy/pixelated in Photoshop than they do when I open up the file in Windows? A diagonal line in a picture will look like it has "steps" in PS as opposed to a nice smooth line like when I open the .jpg to look at it! And no, it's not that I'm zoomed in too far in PS...what's going on?

2) Why I can't I do anything useful with UnSharp Mask? What's the best way to use this or is it something that you generally stay away from?

For me, the tool might as well be called "Create white pixels around the object you're trying to sharpen"! I've tried numerous settings but I admittedly don't understand what I'm doing when it comes to the USM tool. Any help here?

Thanks!
 09/04/2004 01:01:43 AM · #2
I have the same issue with what you are calling "steps", I think. I get "jaggies" on straight diagonal lines. I thought it was my Kodak compression, but I got them on a shot with my new camera,too. I hope someone can help both of us on this! Good luck, and I will stay tuned!
 09/04/2004 01:31:52 AM · #3
The jaggies, are most likely from the image being resized. Put the view to actual pixels, and see if that gets rid of them.

The white in USM, is because you have the settings too high. Keep the threshold & radius pretty low, then increase the amount untill it looks good. You can probably find some good tutorials online.
 09/04/2004 03:24:53 AM · #4
Originally posted by thatcloudthere:
Actually, I have PS Elements 2.0 but I don't think that affects these questions:

1) Why is it that while I'm editing my pictures they always look more grainy/pixelated in Photoshop than they do when I open up the file in Windows? A diagonal line in a picture will look like it has "steps" in PS as opposed to a nice smooth line like when I open the .jpg to look at it! And no, it's not that I'm zoomed in too far in PS...what's going on?

Are you viewing the exact same file? And what do you mean by 'open up the file in Windows?", windows doesn't display images -- but it does come with programs that do. What program are you viewing them with?

Originally posted by thatcloudthere:
2) Why I can't I do anything useful with UnSharp Mask? What's the best way to use this or is it something that you generally stay away from?

For me, the tool might as well be called "Create white pixels around the object you're trying to sharpen"! I've tried numerous settings but I admittedly don't understand what I'm doing when it comes to the USM tool. Any help here?

Unsharp Mask is a standard tool that I use on every photo I take. I recently did a study of various methods of sharpening, and learned a great deal but am still learning to master the application of that knowledge. Anyway, here is some of what I learned about USM from that study:

What USM does is to look at and selectively increase the local contrast between a pixel and its neighbors. Note that I said pixel, not edge, USM in itself does not care if that pixel is on an edge or not, it just looks at the pixel value relative to its neighbors. It increases the contrast by lightening the lighter pixels and darkening the darker ones. This (at high settings) produce the haloes you are seeing. These haloes can be any color, not just white; although white and black are the most common. As the bright pixels are made brighter still, they get closer and closer to absolute white and losing any detail they once had -- blowing out the highlights with this is one of the biggest concerns when using USM.

The key to being able to do anything useful with it is understanding what the three settings are doing; and understanding that each image is unique in what settings are best for it. The three settings are:

Amount: This setting determines how much of a change in contrast is to be made to the pixel. PS has values (as percentages) all the way up to 500% -- which means the pixel will be given 500% more difference between it and its neighbors than it had before. (see Radius below for how that difference is figured)

Radius: This settings controls how it looks at the pixels around the target pixel. It is not an actual circle drawn around the pixel that is radius pixels away. Instead the value in radius is a weight that is given to the central pixel; the more weight, the more it spills over into neighboring pixels. Think of pouring salt (or sand) into a pile, the more salt (sand) you pour the higher the pile becomes -- but it also spreads out and becomes wider. The value of the Radius setting is more the height of the pile than how far out it has spread. In deciding how much of a difference there is between the pixel and its neighbors, all the pixels under the pile are used, but those with more of the pile on top of them count more. I hope that all made sense; all it is really saying is that the Radius value is not an exact measurement of the number of pixels around the target pixel and that those pixels closer to the target pixel count more when determining how much of a difference there is. This, by the way, is why it makes sense to use values less than 1, as that is not saying it is looking in a circle that is less than 1 pixel wide.

Threshold: This value is used to decide if the pixel is worth increasing. If the difference between this pixel and its surrounding pixels (see Radius) is equal to or less than the value of the threshold, that pixel is ignored.

To help decide what values work best, start with the Amount set at its maximum value (500%) and Radius and Threshold at default values (1.0 and 0, respectively). Then start adjusting the Threshold up. Remember the threshold decides what pixels get sharpened, so you are wanting to raise it until only those pixels you want sharpened are being affected. This is most effective for removing subtle noise in the image; masks are far more effective at isolating areas of the image to be affected.

Once you have USM affecting only the detail you want, turn you attention to the radius; which should then be adjusted to suite the image. One effect of the above is that a smaller radius preserves subtle detail (such as the texture of fabric), but a higher radius preserves fine details (such as hair). The difference between subtle and fine is usually in the perspective, for instance a persons skin has fine detail in a close up, but becomes more subtle as they (or you) back up. So, look at the detail in your image and adjust the Radius up and down until it looks right. Making more than one pass (with masks if needed) may be needed to get a sharpening when the image has both fine and subtle detail.

Now that USM is adjusted to only affect the pixels you want, and in just the way you want it to affect them, lower the strength until it has the affect you want. This is where you remove the haloes if they are still affecting your image. You will likely find, with experience and possibly masks that once you have the Radius and Threshold set well you can get away with much higher Amounts than you would otherwise be able to.

There is much more to USM, but I believe that covers the basics. Above this, it gets into multi-layered approaches to dealing with haloes and masks to deal with the varying needs in different areas of your image, and multi-pass work-flows to deal with the different reasons to sharpen. There are also other ways, such as 'high pass sharpening' that several have said they prefer since, while it is perhaps less flexible than USM, it is easier to control haloes with it.

Originally posted by thatcloudthere:
Thanks!

No problem. I needed something to take my mind off of other things happening on the site. ::roll eyes:: (<-- we need smilies! and put them in blue shirts while your at it!)

David
 09/04/2004 03:29:04 AM · #5
Originally posted by Kylie:
I have the same issue with what you are calling "steps", I think. I get "jaggies" on straight diagonal lines. I thought it was my Kodak compression, but I got them on a shot with my new camera,too. I hope someone can help both of us on this! Good luck, and I will stay tuned!


SO? Besides the jaggies.. how are you lovin' the new camera?? I've put some shots I took around town today in my portfolio, all from my new S7000.. I'm absolutely loving it. :)
 09/04/2004 04:09:00 AM · #6
I don't know about anyone else, but on my computer when I'm zoomed out on an image in intervals of 25% (i.e. 25, 50, 75, 100%), I get a nice smooth image being displayed. All other zoom levels produce jaggies on my monitor.

When you're fine tuning settings such as USM, be sure to check diagonal edges while zoomed at 100%.
 09/04/2004 09:38:53 AM · #7
Thanks for the help on the USM, Britannica!

Let me rephrase my first question, though as it's the one that's really buggin me.

When using the zoom tool and selecting "Actual Pixels" all the diagonal lines look smooth in PS Elements. If the image is resized at all ("Fit to Screen"), the diagonal lines become jaggies.

However, when viewing the pictures in windows (Select the file, then "View as slide show") it resizes the image automatically to fit the screen and I don't get any jaggies at all!

What's going on? Thanks for your help!
 09/04/2004 10:22:19 AM · #8
It is sort of like interpolating. If it looks right at 100% then you are good.
the software assumes things and then adjusts the view to it. it is like at 100% it is perfect (and if it is a big file you don't see the whole image on your screen) and then look at it smaller (fit to view), it compresses info, so it is viewable.
Try taking that file, opening it and then change the image size to a size it will fit on the screen (say 800x600). Save it with another name (never overwrite your original), then open that one. See what it does.
 09/04/2004 06:05:59 PM · #9
Originally posted by thatcloudthere:
Thanks for the help on the USM, Britannica!

Let me rephrase my first question, though as it's the one that's really buggin me.

When using the zoom tool and selecting "Actual Pixels" all the diagonal lines look smooth in PS Elements. If the image is resized at all ("Fit to Screen"), the diagonal lines become jaggies.

However, when viewing the pictures in windows (Select the file, then "View as slide show") it resizes the image automatically to fit the screen and I don't get any jaggies at all!

What's going on? Thanks for your help!

When the viewing software enlarges the image it uses was is called anti-aliasing to smooth out the 'jaggies'. This works great, and is used when resizing the image in PS as well -- but it takes a lot more processing power to do. For a one time calculation (in a viewer or when resizing the image) that cost is not important, but when you are working on the image every change you make would cause it to be recalculated. For this reason, when PS is viewing an image zoomed in or out from 100% it does not use anti-aliasing at all. This results in the the edges of the image getting the jaggies as you described.

David
 09/04/2004 06:21:21 PM · #10
Originally posted by thatcloudthere:
Actually, I have PS Elements 2.0 but I don't think that affects these questions:

2) Why I can't I do anything useful with UnSharp Mask? What's the best way to use this or is it something that you generally stay away from?

For me, the tool might as well be called "Create white pixels around the object you're trying to sharpen"! I've tried numerous settings but I admittedly don't understand what I'm doing when it comes to the USM tool. Any help here?

Thanks!


I'm not familiar with your camera, but it might be sharpening the images internally and too much USM will give you white halos. Try positioning the 100% view in an area of contrast and adjusting the settings until you just begin to see the halos, then back off just enough that they go away. Some cameras let you adjust the in-camera sharpening, try setting that to low or off.
 09/04/2004 06:59:24 PM · #11
This is why I love this website!

Thanks for your help, everyone...

Matt and Tracy, you were right...it did end up having to do with resizing because at 'actual pixels' the photograph looks fine.

David, thanks for your indepth USM help and for explaining the resizing issue in PS.

Dan (spazmo99), you're probably right on as well...The A40 I use is just a little point and shoot and does not have sharpness adjustments so I'm assuming that being a p&s it automatically does some in-cam sharpening.

The $25 I've spent on this site couldn't be more worth it...what a great learning environment...Thanks again everyone!

09/04/2004 07:48:40 PM · #12
Does anyone else use the USM on the Lightness layer in Lab Mode?

I find it to sharpen the image just as good as applying it to the image itself all the while keeping the colors' crispness.

Am I crazy or am I seeing right?
 09/04/2004 08:04:27 PM · #13
Originally posted by _Armadildo_:
Does anyone else use the USM on the Lightness layer in Lab Mode?

I find it to sharpen the image just as good as applying it to the image itself all the while keeping the colors' crispness.

Am I crazy or am I seeing right?

This is indeed seeing right! This is a much better way of sharpening (my favourite). It actually sharpens the detail layer only without creating nasty halos you get in RGB mode.

If you have noise in the image then some subtle blurring of the colour channels 'a' and 'b' often helps to reduce or eradicate it. Just don't overcook the blur as it will begin to bleed outwards.
 09/04/2004 08:36:05 PM · #14
Thanks for the blurring tip...
Will look into it when I have a little noise problem...
 09/04/2004 08:54:17 PM · #15
Originally posted by _Armadildo_:
Does anyone else use the USM on the Lightness layer in Lab Mode?

I find it to sharpen the image just as good as applying it to the image itself all the while keeping the colors' crispness.

Am I crazy or am I seeing right?


Here is another method that I learned in a tutorial. (I only use this when Advanced Editing is allowed!) I set up a Layered Sharpening Action in PS like this:

-Create a copy on a new layer.
-Set this layer mode to Luminosity and opacity to 92%
-Apply USM (I have defaults of 300, .7, 0, but let the action pause here for adjustments.)
-Now make a new layer copy of this sharpened layer and apply a 3 pixel gaussian blur to this new layer.
- Change this layer mode to Color (this will reduce noise)
-Flatten

I like this because I can preview the effects of sharpening on the full color image. It's essentially doing the same thing as the Lab Color method and we can start an endless thread now on the relative merits of each method! :)

09/04/2004 09:52:26 PM · #16
Originally posted by davidbedard:
Originally posted by _Armadildo_:
Does anyone else use the USM on the Lightness layer in Lab Mode?

I find it to sharpen the image just as good as applying it to the image itself all the while keeping the colors' crispness.

Am I crazy or am I seeing right?


Here is another method that I learned in a tutorial. (I only use this when Advanced Editing is allowed!) I set up a Layered Sharpening Action in PS like this:

-Create a copy on a new layer.
-Set this layer mode to Luminosity and opacity to 92%
-Apply USM (I have defaults of 300, .7, 0, but let the action pause here for adjustments.)
-Now make a new layer copy of this sharpened layer and apply a 3 pixel gaussian blur to this new layer.
- Change this layer mode to Color (this will reduce noise)
-Flatten

I like this because I can preview the effects of sharpening on the full color image. It's essentially doing the same thing as the Lab Color method and we can start an endless thread now on the relative merits of each method! :)

Well, since you bring it up. :D

The above with the layer set to luminosity is one that I have known, but why the new layer with the gaussian blur in color mode? What effect is that suppose to be creating or controlling? You say the changing the layer mode is to reduce noise, or is that the purpose of the new layer? Isn't better to do your noise reduction before sharpening instead of after? Why don't I stop asking questions and let you get a word in edgewise? Do you still have a link to that particular tutorial?

David
 09/04/2004 09:55:10 PM · #17
Originally posted by _Armadildo_:
Does anyone else use the USM on the Lightness layer in Lab Mode?

I find it to sharpen the image just as good as applying it to the image itself all the while keeping the colors' crispness.

Am I crazy or am I seeing right?

yes, that works, as does the above post. But in basic editing you can do basically the same thing by applying USM and then immediately fading to luminousity in the edit menu. No layers used, and affects the entire image the same, so it stays basic editing rules legal.

David
 09/04/2004 10:16:37 PM · #18
Originally posted by _Armadildo_:
Does anyone else use the USM on the Lightness layer in Lab Mode?

That's how I do it.

I used to USM the entire image, but after finding out how much better it works on the lightness channel, I have yet to be unhappy with it.
FWIW, on a 640x480, I typically apply 150, 0.3 and 0.0, and if I see it brought out too much on the edges, I edit and fade USM as needed, then convert back too RGB.

HTH

Message edited by author 2004-09-04 22:17:12.
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