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11/05/2004 11:05:49 AM · #1 |
I just read I an article that I should unsharp mask every single photo that I put on the computer. I'm a total PS newbie, and though you only had to unsharp mask when there was detail you wanted to bring out.
Anyone care to clarify? |
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11/05/2004 11:09:04 AM · #2 |
| USM should be the last step in your workflow when you resize for printing or online publication, and it is not "reversible" so you should not apply it to your full-size "masters" on your hard drive. |
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11/05/2004 11:17:54 AM · #3 |
If you are shooting jpg in the camera you will want to limit your sharpening to a minimum if any at all. The camera will be doing a given level of sharpening inside the camera.
If you shoot in the RAW format you can do all the sharpening before the camera does and it will probably give you much better results in most cases.
It has been my experience that not every image needs sharpening IMO is a judgement call.
If I use USM I do it on a separate layer so I can tweak the effects if needed before saving it as a jpg.
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11/05/2004 11:39:47 AM · #4 |
All digital camera sensors have a certain dgree of noise they generate. As a result, a given image from a digital sensor will be softer than a similar image on film. It's not subjective, it's physics. Granted, you might not care in some cases because the difference is subtle but as a rule, every image that comes out of a digital camera will need some degree of sharpening if you want it to be equivalent in detail to a film exposure.
OutbackPhoto has many documents about workflow, but this one in particular supports my statement in the first paragraph.
Note that there are MANY ways to sharpen. You don't HAVE to use USM. You can use midtone sharpening, luminosity sharpening, edge sharpening, selective sharpening, 3rd part sharpening tools, etc. The choice is yours, but if you care about image quality, you need to do something.
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11/17/2004 01:27:56 AM · #5 |
I think I read that same article you are talking about, but as I recall they were talking about in the case of using raw files which would have had no in camera sharpening applied.
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11/17/2004 04:44:22 AM · #6 |
When an image is digitized -- regardless of how it is digitize -- the image is reduced to a series of dots (pixels). This is the make-up of a digital image file (a matrix of pixels), but in pixelating an image in this manner the image is made less sharp. To clarify, consider taking a picture of a railing on a staircase. The railing is smooth unless you look very closely (microscopically close in some cases), but a digital image can not reproduce that kind of clarity. The railing in the digital image will have jagged edges instead of smooth. Cameras (and I would assume scanners) have anti-aliasing circuitry that smooths out these 'jaggies' by blurring the edges a bit, which helps the image look 'real' -- but it comes with the price of making the image softer.
The image will likely need sharpened to look crisp and ... well, sharp. :D The sharpening used in the camera will likely be the manufacutures best quess at what will make the most images look reasonably good most of the time. Use it with caution; when it works it does the job well enough -- but when it doesn't, the affect is a part of the image and can not be undone. The manufactures provide the means of turning in-camera sharpening, and thus allowing any image to be sharpened as best suits that image.
So, yes; every image that is digitized needs to be sharpened to be as clean and crisp as it can. However, not all images will benefit from being sharp, and many benefit from being made even less sharp -- a softer focus.
David
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11/17/2004 08:35:41 AM · #7 |
In my experience, when a photo is resized to 640 (ie, for a challenge), ALL photos need to be sharpened after the resizing. USM/sharpening will bring back the detail.
Chad |
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11/17/2004 03:07:35 PM · #8 |
When an image gets unsharp the location of each pinpoint of light increases. This lack of definite location causes each point of light to blur about a bit, and appear to cover more area; this is what creates depth of field and what is considered in focus. When the image is digitized, there is a point at which the size of the bluring becomes larger than the size of the pixels used to represent it. The point at which this happens is referred to as the 'Circle of Confusion', or CoC (I believe it actually refers to the blurring effect itself, but it is most usually referring to when it reaches this particular size).
Anyway, the reason I mention this is the circle of confusion defines how sharp a pixel is; the pixel is sharp as long as the CoC is smaller than the pixel, but becomes less and less sharp as the CoC becomes larger. But the CoC depends not only on pixel size (on the sensor that records it), but also final image size. As the pixel is made smaller by resizing the image becomes less and less sharp because more pixels are becoming smaller than the CoC -- and the opposite happens when the image is resized larger.
So, yes the image needs more sharpening after resizing down to appear just as crisp and clean as it did before resizing, but the same image resized larger would need to be softened with blurring to have an image with the same degree of sharpness.
David
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11/17/2004 03:20:16 PM · #9 |
I end up sharpening just about everything unless I'm going for the soft focus look.
My $.02, do it on every photo. If you don't like it, Ctrl-Z to undo it then re-do with more/less/none as required.
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11/17/2004 03:26:00 PM · #10 |
Originally posted by Britannica:
When an image is digitized -- regardless of how it is digitize -- the image is reduced to a series of dots (pixels). This is the make-up of a digital image file (a matrix of pixels), but in pixelating an image in this manner the image is made less sharp. To clarify, consider taking a picture of a railing on a staircase. The railing is smooth unless you look very closely (microscopically close in some cases), but a digital image can not reproduce that kind of clarity. The railing in the digital image will have jagged edges instead of smooth. Cameras (and I would assume scanners) have anti-aliasing circuitry that smooths out these 'jaggies' by blurring the edges a bit, which helps the image look 'real' -- but it comes with the price of making the image softer.
The image will likely need sharpened to look crisp and ... well, sharp. :D The sharpening used in the camera will likely be the manufacutures best quess at what will make the most images look reasonably good most of the time. Use it with caution; when it works it does the job well enough -- but when it doesn't, the affect is a part of the image and can not be undone. The manufactures provide the means of turning in-camera sharpening, and thus allowing any image to be sharpened as best suits that image.
So, yes; every image that is digitized needs to be sharpened to be as clean and crisp as it can. However, not all images will benefit from being sharp, and many benefit from being made even less sharp -- a softer focus.
David |
Anti-aliasing filters are hardware rather than software, aren't they? All the more reason why digital cameras were designed with the assumption that users would use software sharpening to counteract the effects of the filter. In-camera sharpening is pretty hideous... look at the textures of beaches, dense foliage, anything with very fine, bitty detail is ruined by in-camera sharpening.
(Edited for typo)
Message edited by author 2004-11-17 15:26:44. |
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11/18/2004 12:58:39 AM · #11 |
Yeah, hardware -- although the better cameras will likely have it in firmware so it can be upgraded, if needed.
David
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11/18/2004 01:30:22 AM · #12 |
Nice explanation(s), thanks so much. I learn so much from reading discussions on this site.
stevie |
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11/18/2004 01:46:26 AM · #13 |
It doesn't look like it's been mentioned here, so I'll say it.
Doing 'smart sharpening' provides superior results by not increasing the noise present in the image. Basically, you do an Edge Detection, creating a mask that's used to selectively apply the USM filter only to actual edges, not noise pixels that are randomly placed. You'll notice a HUGE difference in the noise level at 100% zoom in skies and other large, solid color areas in your photos.
There are a couple of places you can read about how to do this:
Fred Miranda on sharpening:
//www.fredmiranda.com/article_3/index.html
For GIMP users, but it also applies to Photoshop:
//www.gimp.org/tutorials/Smart_Sharpening/
(easy to translate to PS if you're reasonably good at PS)
Edge Sharpening in Photoshop Elements: Preparing for Print
//www.naturescapes.net/042004/ps0404.htm
Message edited by author 2004-11-18 01:47:28. |
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11/18/2004 08:20:46 AM · #14 |
i'll have to give that edge sharpening a try.
not legal in Basic Editing - though.//..
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11/18/2004 10:04:08 AM · #15 |
There's a lot of confusion about anti-aliasing filters. Hopefully this explanation won't be too technical, but it is relevant to the topic of this thread...
Aliasing occurs when a sensor doesn't have enough resolution to capture all of the detail in an image. Consider taking a picture of very fine black and white stripes, so close together that several stripes fall on each pixel of the sensor. Ideally, the picture would be a uniform gray, but depending on where the stripes fall, some pixels will get more light than others, resulting in an unwanted pattern. To prevent this, camera manufacturers put a piece of very finely ground glass in front of the sensor that blurs extremely fine detail to prevent aliasing. This is called an anti-aliasing filter or a low pass filter since it filters out the high frequency detail.
A ground glass shower door is also a low pass filter; the image you see through it is stripped of the high frequency detail. Of course, an anti-aliasing filter allows much higher spatial frequencies through than a shower door! But it does blur edges a little, which is why most digital photos need some sharpening (whether USM or some other method). Just a little, at the beginning of the workflow, to compensate for the anti-alias filter. As mentioned, many cameras do this, and the feature is also built into most RAW converters, so it doesn't necessarily have to be an explicit step.
Many (not all) photos can also benefit from a sharpness boost later in the workflow as well. In this case, it should be one of the last steps, when the photo is at its final resolution (e.g., after downsizing for web display). |
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11/18/2004 10:33:00 AM · #16 |
There are also some cameras that don't have an anti-aliasing filter at all (such as the Sigma SD9). While an anti-aliasing filter results in a "softer" picture, the lack of an AA filter has its own set of problems, such as moiré.
For a good introduction into "aliasing" and some sample pictures showing the effect of (or lack of) an AA filter, check out this link.
For some good insight on sharpening digital camera images, I recommend this article by Bruce Fraser. |
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