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DPChallenge Forums >> Tips, Tricks, and Q&A >> sharpening
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08/09/2002 10:09:10 AM · #1
I've read a lot of critiques which say the photo could benefit from sharpening. And others complaining that a given image was oversharpened.

I admit, I can only take little baby steps in Photoshop.

But I've never seen a significant difference in any photo I've tried to sharpen or unsharpen mask in Photoshop. Would someone be so kind as to explain the type of image these techniques benefit most and the combination of commands necessary to produce the desired effect, please.
08/09/2002 10:12:18 AM · #2
Originally posted by crisa58:
I've read a lot of critiques which say the photo could benefit from sharpening. And others complaining that a given image was oversharpened.

I admit, I can only take little baby steps in Photoshop.

But I've never seen a significant difference in any photo I've tried to sharpen or unsharpen mask in Photoshop. Would someone be so kind as to explain the type of image these techniques benefit most and the combination of commands necessary to produce the desired effect, please.


It all depends on the specific image... as for the result of those filters, don't use them until you have resized to 640x480. The results are more prominent at smaller image sizes...

I never use the unsharp mask. I don't find that it produces a great difference for most of my photos. If I need extra sharpness, I use the standard sharpen filter...
08/09/2002 10:27:07 AM · #3
Agree with John about the size of the image you apply filters to.

Disagree with the sharpen vs. unsharp mask. *grin*

Unsharp mask is basically the same as the sharpen tool, it just allows you to fine tune the degree you sharpen your image. (For those of you out there who like to go to Star Trek conventions and debate about how tribbles mate, please don't debate with me over the actual differences between unsharp mask and sharpen. *grin*)

At a recent seminar, the following setting was suggested as a good starting point for using the unsharp mask:
Amount: 85%
Radius: 1.0 pixels
Threshold: 4 levels

This is just a starting point, however. You may find this sharpens your image too much or too little or alters the colors of your image or whatever... Play around with the numbers and see what happens when you change one. (May I suggest seeing what happens when you plug extra large numbers into the slots? It gives you a better idea of what is going in with each portion of the settings.)
08/09/2002 11:07:21 AM · #4
...At a recent seminar, the following setting was suggested as a good starting point for using the unsharp mask:
Amount: 85%
Radius: 1.0 pixels
Threshold: 4 levels
....


I can understand what Amount and Radius affect. That does Threshold refer to?

08/09/2002 11:23:22 AM · #5
Here's a simple unsharp mask tutorial. In my opinion, the two methods described for using unsharp mask are actually illegal at dpc, but then I'm constantly amazed at what people are actually doing that I'd previously thought was illegal, so who knows.


* This message has been edited by the author on 8/9/2002 11:25:00 AM.
08/09/2002 11:25:39 AM · #6
Unsharp mask is a skill all by itself.

You MUST sharpen your final resolution image right before you pring/publish or whatever.

If you are viewing your image on the web you should refrain from too much sharpening.

Printing benefits from a sharper edge as most printers soften an image up a bit.

but as far as numbers..it's all about the art. Once you do about 1,000 images you start to get a feel for it.

At about 4,000 you are competent.

Obviously the biggest mistakes are too much and not enough. And it just takes an eye to figure it out.

At web resolution of 72 dpi a figure of about 150%, 1 pixel OR LESS and a threshold of about 0-3 should work on a good image.

IOn my really nice and contrasty images from my camera I usually get good results at 150%, 0.5 and 3. Ranges of 85%-200%, 0.3-0.7 and 0-5 are good. If you are needing larger perecentages bigger radiuses then artifacts will start to show up on diagonals and moire (fringing) will start to appear a lot of the times.

On images of 200 dpi (what I normally save my images as tif files at) I dont sharpen the stored file but when I want to print it at 200 dpi I copy it and pump the numbers up to roughly 250% and 1.2 on the radius with a 3-7 threshold. More pixels in the photo means it will survive greatre levels of sharpening.
08/09/2002 11:34:21 AM · #7
The Unsharp Mask filter evaluates contrast difference. You are interested in sharpening only real edges but, unfortunately, the filter cannot differentiate between real edges, texture, or noise. By specifying threshold you say how far apart two pixels' values need to be before the filter applies them. It's best to start off with a threshold of between 0-4. In other words, the lower the threshold the fewer areas will be excluded and you will get sharper images.
Click on an area of the image where the sharpening effect will be most prominent (check the preview too)and run the filter. Be sure to look at the entire image before continuing with the next step.
The problem is it will also sharpen problems. Since my original jpeg tend to have quite a bit of compression, I tend to do a few undo/redo of the unsharp mask filter to decide on some compromise of sharper image without highlighting the artifacts. Typically, I end up "Fading" the filter to about 60%.
08/09/2002 11:36:53 AM · #8
I just posted and quick and dirty comparision of a raw image, and how it looks sharpened using the "Sharpen Filter", and how it looks sharpened using "Unsharp Mask".

Take a look and see what an effect it can have.
08/09/2002 11:43:35 AM · #9
Originally posted by sohr:
I just posted and quick and dirty comparision of a raw image, and how it looks sharpened using the "Sharpen Filter", and how it looks sharpened using "Unsharp Mask".

Take a look and see what an effect it can have.


Wow, excellent comparison! I learn something new every day on this site. :-)

Do you remember what settings you used on the unsharp mask?

-Terry
08/09/2002 11:53:09 AM · #10
Do you remember what settings you used on the unsharp mask?


Hmmm... I suppose that would've been useful information :-)

If I recall, it was rather high: Intensity = 150%, Radius = .06, and Tolerance = 0. I could've reduce the ehancement of the noise (texture?) of the background by slightly raising the tolerance, but I wanted to show a rather extreme example of what Unsharp Mask can do.

08/09/2002 01:43:44 PM · #11
Originally posted by Journey:
The Unsharp Mask filter evaluates contrast difference. ...

Thank you, For the very concise explanation of the Unsharp Mask.

Finally I think I understand how each of the variables affect the result.


08/09/2002 01:57:26 PM · #12
could someone please explain unsharp, radius, and tolerance to those of us who don't have photoshop? or at least explain it to me because i swear i'm the only one on the planet who doesn't have it and i hate being left out
08/09/2002 05:08:35 PM · #13
This is precisely why I am willing to pay for use of dpchallenge.

Not only do you answer my question, link me to a tutorial and show me examples, you also generate further questions so the topic can be covered in depth.

Thank you seems so incomplete...

08/09/2002 05:43:04 PM · #14
unsharp mask filter has 3 components: amount, radius, and threshold.

Amount is simply how much you want the effect. Be careful; high settings will generate intense halos. Better to stay with 80-90 and if necessary REPEAT the effect.
Radius: determines the number of pixels around your edges that will be affected. A large radius will cause an "oversharpened" look. Better to stay in the 0.6 -1.2 range.
Threshold: determines which value pixels will be affected (see my post above). If your threshold is 3 but two adjacent pixels have values of 100 and 102, neither one will be affected by the filter because their difference is only 2 and you have just specified to Photoshop to only bother if their difference is 3 or higher.

My basic settings for starters are 80, 1, 0-4. Next I play with the thresholds. I seldom go with an amount over 90 because in that case I rather run the filter twice. I also experiment with the Fade of the Unsharp Mask filter.

Again, I suggest playing with this filter until you have the best result. I always play it safe by dupping my image, run the filter, look at it, undo it, redo it, before settling on what I want. And sometimes, I am not happy with it after all and then I can always revert to the unsharpened original copy of the image.
08/09/2002 05:57:11 PM · #15
lecook,

Most image editors nowadays have unsharp mask, so you need not have to buy a $500 image editor (like Photoshop) to get the job done. In fact, there is a light version of Photoshop called Photoshop LE (~$60-$70) which will can do everything you'll ever need to for DPChallenge.

There is also Paint Shop Pro, which has all sorts of graphics features and isn't too expensive either (I believe also between $60 and $70), but you can download a 30-day trial first to test it out.
08/11/2002 06:14:45 PM · #16
Originally posted by crisa58:
This is precisely why I am willing to pay for use of dpchallenge.

Not only do you answer my question, link me to a tutorial and show me examples, you also generate further questions so the topic can be covered in depth.

Thank you seems so incomplete...



I agree completely! (well said) THANK YOU everyone!!!

08/11/2002 09:37:44 PM · #17
Originally posted by sohr:
lecook,

Most image editors nowadays have unsharp mask, so you need not have to buy a $500 image editor (like Photoshop) to get the job done. In fact, there is a light version of Photoshop called Photoshop LE (~$60-$70) which will can do everything you'll ever need to for DPChallenge.

There is also Paint Shop Pro, which has all sorts of graphics features and isn't too expensive either (I believe also between $60 and $70), but you can download a 30-day trial first to test it out.


And there's THE GIMP!!!! Which has all these features and is free. I highly reccommend it to people who want to experiment with all those things photoshop users talk about here, because it has most of them and you can learn about them without having to pay a cent. You can download the windows version here at the moment, although at times it gets hard to find.
08/11/2002 10:17:17 PM · #18
Originally posted by Journey:
unsharp mask filter has 3 components: amount, radius, and threshold.

Amount is simply how much you want the effect. Be careful; high settings will generate intense halos. Better to stay with 80-90 and if necessary REPEAT the effect.
Radius: determines the number of pixels around your edges that will be affected. A large radius will cause an "oversharpened" look. Better to stay in the 0.6 -1.2 range.
Threshold: determines which value pixels will be affected (see my post above). If your threshold is 3 but two adjacent pixels have values of 100 and 102, neither one will be affected by the filter because their difference is only 2 and you have just specified to Photoshop to only bother if their difference is 3 or higher.

Again, I suggest playing with this filter until you have the best result. I always play it safe by dupping my image, run the filter, look at it, undo it, redo it, before settling on what I want. And sometimes, I am not happy with it after all and then I can always revert to the unsharpened original copy of the image.


I agree with this advice except I recommend a higher initial threshhold setting. Otherwise, you run the risk of introducing "banding" effects into areas of smooth color transitions (like flesh tones) where sharpening is undesirable. For a "realistic" look I highly recommend undersharpening vs. oversharpening, and running a low-value setting twice vs. higher settings. My usual starting settings are ("my default"):
Amount: 66-88% (88%)
Radius: 0.6-1.3 (0.8)
Threshold: 5-7 (5)
08/12/2002 12:00:15 AM · #19
Originally posted by Patella:
Here's a simple unsharp mask tutorial. In my opinion, the two methods described for using unsharp mask are actually illegal at dpc, but then I'm constantly amazed at what people are actually doing that I'd previously thought was illegal, so who knows.

From the DPC rules:
However, no filters (or non-Photoshop equivalent) maybe be applied to your image with the exception of sharpen and despeckle, the two of which are allowed.

Since "Unsharp Mask" is practically the same as sharpen except it allows you to control the settings... also the folder name is sharpen and the filter name is Sharpen.... I thought "unsharp mask" was legal..
it is applied to the whole image. Don't think that the Mask in it's name means it is a spot edit tool.

Also I will point out / argue there are tools (neat image) that remove CCD noise from digital images and have much more impact on a photo than "unsharp mask" and according to this rule are legal..
Post-shot Adjustments may be made to your image in a photo editing program, so long as the modification is applied to the whole image.

I think that what they are trying to stop are:
1) spot edits (removing unwanted items)
2) addition of items
3) artistic effects like "color pencil"

For advertising and portrature etc I use 1 and 2 heavily at times, though I will not use 3 except for an emergency (it look's really bad so apply a few select filters and you get an amazing effect, this is a skill in itself) or where the breif calls for an illustration not a photograph (and I don't have time / can't be bothered actually drawing)

Bassicly 1 , 2 and 3 hide poor photography.. unsharp mask will not hide poor photography, actually it will emphesze it in many cases!

Also with cropping, color mixing, Hue/Saturation adjustments and layer blending many things that I would usually spot edit can be hidden..
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