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Photoshop permutations Adobe Photoshop comes in a variety of versions and guises and is the most popular family of photo editing packages. Seeking help or happy to provide advice on Photoshop use? Then this is the place for you.

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Old 08-01-07
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Unsharp Mask

Did some exercises using unsharp mask which were very interesting. Discovered it can be used to good effect on pics that are already sharp to increase contrast and make more of the detail stand out. Of course its also good for sharpening but does not work in this respect in all cases.

The theory behind it comes from film darkroom processing where in inverted (i.e. negative) of the same blurred picture that was was sandwiches behind to cancel out the blurry bits.

Here are some results of my fiddling. the first is just the B&W without any unsharp mask at all. The second is with the unsharp mask on high settings. The third is without the PS unsharp mask but using an inverted overlay of the image with a gaussian blur filter applied. The last is as for two plus three on top of that.
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FLAMINGO-1.jpg   flamingos-(9)bw-USHM-high-.jpg   flamingos-(9)bw-manual-uns.jpg   flamingos-(9)bw-2-unsharps.jpg  
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Old 08-01-07
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Re: Unsharp Mask

Sorry I post up the wrong one for the first - just ignore the coloured bit - the rest of the pic is as described.
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Old 08-01-07
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Re: Unsharp Mask

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Originally Posted by spl View Post
Did some exercises using unsharp mask which were very interesting. Discovered it can be used to good effect on pics that are already sharp to increase contrast and make more of the detail stand out. Of course its also good for sharpening but does not work in this respect in all cases.

The theory behind it comes from film darkroom processing where in inverted (i.e. negative) of the same blurred picture that was was sandwiches behind to cancel out the blurry bits.

Here are some results of my fiddling. the first is just the B&W without any unsharp mask at all. The second is with the unsharp mask on high settings. The third is without the PS unsharp mask but using an inverted overlay of the image with a gaussian blur filter applied. The last is as for two plus three on top of that.
Yes, sharpening will increase contrast as the difference in density between pixels, which affects sharpness, is affected by contrast too.

Ian
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Old 08-01-07
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Re: Unsharp Mask

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Originally Posted by spl View Post
Sorry I post up the wrong one for the first - just ignore the coloured bit - the rest of the pic is as described.
The great problem with increasing unsharp mask as you describe is it creates fringing a halo effect on the image which I for one find unacceptable.
It is noticeable on the backs of the Flamingo’s and would show particularly badly on a decent size print. Unsharp mask does indeed increase contrast because that’s how it works on the pixels. Unsharp mask should be used in relation to the size of the image to be made.

There are a number of other ways of sharpening here is my method, it’s the best I have tried to date, well at least that’s my opinion.

This method sharpens white areas the most and grades the affect through to black an insignificant amount.
Create a duplicate image in layers and select it.
Go to channels, select one of the channels (rule of thumb red for portraits green for landscapes) but you have to use judgment. A landscape using the green channel will have everything sharpened except the sky, thus stopping that gritty look the sky can get using other methods.
Having selected a channel you will now be looking at a B/W version of the picture, now copy this by dragging it to the little note book symbol at the bottem of the palet. This method of sharppening will only work using this copy in channels. Asses how much black or white there is. If the image is predominantly light proceed as is, if predominantly dark invert by Ctrl+I. the contrast of this can be increase if required by going to Image>adjust>levels (this will not affect the contrast of your RGB image). Now left click mouse + Ctrl and a selection is made with the marching ants.
Select RGB in channels and then go to layers and the duplicate image, if you don’t want the marching ants at this stage go to view> extras and untick , the selection is still there but the ants are switched off.
Now select Unsharp Mask and decide on your sharpening in the usual way. You can use it very heavily with out fringing (halo) if less sharpening is required at a later date it can be adjusted by modifying the transparency of your duplicate layer. Provided you don’t flatten the image of course.

If your channel is self coloured and not B/W then you need to change settings in Photoshop, to do this go to Edit> Properties> Display & Cursers and untick “Color Chanels in Color”

That's it I don't think I have left anything out.

Patrick
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Old 08-01-07
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Re: Unsharp Mask

Thanks Patrick for taking such a lot of trouble with your explanation.

I totally agree about the halo effect and in fact this was mentioned in the book I was following. Although I only have photoshop elements (a sub programme of the full CS2 or is it CS3) I think what you are describing can also be achieved in elements (which doesn't have components functionality) by creating a RGB colour component separation using the layers pallette and then sharpening only one of those compoents eg. green in landscapes. I think I will give that a try when I get home and see how it works.
cheers
sue
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Old 08-01-07
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Re: Unsharp Mask

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Originally Posted by spl View Post
Thanks Patrick for taking such a lot of trouble with your explanation.

I totally agree about the halo effect and in fact this was mentioned in the book I was following. Although I only have photoshop elements (a sub programme of the full CS2 or is it CS3) I think what you are describing can also be achieved in elements (which doesn't have components functionality) by creating a RGB colour component separation using the layers pallette and then sharpening only one of those compoents eg. green in landscapes. I think I will give that a try when I get home and see how it works.
cheers
sue
Patrick/spl you have both helped me make my mind up regarding purchasing Photoshops. It all seems far to complicated to me. I have resently run the demo of CS2 and then Elements and found them quite hard work. I downloaded Sue's flamingoes image and even though it's not the original I was able to get almost the same results with Microsoft's Digital Image. All I did was convert to B&W then reduce contrast by 50% then with the Unsharp mask set to 4.5 pixels and 37% sharpen to get just the same as Sue got with her final image, and the halo was hardly visible. And there are no layers involved. Just three sliders easily adjusted. It's beginning to look like I will be saving my money.
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Re: Unsharp Mask

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Originally Posted by lumix View Post
Patrick/spl you have both helped me make my mind up regarding purchasing Photoshops. It all seems far to complicated to me. I have resently run the demo of CS2 and then Elements and found them quite hard work. I downloaded Sue's flamingoes image and even though it's not the original I was able to get almost the same results with Microsoft's Digital Image. All I did was convert to B&W then reduce contrast by 50% then with the Unsharp mask set to 4.5 pixels and 37% sharpen to get just the same as Sue got with her final image, and the halo was hardly visible. And there are no layers involved. Just three sliders easily adjusted. It's beginning to look like I will be saving my money.
Sorry if it all sounds complicated, but its less so than the description comes over.
Much depends on what your images are going to be used for, if they are gong to be printed to 7x5 or even not printed at all but viewed on the computer only, then what you are taking about is fine. But then you dont need the mega pixal cameras either if this is the case.
However if maximum quality is required to be pulled out of the file then some sort of program like Photoshop that uses layers (and many other tool)which emphasis control of what you are doing, then they earn their keep.
There are many less expensive image editors out there that will serve perfectly well.

Patrick
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Old 09-01-07
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Re: Unsharp Mask

Tired working with components last night but didn't really get good results - OK so you lost a bit of the halo but you also lost a bit of the definition as well - swings and roundabouts really

My feeling is that there are certain pictures where halo's are less of a problem and this is one of that kind i.e. where there are a lot of different objects and also in this case where the way the light falls creates natural halo-like effects on the original before any sharpening has taken place. I am not denying that halos were created in some spots where they weren't there in the original but I felt that they did not really disturb in a picture like this.

Now if you have a picture with a few big objects especially if the edges tend to be straight then I think halo effects would be much more obtrusive.
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Re: Unsharp Mask

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Originally Posted by spl View Post
Tired working with components last night but didn't really get good results - OK so you lost a bit of the halo but you also lost a bit of the definition as well - swings and roundabouts really

My feeling is that there are certain pictures where halo's are less of a problem and this is one of that kind i.e. where there are a lot of different objects and also in this case where the way the light falls creates natural halo-like effects on the original before any sharpening has taken place. I am not denying that halos were created in some spots where they weren't there in the original but I felt that they did not really disturb in a picture like this.

Now if you have a picture with a few big objects especially if the edges tend to be straight then I think halo effects would be much more obtrusive.


One of the misunderstandings of Unsharp mask is it will sharpen an unsharp image, well it won’t. The picture has to be sharp in the first place, if the images was exposed out of focus its stays that way. With an increase in contrast the apparent sharpness can be improved but no more. Since unsharp mask has a contrast increase when used, it can make you think the image is sharper.
Unsharp mask will only sharpen the softness that has taken place during the process of converting the electronic image from the sensor to the image you view on the screen or print. Indeed if you have used JPG when taking your pictures then very little or no sharpening should be needed, as sharpening is applied to a greater or less degree by the camera itself, depending on the camera set up which by default on many consumer cameras is quite aggressive. It’s this sharpening again in the edit program that brings out many problems.

If RAW was used then quite often the converting program will do a 25% sharpen by default, I should recommend it to be changed to zero and sharpening be applied when editing is complete and then on a layer.

Accepting any halo effect on any image is as far as I am concerned is accepting a compromise in quality.

Patrick

Last edited by Patrick; 09-01-07 at 11:22 PM.
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Old 09-01-07
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Re: Unsharp Mask

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Originally Posted by Patrick View Post
One of the misunderstandings of Unsharp mask is it will sharpen an unsharp image, well it won’t. The picture has to be sharp in the first place, if the images was exposed out of focus its stays that way. With an increase in contrast the apparent sharpness can be improved but no more. Since unsharp mask has a contrast increase when used, it can make you think the image is sharper.
Unsharp mask will only sharpen the softness that has taken place during the process of converting the electronic image from the sensor to the image you view on the screen or print. Indeed if you have used JPG when taking your pictures then very little or no sharpening should be needed, as sharpening is applied to a greater or less degree by the camera itself, depending on the camera set up which by default on many consumer cameras is quite aggressive. It’s this sharpening again in the edit program that brings out many problems.

If RAW was used then quite often the converting program will do a 25% sharpen by default, I should recommend it to be changed to zero and sharpening be applied when editing is complete and then on a layer.

Accepting any halo effect on any image is as far as I am concerned is accepting a compromise in quality.

Patrick
Patrick perhaps you could explain why it has this misleading name. When I first came across it I thought to UN sharpen was do soften the image. I now know that it is a method of sharpening but where did the term come from.
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Old 10-01-07
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Re: Unsharp Mask

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Originally Posted by lumix View Post
Patrick perhaps you could explain why it has this misleading name. When I first came across it I thought to UN sharpen was do soften the image. I now know that it is a method of sharpening but where did the term come from.
It is an old darkroom technique, where a copy is made from a negative to be sharpened which is slightly blurred, unsharp in fact. This has been referred to earlier in the thread I believe.

To read more on the subject go to http://www.photocritic.org/articles/usm.php
It must be made clear there is no substitute for getting exposure and focus right in the first place, there never was. We can do so much very easily digitally that it’s easy to become sloppy with technique and use our new found skills to rescue images rather than interpreting them to what we visualised when pressing the button.

Patrick
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Re: Unsharp Mask

If you look at the long necks of the flamingos in the original i.e. first pic you will see that the tone varies across the width simply becuase the sunlight is hitting it from the side. So down one side of the neck there is a very bright strip which is completely natural and is like that to the eye before the picture is taken. This bright strip could be defined as a halo but in this case is a natural one and I cannot understand why you would try to elliminate it.
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Re: Unsharp Mask

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If you look at the long necks of the flamingos in the original i.e. first pic you will see that the tone varies across the width simply becuase the sunlight is hitting it from the side. So down one side of the neck there is a very bright strip which is completely natural and is like that to the eye before the picture is taken. This bright strip could be defined as a halo but in this case is a natural one and I cannot understand why you would try to elliminate it.
I wouldnt say at least on the small posted images the brightness of the necks does not resemble a halo effect, its a highlight a world of differance.
No you would not want to change that.

If you want email me the original full file untouched, just as it was from the camera and let me sharpen it with my method and see what we get.

Patrick
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