Unsharp Mask

[spl]

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.

[spl]

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.

[Ian]

Re: 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.

Yes, sharpening will increase contrast as the difference in density between pixels, which affects sharpness, is affected by contrast too.

Ian

[Patrick]

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.

This method of sharppening will only work using this copy in channels.

[spl]

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

[lumix]

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

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.

[Patrick]

Re: Unsharp Mask

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

[spl]

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.

[Patrick]

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.

[lumix]

Re: Unsharp Mask

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.

[Patrick]

Re: Unsharp Mask

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

[spl]

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.

[Patrick]

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.

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