Unsharp Mask

#1 11-04-2005, 10:41 AM

Can anyone give me some idea how to use this feature, a tute or some sort of run through the process. The old fart factor has kicked in and I cant seem to get my head around it.

Thanks in advance.

iceman (Mike) · #2 11-04-2005, 10:50 AM

You can try this page by Jerry L, astrophotography guru..

http://www.astropix.com/HTML/J_DIGIT/USM.HTM

I haven't tried that technique myself, but it looks good!

(ps: moving to techniques forum)

#3 11-04-2005, 02:00 PM

Thanks Mike, will have a gander.

Striker (Tony) · #4 11-04-2005, 02:38 PM

Your not wrong...it looks great.....cant wait to start doing my crappy noob images.....

Robby · #5 11-04-2005, 04:03 PM

That's amazing.... Soo Easy... Just look at what I have done to my boring old M42 image! This process is simply amazing!
Before....
http://www.star-mate.com/DSO/M42_Pro2_normal.jpg
And after....
http://www.star-mate.com/DSO/M42_Pro2_unshape.jpg
Every now & then a wee gem of info comes around. This is one of the better ones!!
Only problem is now I have hours & hours of work ahead of me re-processing all my images...
Thanks Mikey!

janoskiss (Steve H) · #6 11-04-2005, 05:22 PM

Sorry Robby, but I like your original image much more. The processed one looks too artificial to my eyes.

gbeal · #7 11-04-2005, 05:35 PM

Yep, me too. I have read about this idea before, and while a little application may be OK, the before and afters seal it for me. I like the before. Having said that I WILL get the slave to try it.
Gary

Robby · #8 11-04-2005, 05:42 PM

Steve, Gary,
I think that's the idea.!

. The point being, how much more detail is there in the new one. But for pure asthetics it's kinda like the valve arguement for audio.
People like the valve sound cause it is softer and easier on the ear, but it's not actually a "true" acurate representation of the recording. I digress!..
Similary with a softer image, while it might look more pleasant to the eye, that is at the sacrifice of detail. The fact here is that I was stunned at how much extra detail this unshape process extracted. And whats more, for such little effort. I proably over did it for sake of the point, but there you go. Astheticially I'm not sure which one I prefer

Cheers

[1ponders] (Paul) · #9 11-04-2005, 07:15 PM

I'm sitting on the fence on this one. If you split the difference I think you might get it just right.

Nice to see people playing with ideas. Both are nice shots Robby. I've just notices the unsharp mask has tended to bloat the stars. Wonder if there's a way around that.

Robby · #10 11-04-2005, 07:29 PM

Darn fence sitters!!
I used to be indecisive now I'm not sure

...
Bloating stars are forever a problem for me, just ask Gary! The last thing I need is something to make them worse, and yes this unshape does seem to do that. I got lost in the nebula detail to notice initially...
Cheers

Striker (Tony) · #11 11-04-2005, 07:54 PM

I like the middle one...

hahaha..

Ok I like the first one Gary.....Sorry

robin · #12 11-04-2005, 10:57 PM

In Step 5 - 'final levels adjustment', what do they mean when they say ...'go back to the levels dialog & adjust the unsharp-masked image to "reset the black & white points if necessary".'
I get all the other steps no probs, just not sure on that one.

Incidently, I prefer the 1st one Robby......

http://www.astropix.com/HTML/J_DIGIT/USM.HTM

janoskiss (Steve H) · #13 12-04-2005, 12:42 AM

They mean that after the previous steps, the intensities may not span the full allowable range (usually 0 to 255), so you might need to readjust. But your image processing software should already do that when you apply an unsharp mask.

Bottom line: This filter subtracts a blurred version of an image from itself. Hence, it is a high pass filter, meaning that it throws out long range variations so that short range ones are emphasised. It may appear that it brings out more detail, but it does so by throwing away information. It mutes the bass so you can better hear the lead.

ballaratdragons (Ken) · #14 12-04-2005, 12:54 AM

Robby,

They are both excellent in different ways.

The 1st one is excellent for magazines, posters etc. whereas the 2nd one would be fantastic for a technical book on astonomy/astrophysics as I feel that the 2 pics tell 2 different stories.
No.1 is of the "Oooh-Aaaah!" factor.
No.2 is of the "Wow, look at the structure" factor.

Be proud of both!

iceman (Mike) · #15 12-04-2005, 06:08 AM

I think if you averaged the two it would be the best of both worlds robby..
Good experiment though!

Robby · #16 12-04-2005, 06:33 AM

Ok, in the pursuit of the "perfect" image, I have bowed to the pressure.. Here's a shot with quite a bit less of the real unshape mask.
Someone else can try now.....

http://www.star-mate.com/dso/m42_pro2_half.jpg

[1ponders] (Paul) · #17 12-04-2005, 10:50 AM

Now that's great. The fence sitters win again. How can we not

And your bloating is lets as well. Any chance of bringing out a bit more colour Robby

gbeal · #18 12-04-2005, 01:41 PM

Now you're cooking, much better.
I had a bit of time to read while at work yesterday (don't ask), and recall reading something on this bloated subject. I'll dig it out.
Gary

robin · #19 13-04-2005, 10:44 PM

Ok...can some one help me.I've followed those steps & the results are certainly looking up.However, this process seems to really dim the finished image.I adjust the levels & brightness/contrast but it still seems really dim & flat.Any suggestions....

janoskiss (Steve H) · #20 13-04-2005, 11:34 PM

Robin, how are you trying to do it? In the Gimp (and presumable in Photoshop) there is an "Unsharp Mask" filter to do the job. It's under Filters -> Enhance -> Unsharp Mask.