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Help needed on instruction....

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  #1  
Old 06-29-2003, 07:08 PM
anon_uno anon_uno is offline
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Posts: 29
Help needed on instruction....

Hi,

I have a problem here and hope that someone can point out where I've gone wrong.

I often take digital picture and try to darken the corners of the photo via the following way in PS:

(Assuming I have a single subject in the middle of the pic)
1. I roughly mark the area outside the subject with Lasso Tool

2. Invert the selection area (so the mark area is on the background and not on the subject)

3. Enter a Feather value of 200-250 (hoping to achieve a gradual change so there won't be any hard edge showed).

4. Created a new layer

5. Select BLACK as the fill/paint color and filled the marked area with this color.

6. Adjuect Opacity level to achieve the desire darkness level.

My problem is instead of getting gradually changing in color (from Dark to Ligt or from Light to Dark depends on which way you look at it from), the result seems to be ended up in steps. ie. showing different levels of tonal changes...

Anyone know what I've done wrong? I need gradually/smooth change in brightness level and not levels.

Here is an example of the result I've got:
http://members.tripod.com/~oz_panda/s2/d1.jpg

(oops, now everyone know what I look like...)

Any pointer will be greatly appreciated.

(p.s. I know some may say because I am saving the file only in High Compression level instead of no-Compression mode, but this also happen even if I have te file in no-compression mode).

Thank you in advance.

Regards,
Anon
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  #2  
Old 06-29-2003, 07:33 PM
anon_uno anon_uno is offline
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hmm... ok, I try to attach the file in this message.....
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  #3  
Old 06-29-2003, 09:29 PM
Mig Mig is offline
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Posts: 265
Hello Anon,

Looks like you are having a little problem with what's called "banding". It happens with gradients. To lessen the problem you can add some noise. That's the trick.
The picture you posted is nice, but it looks like you'll have to start over with it. In the background there appears areas that have been worked on sort of hodge-podge, when what you want to do is create the effect in one swoop (usually). Look at the mask that's posted here for an example of what you need to work with.
If you know how to build a mask like the one posted here, then go from there. If you don't know how, then just add noise to the problem areas.

Mig
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File Type: jpg mask.jpg (55.3 KB, 54 views)
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  #4  
Old 06-29-2003, 11:15 PM
anon_uno anon_uno is offline
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Mig,

Thank you for the info. I will give that a shot (better go and look up topics relating MASKs). Thanks again.

Regards,
Anon
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  #5  
Old 06-29-2003, 11:26 PM
anon_uno anon_uno is offline
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Mig,

If I am going to add noise to the Mask/Masked areas, then it would generate a lot of tiny dots.... would it work if I then blur the noise area again?

Regards,
Anon
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  #6  
Old 06-30-2003, 08:16 AM
Stephen M Stephen M is offline
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Anon, the idea is to just add enough noise to break up the bands without being too strong. You should not have to correct the correction by blurring or adding more destructive moves to the image.

Presuming Photoshop, the filter/noise/add noise command would be used. Often uniform noise is chosen, but it can pay to experiment with gaussian noise, or smaller amounts of both noise types.

The noise added would commonly be monochromatic noise.

The fade command and opacity or blending mode changes are often used to tweak standard noise.

For more subtle noise, add the uniform noise but not monochromatic - but then fade to luminance mode so that you do not get coloured noise but only the relative luminance of the colour noise, with is often more subtle than monochromatic noise.

A very good option is to use "smart noise" - which does not affect the highlights or shadows. I like to do this with layer option blend if sliders - but an endpoint mask would produce similar results too.

More detail on the above techniques can be written if required. <g>

Hope that helps,

Stephen Marsh.
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Old 06-30-2003, 09:55 PM
Mig Mig is offline
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Anon, you're right here, in that it would make more sense to add the noise later. Build the mask w/out noise, apply the changes using the mask as a selection, if you will, then go back later and add the noise. So it would be a two step process.

Read what Stephen says about this a couple times. If you want some strange evidence of what happens with banding, here's a straight gradient that's been butchered with curves (the one on the left). Shows just how screwy gradients can get. Beside it is what it looks like with some noise added. Exact same gradient. Go figure.

You have good instincts with your camera. Keep it up.

Mig
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  #8  
Old 07-01-2003, 12:08 AM
anon_uno anon_uno is offline
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Posts: 29
Hi Mig & Stephen,

Thank you both for your common and work instructions.
I only know the basic of PS and I have more interest in digital photography, so I will need to use PS a lot of time to 'generate' the final image that I have in mind.

That's why I am so glad to have found this site. There is a hugh bunch of very knowledgable people here which I am very gladful for. Unfortunately, I haven't been doing too much contribution ('case of my shadow knowledge in this field). So I am more of a reader than a writer I am afraid : )

Thank you all once again for your assistance to resolve my problem. Much appreciated.

Best regards,
Anon
Melbourne, Australia.
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  #9  
Old 07-06-2003, 08:54 PM
TheTexan TheTexan is offline
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Are we sure this is not a factor of the jpeg compression. What does the photo look like as a tif or gif? Did you have dithering set when you saved it to jpeg. Are you working with a indexed color pallette? All of these things could result in the dithering and banding you are seeing. Im not seeing too much on my system. I dont think you should have to add any noise to break up the banding if you are using an unrestricted color pallette in sufficient resolution saved with proper compression settings.

Tex
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