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  #21  
Old 29-06-2008, 02:00 AM
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Tandum (Robin)
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Unsharpen Mask

Unsharpen Mask.

Just tried this one tonight for the first time and it worked a treat. Good for bringing up nebula detail. Can take a bit of fiddling to get the desired result.

Make a duplicate of the original image. (Select all > Copy. File New > Paste.)

Blur the copy to remove stars or clone stamp if they won't blur. You don't want any stars left in the copy and you don't want a totally blurred blob as an image. (Filter > Blur > Gaussian Blur)

Reduce the brightness and contrast of the duplicate to about -30. (Image > Adjustments > Brightness and Contrast.)

Subtract the duplicate from the original. (Image > Apply Image. Scale=1 Offset=0)

Adjust the white point in levels of the resulting image as it will be dark.

The end result changes with the blur amount as well as the Brightness and Contrast settings on the copy. In CS3 click on the original and do a Window > Arrange > New Window and it should show you a preview image.
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  #22  
Old 06-07-2008, 06:04 PM
TrevorW
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Latest copy of Australian Sky and Telescope has an article on PS layers etc quite helpful
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  #23  
Old 27-07-2008, 08:41 AM
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Hi,

I tried this but perhaps I did the wrong thing near the end when you say select the original image. To do this you click on the background image in the layers box? Or do you alt click on the original image in the layer 1 box?

When I moved the white point doing the first above it made everything brighter the same as if I just opened the image and moved the white point to the left.

Greg.


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Originally Posted by Tandum View Post
Highlight Mask or Brighten DSO. This lets you brighten up a DSO without effecting the sky and stars.

Press Control-J. (Layer via Copy).

Select all of the original image and copy to clipboard.

Layer > Layer Mask > Reveal All. (Create a layer mask).

Alt Click on the new layer mask icon in the layers palette and paste, then invert that layer. Image Adjustments > Invert.

Increase the contrast of that mask with levels or curves. Move the black point to about 64 and the white point to about 220. Experiment with these points.

Apply a small gaussian blur to the mask.

Select the original image and drag the white point to the left in levels to brighten the DSO.

The opacity of the layer may also be adjusted.

Flatten the image when done.
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  #24  
Old 27-07-2008, 11:01 PM
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Tandum (Robin)
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Quote:
Originally Posted by gregbradley View Post
Hi,

I tried this but perhaps I did the wrong thing near the end when you say select the original image. To do this you click on the background image in the layers box? Or do you alt click on the original image in the layer 1 box?

When I moved the white point doing the first above it made everything brighter the same as if I just opened the image and moved the white point to the left.

Greg.
Quote:
Alt Click on the new layer mask icon in the layers palette and paste, then invert that layer. Image Adjustments > Invert.
Yes, you click on the background and move the white point. Did you paste from the clipboard to the layer? The layer will be a black and white image and should look like a negative of the original image once inverted. When adjusting levels on the inverted image, the dark bits are the bits that will be acted on when moving white point or adjusting curves on the background. So the sky should be white and the object of interest should be darkish. The amount of blur will also effect the result. It's just a mask really so you can use it to colour mix etc etc as well. I tend to be just lassooing the objects lately to mess with them, but I'm just being lazy
robin

Last edited by Tandum; 27-07-2008 at 11:26 PM.
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  #25  
Old 13-08-2008, 01:50 PM
jase (Jason)
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RE-selections
Control + D can be used to deselect an area or selection criteria. However something pretty cool is the the reselect feature - Control + Shift + D. PS will only remember the last selection criteria.

Drag Selections (oops - just realised I've already mentioned this in post #9)
This works really well if you want to chase filter reflections or star halos for what ever reason. Use the selection tool of choice, typically the Elliptical Marquee Tool (hot key - Shift + M twice), select the halo or reflection, before releasing the left mouse button, hold down the spacebar to move the selection around - release the spacebar to resize the selection if desired. This will allow you to precisely select the reflection/halo and unselect the star to form a "donut" selection to ensure specific processing does not alter the stellar profile.

Zoomie Zoom
Control + Alt + mouse scroll wheel up or down to zoom in or out respectively. Also, double clicking the magnifying glass (zoom) button in the tools palette is a quick way of zooming to 100% (1:1).

Brush size and hardness
Mentioned in a previous post, the [ ] (square bracket) keys alter the brush size...an extension to this is the hardness of the brush. This can be altered by pushing Shift + [ or ] to alter on the fly. I don't alter hardness often, but it is useful.

Supafast layer opacity adjustments
This is not really a tip, but I use it all the time as its a time saver compared to fluffing around with the mouse. Select the layer you want to change the opacity on, say a rich Ha data set that when blended at 100% is too rich for the RGB data. Simply use the numerical key pad to enter the opacity value. 1 = 10%...9 = 90%. If you type specific numbers in quick succession, say press 4 then 5, the opacity will be 45%. Too logical huh?

Tool-less view
If you're working on a system with a restricted desktop resolution and you find you're for ever scrolling about and shift tool palettes to get a better view of the image you're working on, simply hit the TAB key to hide them, hit it again to bring them back. This is a cheaper option than setting up a dual display graphics station where you have one monitor for the image and the other for your tools.

OK, here's one from my friend the Pixel Princess (had better give credit where its due as this is cool, well I think so as I've used it a few times).

Visible layers into a single new layer (w/out flattening of other layers)
In the layers, select the layers you'd like visible i.e. have the "eye" beside them. For example, an Luminance and RGB data set. Then press Control + Alt + Shift + E. This will merge the visible layers into a new layer while still leaving the original layers intact. You can then go on to use a hard stretch, saturation pump up activated as softlight blend for a LRGB colour boost.

Enjoy!

Last edited by jase; 13-08-2008 at 01:58 PM. Reason: Opps
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  #26  
Old 30-04-2009, 09:10 PM
jase (Jason)
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Colour Dodge

Colour dodging is an alternate method to boost colour saturation.

Here are the basic PS steps. You can add to the routine as you see fit.

  • Duplicate the RGB layer twice, so you have three layers.
  • On the top layer, set the blend mode as “colour dodge” and leave the second layer as a “normal” blend.
  • Uncheck the original layer (select the eye icon) so it’s no longer visible, then go to Menu | Layer | Merge Visible. This will obviously merge only the visible layers (the top two layers).
  • Now you’ve got two layers, the top one will look heavily saturated. Set this as “colour” blend and recheck the eye on the original layer (bottom layer). You can alter the opacity of the colour blend layer to taste (50% is a good start) – be careful you don’t wash out the star colours. I usually apply a hide-all mask to the layer to selectively apply the colour enhancement, but the choice is yours.
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  #27  
Old 06-06-2009, 07:55 PM
ColHut (Colin)
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Gosh thanks all Unfortunately Ii use JASC paintshoppro 9.11. The ideas are great though - just need the keys!
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  #28  
Old 03-07-2009, 12:28 AM
jase (Jason)
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Repairing colour flares and/or other colour anomalies

The technique defined below can be used to address colour related issues due to stars that are off the edge of frame. These stars, if bright enough, often cause colour flares that detract from the images appearance. The technique can also be used to address other colour related issues. In summary the concept is to copy a "good" piece of the sky that has contains the desired colour hue over the top of the offending colour flare. A follow up step brings the stars of the repaired area back to their original form.
  • Click on the lasso tool and set the feathering to approx 20 pixels
  • Using the lasso tool, select an area that is of same size and is relatively close to the colour flare area you wish to remove. The purpose of this exercise is to match the background hue of the surrounding area so the proximity to the area you're trying to fix is fairly important. At this point, don't worry if the selected area contains stars.
  • Copy and paste the lasso area so you now have a new layer that contains the small patch of the sky in which you've just copied.
  • Hold down the control key and move the mouse to shift the small patch over the colour flare area you wish to remove.
  • Now go to the Filters | Noise | Median
  • Increase the radius until you see no more stars in the small patch of sky that you've copied. If you don't like the median tool, dust and scratches, or the minimum filters can do a similar job. Median I've found works well in general.
  • With the patch layer selected, change its blend mode from normal to colour
  • You'll now notice that your colour flare has disappeared i.e. has been blending into the surrounding background hues. If it hasn't you may need to increase your selection size or reduce the feather.
...but don't stop there...look what you've done to the stars in the area that's been repaired...they've inherited the same background tone you copied. Easily fixed...
  • Select the original layer and use the colour range tool to highlight the stars. Alter the fuzziness slider until you get a good match.
  • Expand the selection by 2 or 3 pixels (or to your taste)
  • Feather by 2 pixels (or to your taste)
  • Then select the patch layer (important, make sure its selected!!)
  • Hit the delete key
  • POW! You've now brought the star colours back in the repaired area...as you've deleted the selections from the patch layer so the colours come back through from the original layer.
  • If you find that the colour range tool selection wasn't ideal, you can always use the eraser tool to do a similar task, but I would recommend going back a few steps until you get the right selection i.e. manipulate fuzziness.
Enjoy!
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  #29  
Old 30-07-2010, 12:04 AM
luigi
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Sometimes I like to use the asinh command of IRIS to stretch colors, it can be either very good or very destructive.
I try asinh 0.005 30 as a way to start
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  #30  
Old 30-07-2010, 12:31 AM
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Octane (Humayun)
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asinh is the bomb.

H
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  #31  
Old 30-07-2010, 02:32 AM
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troypiggo (Troy)
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Quote:
Originally Posted by luigi View Post
Sometimes I like to use the asinh command of IRIS to stretch colors, it can be either very good or very destructive.
I try asinh 0.005 30 as a way to start
Quote:
Originally Posted by Octane View Post
asinh is the bomb.
If you're using it with PS, at what stage do you use IRIS? Beginning, middle, or end?
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  #32  
Old 30-07-2010, 03:54 AM
luigi
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Quote:
Originally Posted by troypiggo View Post
If you're using it with PS, at what stage do you use IRIS? Beginning, middle, or end?
In my case before PS.
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  #33  
Old 30-07-2010, 03:55 AM
luigi
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Quote:
Originally Posted by Octane View Post
asinh is the bomb.

H
If you have some other bombs to share I'm all eyes
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  #34  
Old 09-08-2010, 01:41 AM
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Tandum (Robin)
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Can anyone fill me in on how to remove stars from an image?
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  #35  
Old 09-08-2010, 09:53 AM
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Think there's a tutorial here: http://astroanarchy.blogspot.com/2009/04/neaic.html and he also has a PS action you can download to do it for you.
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  #36  
Old 09-08-2010, 01:50 PM
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Tandum (Robin)
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Cheers Troy, I'll check it out.
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  #37  
Old 28-10-2010, 03:07 AM
Bolts_Tweed (Mark)
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No Noise Colour Saturation boost in PS

Gday

Still waiting for the presentations from AIC but heres one I remember from Tony Hallas that I wasnt aware of (not saying much).

Usually using the saturation slider in Hue and Saturation introduce noise into the image (I knew that bit) - Hallas suggested this.

Change the mode of the image to lab colour. You will then have 3 channels Luminosity, A and B. Dont touch luminosity. Channel A contains the reds and yellows (from memory) and Channel B the Blue and Greens. Add a curves layer on top of the background layer (clip it if you are doing anything else) and adjust the curves for the required layer. eg if you want to increase reds select the A channel from the pull down menu and lift the centre of the curve (actually you can do whatever adjustments to the curve you like. lifting the curve will boost the red - lowering the curve will desaturate these colours.

Season the colour satruation to taste and then flatten the image. You can then save it back into RGB mode. You have then adjusted the saturation without the introduction of any noise (provided you didnt touch the luminosity channel). Obviously it can be done on masked sections, lassooed sections etc of the image etc etc like any normal processing.

Works well

Mark Bolton
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  #38  
Old 28-10-2010, 09:06 AM
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Octane (Humayun)
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Mark,

That method screws up the histogram once you convert back to RGB.

If your histogram is unclipped prior to LAB conversion, watch what happens to it after converting back to RGB -- especially if more work is still required post-conversion.

Seems LAB colour mode comes in and out of fashion every now and then. The trick to it is to use it sparingly as it is very, very easy, to overdo it!

H
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  #39  
Old 28-10-2010, 12:28 PM
Bolts_Tweed (Mark)
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Thx H

As i said i havent tried it (still on hols - no data)

M
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  #40  
Old 15-12-2010, 09:29 PM
jase (Jason)
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Stellar Profiles

Rediscovered this document which I developed as a basis for a planned presentation which fell through. It was produced back in 2007 and seen a few updates but overall is incomplete so take it with a pinch of salt.

Despite this, I thought I'd share it as its benefiting no one sitting on my hard drive, plus I have no inclination to complete. I take no responsibility for errors or the 'stuffing up' of data sets if you follow these principles, though I still use the analysis techniques today.

Enjoy!
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File Type: pdf Stellar Profiles - Jase.pdf (390.3 KB, 110 views)
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