1. Improving Your Astrophotos
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

2. Covering Tonight Photoshop UI & Tools Processing Basics Histograms
Levels & Curves
Colour Processing
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

3. Covering Tonight Filters Layer Processing Noise Reduction Sharpening
Removing Gradients
Rounding Stars
Improving Dynamic Range
All Together and “Zone System”
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

4. Not covering (tonight)
Taking the image in the first place
“Calibrating” the image (Darks & Flats)
Calibrating Monitors and Printers
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

5. Processing Software Adobe Photoshop Paint Shop Pro Gimp (Free)
Various versions Elements doesn’t have layer masks but this can be simulated easily
Older versions are 8 bit only New versions are up to 32 bit. 8 bit versions are fine for jpgs
Paint Shop Pro
Gimp (Free)
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

6. Photoshop UI Menu Bar Image Window Tool Palette Information Window
Brushes Palette
Layers Window
Load Orion image
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

7. Processing Basics Histograms Levels and Curves Colour Processing
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

8. Histogram Always keep an eye on the histogram!
Plot of pixel value (x axis) vs number of pixels with that value
Get histogram using Levels menu option (Later versions have a Histogram window)
Value of 0 (left) is Black, Value of 255 (right) is “White”
Load Vallis Alpes to demonstrate histogram & Curves
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

9. Levels
Move Black and White point cursors to change dynamic range (brightness)
Move Mid-point cursor to change the contrast
Use droppers for Black and White point
Use Preview for “before & after” view
Auto levels can be useful but is usually too bright
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

10. Curves More sophisticated way of altering pixel brightness than Levels
Moving top of curve changes White point
Moving bottom of curve changes Black point
Can add points to the curve (and remove them – process varies by version)
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

11. Curves Move curve up to increase brightness
Move curve down to decrease brightness
Can increase brightness in the shadows and decrease in the highlights (S-curve) or vice versa
Black and white point droppers as for Levels
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

12. Curves Can use Curves a number of times in small increments
Try to get the top of the curve linear to keep “headroom” for modification
Use Kepler image
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

13. Colour Processing Histogram shows separate RGB lines
Adjust black points, leave white points
Auto-colour usually saturates
Use Colour Balance to adjust colours
Use Saturation to change depth of colour
Use Hue to change colour (use with care!)
Use M42 Image
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

14. Photoshop Tools Enlarge / Reduce tool Zoom in/out Ctrl+, Ctrl-
Fit to screen
Actual Pixels
Always work with Actual Pixels if possible
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

15. Photoshop Tools Brush Tool
Allows us to paint on an image (or layer mask – later!!)
Select size and shape of brush from the palette
Select colour using the dropper
Set colour to black/white
Swap Brush and Erase colour
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

16. Photoshop Tools Erase Tool Clone Tool Paints using the Erase colour
If the Erase colour is black then fades the pixels under the Eraser tool
Clone Tool
Copies pixels
The copy source moves with the Clone tool
Useful for touch-up
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

17. Photoshop Tools Burn Tool - Makes the area darker
Dodge tool – Makes the area lighter
Selecting Dodge and Burn varies by version
Marquee tool – Used for selecting a rectangular area
Lasso tool – Used to select a free-form area
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

18. Magic Wand and Select Click Magic Wand to select
Shift-click to add to selection
Alt-click to remove from selection
Select/Similar (or Select/Colour Range) to get all pixels of the same colour
Select/Modify/Expand
Select/Modify/Feather
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

19. Filters Noise reduction & Blurring Sharpening Minimum filter
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

20. Noise Reduction Gaussian Blur. Quite coarse
Dust and Scratches. Blur but with some fine control
Despeckle. Mild Median filter
Median. Probably smoothest effect
Smart Noise Reduction (New versions only) Very good control Similar to Focus Magic
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

21. Sharpening Sharpen & Sharpen More. Tend to increase noise
Unsharp Mask (USM)
Use with small radius, say 1, to sharpen
Use with large radius, say 32, to increase contrast
Use the Amount slider to control effect
Smart Sharpen Cleverer version of USM
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

22. Layers
Can be confusing at first but most powerful feature of Photoshop
Create new layer by
Duplicating current layer
Pasting another image on top of existing image
Change the effect by changing the blending mode
Turn layer off and on with “eye” box
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

23. Layers (continued)
Can process one layer and use the blend mode to affect the whole picture
Flatten image to get a single image again
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

24. Gradient Removal Duplicate Layer Blur the top layer
Change Blend to Difference
Adjust Opacity
Works best on stars and small DSOs Can clip extended DSOs
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

25. Rounding Trailed Stars
Duplicate Layer
Change Blend to Darken
Use Filters/More Filters/Offset to move top layer
Will remove faint stars unless you use a mask (Later!!)
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

26. Flattening Contrast Duplicate Layer Gaussian Blur (say 5 pixels)
Image/Adjustments/Invert
Change Blend Mode to Overlay
Adjust Opacity
Very good on Lunar images
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

27. Sharpen Details Duplicate Layer Set Blend mode to Soft Light
Filters/Others/Hi-pass
Use small radius for small details, larger radius for coarser effect
Blend mode of Overlay is stronger
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

28. Increase DSO Colour Duplicate layer Blur the top layer, say 10 pixels
Set Blend Mode to Colour
Image/Adjust/Saturation
Increase the saturation
Increases colour in DSOs without increasing star colour and halos
Try this with lunar images, especially full Moon
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

29. Masks Used with layers Allows control of what “shows through”
White passes upper layer
Black passes lower layer
Grey mixes upper and lower
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

30. Creating a mask Click the Mask button on the Layers palette
Use Menu/Layers/Add Layer Mask
Select the Mask with left click
Display the Mask with Alt+left click
Usually want to blur a mask for smooth transition
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

31. Painting on a Mask Useful for enhancing or reducing small areas
Alternative to fiddly selection
Excellent for “painting in” detail without increasing general noise
Don’t forget to blur the mask for smooth transitions
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

32. Mask from Copy & Paste Select and copy the image to use as a mask
Usually Ctrl+a,Ctrl+c
Open the Mask (Alt+left click)
Paste using Ctrl+v
Blur (and/or Median)
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

33. Changing a Mask
Use straight line Curve to increase or decrease strength of Mask
Use Curve to increase the strength and scope of a Mask
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

34. Increasing Dynamic Range
Duplicate Image
Darken the copy
Ctrl+a,Ctrl+c
Select Original
Create Layer with Ctlr+V
Create Mask and Select
Copy image to mask (Ctrl+V) and Blur
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

35. Increasing Dynamic Range
Best use is with different images with different exposures (High Dynamic Range)
Remember the 8 bit limit. Work in 16 or 32 bit if your software allows it
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

36. 5 Level Plan Signal Action None Set Black Point Poor
Blur (or Reduce Noise) OK
Leave alone
High
Sharpen (if necessary)
Saturated
Set White Point
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

37. How I Process DSOs Take as good a picture as possible 
Stack in Maxim using SD Combine to reduce random noise
Create 2 or 3 different DDP versions highlighting the Outer, Mid & Core of the DSO
Open them up in Photoshop
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society

38. How I Process DSOs
Create a composite of the images, brightest on the bottom (Actions help this process)
Use Reduce Noise on the Outer layer
Use Smart Sharpen on the Core layer
Flatten down
Do any further processing (usually masked hi-pass)
2010 Feb 10th
Terry Evans Bridgwater Astronomical Society