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

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

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

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

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

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

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

Histogram Always keep an eye on the histogram! Plot of pixel value (x axis) 0-255 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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