Methodology for processing images in Photoshop/Aperture?

[Davi5678 (Dave)]

I'm using Aperture to process some widefield and scenic images.
This is what I've done to date, learning as I go.
https://picasaweb.google.com/1127655...eat=directlink
My method for processing is to slide adjustments up and down until the image looks better in my opinion.
I find sometimes I seem to be making adjustments at cross purposes.
I don't have Photoshop but I assume Aperture is similar if not as sophisticated.

A quick overview of Aperture Palette -

White Balance - Temp, Tint
Exposure - Exposure, Recovery, Black Point, Brightness
Enhance - Contrast, Definition, Saturation, Vibrancy
Highlights & Shadows - Highlights, Shadows, Advanced -Radius, Colour Correction, High Tonal Width, Mid Contrast, Low Tonal Width
Levels - Channel, RGB, Luminence, BGW
Colour - Hue, Saturation, Luminence, Range

I don't really understand histograms.
Generally I try to find a good level for the Exposure, then work through the Enhance and Highlights.
I'll adjust the temperature in White Balance to make the light more natural.
With the Levels I pull down the W (white?)in BGW which seems to trim out some noise and reset the G (grey) accordingly.
At this point I through a few of the brushes over the image, usually Noise Reduction, Sharpen and sometimes Polarize and set those levels to what looks right.
Any advice or hints would be appreciated, in the meantime I'm off to google for some tutorials.

[irwjager (Ivo)]

Hi Dave,

Your question is very, very broad.

Processing astro images does require a bit of a rethink as the data you're working with is quite different from terrestrial daytime images.
Effectively processing astro images is all about making the most of very faint signals and controlling noise. The two are always at odds and they're an art more than a science.

Issue #1 to get your head around, would be clipping. Histograms are a tool to help you avoid white and black clipping when you're stretching your signal, so getting familiar with them is highly recommended (unless you're ready to leave those archaic ways behind and use StarTools of course ).

Issue #2 is knowing when an image is done and getting it right the first time, so you don't keep running around in circles 'overcooking' the image in the process.

Issue #3 is knowing why an image looks like it does before you have even touched it. Understanding why the color is off, what that black blob is doing there, why those stars are elongated or discolored etc., will help you pick the right tools and lets you troubleshoot effectively. E.g. if you don't understand the problem, how can you effectively and consistently solve it?

There are heaps more things to think about, but once an absolute beginner myself, these are the things that helped me most.

Hope this helps!

Cheers,

[Poita (Peter)]

Some histogram help...
http://www.astropix.com/PFA/SAMPLE3/SAMPLE3.HTM
It is old and about scans, but the first bit with the coins explains histograms in a good way for beginners.
Then this has more specific details
http://www.corius.net/cont/artic/basimpro.html