Six Photoshop Image Processing Steps for Mars

     

      

      

Introduction

Please note that alternative ways of processing are possible.

This guide only refers to the steps in Photoshop's language. All these steps can also be easily applied in any image processing package with similar capabilities.

When I started processing my images of Mars this morning, this is what worked best.

You can clearly see from the results above that there are some truly horrendous intermediate results. I still need to do many more experiments - one example would be to have better looking images right at the beginning of the processing and not at the end.

However I try to keep the maximum detail between each step. Only at the end do I fix the final color scheme.

If you swap any of these steps you might get significantly better results - so feel free to experiment.

Actually if you do these steps or their microsteps in a different sequence you might get much better results as well.

The main message here is that there are many intermediate steps in processing webcam images and these steps consist of various Photoshop image processing options. There are many other useful Photoshop features that are not even used here.

Do not follow these steps slavishly. Try to understand the reasoning behind the processing and adapt to get best results from your specific image.

For the purposes of this six step image processing method, K3 CCD Tools is not even considered - that process justifies its own study all by itself.

I kept all these steps on this one long webpage - so it is easy to print. You can also more easily page up and down on this one webpage that way.

Here are those steps:

Step 1 - Align the red, green and blue channels

   

The image on the left is the raw stacked result directly from K3 CCD Tools. 1500 frames were initially captured. 234 of the very best frames were hand picked for this process.

The image on the right has its red, green and blue channels aligned. Actually it is the image on the left from K3 CCD Tools with some slight unsharp masking done in K3CCD Tools. The 3 color channels were then aligned. ( I did not make the 3 different channels' images the same size - to simplify this 6 step guide )

Even at this early stage you can see that there are some detail in the image just 'begging to be made visible'. So image stacking is not the end of webcam image processing but the starting point.

( I overdid the gamma setting in this image - the dark areas on Mars are just that: DARK and featureless. No processing can now make visible the details in those areas that I failed to capture properly. )

If you are happy with just your stacked webcam image - VERY good news: your image can still be significantly improved by 'tinkering' with it in Photoshop / or any other similar image processing program - like GIMP.

Step 2 - Despeckle the image and overlay

  

The image on the left is the result from the previous step.

The image on the right has been despeckled to reduce some of its noise

The reason and effect of the despecking is not too obvious at this point. Only when we sharpen the image will its benefits be realized: speckles/noise will not be unsharp masked since it were reduced at this point.

Then I made a duplicate of the layer and blended it using overlay mode. The idea here is to increase the contrast between the features on Mars.

Step 3 - LRGB Processing

   

The image on the left is the result from the previous step.

I used the high quality red channel as luminance channel.

( How ? - select the red channel, then edit-copy it, change image mode to Lab color, select the lightness channel, paste the red channel into the lightness channel. Select the Lab channel to look at the result. Convert the image mode back to RGB for the next step. )

Step 4 - High pass filtering

   

The image on the left is the result from the previous step.

I applied a high pass filter to the RGB image. Next I did some unsharp masking to the lab channel.

So actually the image can stay in Lab color mode going from step 3 to step 4.

When you have experimented some time with these steps (you ARE experimenting, are'nt you), you will realize (as I just did) that step 3 and 4 can be combined and at the same time reduce the number of microsteps.

Example: select red channel, apply high pass filter, then copy to lightness channnel, unsharp mask the lightness channel.

When you have experimented some more, you will come up with all sorts of insightful, excellent questions and suggestions, like:

• Why is only the red channel involved, why not the green and blue too?
• Why copy the red channel to the luminance channel?
• Why not copy the green channel to the luminance channel?
• Why not copy an average of the red and green channel to the luminance channel?
• Why not just apply a high pass filter to the RGB image and leave out the Lab mode entirely?
• What is the purpose of the high pass filter, why not use despeckle or something else?

There are even more such questions for the other steps in this process. The topics addressed on this webpage justifies a whole 100-page book.

All I am saying is that the more you experiment and read up on these matters, the better you will get.

Grow your webcam image processing skills one day at a time. You can still get good results by applying only the minimum filters and processing.

Step 5 - Screen blend mode

   

The image on the left is the result from the previous step.

Then I made a duplicate of the layer and blended it using screen mode. The idea here is to make the image of Mars lighter.

You should determine for your image what looks like an acceptable opacity percentage. Experiment.

Step 6 - Adjust the color

      

The image on the left is the result from the previous step.

I adjusted the RGB image in the center using curves in Photoshop.

As an alternative adjusted the last image in this row using the color balance menu option in Photoshop.

Photoshop experts use curves and beginners use color balance. Try both to see the vast untapped potential of curves in Photoshop. Applying curves is another study all by itself.

Photshop guru-experts apply curves in Lab mode and not in RGB color mode. Play around to see the effects you get - small adjustments in curves make a major difference to the image.

Stay away from the brightness/contrast menu option since it throws information away. You can do what it does and a whole lot more in curves.

Actually the curves-image should have been better than the image of Mars done with color balance. I did not spend more than 60 seconds with it, since today I put my effort into writing this step by step webcam processing guide. So please do not think color balance is superior to curves. It is not.

The curves-applied image has more shades of red and orange than the color balance one. More shades means more detail.

The shades of red also flow more naturally into each other. Curves naturally does this - it allows you to adjusts your images using smooth curves.

The dark areas of Mars also looks much better in the curves-applied image. The dark areas in the color balanced image (the last image in the row) is ugly - to put it family-friendly nicely.

Optional - Step 7 - Another light unsharp masking

      

The 2 images on the left are the result from the previous step.

I took the image on the left and applied another unsharp masking to it.

Many astrophotographers leave their images of Mars as illustrated in the first image - very slightly blurred, however I like to make my images of Mars a little bit sharper.

Conclusion

While writing this step by step guide I made a short (no, a long) list of things that I can improve upon.

So this is not my final guide, but hopefully only the first one in a series of progressively better step by step guides.

In this guide I did not apply slightly different processing to the polar ice cap, lighter and darker areas on Mars. All areas received the same 'treatment'. By applying area-specific processing it would have been possible to show slightly more detail at the South Pole of Mars for example.

I would also like to reduce the number of processing applied to my images. More and more image processing does not necessarily mean better images.

You can only use processing to enhance details captured in your raw images. Image processing cannot create detail that is not there in the first place.

Please tell your astrophotography buddies about this webpage. If they do some experiments and you do your own, you can get together (even just via email) to compare your findings.

You are welcome to send me your questions, however I would like to see you did put some effort into image processing as well.

IMPORTANT: Please do NOT send email attachments, but provide a link to your images on the Internet. If you have no webspace ask via email first if you can send attachements - specify the total size you plan to send as well. No need to be fancy - just upload images to their own Internet-based directory where I can get it.

You are also welcome to experiment using my raw image. Just right-click on this link to save my uncompressed red green blue aligned image (118 KB). All other images on this webpage are compressed slightly to ensure faster Internet download times. You can, but do not have to, let me know if you get better results than me. Please give me credit by linking to me if you use my raw image and process it to put on your / another website.

If you spot any (english grammer, tense, spelling, logic, HTML, ...) errors or have other ideas that is most welcome as well.

alwynbotha --- at --- webcam-astrophotography.com

Here are the technical details for the webcam images of Mars used in this guide: