Processing
Process your images to bring out the subtle, colourful textures of the lunar surface
The Moon looks more or less colourless through a telescope. Even the Apollo astronauts observing it up close, described it as mainly grey, or slightly brown. But the Moon’s surface material, known as regolith, does have very subtle colour differences, which are dictated by the mineral composition in any particular area. This mineral distribution on the lunar surface was mapped in great detail by the US Clementine probe in 1994, but the good news is that you can produce images showing these colours without having to launch a spacecraft to do so. It’s easily achieved and all you need is a one shot colour (OSC) camera and a telephoto lens or telescope, plus a bit of image-processing knowhow.
As with most image processing, the success of the technique relies on having a decent image at the start. The best image for creating a mineral Moon will be evenly exposed, such as the one shown here taken with a DSLR (see top image, opposite page). Keeping the exposure as short as possible helps to keep the image sharp; the settings used here were ISO 100 with an exposure of 1/640”. Most DSLRs come with a preview mode that flashes to show areas of overexposed pixels, which is invaluable in helping you set the camera to an exposure that doesn’t overexpose. If you have been taking photos of the Moon for a while you will probably already have many lunar images at different phases that would benefit from this technique.
Getting started
To begin, open your image in Photoshop. This would preferably be a RAW image or, depending on your Photoshop version, it may be better to convert it to TIFF format first. Images in JPEG format can be used, but JPEGs compress the data so the image quality will suffer, plus it won’t be as detailed. The first step is to create a ‘Luminosity Layer’. This will enable you to make some changes to the colour and hold back any adverse artefacts that could quickly manifest themselves as a result. A ‘Luminosity Layer’ locks the value of the pixels in the image, up to a point, so that the brightness of any pixel in the resulting image does not change too much as adjustments are made.
From the ‘Menu’ select ‘Layer > Duplicate Layer’ (see Screenshot 1, right). Name the new layer ‘Luminosity Layer’ and click ‘OK’. From the ‘Menu’ make sure that ‘Window > Layers’ is ticked to reveal the ‘Layers Window’. This ‘Layers’ menu should now be visible on the right-hand side of Photoshop. Click on ‘Layers’ to reveal the two layers in the image, before clicking on the newly created upper ‘Luminosity Layer’ so it’s selected. From the drop-down menu just above the layers, which shows the default ‘Normal’ setting, select ‘Luminosity’ at the bottom of the list (See Screenshot 2).
Adjustments now need to be made to the saturation of the lower layer. Depending on your camera, the colour balance may need to be changed as an OSC camera usually has a green bias due to the built-in Bayer matrix that produces the colours. Click on the lower layer to select it and from the menu click ‘Image > Auto Color’, or press ‘Shift+Ctrl+B’. Not much change will be noticed at this stage, but the Red, Green and Blue colour channels have now been balanced in the lower layer image. Next you need to increase the saturation; making sure the lower layer is still selected from the ‘Menu’, go to ‘Image > Adjustments > Hue/Saturation’. Adjust the ‘Saturation’ slider to somewhere between +30% and +40%, but no more than this, and then click ‘OK’ (See Screenshot 3).
You may already see some colour appearing, but not much at this stage. So, repeat this saturation increase step a number of times. Remember that it always gives better results if this is done in a series of smaller more subtle steps, rather than fewer more drastic increases. It’s very easy to overdo it so stop when you reach the colour you like. Once completed, flatten the image and save it with a different file name. This ensures that you do not overwrite your original starting image. In our final completed image (on the opposite page) you’ll notice that brown iron-rich areas can be seen, while titanium-rich areas within Mare Tranquillitatis appear bluer.