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The Photoshop cloning tool is the standard dirt bailout tool of extreme macro focus stacks, but beware! Nothing can make a picture look sillier than bad cloning, and its use should at best be circumspect in science "documentation".

Microscopic Dirt

Despite cleaning our specimens religiously, microscopic 'stuff' won't always come off and this is where the cloning tool comes in as a last resort. By taking clean areas and cloning them over the grit and dust detritus, your extreme macro image can and will become beautifully clean.

How To Clone

The Photoshop clone tool is the oldest and most widely known of inbuilt Photoshop photo goodness. The basic concept is that the user duplicates portions of an image using a source, destination and brush.

1. In open image, choose clone stamp tool icon ›› choose clone stamp tool.
2. Hold down alt (on PC) and select the area that you want to copy from
3. Release alt, move cursor to area where you want to clone into and click left mouse button to start cloning.

Good Cloning

Photoshop does not restrict cloning to one brush. Instead, it allows you to use any brush you want, allowing you to create many effects. In most cases, a small to medium-sized brush gives the best result.

Have a 100% pixel:pixel view of your image and use the smallest possible cloning brush

It is much much better to have a 100% pixel:pixel view of your image and to use the smallest possible cloning brush than to try and clone with an image at 25%.

I always start out with the softest brush that I can find and usually clone into a separate layer so that I can play with the transparency of the cloned area to get the smoothest possible setting.

Cloning insect eyes is really really hard because they are usually regular arrays in which errors can be spotted very easily. I tend to start at 100% and start with the very middle of any single compound eye working my way outwards, rather than with the lines. Works for me.

The spot healing brush is a cloning option that seems to works reasonably well for me in colour gradient areas to get rid of sensor spot issues and hot pixels, and the patch tool is the best way to clone large, relatively uniform areas.

How Much

You have to be careful with all of these tools though because essentially you're letting Photoshop fabricate part of the image, the ethicality of which is a debate all on its own and has no place in scientific illustration. The conventionally accepted guideline is that it is the photographer's responsibility to declare what has been done to an image and not to pass it off as untouched when it has been reworked.

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