Retouching techniques
Most images will require some retouching. Dust on the camera sensor shows up as dark, circular marks, particularly noticeable in the sky and similar areas. Scanned images are not immune. Digital files from film can also show dust specks or hairs picked up at the scanning stage, or blemishes from the original image.
Software for retouching
Software such as Photoshop’s ‘dust & scratches‘ filter may save you time, but these techniques (including Digital ICE on the ‘Fine’ setting), generally work by softening the image. They do have their place, but try to use them selectively and sparingly. Take care that image detail is not degraded to an unacceptable degree. Again, you should check this at 100%.
Clone Tool/Healing Tool
Perhaps the most useful tool is the Clone Stamp Tool (keyboard shortcut ’S’), (fig.1). This can be used to copy pixel for pixel areas of tone, to eliminate defects such as spots or hairs.
First choose a suitable size of stamp (for this purpose ensure that in the preferences of Photoshop, you check the "brush size" box: File > Preferences > Display and Cursors > Brush Size, so you can see exactly the diameter of brush chosen), then put it into an area immediately next to the blemish to be removed. You can quickly alter the size of the brush using the keyboard shortcut ‘[‘ to decrease or ’]’ to increase. Using the command Alt+Click, samples this area.
Now move the stamp to the blemish and click the mouse. You will now see two cursors - the sampled point and the area to be improved. This starts to replace the pixels under the cursor with the ones sampled. This may take some getting used to but with practice even large blemishes can be effectively removed (fig.2).
Figure 1.
Figure 2.
The Healing Brush Tool (keyboard shortcut ‘J’) works in a similar way, but in addition tries to match the colour and tonality of the destination area, so selection of the source area is not quite so critical. The Healing Tool is very effective in open areas, but you’ll need to revert to the Clone Tool when near other objects.
The opacity of the tools can be altered, but, more importantly, the "blend mode". In normal mode the stamp literally clones pixels from one area to another. Try using the lighten and darken modes. In darken mode, the tool will only paint colour if the destination is lighter than the source, whilst in lighten mode the opposite will happen.
You may need to sample an area several times to prevent tell-tale repeat patterns. The Clone Tool can also be used like a spotting brush for removing small areas of dust and blemishes like the one shown in the illustration. Rather than painting with the tool, a single click is used to lay tone over the blemish. Use a soft edged brush slightly larger than the area to be removed (fig.3, 4).
Figure 3.
Figure 4.
The History Brush Technique
The History Brush Tool (keyboard shortcut ‘Y’) technique allows you to clean up large areas of dirt/dust quickly - so long as the area to be cleaned contains very little detail, or is out of focus or blurred, e.g. the sky or other background area.
- First go Filter > Noise > Dust & Scratches... and choose a radius large enough to remove all the dust or blemishes. The whole image will be blurred but don’t worry about that for now.
- Select the History Brush and in the History Palette, click on the small square box on the left of the Dust & Scratches history. This sets the origin for the History Brush.
- Now click in the previous History state - the larger rectangular box immediately above and slightly to the right. This returns us to the un-blurred image.
- With the Mode set to "Lighten" for transparencies, or "Darken" for negatives, paint over the dirt/dust with the History Brush. Magically, all traces of dust will vanish.
Level a Tilting Horizon
- For this trick we need the Measure Tool. If it’s not visible in the Tools Palette, click on the Eyedropper Tool to reveal it.
- Now draw along your tilting horizon.
- Next, go Image > Rotate Canvas > Arbitrary... The precise angle required will already be entered - just click OK.
- Also works with leaning verticals.
Remove Chroma Noise or Colour Aliasing
Noise can be a big problem with some cameras, especially at high ISOs.
- Go Filter > Blur > Gaussian Blur, select a large radius (e.g. 6 pixels or more) and blur the image so that you can no longer see the noise. The whole image will be completely blurred, but don’t worry about that.
- Now go Edit > Fade Gaussian Blur and select Mode > Color from the drop-down menu, and click OK. This will return us to the unblurred state and should remove all the intrusive colour from the noise or aliasing.
Further Photoshop training and tutorials are available from Adobe.
Further help
- Achieving the best results:
- The Alamy Forum - the answer may be there.
- Resources - photographer tips and a directory of scanning and keywording providers.