Digital Photography
Image Manipulation
This section
covers basic image manipulation to improve your digital images.
It will cover brightness, contrast and colour
balance. All the examples below are made using Photoshop 7
but they should work equally well with other decent imaging software
such as Paintshop Pro.
Colour balance is particularily usefull for underwater photography. Most underwater images will suffer from a severe green or blue cast and this is easily changed by adjusting the 'curves' - images 1 and 2 below illustrate what's possible.
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Image
1 : Unchanged digital image with overal green cast.
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Image
2 : Adjusted with 'Auto' curves. Note no green cast and
better contrast.
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Open your image then select the 'curves' [Image>Adjustments>Curves] and you'll see the box similar to image 2 below. To start with, simply click on the 'Auto' button in the box and observe the changes this makes to your image. If you are happy with the change simply click 'OK' to accept it - this is all that was done to achieve the difference in Image 2 above.
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Image
2 : Basic unchanged curves.
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The 'Auto' option works fine for some images but you may find that it will not work on all. If it doesn't, you'll have to start manipulating individual curves in each colour 'Channel'.
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Image
3 : Red channel to change the reds in your image. There
is one channel for each colour. |
Image
4 : RGB channel to change Red/Green/Blue together. |
The best way to learn how to use curves is to start playing with them! Simply open your file and the curves settings and see what happens when you start manipulating the line in each channel.
To change the brightness of your image, simply click in the middle of the line on the RGB channel and drag according to requirement.
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Image
4 : In the RGB channel click on the line at a middle point
and create an curve to increase/decrease brightness. |
Contrast can easily be achieved using the curves again but in order to keep plenty of detail in the shadows and highlights (darkest and lightest bits of your pictures), you'll need to create an 'S' shaped curve. Image 4 shows they line to create.
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Image
4 : In the RGB channel click on the line at two points
and create an 'S' curve to increase contrast. |
Alternatively select the 'Auto Contrast' option in your software. This will often work but may not achieve the best results.
Read
more about:
Pixel
Basics
Table
Of Resolutions
File
Types
Image
Manipulation
Images
For Internet
Use
Images
For Print