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Basic Enhancements (part 1)
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This section looks at some of the ways you can manipulate an image to improve its overall appearance. Note that there is no substitute for getting a good picture to start with. All the manipulations in this section can only work with the data in the original image - you will not be able to recover information that is not in the original image. What you can do is change the information to alter how a photograph is perceived by the human eye. That's what we are going to look at in this section.
Most of the options in this section can be found on the Image --> Adjustments menu as shown on the right.
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Brightness and Contrast
This is one of the simplest enhancements to do on an image, however, unless you are using Photoshop CS3, it is also one that can destroy a good image. The problem lies in how it actually implements the brightness and contrast adjustments.
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In the dialog box you will usually see two sliders - one for brightness and one for contrast which by default will be in the centre. Moving the slider to the right increases brightness or contrast, and moving it to the left decreases it. The check box labelled 'Preview' allows you to see how the changes you make affect your image. |
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In most photo software, if you move the brightness slider to the right the software will increase the brightness of all pixels in the image by the same amount. This means that your lovely jet blacks become dark grey, and the subtle details in your highlights all burn out to pure white. A similar problem with the contrast slider causes you image to contain a lot more pure blacks and pure whites - again losing detail in your photograph.
Photoshop CS3 is the first package we are aware of to actually implement a sensible approach. Brightness is achieved my manipulating the midtones of an image but doing very little with the extreme shadows and highlights. Contrast will manipulate the medium-dark shadows and medium-light highlights to vary the contrast without the loss of any detail. PS-CS3 does give you the option of using the traditional method by selecting the 'Use Legacy' dialog - but please promise us that you will never do this.
For precise control over brightness and contrast in your image you should not bother with this control at all and instead use the 'Levels' and the 'Curves' features which we will cover a little later.
Hue, Saturation and Lightness
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Like the brightness and contrast control - this is a fairly easy one to understand however it’s use is limited and should be used sparingly.
Of the three sliders you get in the Hue/Saturation dialog box, you will probably find the saturation slider the most useful as this can be increased slightly to make the colours in the image more vibrant. It is of course very easy to overdo it and end up with a very unnatural image but that may of course be the effect you are after. |
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For abstract images and flower shots it can work well but any change to portrait pictures can really mess things up.
Shadows and Highlights
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We mentioned in a previous section what is meant by these terms. Photoshop gives you a 'Shadow/Highlight' tool to help you control them and correct common problems. Note that the dialog box shown on the right is the one that appears when the 'show more options' is checked.
One common use is to correct an image where the subject is silhouetted against a brightly lit background. It can also be used to correct overly bright images (such as when the subject was too close to the flash). It does these corrections based on the surrounding pixels
The 'tonal width' controls the range of shadow and highlight tones that are corrected. A small value will only correct the very darkest shadows and very brightest highlighs.
'Radius' controls the size of the region used to decide whether a pixel is in the shadow or highlight region and should therefore be acted upon. There is no ideal value for this and it is best to experiment with each individual picture. If the radius is too large, then the whole image will be affected, so try and set it to the size of your subjects. |
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Sometimes when you brighten the shadow area of an image, the colour saturation can appear to increase as you are bringing out colours that were previously hidden. The 'Colour Correction' slider can be used to increase or decrease the saturation level. Note that it only affects the changed portions of your picture, and the strength of the effect is dependent on the strength of the shadow and highlight change.
'Brightness' is only available for greyscale images.
'Midtone contrast' is used to increase or decrease the amount of contrast in the midtones (hardly a surprise there then!).
Finally the 'Black Clip' and 'White Clip' values allow you to control the amount that the shadows and highlights are allowed to clip (i.e. how much they are allowed to exceed the maximum and minimum values available. By default, black is set to 0 and white to 255 - this means no clipping is allowed. If you lower the white clip value, then you are saying that colours greater than this value can be clipped. Although clipping of highlights and shadows can leads to higher contrast images, it can also produce some undesirable effects such as burnt out highlights (large areas of pure white, and therefore no texture).
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Photographs
This is a site about photography so I'm sure you are expecting to see plenty of pictures.
For now, why not take a peek at the flickr galleries belonging to the two authors of this site.
Colin's Flickr Page
Phil's Flickr Page
"Color is very much about atmosphere and emotion and the feel of a place." - Alex Webb
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