Thread: Removing color casts and correcting exposure

The free IrfanView offers many subtle functions for managing large photo collections and for converting images to different file formats. Unfortunately, some important photo correction functions do not give you the effect you are looking for. Nevertheless, you need not switch to an expensive program such as Photoshop.

Instead, you can expand IrfanView with the most important functions, for example, the gradation curve. This is the most frequently used function for post processing of photos. It enables manipulation of brightness values and color channels-ideal for upgrading photos with dull colors. Image editors such as Photoshop or Paint Shop Pro have been equipped with this function for a long time. IrfanView can easily be upgraded with Photoshop plug-ins. These are often available as freeware. The SmartCurve plug-in is also available: it adds the missing gradation curve.

Start IrfanView and open 'Image I Effects I Adobe 8bf-Filter'. In the next dialog, select the location of SmartCurve. The program offers other functions in addition to gradation curves, including automatic correction, a warning for cut highlights and shadows, a grey eyedropper for quick white balance as well as support for 16 bit and LAB color modes.

Checking Exposure: The first step is to analyze the image. If the levels in the histogram are close to the edges, image information in the bright and dark parts may get lost. Check 'Shadows' and 'Highlights'. The plug-in now shows under or over exposed zones with false colors. This way, you will immediately know which areas you must pay special attention to in the next steps.

White balance with grey eyedropper: For example, winter photos have a distinct blue cast, which can be easily removed. To do this, activate the central eyedropper and then click an area in the image which should actually be neutral grey. The gradation curves of individual color channels move when you click them. Now you can make another fine adjustment by separately moving the curves with the mouse. Darkening the exposure: If the subject of the photo is slightly overexposed, pull the gradation curve slightly down towards the center. This darkens the picture evenly.

Increasmg Contrast: Now form a slight S curve by pulling the left part down and the right part up with the mouse. The overall effect will be to make the picture much crisper.

Brightening Shadows: Now deactivate the gray eyedropper. Set 'RGB' as the color channel for precise brightness control. Distort the black curve in the SmartCurve dialog. Brighten the shadows by pulling up the lower part of the curve at several points. A more practical approach would be to click the area to be corrected in the picture; the corresponding point appears on the gradation curve. It is thus easy to assess which section of the curve you should lift or sink to achieve the desired effect. But you also need to be careful here. This is because stark curve distortions lead to distinct color distortions in the photos-a side effect which is most unwanted. But this too can be used creatively if you are looking for such effects.