Adjusting Images in Photoshop

Introduction

Raster image editing is the main function of Photoshop. It will allow the user to change, add or erase information of a raster image. It can be used to create complex compositions of combinations of different images, repairing artifacts in the image, erasing unwanted elements in the image and enhance the quality of the image in general. The tools which are available to change the content of the image are at this moment so powerful that it is increasingly difficult to see if a digital image is edited or not. There are 4 levels of image editing;

Image adjustment

The actual content of the image isn’t changed. This option is used to enhance parts or the whole image. In this case the color and brightness/lightness information of the image is changed. An example is the adjustment of a digital photograph which was originally to dark, or the colors where of as the result of a wrong gamma setting on the digital camera. Extreme forms of changing the color or brightness/lightness of an image can generate quite alien images and can be used to generate an art like image.

Image repair/alteration

The actual content of the image is adjusted. A good example is the current practice to edit advertisement photographs. Due to the high resolution of the images the slightest imperfections become visible, these imperfections are edited out of the image. This will create a perfect although unrealistic image. Parts of the image can also be erased, a technique which was in its analogue form used by dictatorships to erase party members from photographs who fell out of grace. The difference with the next level is that the content of the image itself is used to repair or alter the image, so no new images are introduced into the image. Although this sounds quite harmless, it is this grey area of image editing which blurs the lines between authentic and artificial.

Image composition

The actual content of the image is adjusted by adding additional external image data. This technique enables the user to combine different images into one image. It will give the user the possibility for example to add or change backgrounds ,add or replace objects, people and trees and combine renders of virtual objects with digital photographs. The final image is a composition of different images and therefore doesn’t represent an true representation of the actual original image. This technique is especially interesting for people who want to combine different images together to simulate a photograph. The combination of the content isn’t real but it looks like it is real. Architects can use this technique to make photomontages of a render of the virtual model of the design and paste it in a photograph of the location. In the film industry this technique is used for so called Matte paintings, a technique for generating surrealistic and simulated backgrounds.

Image filtering

The actual content of the image is not altered but the appearance is changed. The filtering of images can be used to change the appearance of an image. The filters will add an effect to the image to generate for example an oil painting look to the image. These techniques can be used to match the appearance of the image with the purpose of the image. A concept design render of a building can be to realistic to be used for a presentation for the client. Filtering the image can remedy this problem.