Digital Scanner Image and Copies, Undo and Redo, Layers

A digital image can be printed as many times a we like without loosing quality. Nonetheless, size adjustments, tone and color, mode conversion and other effects can reduce sharpness. It is advisable to preserve the original image and make modifications in copies, which become new versions. In Photoshop there are two ways of doing so: open the file, duplicate it, give it another title ( image > Duplicate ) and work on that copy, or edit the original file and save it with another name when finished ( File > Same as. ). We have also seen that the JPEG file means a loss in quality of the image each time we modify it and resave. If an original image is in JPEG format, it is convenient to save the next versions in a no quality loss format (such as Photoshop or TIFF) before reaching the final version.

Undo and Redo

We can rectify the last action with the command edit > undo . If we use the command twice, which don't rectify two steps, we go back to were we where. Some action in Photoshop can only be undone with this command, specially when the action is in a dialog box without it being recorded in the history. All the changes we make in the image are registered in the History ( Window > Show History ). In it we can see a determined number if steps from when we opened the image. The number of steps in the history can be adjusted in the history options which we access by clicking on the arrow in the top right hand corner. A large number of steps in the memory requires a large amount of working memory (RAM), which will be greater the greater the file size. When we take a step that exceeds the set number, the first step disappears successively. In the steps the history contains we can go back and forth at our convenience. When we go back, all the following steps are shaded, which indicates that if we now do a new step they will disappear (this can be avoided with the option of non lineal history , which requires even more

memory). When we foresee that we are going to give a large number of steps from a step we find interesting, we can conserve it by saving the changes until that moment without closing the file. When the document is closed all steps in history are lost . Another way of saving a step is by saving a copy of it ( File > Save copy ) and giving it a different name; and we can save changes creating a new document from the original state with the save as option: the original document with the changes made until the last time they were saved is copied into a new document with a different name. When working with large files there can be memory problems which are in part caused by the history. To free the memory you can erase history (in options ) and other elements saved temporarily, like cutouts or image motives which are stored in the computers trashcan (with the command File > Empty.

Digital Image Layers

A great advantage of Photoshop is the possibility of working with image layers, of text or adjustment, which are comparable to images printed on a transparent medium and superimposed on the original (or background ). When we write a text in the image or include a cutout from another, Photoshop automatically creates a new layer. We can create new layer to include more images or drawn elements that can be moved and place independently of the background. The layers can be visualized and activated in Window > Show layers . When the image is made up of various layers it is necessary to select the working layer or active layer . The layers are "piled" one on top of each other, and the superior ones cover inferior ones, but the order can be changed by dragging them. Besides the layers of an image and text, it's possible to create adjustment layers to make changes in brightness, contrast, color, etc. of the image. An image made up of layers can only be save in Photoshop format. To save the image in another format it's necessary to unite the layers ( Layer > Join Image ).