If you want to zoom the picture when processing small parts, on the toolbar, select tool Zoom Tool (Magnifier). The same effect is achieved by using the hot keys Ctrl+"+". To zoom out the image, use the magnifying glass, hold down Alt on the keyboard, or use Ctrl+"-".
To increase drawing in the Edit menu ("Edit") then click the Free Transform ("Free transform"), or press Ctrl+T. Move the cursor over one of the knots, hook his arm and pull to the side. Depending on the movement direction, the image will increase in width or height. The size was varied uniformly, hold down the keyboard Shift key.
There is another way. To menu Image (Image) select Image Size ("image Size"). Enter the new size in the boxes Width ("Width") and Height ("Height"), under Pixel Dimensions ("pixel Array") or Document Size ("Size"). It should be borne in mind: the more you increase the value, the stronger the distortion in the final document. You may receive color noise, blurry areas, artifacts, etc.
If you increase the picture 10% distortion is not seen. So you can change the size in stages by enlarging the image at each step within these limits. In the Document Size section in the right window expand the list and select percent ("interest"). Put the flag in the checkbox Constrain Proportions so the image proportionally.
The value of height and width will be set to 100%. Type in any window 110 to increase the figure to 10% and click OK. Repeat this procedure until the image does not increase to the required size.
Of course, in this method, the image quality suffers. You can increase the sharpness. Duplicate the layer Ctrl+J and in the menu Filter ("Filter") Other ("Other") select the High Pass ("Color contrast"). Install a small radius, so that the image is slightly shone through the gray film. Apply to the layer blend mode to Overlay ("Overlay").