To determine details of the image format, use Autoview (F7). This does not display the image but shows directory information (filename, size, date, time), graphics format, number of colours (with 2 colours signifying monochrome, or black and white) and image size in pixels.
Once the file has appeared on the screen, it is useful to know about the action of the first four function keys. If you have a colour screen and the image is in colour, it will display in colour. F1 will convert it to monochrome and F2 will restore the colour. This can be useful if you wish to preview how the image will look when printed on a black & white printer.
Images are recorded in 2,4,16 or 256 colours. 2-colour, 4-colour and 16-colour images will normally display with one image pixel to each screen pixel, i.e. a standard VGA screen will show 640 x 480 pixels, whatever the size of the image file. Thus if there are fewer pixels in the file, the image will not fill the screen. Conversely, if there are more pixels only part of the image will be shown. It is then possible to move the image around the screen with the cursor keys, or centre it with the space bar. The cursor keys move it in rather large steps, but in conjunction with the shift key they move the image one pixel at a time.
The four diagonal keys on the numerical pad, Home End, PgUp and PgDn, move the image diagonally to the edges. F3 is a toggle which puts them into a mode similar to the cursor keys, i.e. large steps when used solo or a pixel at a time when shifted.
256-colour images are displayed at twice the scale of 2- and 16-colour images, with each image pixel being mapped to a 2x2 block of screen pixels. If the image extends beyond the boundary of the screen, F4 shrinks it to fit the screen, with some loss of detail and possibly distortion if the horizontal and vertical reductions are not equal. A touch on the space bar restores the original size. F4 works only on 256-colour oversize images.
Thanks to John Parmigiani for alerting me to the use of function keys when viewing graphics.
Tom Ruben