Generations: Inter-generation loss of quality, sharpness etc - text and particularly, images

Scenario 1: A photo print from a film camera is scanned and printed. How many generations is the final print from the original scene?

Negative - first generation

Print - second generation

Scanned Image - third generation

Final Print - fourth generation.

Scenario 2: A digital photo is edited (cropping, resizing, red eye removal etc) then printed and cut to be part of a paper master which is then photocopied.

Image in camera - first generation

Edited image - second generation

Printed image - third generation

Photocopy - fifth generation {fourth generation is the photocopier scanning, fifth generation is the photocopier printing!}

Scenario 3: A digital photo is edited (cropping, resizing, red eye removal etc)and saved. More editing was required. The image is then printed.

Image in camera - first generation

Edited image - second generation

Re-edited image - third generation

Printed image - fourth generation

Minimising intergeneration loss of quality and resolution particularly for digital images

1. Always take digital photos at the highest resolution. (The more photos you can fit on a memory card the lower the initial resolution - so set the camera to the highest resolution you can manage).
2. Never save an edited image with the original filename. Always use: Save As. This means that you save a generation of loss if the image needs re-editing. (Scenario 3 printed image would become third generation)
3. Where possible always print from an electronic copy of an image. {Scenario 2 print from an electronic copy would be third generation rather than fifth generation.
4. If high quality images are being edited then take the images in RAW mode or lossless TIFF if the camera permits. Then do all editing in a lossless image type (eg TIFF lossless). Lossless images have no inter-generation loss when saved. If an image can be photographed using a lossless image file type then the print in scenario 3 would have been second generation.
5. To minimise intergeneration loss - take or scan images at high resolution, save edits as high quality or lossless and print at high resolution.

Wikipedia on editing digital images 

Sharper JPEG images