How do I make an image "sharper" or "clearer".

To sharpen flat images in Photoshop, I use the unsharp mask filter.

It is the opposite of what it's name implies.

This filter adds "edge definition" to create meaningful contrast without affecting color.

It works best when applied a few times at low values.

The name comes from an old darkroom technique to improve low contrast images.

Illustrator allows export of png and jpeg files directly in RGB and specified resolutions.

The name "unsharp mask" confuses people.

It is actually the name of a darkroom technique to sharpen up soft photgraphic images.

It works well with some adjustment for each photo.

At one time the tiff format was standard for photos.

Tiff files had a problem with page layout programs that could not discern the difference between white and transparent backgrounds.

Jpeg file are the standard for photos now. However problems can occur because the format is "lossy".

Every time you open, edit and resave the file more data is lost in compression.

So when creating a jpeg keep compression at the level which creates the largest file size for print or further editing.

For web, you can go back and and save it as a smaller more compressed file for fast internet loading.

When working extensively on a photo, just keep it as a psd until your done.

When working on jpegs from phones, digital cameras and stock photos, remember to save an original backup copy.

Use Unsharp option in filter so that picture will sharp without losing quality.

Um, in the old days when I worked in PS to bring scans and photos upto reproductions levels, first I would adjust levels, then I would use unsharp masks. The image might need adjusrment to yellow for asian publication, cyan for european use, and magenta for american usage.

Print color is culturally speculative. 

Just say'n, the world is much more different than Your eye.

Your vision is not the end, but jut the beginning

Thank you all for your replies. I think that your recommendations are really professional and showcase your competence in this field. 

Nice