"Watermarks" are deliberately large and intrusive. They're intended to reduce pirating and theft of images. Watermarks are a copyright protection and a "necessary evil".



"Signatures" are another matter.... should be subtle and not detract from the image. IMO it's simply more "professional" to sign your work, for many uses.



Above signature is sized for online, low resolution display.... for prints and larger sizes I always scale it down and make it more transparent and unobtrusive.

Signatures (and certainly watermarks) are not appropriate for some commercial and most editorial uses. Editorial use often offers a photo credit instead.

Both watermarks and signatures can be created and added to images the same way.

Some software you can simply type and add it to each image. Or, more complex graphics can be prepared in advance for the purpose, then added to image(s). With Photoshop, it's simply a new "layer" added to a specific image (either a type layer or a graphic that was prepared in advance). It's also possible to set up an "action" or even make a "stamp" in Photoshop, to add sigs and watermarks. With Lightroom, it's added during Export. LR typeset is rather limited, so graphics prepared in advance are usually better. LR Export can add them in batches, with multiple image files... LR also can store different sigs and watermarks to choose from, and can scale them up or down automatically for different size images and different orientations. FastStone Photo Resizer is a freeware that can add a sig or a watermark to images in batches, but cannot scale it.

My watermarks use gray colored type with white outline, so they'll work on any virtually any image. I also make both my signatures and watermarks semi-transparent. Graphics that are prepared in advance are saved as PNG files (not as JPEGs)... because that file type allows use of a transparent background. My signatures are typeset in Photoshop, usually use a color that appears in the image (simply done using the "eyedrop" tool to sample the colors) and also are semi-transparent.

Since about 1999 there has been no longer been any requirement to use the © copyright symbol or the year in either sigs or watermarks. Any unique mark offers the same degree of copyright protection. Unmarked images are not entirely unprotected from theft... just as marked images can't entirely prevent it. But, if an image is marked and the copyright has been registered, there is up to $30,000 per instance additional penalty for deliberate removal of a copyright protection such as a signature or watermark.

My images are taken and shared a lot on Facebook and elsewhere. I even encourage it. But for this reason I make my watermark sort of an advertisement.... It seems only fair that I get something out of the "piracy" of my images. (I also usually limit my images online to no more than 700 or 800 pixels on the longest side, in hope of preventing misuse of them).