What are these artifacts I see in print?

Question

I printed one of my photos, and I found it has some artifacts, such as horizontal lines running through the sky. This is most apparent above the pylon (to the right of the train). There's a horizontal line running all the way from the right of the photo to the left, where it meets the top of the train:

The sky also seems to have a texture of its own, which it doesn't in the original:

This is on a laser printer (Ricoh Aficio MP C2051 / C2551), on ordinary office paper (GSM 75 or so). I printed at the best settings: highest DPI available (1200), toner saving off, image smoothing off, and gradation fine (rather than fast).

I found a question on photo.SE that said that office laser printers are not meant for printing photos, so I tried again, this time on an inkjet printer (HP Desktop Ink Advantage 3525), but it wasn't any better. This time, there are bright dots in the sky, and the sky stil has a texture :

Why am I seeing these lines, dots and texture? What do I have to do to better reproduce the original? Is it a more a limitation of the paper or the printers?

Answer 1

The problems you're seeing in the first is absolutely a limitation of the Laser printing process and are to be expected.

In Laser printing 'toner' (a powder) is applied to the paper using static electricity then heated to fuse that toner to the top of the paper. It is essentially stuck on top and not absorbed into the paper / coating as happens in an ink process.

As such you can use any paper that the printer can handle (or even transparency film) but you'll get the same result. You'll also notice that colours don't blend well and shades other than CMYK may look odd rather than printing as a single colour as they would from an inkjet.

The second image looks normal for an inkjet set to use 'normal' paper. The patterning and spacing is to allow ink droplets to spread. In 'photo' papers ink is deposited into the coating where the spread is limited (and more ink can be used in a given area.)