[Wilfrid1]

Here's a new one, with a digital camera I've been using for some time now.

All the images have a subtle cross-hatching in the background, as if re-touched by Matisse. WTF?

You can probably see it here, around the edges of the food, especially top right:

[peppyre]

What kind of camera are you using?

[Wilfrid1]

Sony Cybershot.

[peppyre]

It looks almost as though the focus isn't working. Or it could be a problem with the lens itself. Is there a scratch anywhere that you can see? Have any of your settings changed?

[Wilfrid1]

Wow, the lens was covered in crap. Grease, I suspect, given the circumstances in which it's used.

Cleaned it up, and will try it again.

[Behemoth]

Wow, the lens was covered in crap. Grease, I suspect, given the circumstances in which it's used.

Cleaned it up, and will try it again.

Probably from when you dunked it into that bowl of mussels.

[Stone]

Looks like a thumbprint on the lens. Do you have your thumb in front of it when you turn it on and the lens extends? This could solve two problems.

[Squeat Mungry]

What the heck is that? (Looks delicious, despite lens problems.)

[Stone]

Is it possible that the waiter put a napkin on it when it came out of the oven to sop up some of the grease? And it got pressed into the cheese?

[Wilfrid1]

That is a tartiflette.

It hadn't occurred to me, but I must be pointing the lens into clouds of miniscule particles of grease whenever I take a picture. Will remember to clean in future.

[Squeat Mungry]

That is a tartiflette.

Of course!

Mine never look that good, sadly.

[voyager]

Wow, the lens was covered in crap. Grease, I suspect, given the circumstances in which it's used.

Cleaned it up, and will try it again.

How did you do that?

Edited to add that the other night when I was trying to take a shot of a boiling pot of spaetzle, I realized the jeopardy I was putting my camera in. Backed off. Not a good idea.

[mcj]

Edited to add that the other night when I was trying to take a shot of a boiling pot of spaetzle, I realized the jeopardy I was putting my camera in. Backed off. Not a good idea.

And the jeopardy you were putting yourself in, as well.

Cleaned it up,
How did you do that?

A normal camera lens cleaner should do the trick, using the disposable papers, and several applications depending upon the severity of the contamination.
Use only lens cleaning tissues, since paper towels (and many facial tissues) are like sandpaper and tissues with lotion will leave their own grease behind. Toilet paper varies greatly, but if it doesn't scratch the delicate coatings on your lens, it'll leave a fine dusting of lint all over it.

If you're camera is an SLR or bigger, then get a UV filter (or something similar) to act as a guard for your lens. I'd rather sacrifice a $10-20 filter than a $200+ lens. Besides protecting the lens from direct contamination (not only from dust & grease, but from wind-blown sand and other harsh particulates), it'll also provide a degree of protection from some physical mishaps. This happened to one of my cameras several years ago when one leg of an old tripod gave out and sent the camera crashing to the floor. The full impact was absorbed by the filter. The lens & camera survived without a scratch or malfunction.
If your camera is a point-and-shoot, then you're pretty much out of luck. None that I know of allows the attachment of filters.

[Wilfrid1]

I used an eyeglass-cleaning cloth. The difference was visible to the naked eye; it just took all the crap off.

[Peter Creasey]

I used an eyeglass-cleaning cloth.

Wilfrid, Word is that much care should be taken as to what to use to clean camera lenses. The Nikon Lens Cleaning System seems to work well.