Vanoord,
No, you can scan an out of copyright book, photo or anything at all, and still have it remain out of copyright if you wish. You just need to declare your new work to be in the public domain. It is your right to do that with any copy you make of a copyright-expired work, if you wish.
But that is actually a bad idea, because others can abuse it. It is preferable to retain the copyright yourself, which will go to your successors for 70 years after your death, but licence it for use under a permissive licence, which may allow the public to make copies, but, for example, not allow commercial exploitation without your permission.
We have a bad situation where old-maps.co.uk has applied their new copyright on OS maps for which copyright (50 years as someone else said above) has long expired, and it is a nuisance to some users of this forum, because for most of the interesting maps, originals of which are copyright-free, they charge you an excessive fee for a decent reproduction of a small area. I have a few old maps and I intend, once I solve the scanning problem, that they will be available under a permissive licence. I would recommend everyone here to do the same as far as possible. That way, useful information will always remain free and available. If sufficient people find sufficient genuine old maps, and sufficient web hosting, nasties like old-maps will disappear.
A suitable permissive licence might be one of the Creative Commons variants, but it would be possible to use GPL, but the GNU Free Document Licence
http://www.gnu.org/licenses/fdl.html would be very good for documents including maps. The "artistic" licence is actually not very good. A licence which expressly perpetuates the freedom (for 70 years, when someone else can repeat the cycle) is best, as it will ensure that stuff which we need stays available.
Sadly a lot of copyrighted material which is interesting is long out of print, and there is a real risk that all available copies will disappear before the copyright expires. We can't do anything about that under present law. My personal view is that it should be free as soon as the publisher loses interest, i.e. when you can no longer order a copy from them, but I don't see that happening any time soon.
It almost goes without saying that we can't condone any illegal copying of things which are still copyrighted. That can cause serious legal problems!
Alan