Sometimes it is hard to define the concept of "hobby" because, in general it is intended as pastime.
In the opposite, an hobby for many people is a way to express themselves, sometimes is the way to express what the ways of the life can not permit to express.
In this case, a hobby serves not to spend in a funny way our time but it is much much more.
I fully see myself in this description.
My hobbies, are in general not a way to spend my time, but a way to express myself considering that the life does not permit me to do it in other ways.

This is true, for example, for the music.
I like listening to music, but probably it is better to say "feel music", because I take an intimate stimulation from the sound, and I feel me richer after an audition. In fact the music has a chapter apart in this site.
Anyway one of my greatest dreams was and is, to play and compose music. 
Unluckily I did not have the occasion to learn to play an instrument in a serious way. I play guitar, but I had a self-made training, that does not authorize to declare me a guitar player!. (sigh!)
And despite my ability (many acclaimed guitarists, have a poor technique for the truth) I did not have also the occasion to form a my own band.

This is true also for photography.
In this case I was more lucky, because I worked for 16 years in a photographic studio.
So I am a "photographer" in the real way.
But all the things did not go in the way I was expecting.
The studio where I worked was very oriented to the scientific photography, I have learned a lot of things and I have used my scientific background everyday. I can say that in those years I was enjoyed, very rare to say about a job.
Anyway I am artistically oriented for my own photography, in particular I love to take pictures of portraits and figure (also set figure). I do not dislike also environmental photographs, especially to search interesting particulars.
So a significant part of my job was not oriented in the way I like. For this reason photography is both a job and a hobby, intended in the way I have described before.

I like also very much writing: in this case is a question of force majeure to define it as a "hobby".
Everyone knows how it is hard to publish, in particular here in Italy where it is really useful "to know someone that has influence". Of course I have made all the necessary checks before to affirm that my writings are suitable to be published.
It is frustrating to write for ourselves, but I do it the same because I need to express myself, and one day.... the future is unpredictable.

I do not make further examples, but if you have the patience to visit my site, you can verify how the thing I do are more than hobbies in general.

Thanks for the attention