It depends on what you want to show as the primary focal point. One thing you should do is make sure your horizon line is parallel to the top or bottom of the page - or that at least any vertical line is perpendicular - somehow, get the image so the viewer doesn't have to cock their head to feel like they are not falling off the edge of the frame. Yours are just a bit cock-eyed.
On all three, I would have had more foreground as the sky isn't really doing enough to generate a huge pictoral impact on the image.
That depends.
Really there is no 'correct' answer to your question. It is all about the vision you have of the finished picture as to how you will compose it and then process it. For some, a large expanse of sky will be 'right'. For others having more land or water and less sky, will make the better composition. It's a judgement that you have to make for every image.
One guideline to always understand is the 'Rule of Thirds'. If you have not already done so, please do study the CiC tutorial on composition, which you can access here. This will, I am sure, help you think about how you place the important elements in your picture.
Hello Marie Josee: The others have answered your question and it really is up to you to decide, but I will tell you what I think about these 3 in particular.
#1. The sky could be interesting in this one so perhaps leaving more sky would be the answer. However there is really not a subject here or anything to give the shot depth. If you try to work on the sky to bring out the colours and contrast of the clouds I think that would help. Before you do this though I would crop out the Blown highlights top left.
#2. Very nice! The sky really does not add much to this shot, so if it were mine I would just leave the top third as sky. Please please do level the horizon though. This is such a nice shot and the skewed horizon really ruins it.
I love what Yegor has done with the shot. If you think it is an improvement then you might want to ask him about it. I'm sure he would be happy to share. That way we can all learn.
#3. Another interesting view, from the horses perspective. Again, Please please level the horizon, and with this one I would just leave a bit of room above the horses ears and crop. The sky does not add to the shot so just keep the upper third.
Thanks for posting and asking for advice. As you analyze your finished shots, it will start to come naturally to you as to what you want the shot to look like and how you want to compose it.
Vancouver is such a beautiful area, I hope to see more
Wendy
Hey thanks all !!
When you all say to level the horizon, even if it's a slow slope in real, you level it by holding your camera crooked ? (english? ) So then, it's more 'pleasing ' to the eyes? Make sense now that I really look at it ! :0) thanks again!!
Maree-Josee, some cameras have a grid in the viewfinder that you can activate so as to get your horizons level. But if your camera doesn't have this function there are sometimes other clues in the viewfinder. For instance in your first image there are some trees reflected. Unless grown in very windy areas where there is a strong prevailing wind, trees will grow straight up, particularly conifers like yours. So simply align the trees and their reflections so they are truly vertical and there you are - nice, straight horizon.
Also, if using water as a focal part of the image, water always sits level, so that is another clue. However, I do like the two top images, regardless.
As far as the bottom one goes, I really like the concept of us seeing the horse's viewpoint, but feel that having him in sharper focus would make a stronger image. I see that you have shot with an aperture of f/5.6, which is close to the largest aperture of your lens. To get the horses head more in focus, you'd need to shoot with a smaller aperture, say f/16. Of course, you may have intended to have him (or her) out of focus, and if so, just ignore me!