How important is it...........
 

........do you think, to get your picture level, especially horizons?

I'd say it's very important - most of the time.

A sloping horizon will make the viewer feel uneasy about the picture. Sometimes that may be the feeling you're trying to instil in the viewer, often it is not.

Yes, it is important unless it is greatly exaggerated, e.g. a raceing car rounding a bend. Don't they call it "Dutch Tilt," or something like that?

What about when the horizon itself isn't quite level - what do you do then?

This shot is 'correct' as the field does slope but does it look 'right?'

OK, I can see there are many cases where its not so important and it can be a creative tool to tilt the camera. However I'm thinking particularly about landscapes, where there is often a horizon, or a shoreline, you know the sort of thing.

In such an instance, can something else be used as a reference, maybe the tree for example, is this the full frame btw?

Your shot is A OK as far as I am concerned, but it's all down to what you intend to convey to potential viewers.

As far as leveling Horizontal and Vertical elements, I tend to restrict this adjustment to pictures with architectral inclusions, and not do anything to Landscapes unless they are obviously out of sync.

Just leveled it and think I prefer the original, in fact yes the original has more character and interest.

The fact is though that Adey's image is effectively a false horizon, a blind summit even. These are often not level, and when put into the context of the surroundings,as with the tree, would be perfectly acceptable, wouldn't they?

However, and I seem to see this often, when a horizon as in 'The apparent intersection of the earth and sky as seen by an observer' is not level in a photograph, is this acceptable

Thanks for bringing this up, Stephen, as it's a topic that troubles me regularly.

First, I am terrible at getting horizons straight: as soon as I'm looking through the viewfinder, I seem to go into a different world and have no idea if I'm getting it straight or not. It's OK if I'm on the level myself (e.g., standing in a normal posture) but the moment I'm doing somehing weird (stooping and twisting sideways to look out from underneath a low branch or etc.) I can get a long, long way out of kilter and not realise it.

I hate the results, and so work on it consciously, among other things, glancing at the horizon first to decide how close to level it should be in the picture, then mentally measuring off the angular distance from the horizon to one of the focus-point marks on the left of the VF, then to the equivalent mark on the right. That works OK. But I'd still give my left unmentionable for a viewfinder with a built-in spirit level!

Second, yes, I do think it matters.

Third, the sloping landscape dilemma. Yup, getting it right can look wrong. I think the answer is that with a sloping horizon you need to think about it in advance and do something to make sure that, in the final result, the horizon is going to be obviously correct - i.e., find something in your composition to make people see something other than the sloping horizon: either provide a vertical reference (such as a tree or a building) somewhere fairly obvious in the picture, or else do something else so that the eye is drawn to the point of interest and the horizon is just accepted unconsciously. In fact, if you are not doing this second thing, then maybe your picture doesn't have enough interest in it to be a keeper anyway.