1. Horizons should be level
Horizons aren't all straight. There are such things as hills (especially a gradual sloping hill that might give the impression the photographer didn't straighten the horizon in-camera) - unless of course you're looking at the ocean, but even then there can be big swells in the distance.
Painting tutorials say because there are no clouds there should be stark shadows. Well there might be clouds just out of the picture covering the sun. Or if it's a cloudy day, why is there a stream of light when there is no sun in the painting - well the sun might be just out of the picture, covered by moving clouds!
3. Sea colour has to match the sky (and this was in a critique of a painting of mine).
Well, I've seen green seas and blue skies. Take a look at that very painting + a comparison photo:
As someone once said when critiquing a digital painting - "there is a confusion about the direction of light source.....all highlights and shadows sort of indicates it's coming from the front left but the moon is in the center rear". Well, not every light has to be shown to have shadows fall a certain way. Let's leave at least something to the imagination.
5. Clouds have flat bottoms.
I stand on my verandah and I can see many clouds right now that do not have flat bottoms. There is lots of wispy stuff hanging from below in many different shapes and sizes.
6. Silver lining. The silver lining should be around the top contours of clouds.
I've seen clouds with the grey tones in the middle and the silver lining all the way round. It depends on where the sun is.
7. Clouds and their colour. The tones of clouds should recede as they go into the distance.
I've seen black clouds (with the full sun on them) in front of grey clouds, and grey clouds in front of white clouds as they go into the distance.
8. Clouds get smaller as they go into the distance.
This speaks for itself. No way!
Let me know in the comments if there are any painting myths you think should be challenged.