In the question Why do breathtaking views turn into “boring” photos, and how can I do better? I read:
The sun was directly behind you, just like it used to say on the old Kodak info sheets that came in every box of film. Worst. Light. Ever. (Most of the time, at least.)
How would I know if sun is behind me or not?
What is the problem if sun is behind me? What does that signify?
Where should the sun be when I take photos?
and where should I be if sun is behind me?
How would I know if sun is behind me or not?
You can feel the sun warming you up, you can also watch the shadows or turn around to check where the sun is.
What is the problem if sun is behind me?
There is no problem at all when the Sun is behind you; it just sets the scene up and you have to deal with it.
What does that signify?
As Jindra lacko already noted, sun behind you suppresses the shadows appearance (they are hidden behind the objects) and thus flattens the landscape.
On the other hand; when objects are close to you, the shadows points to the point somewhere in your picture, or close to it. One can see they are not parallel at all. In sunset, or when shooting from above, you can capture your own shadow or shadows of objects behind you.
Where should the sun be when I take photos?
Where should I be if sun is behind me?
It strongly depends what do you want to shoot and what do you want the picture to say. For breathtaking landscapes you want to have sun on your left or right (in pilot slang: 9 or 3); for sunset/sunrise you want to have the Sun in the picture. If you want to play with your own shadow(s) you can have the sun right behind you.
The time also strongly influences the mood of the picture, cold morning with loong shadows (and mists) is completely different from high noon and it is completely different from warm sunset.
There is no general way to say what is better and what is not.
When the sun is directly overhead and behind you there are no shadows. Such light turns a 3D landscape into 2D cardboard cutouts - it is the shadows what gives a landscape a feeling of depth.
Where the sun should be depends on the kind of photography you do. Photographers shooting color like the twilight hours (late evening and early morning). Shadows are long and colors warm. Photographers shooting B&W like sun hidden behind a light haze. Photographers shooting infrared like the harsh midday sun. They need a lot of illumination and IR and shadows don't mix.
Whatever is your style of landscape photography it pays to plan your lighting ahead (landscape photographers can't take the strobist approach and bring their lighting with them). There are a number of tools to help you with this, The Photographer's Ephemeris is what I use.
What is the problem if sun is behind me?
It is not about boring or not boring. It is about pleasant.
It is well known that diffuse light is better for portrait photography for example. Sunlight is the harshest light on this planet. Ugly shadows, shiny skin, flat light.
Sun behind the photographer means one thing. Direct sunlight on people's faces. They will close the eyes, and wrinkle the face to avoid being blind.
The only worst light you can make on the planet is a direct flash from the camera. The same applies to a building. It will look flat. Remember that light is as important as your subject.
A flat light constructs no mood, there is no romance, mystery, joy, sadness... Just a photo.
I was tempted fo find examples on google. But this is something you should find out yourself.
Go and take some photos to a person on a park, a plaza, and rotate arround; take photos with light behind you, on a side, sun in front of you, etc, and compare.
What does that signify?
If you are on a trip visiting a city in another country and you have limited time, you could potentially only take one photo regardless the sun position. "Se la vi"
But if you can plan your photo, having the sun behind you means that you are not paying attention to, not details, to light itself.
Means that you need to practice a lot more photography and not just be a spectator. You need to control your settings, your environment. Bring a cloth to diffuse the light, move around, use a fill light, wake up early, change location...
One exception is when the shadows including yours are one main subject, and they form a part of the story in the picture.
