I've heard that one of the tricks designers use for a more effective result is placing an object in the visual center.
Where is the visual center in an image, why is it important, and how could it be used in photography?
The visual center of any page is just slightly above and to the right of the actual (mathematical) center. This tends to be the natural placement of visual focus, and is also sometimes referred to as museum height.
The question is why? Is it to do with Western culture where we read top to bottom and left to right? It is said that when a curtain opens in a play, the audience will usually scan the set from their left to right. Would this be true in Eastern cultures?
Or is it to do with left or right-brain dominance?
The Psychology of this is discussed in the boook Art and Visual Perception where the claims are made that
Weight in the upper part of perceived space counts more than in the lower part
Any pictorial object looks heavier at the right side of the picture
If we scan left to right, then having something "centered" slightly to the right would allow the eye to scan from the left, then settle on that centred object.
Whereas the Rule Of Thirds, placing something off-centre, provides a more dynamic image, placing a subject at the visual center should be the opposite, very settling and comforting to the eye.
So if you want a calming image where your subject is centred, it seems that placing it slightly above and to the right will be more comforting to the eye.
This web site has information on visual center and other design situations:
The visual center of an image has to do with a concept called "The rule of thirds". This is when you divide your picture in thirds. Two evenly spaced horizontal lines, and two vertical lines (Most newer model cameras have these lines on the image when you view it through the LCD.). When taking a picture, align the focus of your image on one of these lines. Also, the horizon should be on one of the hrizontal third lines. Other main parts of your image should also be at a third line. Below are a few examples.
In this image, the focus is the little man, the horizon is the horizon, and the sun is a secondary focus.
In this image, the focus is the base,and the "horizon" is the bottom of the wall.