It seems that the battle is almost as old as time but really "auto" settings have only been around on cameras since the late 1970's. The first auto camera on the market were designed to broaden the world of 35mm photography to the average consumer. Those consumers were snapping a lot of photos with low cost plastic cameras some of which were pre loaded with film. Some were 35MM, most though were 110MM or 126mm film cameras.
The clunky, heavy metal bodied 35mm cameras with interchangeable lenses, were reserved for those that were professional or serious amateurs. You really needed to have a grip on the manual operation of the camera to own one of these. The older versions were still using a rangefinder viewer rather than the more commonly known single lens reflex style of through the lens viewing we know today. In the 70”s the newest might have had a simple light meter which was mildly accurate by today’s standards and was nothing more than a needle that traveled up and down on the side of the view finder. Then along came the automatic setting on these new fangled 35mm cameras. People began buying up the new easier to use cameras and replacing their old 110 & 126 MM cameras for the larger format that "did everything for you".
What a lot of people found was that these cameras produced acceptable images to the tune of about 18 frames for every 24 exp. roll. The industry had made a huge leap forward and camera as well as film and print sales flourished peaking about 1999.
The now OLD school photographers were not so quick to jump on this NEW technology. Manual photography was still king among pros and that really rings true even today. So much more is auto today than when that first camera was introduced, yet the pros still shoot on manual. Why? well the answer is control.
A true pro understands that the camera is simply an instrument of the art and using it in the automatic mode is like a painter
putting a motor on a paint brush. It's effective but inaccurate at best. Photographers are artists at heart. Some will tell you that this is the reason they shoot on auto so they can concentrate on the art. The fact is a true artist wouldn't sacrifice their art because it's easier to shoot on auto. When a photographer shoots on automatic they are allowing the machine to control the exposures, in many cases causing inaccurate exposures or poor quality images at the most critical times. This can be frustrating when you demand specific results from your work and more importantly when your clients demand such results.
Don’t get me wrong, a few of the “auto” features have their place. Auto Focus for instance. The auto focus on most cameras today is many time faster than even the human eye. In addition with facial recognition and selective action focusing, this feature is a huge advantage to the photographer. There is a limit to these features though, and just as you wouldn’t use your auto focus in the dark ( try it you’ll find it doesn’t work very well) or with flat lit subjects, you shouldn’t shoot on auto exposure on your camera all the time either.
The only times we use an auto oriented setting on our cameras is when the conditions we are working under are changing so quickly that we can not physically keep up. Even then, we have a manual backup in the form of an assistant shooting in manual. The reason is that while the auto exposure settings on today’s cameras are better than those built in the 1970’s, they still regularly over or under expose your subjects killing your image. When your income depends on the right exposure, Manual settings are the only way to insure you are going to get what you came for.
So why does the automatic setting on your camera screw up your exposures sometimes? Well it all has to do with the light meter in your camera and your auto exposure mechanism is tied directly it. Big deal you say. You do the same thing in Manual, true, however, as an intelligent being that can think for yourself you can make minor adjustments to compensate for what the camera isn’t seeing.
All light meters attempt to make your world 18% gray. That is middle gray on the contrast scale of black and white and widely held as the “normal” within that scale. Again, so what?, Well, let’s say you are photographing a “high key” or white scene. 
The camera’s light meter will see all that white and force it to severely underexpose the scene based on the weighted average of the scene. In the Manual mode you would know that the scene is supposed to be white and while you might slightly under expose the scene, you wouldn’t correct it to middle gray like your camera will in the automatic mode.
The moral to the story is that when you purchase that fancy new digital camera, take it out of the P, S or A mode and put it in M for Manual. The first step to this is to learn what the functions of the camera are by reading through the owners manual. Then test yourself by taking a few shots. Hey it isn’t going to cost you anything but a few fractions of a second, your results will be instant and because pixels are cheap you can simply throw away the images that represent the learning curve. When you learn how to use your camera properly in the manual mode you will be much happier with your results as will those that you take the photos of. - Aloha
