For a long time as I began to use Pentax digital cameras, I made good use of the K100D's green tab on the mode selection wheel. It just seemed so much easier to let the camera decide on all the settings, and I was assured of getting a good picture most of the time.
As I moved up to a better camera (the K200D) I found that using the AV spot on the dial gave me either lots of depth of field or tight focus with softer backgrounds. This became my "most used" setting. I was content to shoot JPGs, letting the camera "develop" the picture. I had no software that could even handle RAW files, so I totally ignored working with them.
Things changed when I got my K-5. To me, this was a truly awesome camera, with capabilities way beyond what I was used to using. I also began to get some nicer glass than the kit lens, and wanted to take advantage of all of this. I was still pretty much using the semiautomatic modes - AV for depth of field, TV for action shots, and TAV where I could control both and let the camera determine ISO. I was using the camera commercially a bit - I'm a firearms writer, and began to carefully utilize the full manual mode and process RAW files using PhotoShop Elements. I found that being able to control all the elements of the "exposure triangle" gave me incredible options. Previously, giving the camera control of even one element often didn't give me what I wanted. Sometimes I wanted black, and camera would give me grey, so to speak. A dark object on a white background could only be handled with full manual control. My two secret weapons for absolute artistic control were a sturdy tripod and shooting in the RAW format.
For those of you not yet using RAW files - stop being afraid. Do it. The "DNG" suffix on the version I use means "Digital Negative" and it's as close to a universal RAW file as you can get. Put very simply, the RAW file is truly ALL the digital information you will need to get a really satisfactory picture. Using computer software, you can control many elements of the picture AFTER you've taken it. Give the photo more exposure, or less. Increase clarity if you wish. Bring up the color saturation. Bring out details in the overexposed areas, or increase the contrast. The possibilities are endless. Then convert the photo to a .JPG, and you'll find the extra work has been well worth it.
With the manual setting, you have complete control over the photo at your fingertips. Adjust the aperture - want it sharper or softer, it's your choice. Get that ISO setting where you want it. ISO 100 for "no noise" in the picture. Or in dim light, use a higher ISO to get shots you never could before, or use the increased noise for artistic effect. When you are using a tripod, unless your subject is moving, you can use whatever shutter speed you want to get the exposure exactly right. I now have the marvelous K-3 camera and some superb limited glass, so when I take product shots, I want things absolutely sharp and perfectly exposed. K-3 + great glass + RAW file + full manual control + tripod = pictures exactly the way you want them. I'm not willing, except for a quick "target of opportunity" shot, to let the camera make any decision for me. Call me a control freak, but that's what makes for great pictures. Here's one example. This is a photo of some Vietnam-era weaponry I took as computer wallpaper for some of my Vietnam veteran friends. I used the K-3, the great SMC-DA 35mm f/2.8 Macro Limited prime lens, a tripod, shot it in RAW, and controlled the aperture and shutter speed to my taste at ISO 100. By the way, when you shoot manual, the shake reduction feature should be off; you should be using a tripod. I generally take a "test" JPG shot, and if I like it, I save it in RAW format also. When you have the shot in memory and displayed on playback, you can press the AE-Lock button to also save it in RAW. At any rate, here's an example of full manual control. The exposure is right, it's sharp as a tack, the colors are realistic, and it has a nice balance of light and dark elements.
I find when taking pictures of things with a very large range of light and dark elements, manual control is essential. In the photo below, I wanted plenty of detail in the dark areas of the firearm itself, and I didn't care if the white background was completely blanked out. Again, using a tripod and exposing only for the subject gave me exactly what I wanted. I adjusted the aperture to give me the sharpest possible result, again using that great 35mm limited lens. and shooting in RAW. This revolver once belonged to my father.
You'll find that if you use either the K-5 series or the K-3 when you shoot full manual, the camera can still help you. When you look through the viewfinder, over in the lower right hand corner, the camera displays either "0" or + or - and a number. These are exposure values, and you can use these as a guide, moving up or down (I generally use the front control wheel to adjust exposure time) to get your exposure just the way you want it. I have my camera set for 1/3 exposure value steps, and I may bracket any particular shot with as many as five increments, selecting the best one in post-processing. While 1/2 exposure value steps will work, if you are a perfectionist, you will want to use 1/3 EV adjustments - often a slight variance in tonal value makes all the difference. Again, using RAW, you still have a lot of latitude through post-processing.
I guess the bottom line is this. If you want pictures as perfect as possible, go full manual. Use RAW. Use a tripod. Process the RAW file into exactly what you want. Letting the camera make any decision on exposure time, aperture or ISO is a distant second choice. Don't be afraid of that manual setting. Use it. Experiment. You'll be glad you did, and proud of the results you can achieve.
John
PENTAX : PENTAX Photo Gallery artist page