If you have been at either camera club or around photographic circles for a while you will realise that most serious shooters tend to sneer a little at those who have their camera permanently in the Auto Mode. It becomes a huge sneer when they see a top of the line DSLR (that they can’t afford) stuck in Auto mode.

Now given that camera manufacturers have spent many years and countess millions on perfecting auto mode you may be wondering “What is wrong with Auto”.

Put simply nothing most of the time. By my very unscientific reckoning around 80% of the time it will probably generate an ok image and some of the time it will generate a stunning image. The odds are also that given pixels are free, you will shoot a lot of images and therefore the odds of getting good ones increase dramatically.

The issue is that when the camera is in auto, it is in charge and its computer is making assessment that while you will get a perfectly exposed image, that image will be useless to you. So how does this happen?

Firstly you need to understand that the camera has absolutely no ideas what you are aiming it at. Its sole purpose is to produce an image that is perfectly exposed based on a theoretical representation of how the number of shadows (blacks), highlights (whites) and mid tones are expressed in the final image. You will have

seen these if you have looked at the histogram on the back of your camera.

According to the theory a perfectly exposed image will contain some information in the shadows, some in the highlights but the majority in between. This is like the top image above. In theory the other two graphs show incorrect exposure because they contain either two much highlight or too much shadow.

Now to achieve this result the camera has three things that it can play with, namely aperture (f-stop), shutter speed and ISO. Aperture is the size of the iris opening in the lens. Shutter speed is the length of time that the shutter is open, and ISO determines the sensitivity of the sensor to light.

The major issue with letting the camera chose the shutter speed and aperture is that you have no idea what combination it is going to come up. Each full s-stop lets in either twice or half the amount of light of the ones either side of it. Shutter speeds also acts in the same way, in that each value tends to be either half or double the time of the one before or after it.

To achieve a perfect exposure the camera will let in a fixed amount of light, but this is not a single combination but rather an option of several as shown in the table below.

Assuming that a combination produces a perfect exposure then the yellow highlighted cells represent those that will expose the sensor to exactly the same amount of light. A setting of F2.8 at 1/1000s will actually give exactly the same exposure as F22 at 1/15s because as you half the light coming in via the aperture you are doubling the length of time the shutter is open.

Full F-Stops

 

F1.0

F1.4

F2.0

F2.8

F4.0

F5.6

F8

F11

F16

F22

Shutter Speed

1/1000

                   

1/500

                   

1/250

                   

1/125

                   

1/60

                   

1/30

                   

1/15

                   

However an image at the F2.8 1/1000s will look completely different than that shot at F22 1/15s depending upon the subject. The former setting is much more suitable to capture a bird in flight but will have too little depth of field for a landscape, whereas the F22 1/15s will provide lots of details for the landscape but is unlikely to even show the bird as anything other than a blur.

If you want to have more control over the image then it is best to shoot in either aperture priority or shutter priority mode. In these you set one value and the camera controls the others.

However if you are not comfortable with moving completely to choosing your own settings then there is an alternative. Use the scene modes that many cameras have and select the one that closely resembles what you are shooting. While this is still a full auto mode you are actually telling the camera what is likely to be more important. For example the sports mode tells it that the action is likely to be moving and therefore it should do its first set of adjustments to aperture and ISO before dropping shutter speed.

Happy shooting.