If you take enough pictures at social events, you are bound to have shot a picture with your subjects in front of a light source (window, lamp etc.). By default, modern cameras, in this case your iPhone, will look at the data they are receiving and try to determine the correct exposure levels. However, if the subjects you’re shooting are standing in front of a window, the camera will more than likely set its level’s to expose to the outside sunlight.
The net effect of this is a picture that is correctly exposed for outdoor light, and significantly underexposed for the indoor subjects; think of pictures you’ve seen where the people are too dark and hard to make out, while their background is easily visible. Luckily, there is an easy photography technique to fix this called a “Blow Out”, and your iPhone actually can do this with its built in camera.
A Blow Out is method used that underexposes an image, literally making background light sources (like a bright window) so overexposed that they turn white or blowing them out, while at the same time making the subjects of your shot exposed correctly.
On a stand-alone digital camera, all you have to do is turn down the exposure to match your subjects light level, instead of the auto-setting’s matching the background. However, on an iPhone, there is a no way to directly change the exposure. You can “lock” an exposure as an alternative. To do this, while using the camera app, tap and hold your finger on the part of the image you want the exposure levels to be locked to.
For an example, I placed my water bottle, my subject, in front of my computer screen, a light source.
The first image is one that my iPhone took using the automatic settings. You will notice that the image is exposed to the light levels of my computer screen. At the same time, the water bottle in the foreground is underexposed, making it much darker and harder to see.
For the second image, I tapped and held my finger on my water bottle. This caused the iPhone to lock its exposure and focus to the foreground of the image, ignoring the data it received from the background. A little AE/AF lock text box will appear on the screen. You can see in that image that my water bottle is correctly exposed, while the computer screen in the background is blown out.
This is a real easy fix that makes your picture taking skills much better in environments where you can’t always position your subject in ideal places. Additionally, you can sound really photo savvy when explaining to people you are using a special technique to improve the picture.