In infrared imaging, precise focus means a lot more than just getting a clear image. It can mean the difference between catching or overlooking a problem. If your image is out of focus, your temperature measurement cannot be trusted. Everything might look just fine, when in fact you’re on a path to some serious trouble. It’s very important to capture in-focus thermal images, as you cannot adjust focus after the fact, while you’re editing a thermal image.
When you’re evaluating an infrared camera, pay special attention to the type of focus it has and make sure it matches your applications and experience level. Here are the most common focus system choices:
- Fixed focus: Also called point and shoot, fixed-focus cameras tend to be relatively low resolution and are used for targets from about a 1.5 feet and further. You can use this type of focus for frontline troubleshooting applications like checking for air duct leakage, overheated bearings, or identifying loose or corroded connections.
- Manual focus: With a manual focus camera, you can precisely focus on targets as close as 6” and still capture sharp images and more accurate results from further away. If you’re a more experienced thermographer you may prefer to have a manual option so you can more precisely focus each image, even if it takes more time than letting auto focus handle it.
- Auto focus: Choosing a camera with auto focus can definitely save you time but, depending on the type of auto focus, you may still have to make manual adjustments. There are often multiple targets within a field of view and some auto focus systems may choose a different target than what you had in mind. If that happens you can simply switch to manual focus and fine tune the focus to capture the target you’re after.
- Laser assisted auto focus: Adding a laser distance meter to the auto focus system gives you the power to zero in on the target you’re interested in. The distance meter calculates the actual distance to the target and displays it on the screen so the focus engine can precisely adjust the focus for the most precise image.
- Multifocal image capture: Some cameras capture and store multiple images of your target from varying focal distances and automatically combines them into one sharp image using special algorithms. This way you get in-focus targets both near and far in one image.