Part 1- Selecting the Correct Focus Mode
Who does not love beautiful and well focused images? Although everyone will likely answer yes, many photographers do you understand the complexities associated with the creation of a sharp photograph. Sadly, without a good understanding of focusing, the chances of creating a sharp image are slim. No amount of beautiful light or amazing subjects can salvage a blurry image. Focusing is so important that I have decided to dedicate my next six “Technical Tuesday” blog posts to all aspects of focusing.
So let’s dive into Part 1 of the “Photography Guide to Sharper Photos Series by looking at two images of ducks, one is sharp and the other is not.
Redhead Duck in Focus.
Mallard with eyes and head out of focus
As you can see from comparing the above two images, the Mallard is out of focus and headed for the trash can. Nothing can save this pretty boy.
Step One- Decide Between Manual Focus and Autofocus Based On The Following:
Consider Photographing In Manual Under These Conditions:
- When there is very little light on a subject.
- When a subject is backlit or is in an area of extreme contrast
- When there is very little contrast in an image
- When there are particles in the air such as fog, steam, or smoke that may interfere with an area of focus. See Focusing under Misty Conditions for indepth guidance for these conditions.
Examples of Manual Focus Conditions
- In this lighthouse scene below there is fog and very little contrast in several areas of the image. Not only does fog and mist wreck havoc on many camera’s autofocus capabilities but different cameras vary greatly in their capabilities to handle these conditions.
2. In the next image the sunset over the Blue Ridge Mountains was backlit. Also, several areas within the mountains had little light to no contrast. Therefore, the likelihood of autofocus failure in these conditions was high. Since I did not want to risk an out of focus sunset, I turned autofocus off and manually focused on an edge of a mountain ridge.
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As mentioned above, autofocus capabilities are constantly improving with newer and better sensors but there are still many differences in autofocus abilities between the various cameras. To determine how your specific camera and lens combinations handle the above conditions, I highly recommend taking test shots with autofocus on in a variety of challenging conditions. Reviewing the results will give you a good idea of when you should change to manual focus. I would rather find out before hand what my cameras can do then lose a great image!
It is important to remember that autofocus is turned on and off on the lens, not in the camera.
Step 2- When in Autofocus, Choose the Correct Mode.
Photographing subjects in the correct autofocus mode in vitally important to ensure sharp images. Although in this post I cover only Canon and Nikon autofocus modes, the basic mode functions remain the same across most brands.
The focus modes are selected by a dial in the camera. To learn where to select the drive mode on your specific camera, please refer to your specific camera model’s manual.
One Shot (Canon)/AFS (Nikon)
In this mode, the camera achieves focus when the shutter is depressed halfway. The focus will not change when the shutter is completely depressed, even if your subject moves. This mode is best used for stationary subjects like the following two examples.
If either of these subjects moves, I need to get out of there fast!
AI Servo/AFC
In this mode the camera begins the process of focusing on a selected area when the shutter is depressed halfway but continues to track a subject and continually adjust focus until the shutter is completely depressed. This mode is best used for subjects that are in motions such as birds, runners, and even flowers that may move in the wind.
Here are a few examples of when to use AI Servo/AFC
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AI Focus/AFA
In this last mode the camera achieves focus when the shutter is halfway depressed and will only track and refocus if the subject moves. In other words, the camera switches between the two above modes as needed. I am not a fan of this mode and never use it.
Despite testing the AI Focus/AFA mode with numerous cameras, I have never found this mode to produce consistent results. I use Canon, so I can’t speak for how well this mode works with Nikon cameras.
Summary
- Stationary subjects– Select One Shot/AFS
- Moving subjects-Select AI Servo/AFC
- Subjects that are in the following conditions– Turn off Autofocus and use Manual Focus
Backlit
Extreme Contrast
Little Contrast
Fog, Mist, or Smoky Conditions
Very Low Light
If you wonder why I don’t just recommend always photographing in AI Servo/AFC mode, there are a few conditions that can cause the mode to lose focus on a stationary subject. For example, in the above picture of Skull Rock from Joshua Tree, what would have happened if wind has caused the foreground branches to move in AI Servo mode? The camera could possibly change focus from the rocks to the branches, provided the branches had been in the focal area. So what is the focal area? Well check back in for Part 2 of the Photography Guide to Sharper Photos Series – “Selecting Focus Points.”
Thank you for visiting my site and I hope you found this post helpful.