Camera Techniques - Manual Focus
I love that my camera can focus automatically. Modern DSLR cameras have so many auto focus functions designed to do many things that cameras were not capable of doing in the past, such as track and maintain focus on fast moving subjects or focus on very precise points most anywhere within the frame, as seen above. While these functions have made photography easier in many ways, the camera’s ability to automatically focus is limited and the photographer must know how to work around those limitations. This sometimes means turning off the automatic focus and resorting to manual focus. And there are several reasons for making this necessary.
Before I give you those reasons, let’s first be clear on what is meant by auto focus vs manual focus. Most cameras today have several focus modes available; these are continuous, one shot, automatic auto focus (the camera decides to use continuous or one shot) and manual. In the photo above, the right red circle indicates where these controls are located on my camera. For all intents and purposes, the first three functions are automatic in that the camera focuses as soon as the shutter release button is depressed halfway. Manual, on the other hand removes automatic focus functions all together. Therefore, in order to focus, the photographer must manually rotate the lens. Just like in the old days! The image above also illustrates where the auto and manual focus button is on the lens. For auto focus to work, the camera and lens must communicate with each other and each must be set to auto focus.
Why would a photographer choose to use manual focus when the auto focus capabilities of cameras are powerful and getting better all the time? Depending on the camera, the lens and the scene you want to shoot, auto focus may not work well or at all. Despite the most modern technology of auto focus, sometimes it just does not work. Here are six situations where automatic focus did not work and I had to use manual.
Focus point too small. The image above is a perfect example. As with any bird photograph I take, I prefer to set my focus point on the bird’s eye. In this image, the bird is almost camouflaged by the grasses and when I tried to auto focus on the eye, the camera failed. It could not figure out where to focus, the eye was only a speck among all the visual noise! Because the bird was stationary, I was able to take the time to switch to manual focus and then rotate the telephoto lens until the bird’s eye appeared sharp in the viewfinder.
Focus point out of autofocus range. This generally happens when I have the camera on the tripod for a landscape image. My camera has a finite number of auto focus points, illustrated at the very top of this page. When I have a foreground object that falls out of the range of those points, such as the mangrove tree in the image below, I switch over to manual focus and adjust accordingly.
Dark scenes. A good example is night sky photography. For the image below shot in the Big Cypress National Preserve, auto focus worked well enough for the lit mangrove tree (I used a flashlight to light it up) and get it in focus and sharp, but to get the Milky Way in focus, I had to find a star in the dark sky to focus on. As with the bird image above, the point of interest was too small for auto focus to detect, so I switched to manual.
Hazy or foggy scenes. The foggy scene below is an example where contrast between dark and light areas is low. Auto focus relies on contrast to detect an object to focus on, so without adequate distinction between objects or between an object and its background, auto focus will struggle.
Multiple focus points for stacking. This is a more advanced reason for using manual, but with Photoshop or similar software, combining several images with differing focus points can be quite easy. This method is called Focus Stacking. For the scene below shot off the Tamiami Trail in south Florida, I used a telephoto lens and a focal length of 120 mm. The greater the focal length, the lower the depth of field which means less sharpness throughout. I wanted to maintain sharpness from foreground to background, so I took at least three shots with varying focus points. With camera mounted on the tripod, I first manually focused on the small grasses in the lowest portion of the frame and took a shot. Then, I gently rotated the lens slightly to move the focus area further up into the scene and took another shot. I continued this with a few more shots until I had captured the entire scene in focus.
Auto focus malfunction. I had this happen more than once! It was not the camera’s fault, rather the lens’s auto focus stopped working. Remember, the camera and lens must work together for auto focus to work and when one of them malfunctions, auto focus will not work. That’s where manual focus comes in!
One last thought, camera’s with Live View function also provide the means to zoom in on an image before taking the shot. While looking through the viewfinder or at the LCD panel, zooming in allows the photographer to evaluate and manually fine tune the sharpness of an object. This is a very powerful tool!
Now you see that a photographer must sometimes take matters into her own hands, that is if she wants to get the shot with correct focus. If you have ever been frustrated because the camera struggled to focus, than it is time for you to get comfortable with manual focus. I recommend you practice and get use to the feel of the lens rotation. While rotating the lens, look through the viewfinder to observe how the focus changes. Once you start using it, there is something oddly rewarding about manual focus. Now get out there and focus on taking control of your camera!
If you are interested in learning more about camera or editing techniques, I offer individualized instructions in the field as well as in Photoshop. Please visit my website to learn more about these workshops or contact me at email@example.com with any questions you may have.