What am I talking About?
I have been and always will be amazed at the accuracy of the Continuous Auto-Focus System built into many of the Nikon Camera Systems. However, there are settings in your camera that can greatly improve your results. Most photographers know the difference between “Single Point Focus” and “Continuous Focus”. If you are shooting stationary subjects such a portraits using the Single Point System is very adequate. But, If you are shooting moving targets such as sports, wildlife and such you need to switch your camera over to the Continuous Focus System. The Continuous Focus System allows the camera to track a moving subject and continually re-focus as the target moves.
If you already know about settings for continuous Auto Focus please skip to the bottom to the crux of what I have to say….
What are the Settings?:
To turn on Continuous Focus on a Late Model Nikon System such as the D4 and D800 /e you need to rotate the focus mode selector to “AF” then press in the AF Mode Button while looking through the view finder rotate the rear Main Command dial and select AF-C for continuous focus. Next you need to rotate the front Sub Command Dial to select the Auto Focus Area Mode. There are six options as follows:
Single Point – Camera tracks a single point and focus will be determined by that one point. This is only recommended for subjects that are moving very slow and not erratic.
9 Point Dynamic Area – Choose when subjects are moving predictably.
21 Point Dynamic Area – Choose when subjects are moving unpredictably.
51 Point Dynamic Area – Use when subjects are moving very erratically and moving in and out of frame.
3D Tracking – Utilize when subjects are moving erratically from side to side such as tennis players and cyclist. Focus will track the subject as it moves.
Auto-Area AF – This setting focuses on the closest moving subject in the frame. Focus will be determined by the nearest object.
Do NOT underestimate this setting. For example, if you are shooting a bird in flight, the auto focus system, if using 9 point up to 51 point or 3D Tracking, will select the point of the subject with the greatest contrast, So let’s say you initially focused on the eye of the bird, that does not mean it will not change to the wingtip if the contrast is greater if the wingtip is within the “points” in the viewfinder. Sometimes, limiting your focus point to 9 point or single point can give you greater focus accuracy with a moving target or even a stationary target. CONTRAST is what the auto focus system uses to locate a focus point. For moving subjects I typically use 9 point and continuous auto focus.
You should also consider your Aperture setting as “Depth of Field” will also influence what is in focus. If you want the bird in focus from wing tip to wing tip, you need to consider the focus plane of how depth of filed will impact whats in focus. If the bird is coming at you head on, perpendicular to your lens then depth of field is suitable at a more open aperture, but if the bird is sideways you will need greater depth of filed to get the bird in focus from wing tip to wing tip. It might take as much as f/16 which in turn may require you to use a higher ISO. Greater depth of field also increases your “keepers” as, if the auto focus system selects a different are of contrast, your image may still be sharp due to adequate depth of field. All of this is subjective to your goal as an artist.
Once you select which AF-Area Mode you intend to use, make your selection. To activate auto focus while shooting just press the shutter button halfway down or press the AF-On button depending on your setting for same.(See AF Activation in the Custom Settings Menu)
Focus Tracking while Locked on a Subject:
This setting is extremely important when shooting a subject or subjects where objects may come in-between you and you subject for short burst of time that could interrupt the AF system. You can change the setting to tell the AF system to ignore objects passing through the frame or short distance changes. See [a3:Focus Tracking with Lock-On] to determine which setting is optimal. For me, unless I am shooting sports, I turn this off as the longer time you set, the greater a delay in re-focusing on a moving target. To practice these settings to see what they do, just try each setting and with continuous focus on aim your camera at some grass on ground in front of you and then slowly move your camera out across the grass to focus at greater distances. You will notice the shorter the setting, the faster refocusing occurs.
What is it that is so Important?!!! The Crux!
AF-C Priority Selection (Under Custom Settings aka the Pencil in the Nikon Menu System)
In the beginning I was greatly disappointed by the number of “keepers” that I obtained. I found the key to increasing that ratio in my Nikon settings! This may be one of the most important settings for Continuous Auto Focus. AF-C Priority Selection allows the photographer to choose when the camera actually relates focus to the instance of capture or shutter release. There are 4 options as follows:
Release – Photos are taken whenever the shutter release button is pressed. So with this option the shutter will trigger regardless if the subject is in focus. With “Predictive Focus Tracking”, this option will achieve the most number of keepers.
Focus+Release – Under this option photos can be taken if not in focus. Priority to focus is given to the first image in each series but after that the priority is given to the frame rate, not focus. In other words priority to the high or low speed continuous shoot speed.
Release+Focus – Again, photos can be taken even if not in focus but in continuous mode the frame rate will actually slow down in order to give improved focus if the subject is in low or dark contrast. (Remember that the focus system uses contrast in the focus area to focus)
Focus – Photos can only be taken when the focus indicator is displayed.
I can tell you that I can increase the number of “keepers” when in Release mode although, I sometimes achieve fair results in Release+Focus mode. Remember, that in AF continuous mode the camera never stops focusing until the shutter is released. Predictive focus tracking will predict the next focus point. You should play with these settings to optimize your keepers. Low contrast subjects such as a solid color subject will be very difficult to capture in focus. Try and target a part of the subject that has contrast and use a higher aperture setting to increase your depth of field. If you are shooting wide open or close to wide open you will need to find some contrast in the in focus critical area. Another rule you can apply is to slow down the frame rate below 10fps or less.
Another option that I have found to be even more accurate is to select “Release” or “Release+Focus” mode for your AF-C Priority Selection and using a two finger technique. When shooting you will need to use the “AF ON” button on the back of the camera to focus and use the shutter release button to release the shutter. Make sure your AF ON button(s) is set in the menu system under “controls” or “Auto focus” to “Focus”. So, once again, its a two finger operation. Use your thumb and press “AF ON” button and your index finger to press the shutter button. Keep the AF ON button pressed the entire time while you are shooting to keep your subject in focus while simultaneously releasing the shutter. I highly recommend this setup.
Aperture is critical as these systems are NOT perfect so wide open Aperture shots may be more difficult especially if you are close to your subject. The further away will give you more depth of field or alternatively close down your aperture to give you more depth of field.
All of these settings work together to optimize your AF system capture and are extremely important so go into your cameras menu system and review your settings before your next action shots. You should end up with better images and more keepers! Most cameras allow you to create a “Profile” with certain settings that allow you to change over quickly without having to go through the menu system. So, create a profile and you will always have these settings.
Most DSLR digital cameras have similar options within their menu system. If you use another brand such as Canon or Pentex just go to the Manual and research the continuous auto focus settings.
Copyright Robert Shreve Photography
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