Thanks to everyone who submitted questions in August! With no further adieu, here are September's "Tech Tips":

In the August "Tech Tips" section, a question was made concerning how to extend the battery life of an EOS-1Ds Mark II. I would offer the following observations:

1) Turn off the auto review of the LCD. Check the LCD manually only when necessary.

2) I would humbly disagree with the one-minute setting for the auto shut off. It takes a burst of energy to fire up the camera. That same amount of energy may actually power the camera for a long period of time after it is up and running. It is akin to gas usage in an automobile. Accelerating to 60 mph uses more gas than maintaining 60 mph. Depending on what one is shooting, one-minute Auto Off may waste a lot of energy while one is changing position. That is to say if it takes 1 minute and 10 seconds to establish the next position, will the 10 seconds of energy savings compensate for starting up the camera?

First of all, thanks for your comments and feedback! I can agree with your first suggestion, although the default two-second review is not very costly in terms of power consumption. I do not agree with your second comment. There are basically five levels of power consumption on an EOS digital SLR. Here they are, from minimum to maximum:

Level 1. The camera consumes the least amount of power when the main switch is turned off. A minuscule drain is used in this condition if a memory card is inserted or a lens is changed, but not enough to affect battery life significantly.

Level 2. The next level of power consumption occurs when the main switch is on but the camera is asleep, i.e., after the Auto Power Off function has operated. The only significant difference between this condition and level #1 is that the shutter button remains active so that the camera can be "awakened" ASAP by a half-press.

Level 3. The next level of power consumption occurs when the main switch is on and the external LCD data panel is active, but the shutter button is not being pressed. This is not a heavy degree of consumption, but it is considerably more than Level 1 or Level 2.

Level 4. This level occurs when the shutter button is pressed halfway. In this condition, the metering system is activated, the LCD data panels and viewfinder data display are illuminated, and the focus motor may or may not be driven. If it is driven, the focusing point may be illuminated in the viewfinder and the beeper may sound to confirm focus completion, depending on the lens in use and user-selected camera settings. Level 4 is significantly higher in power consumption than Level 3 but it only lasts six seconds (or less, if you use Personal Function 23) after finger pressure is removed from the shutter button. At default camera settings, Level 4 is also activated for two seconds after each exposure.

Level 5. This level occurs when the shutter button is pressed all the way down, initiating a sequence that includes mirror release, diaphragm stop-down, shutter release, diaphragm reopening, and re-cocking of the shutter and mirror. When the camera is set for continuous shooting and AI Servo, you can add focus drive between shots to this sequence. This is the maximum power consumption level for the camera.

Waking the camera up from sleep by tapping the shutter button after the Auto Power Off function has operated essentially takes the camera from Level 2 to Level 3, which is not a big jump in terms of consumption. However, leaving the camera in Level 3 by extending the time limit of the Auto Power Off function will almost always consume more power than letting it go to sleep. Of course, one of the best ways to cut down on battery life is by keeping the camera at Level 4 without taking pictures, which is what I was trying to communicate in last month's "Tech Tips" article.

If an EOS Digital SLR is set for the center focus point, will the focus track if the subject (or specifically, the exact part of the subject chosen to focus initially) moves in the frame (across other focus points) during a five-shot sequence?

The only way that can happen with any EOS digital SLR is if the camera is set for the combination of AI Servo and automatic focusing point selection, i.e., letting the camera pick the focusing point for you.

Manually selecting an individual focusing point speeds up AF detection, because the camera doesn't have to decide which focusing point to use, but it puts the responsibility back on you for keeping the focusing point on the subject at all times during single frame photography or continuous bursts. The 1D-class cameras provide an additional option via Custom Function 17, with which you can expand the active area around a manually selected focusing point by a radius of one or two points. This is made possible by the design of the 45-point AF sensor on those cameras. However, the 20D is limited to the nine focusing points you can see in the viewfinder, so if you manually select one of them, you have to make sure that the selected point stays on the subject.

This is usually not a major problem during motorsports photography, because the car is often large enough in the frame that you should be able to track it with a single manually selected focusing point, especially if you're panning to keep the car centered during the burst, as you did in the sample image you sent. Most of the pros I know who shoot cars try to fill the frame.

Bottom line, it's certainly possible to use automatic focusing point selection for motorsports photography, but if you're asking for my opinion, I would recommend using a manually selected focusing point instead. The 20D will do a decent job on race cars, but the 1D Mark II or newly announced 1D Mark II N is noticeably better for this type of photography.

Thanks very much for replying. I know how to handle the panning type of shot. At Le Mans, I believe I just pre-focused manually and waited to shoot, but in the kart photo, taken later, I tried to select the focus point manually with AI Servo. I just didn't know if that was the correct procedure or if there was a better way to do it.

Prefocusing the lens and waiting until the subject enters the frame, then pressing the shutter button down for several frames in a burst is a good way to use a manual focus SLR system, but it's a recipe for disaster with most current AF SLRs because the AF system doesn't get enough "advance warning" to start tracking the subject. All too often, the result is a set of several perfectly exposed but poorly focused blurry shots. Automatic focusing point selection will not solve this problem.

If you want the AF system to help, you need to start tracking the subject for at least a second or two while keeping the shutter button pressed halfway before you start taking pictures. If you intend to "wait and pounce" on the shutter button when the car gets to the area you want to photograph, you might as well shut off the AF altogether and operate the camera as a manual focus system.

Last week on a job I was using a Canon 550EX speedlight on my EOS 1D MkII. After the first few photos were taken, I noticed on the LCD panel that the camera was simultaneously flashing 1/250 shutter speed at f/22. Some of the photos were completely blown out. I put the camera away and went to my EOS 20D. Next day I tried it again and did not have a problem and I cannot get it to do the same thing again. What did I do wrong?

What you describe (1/250 and f/22 blinking on the camera) is normal when you try to combine Manual flash exposure mode on the 550EX with Shutter-priority or Program mode on an EOS camera. It's the camera's way of telling you that you've selected an incompatible combination of settings. If you intentionally want Manual flash with your EX Speedlite, the camera should be set for either Aperture-Priority or Manual mode. When Manual flash is combined with Aperture-Priority, the camera will set a shutter speed based on the level of available light, and such shutter speeds can be very slow in low-light and/or small aperture/low ISO situations. It's great for fill-flash, but fill-flash is not optimum in many situations, especially in low light with moving subjects or a hand-held camera. If you want more control, I would suggest combining Manual flash with Manual exposure mode on the camera. This will allow you to set the shutter speed and aperture yourself while maintaining full manual control of flash exposure.

Thanks for reading "Tech Tips"! That's it for now. See you in October!

You are invited to submit questions about photo equipment, imaging technology, or photo industry trends that may have a bearing on your work or interests. I cannot promise to answer everything, but I pledge to do my best to address the issues that concern you. (Please use the e-mail link provided at the end of this article.)