Is there a list somewhere that mentions whether a Canon IS lens has tripod-sensing capabilities? It is my understanding that a lens without that ability would suffer damage from being mounted on a tripod with IS engaged. I own several different IS lenses and plan to buy more, so it would be nice to have this information at hand.

First things first: It is impossible to damage any Canon Image Stabilizer lens simply by using it on a tripod. That's essentially a non-issue. The only thing you need to avoid is removing the lens from the camera while the IS mechanism is actually running. It's rare for this to occur, because the IS mechanism typically shuts down within a second or so after you remove your finger from the shutter release. You'd have to be pretty quick to remove the lens while the IS mechanism is running unless you were half-pressing the shutter button intentionally during removal. If you want to preclude the possibility altogether, just shut off the camera or the IS mode switch on the lens before removing it.

Next, virtually all Canon Image Stabilizer lenses except the now-discontinued original 1995 EF75-300mm IS model have some degree of tripod-sensing. In most cases, what that means is that when the lens senses that it's completely steady, it effectively prevents the IS mechanism from moving. With typical IS lenses like the EF70-200mm f/4L IS USM or EF24-105mm f/4L IS USM, that’s about as far as it goes. In other words, the IS mechanism doesn’t move when the lens is mounted on a tripod, but by the same token, it doesn’t compensate for other sources of vibration such as the slap of the camera’s reflex mirror prior to the beginning of an exposure. As I mentioned in an earlier edition of Tech Tips, I recommend shutting off the IS mechanism when using these lenses on a tripod in order to save battery power, and also to lock and center the IS mechanism.

However, there is a group of high-end Canon lenses that actually does compensate for mirror slap during tripod use. This list currently includes the EF200mm f/2L IS USM, EF300mm f/2.8L IS USM, EF400mm f/2.8L IS USM, EF400mm f/4 DO IS USM, EF500mm f/4L IS USM, EF600mm f/4L IS USM, and EF800mm f/5.6L IS USM. With these lenses, it's usually a good idea to leave IS on for long exposures on a tripod unless you plan on locking the mirror prior to exposure.

Last week, I purchased the WFT-E2A wireless transmitter for my EOS-1D Mark III camera. It works very well as a wireless transmitter (FTP, PTP and HTTP). However, whenever I try to connect my external hard drive to it, the WFT-E2A refuses to connect to the hard drive. I keep getting the message "Incompatible USB device" after the camera and the drive attempt to "talk" to each other (both transmitter and drive LED lights blink away) for a few seconds. The external device I'm trying to connect is the Western Digital 320GB Passport Essential. I know there's nothing wrong with the hard drive because it works fine with my Apple computers and Dell laptop. I e-mailed Canon Tech Support about this problem yesterday but I'm not sure their diagnosis of the problem is correct. They said that the transmitter may not be providing enough power to the external drive. The reason I question this is because the drive spins up just fine and the drive LED light blinks while the camera is trying to connect with the drive. It is only after the connection attempt fails that the drive turns off again. According to the WFT-E2A manual, I should be able to connect a drive up to 1 TB in size to the transmitter. I was wondering, do you have any idea why the WFT-E2A is not connecting to the hard drive? I've tried partitioning and formatting the drive a smaller 30 GB drive (not that this would help if the problem were truly power related) thinking that maybe 320GB is too large, but that was to no avail. Whatever assistance you can provide to help me resolve this problem and get my hard drive talking to the WFT-E2A will be greatly appreciated.

Your external HDD may require its own independent power source to work properly with the WFT-E2A. This would definitely be true if the disc diameter is larger than 1.8 inches.

I've been a very happy 40D and (among other lenses) EF-S55-250 IS lens owner for quite some time and have gotten some great pics. Canon's engineers did a nice balancing job with this lens and reasonable tradeoffs between IQ, weight, size, cost, etc. But one thing that's occasionally a bit annoying about the 55-250 lens is that if I'm shooting distant animals/sports/etc. and it loses focus, it takes a long time to reacquire as it ratchets focus all the way in (minimum focus distance on this lens is great, BTW), and then back out. I figured that was the price I paid for non-L glass and non-USM. But I recently tried a 100-400L lens and saw the similar behavior. However, this lens has a Focus Limiter which limits how close focus will be attempted. This makes all the difference in the world for long-distance shooting. So ... I'm curious why Canon didn't put a focus limiter on the 55-250? Sure, this is a consumer lens for budget-limited people such as myself, but I have to believe the cost would have been minimal. And is there any reason Canon would not have this feature on all telephoto lenses?

I'll be happy to forward your request to add a distance limiter switch to lenses like the EF-S 55-250 IS, but frankly I don't expect to see this feature on lenses lower than the L-series anytime soon. It's a marketing decision, and it also helps to control the cost of the lens. In the absence of that feature, there is a custom function on the EOS 40D that can be helpful: Custom Function III-1, Lens Drive when AF Impossible. Turning on this CF will prevent the lens from hunting when it loses track of the subject. It can really save a lot of time in the field. I also recommend using Custom Function IV-1 with the setting of your choice to control the AF process. Some photographers prefer IV-1-1, which allows you to keep AF on the shutter button and use the back button to suspend it; other prefer IV-1-3, which places AF on the back button and separates it from shutter release. In either case, you gain the power to stop and start lens drive instantly. This can also prevent unwanted AF search, and it can be used in tandem with Custom Function III-1-1.

To follow up on your August 2007 answer on AF in low light, I'd like to know if there's a way to use only the AF Assist beam of the Speedlite 580EX II on the EOS-1Ds Mark III, without the flash firing at all. This would be for those situations where flash isn't allowed, but the ambient lighting doesn't allow the on-camera AF to function.

Custom Function II-6-1 on the EOS-1Ds Mark III camera allows the AF Assist beam to function while preventing the flash from firing. If that's what you want, be sure to leave Custom Function III-14 set to 0, the default setting. Also, make sure the camera is set for One-Shot AF, since the AF Assist beam is never emitted in AI Servo AF or manual focus.

Currently I'm using a card that was rated by Rob Galbraith at about 5 MB/sec. with the EOS-1D Mark III camera. A 16GB Sandisk Extreme III is rated at about 9.75MB/sec, and Sandisk Ducati 8GB (largest size available for Ducati) is at 10.9 MB/sec. I do have a serious issue where the buffer fills up after a short burst and I have to wait...and typically watch the best moments pass by. If I went from my current 5mb/sec. to 9.75mb/sec. ... will that give me a much longer burst range? Like double the number of continuous frames then stop? How about 10.9 MB/sec.? How fast does a card have to be in order to stay ahead of the camera's buffer if this is possible at all? Oh...I am shooting writing RAW to both CF and SDHC Transcend 16 GB (full redundant backup) media and need to record on the same setting with the faster cards.

The camera's buffer memory is used before the image data is written to a memory card, so the card's speed is not the big issue here. At best with the 1D Mark III, your burst rate is going to be approximately 33 to 36 RAW images or 110 consecutive Large JPEGs at 10 fps, even with the fastest memory cards available. The number of shots will vary according to other settings; for example,you'll get fewer frames if you are shooting RAW + JPEG, etc., but one of the biggest buffer "killers" is setting the custom function for in-camera high ISO speed noise reduction. If you want to maximize the 1D Mark III's burst rate, shut that one off and do your noise reduction in post-processing.

Great tip. But I noticed that my N.R. CF is off already. Hmmm .... Canon Tech Support advises to use only 133x card due to error-prone faster cards ... also that a 16-gig card must be read entirely first to find available blocks; hence, use the smaller cards. Am I wrong to believe technology is simply not here yet to not have a camera hang after depleting the buffer, since no card can write fast and reliable enough to prevent the buffer from filling? FYI...I get nowhere near the 33 consecutive RAWs (writing CF RAW and backup RAW on the SDHD). Again, my cards are rated at 5 MB/sec., but even at the top 14 MB/sec. ... the card will not be able to empty the buffer fast enough ... no?

You may have misinterpreted part of what Canon's customer support was saying about the choice of memory cards for the 1D Mark III. The camera does not support UDMA, which means that there's a limit on the data transfer speed when writing to the card. Because of that, if the camera's card writing speed is the only consideration, ultra-high-speed memory cards won't make much of a difference if any in terms of camera performance. For what it's worth, I have not been hearing any complaints about data errors with the 1D Mark III, either through my own professional photographer contacts or through CPS. If this were a chronic problem, it would have been widely reported by now. Also, the 1D Mark III is clearly compatible with a wide range of memory cards with speed ratings exceeding 133X, as shown in Rob Galbraith's online database for CF and SD card performance.

http://www.robgalbraith.com/bins/camera_multi_page.asp?cid=6007-9038

As you noted, this table shows that the 1D Mark III's card writing speed is limited to approximately 10MB per second with CF and 14MB per second with SD. That's nowhere near the transfer speed capability of the high-speed cards themselves, as shown by their performance when connected to a personal computer with a high-speed card reader. In some cases, you could be looking at transfer speeds of 30MB per second or more, so in this context, the camera is clearly the limiting factor. On the other hand, a slow memory card like the 5MB per second example you mentioned could very well reduce the 1D Mark III's burst rate below its maximum potential. Coming back to your original question, there is no doubt that using a higher speed card could maximize the number of shots per burst. But it should be clear that the best you're going to get under any circumstances with the 1D Mark III is approximately 33 to 36 RAW images per burst at 10 fps. In other words, once the card speed exceeds a certain point, the camera becomes the limiting factor as I previously mentioned. And conversely, once the card speed falls below a certain point, it becomes the limiting factor instead.

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

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