The Digital Journalist
Tech Tips
March 2007

by Chuck Westfall

I was playing around with my wireless flash setup just now in preparation for my wedding tomorrow and then I remembered that I can control the 550EX slave flash in Manual mode via the master 580EX (i.e., I can set the 580EX to Manual and to not fire and the 550EX will fire at the specified Manual power setting). However, when I set the Master to Manual (i.e., 1/32), my 5D locks the shutter speed at 1/200 in Av mode, even though I've set the custom function to "Auto." If I set the Master back to E-TTL, the shutter speed goes back to Auto. Does anyone know of a way to get this setup to work with an auto shutter speed?

When an EX Speedlite flash is set to its manual mode, wireless or not, the only way to set the shutter speed to something other than maximum X-sync is by setting the camera to its manual mode.

Is there a technical reason for that? I assume maybe it's because the camera can't meter the scene not knowing how much light the flash is going to output, and therefore, what's the point of a slower shutter?

Actually, that behavior extends all the way back to Canon's first TTL flash system in 1986, the T90 camera and 300TL Speedlite. As I recall, the explanation at the time was that setting up Av mode to default to maximum X-sync when the flash was set to manual mode was to make it more intuitive for photographers to set apertures using the main dial and LCD data panel. Fixing the shutter speed at maximum X-sync was (and still can be) appropriate for handheld flash photography indoors, in situations where the ambient light is contributing nothing significant to the overall exposure. Manual mode on the camera combined with manual mode on the flash makes it possible to control shutter speed and aperture freely and independently, which becomes useful when you want to drop the shutter speed to pick up more of the ambient lighting in indoor scenes.

I guess there's no way to use High-Speed Sync with Manual flash, eh?

FP flash mode (high-speed sync) is still supported when manual flash is combined with manual exposure mode on the camera, but if you set high-speed sync with manual flash when the camera is set to Av mode, the shutter speed defaults to the camera's maximum shutter speed, such as 1/8000 for most current EOS digital SLRs.

I recently posted a question regarding the safe maximum sync voltage for an EOS 30D on A reply led me to an article called Tech Tips answering a number of Canon-related FAQ. You addressed the safe sync voltage for a number of models, including the 20D, but I was wondering where I might be able to find published data on the safe sync voltages for the entire range of Canon cameras (or maybe just the 30D, as that's the body I'm using now).

It's likely you'll never see an official list of all Canon SLRs according to this specification, because Canon Inc. (our parent company in Japan) simply doesn't do things like that. I've been with Canon USA since 1982, so I'm in a pretty good position to know Canon Inc.'s habits. However, I'll be happy to provide you with my unofficial list:

Canon Digital SLRs safe for TCV up to 250 volts:
EOS-1D Mark II N, EOS-1D Mark II, EOS-1Ds Mark II, EOS-1D, EOS-1Ds
EOS 30D, 20D, 5D
EOS Digital Rebel XTi, XT (400D/350D)
EOS D6000/D2000, Kodak DCS560/DCS520 (circa 1998)
EOS-DCS series (circa 1995)

Canon Digital SLRs safe for TCV up to 6 volts:
EOS 10D, D60, D30
EOS Digital Rebel (300D)

Canon 35mm SLRs safe for TCV up to 250 volts:
EOS-1V, EOS-1N, EOS-1, EOS 3

Canon 35mm and IX240 SLRs safe for TCV up to 6 volts:
EOS 650, 620, 630, RT
EOS 850, 750, 700
EOS Rebel Series
EOS Elan Series
EOS 10s, A2E, A2

Canon SLRs released earlier than the T90 did not have TTL flash circuits, and comprehensive information on safe TCV levels is not available.

The trigger circuit voltage (TCV) rating for any EOS SLR is the same on the hot shoe as it is on the PC terminal (if the camera has one), but the acceptable TCV level varies according to the camera model. Incidentally, the main reason for the difference is the way the X-sync signal is generated. With the 250V cameras, the X-sync signal is generated electronically. With the 6V cameras, the X-sync signal is generated mechanically. There are no guarantees, but going forward I anticipate that most if not all future EOS SLRs will be safe for TCV up to 250 volts.

I typically shoot in Av mode with the flash in High-Speed Sync, for fill when I'm out shooting bird photos. This is because I always want a shutter speed above the X-sync speed of the camera if possible. I realize that in HSS mode, the flash output will be less than normal flash with shutter speeds above 1/250 (EOS-1D Mark II N). But what occurred to me is if I happen to shoot in that scenario in lower light, and I'm getting a shutter speed such as 1/100 (in Av mode) will I get less flash with the 580EX Speedlite still in high-speed sync mode than if I had switched it to normal? I have always believed that it doesn't matter, and that the flash output is the same if you are shooting below the X-sync speed of the camera, but I'm not positive about it. In other words, I keep the flash in HSS because if the situation calls for a shutter speed above 1/250 on the Mk II N, then I won't have the problem of the camera shooting at exactly 1/250 and overexposing the shot. In my mind, it's fail-safe fill flash. But am I correct?

Here's what our "Flash Work" Web site says:

"...the FP high-speed sync flash setting fires repeatedly at roughly 50kHz intervals during the exposure to achieve flash synchronization at all shutter speeds. The camera automatically reverts to normal flash firing when the shutter speed is set slower than the flash X-sync speed."

I would modify this somewhat:

"...the FP high-speed sync flash setting fires repeatedly at roughly 50kHz intervals during the exposure to achieve flash synchronization at all shutter speeds faster than the camera's maximum X-xync speed. The camera automatically reverts to normal flash firing when the shutter speed is set to be equal to or slower than the camera's maximum X-sync speed."

In other words, you can safely leave the Speedlite set to high-speed sync at all times if you like, without worrying about losing range when the shutter speed is equal to or slower than the camera's maximum X-sync speed.

On a somewhat related note, why is HSS an option and not just automatically enabled if shooting with a shutter speed faster than maximum X-sync speed? Why isn't it just always on?

Canon has never officially commented on that question, so I can only speculate that they intended the use of high-speed sync to be an intentional decision on the part of the user. There's no harm in leaving the function turned on all the time, but it's the photographer's responsibility to realize that maximum flash-to-subject distance range drops off substantially as soon as a high shutter speed is used.

I'm using a 20D to do time lapse photography, and I'd like to minimize the wear and tear on the camera, and maybe make each shot a little quieter. If I fix the focus and metering before starting, is it possible to lock the mirror up and keep it up while shooting several thousand frames? Typically I'll take an image every second or two, but it could be as slow as one shot a minute. On a related note, it would be helpful to be able to set some custom image sizes instead of using the fixed factory ones. For example, I'd like to shoot at 1920x1080 directly for HD work - this would save me a whole resizing step later, and fit more images on a card. And lastly, why did Canon engineers use a IMG_xxxx naming format on a camera whose shutter should be good for tens of thousands of images? I suppose there's some value in sticking with 8.3 naming for old systems, but surely they could have done IMGxxxxx instead. Now I have an extra renaming step every time I download a card.

It's not possible to shoot more than one exposure with the mirror locked up on an EOS 20D, but this capability has been added to the newly announced EOS-1D Mark III. It's a default feature of the new Live View mode, but it can also be activated during normal shooting via Custom Function III 15-2.

Thanks for your suggestions on variable resolution settings and in-camera file naming options. They are both good ideas, but they are also both unlikely to be implemented on future cameras for different reasons.

1) All of the downsampling and compression for in-camera JPEGs is executed in hardware by the DIGIC image processor for speed reasons, so the resolution settings have to be burned into the chip when it is programmed and cannot be adjustable.

2) All in-camera file names must adhere not only to the 8.3 convention, but also only the last 4 characters can be numerical. This is the requirement of the file format that all Canon (and all other Japanese-manufactured) digital cameras use. This format provides some limited flexibility in terms of the ability to adjust the first 4 characters in an individual file name, and we exploit that capability on the EOS-1D Mark II N and EOS-1D Mark III. But there will never be any ability to customize in-camera file names to any greater extent unless the camera's file format is updated. For more information on the file format currently mandated by the Japanese digital camera industry, see the following information:

I have an EOS-1D Mark II and Mark II N. I recently noticed that I had inadvertently created some folders on the SD card in my Mark II. There was nothing in the folders. I tried hooking up my camera to the computer to delete these empty folders, and could not get the computer to communicate with my camera. I'm on a PC, and the Wizard opened and wanted to look for or install some software. I thought I had what I needed – EOS Utility 1.1. But even this didn't work. None of the other software programs I have would connect or let me connect to the camera to manage the folders. I also have EOS Viewer Utility 1.2, ZoomBrowser EX 5.7 and Digital Photo Professional 2.2. Can you help me figure this out? What software do I need and how does if need to be configured for me to be able to manage files on cards in-camera? Thanks for any help you can give me.

If you are using Windows XP, you can manage folders on memory cards in your EOS camera by means of Windows Explorer, after you install the WIA driver for your camera from the EOS Solutions Disk supplied with the camera. You can install just the WIA driver if you wish, but the driver is a prerequisite for accessing the camera and its folders. Assuming the WIA driver is installed, here is the procedure for accessing folders and files in the camera:

1. Open "My Computer" and locate the camera icon at the bottom of the screen.

2. Open the camera icon and select Detail View. "CF_Slot" and/or "SD_Slot" folder(s) should appear, as long as there is at least 1 image on the card.

3. Open the "CF_Slot" and/or "SD_Slot" folder(s) to locate the image folders in each memory card.

4. Right-click the desired folder and select a task, such as Delete.

For what it's worth, you can also manage folders on your SD or CF cards in Windows Explorer by means of a card reader.

I have a few questions in regard to using the EF12 II &/or EF25 II extension tubes with the current version EF70-300 IS USM lens. The book for this suggests that it be used in manual focus but does not say if AF will work. Do you know if AF will work, especially in bright light? Also will the Image Stabilizer still work with either or both of these tubes on that lens?

Someone asked a similar question in last October's Tech Tips, and here is my answer: The main reason why Canon advises users not to stack extension tubes or other coupled lens accessories like extenders is the possibility that the camera's shutter may not release. Each extra accessory increases the level of electrical resistance. But, you are welcome to try; many users have reported successful results using 2 or 3 coupled extension tubes.

Autofocus performance with extension tubes is a separate issue. Assuming no problems with shutter release, there is still the possibility that the effective maximum aperture of your coupled lens with one or more extension tubes may become smaller than f/5.6, which is the limit for most EOS cameras other than the EOS-1D series. If so, the camera's AF system may not get enough information to determine an accurate focus. Additionally, extreme close-up photography results in extremely shallow depth-of-field. Even if the subject matter is reasonably contrasty and the effective maximum aperture isn't an issue, the focusing motor in the lens might be driven so fast during the AF search procedure that the AF sensors won't have enough time to recognize and lock on to the subject. This is not to say that AF with extension tubes is impossible, but it's important to realize that the odds are stacked against it. Manual focus is often the only practical option, even when autofocus is technically available. Under such circumstances, you may find that focusing manually while pressing the shutter button halfway allows the circular green LED in-focus indicator in the camera's viewfinder data display to function as an effective focusing aid. The Image Stabilizer function of the EF70-300mm f/4-5.6 IS USM lens is supported when using a single extension tube. As I mentioned earlier, we do not recommend stacking extension tubes, but it's entirely possible that IS will function when two tubes are mounted between the lens and the camera body.

The Canon PowerShot A95 has been discontinued. Which of the new Canon compact cameras would be best to use with a spotting scope for digiscoping. (Have a KOWA TSN 883 88 mm spotting scope). Thanks for your help!

In our current lineup, the best cameras for this purpose are the PowerShot A640 and A630 models. They are the "descendants" of the A95, and both of them share its key attributes of folding screens combined with fully manual exposure control. The two cameras are functionally nearly identical except that the A640 is a 10-megapixel model with remote control capability, while the A630 is an 8-megapixel model without remote control capability. In order to fit either of them to a spotting scope, you'll need the optional Canon LA-DC58F Conversion Lens Adapter. For more information on the A640 and A630 cameras, see these Web pages:

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

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.)

© Chuck Westfall

After earning a degree in Professional Photography from the Rochester Institute of Technology and accumulating some valuable on-the-job experience during a 10-year stint in commercial photography and photo retail, Chuck Westfall began his corporate career with Canon U.S.A. in 1982 as a Technical Representative. He has steadily advanced through the ranks to achieve his present position as Director of Media & Customer Relationship for the company's Consumer Imaging Group, working out of Canon U.S.A.'s headquarters office in Lake Success, N.Y. Among his many assignments, Chuck Westfall is currently Canon USA's main media spokesman for new camera products. He also provides a unique insider's perspective to financial analysts who follow the company's CIG sales and marketing activities.

Chuck's involvement with digital cameras began in 1994, when he assisted Canon and Kodak engineers in developing the EOS-DCS series of professional SLRs. Since then, his responsibilities have expanded to include participation in the development and launching of many other Camera Division products, including Canon's professional and consumer-oriented digital cameras. Over the last 10 years, Chuck has continued to participate in the design, development, introduction and marketing support of camera products. Most recently, he supervised the launch of a comprehensive on-line and on-site dealer training initiative for the Camera Division.

On the personal side, Chuck married his beautiful wife Ying in 2000 and they have been blessed with a wonderful daughter, Anna. As Chuck says, "Bringing up the baby is a blast, and we're enjoying every minute of it."