The Digital Journalist
Tech Tips
October 2006

by Chuck Westfall

A criticism of Canon digital SLRs for a long time, and in fact DSLRs from a number of manufacturers, is the lack of a permanent place on the top LCD, and more importantly in the viewfinder, to display the active ISO speed. One of the most wonderful things about shooting digital is the ability to change ISO on the fly. Unfortunately, being a human being, I sometimes forget to dial down a high ISO setting after using it, and end up shooting a series of shots at an ISO I didn't intend to use. I know that this is a feature of the more expensive 1-series cameras, but this should be a standard feature of all DSLRs. Do you agree?

Thanks for expressing your opinion. I'll be happy to pass it along to Canon Inc. for consideration towards future EOS Digital SLRs. I can certainly agree that the ability to change ISO from shot to shot is a tremendous feature of digital cameras in general. Full-time display of ISO settings in the viewfinder data display would be welcome for many SLR users, and as you say, it's currently available in the EOS-1 series. It's also available on demand with the 5D and 30D. The ISO value remains visible in the viewfinder while it's being adjusted, which is very helpful. If enough of our customers make it known that they wish full-time display of ISO speed to be a standard feature for all Canon SLRs, I'm sure that Canon will consider it.

I recently discovered the benefit of switching DPP's preferences for tone curve mode to Luminance instead of RGB. But I was wondering why a lot of the photos still show the RGB Tone curve in the edit window rather than the selected preference of Luminance.

One thing that could cause a problem of this type is making a set of initial adjustments in RGB mode, then resetting DPP's preferences to Luminance. You can't have both kinds of adjustments in the same Recipe. If you want to edit your images in DPP's Luminance mode, it's important to make sure that any previous RGB edits have been deleted. Also, switching the Tone Curve Tool mode from RGB to Luminance or vice versa is one of the few preferences in DPP that require you to shut the application down and restart before it takes effect. Please try these tips and let me know if there are any other questions. Incidentally, I just leave DPP in Luminance mode all the time, because there are some huge benefits to doing image corrections this way.

I'm an EOS 20D owner and heard something about Canon lenses: picture sharpness varies according to the aperture setting. If it's true, what is the sharpest aperture to use on my EF70-200mm f/2.8L lens? By the way, I already apply unsharp mask in Photoshop (a trick I learned from your column) and the sharpness setting in my 20D is already at its highest level.

You're going to find that most if not all EF lenses are at their best in terms of sharpness when used about 2 to 4 f/stops smaller than their maximum aperture. In the case of the EF70-200mm f/2.8L IS USM, that would be from approximately f/5.6 to f/11. However, it's important to note that L-series lenses like the EF70-200mm f/2.8L IS USM produce tack-sharp image quality even when they're used wide open. The improvements you get by stopping down can be seen on close inspection, but they're often subtle. It's more likely that images of real-life 3D subjects will look sharper at mid-range apertures simply because there is more depth of field than when you shoot wide open. Bottom line, I wouldn't obsess over using the sharpest possible aperture on any of your L-series lenses, if I were you.

My son has just persuaded me to buy an EOS 5D to replace my aging Pentax SF7. A large part of the photography I do is macro work at night. On the Pentax I used up to three extension tubes with an off-camera flash to get perfect results. The Canon literature says never to use more than one tube with a lens ... Is that true and, if so, why? Also, what is the reason Canon recommends not using AF when a tube is fitted? I had been hoping the Canon tubes would drive Canon lenses and so automate focusing in difficult conditions.

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 two or three 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 the EOS 5D. If so, the camera's AF system may not be getting 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 that the AF sensors can't recognize 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.

I have a question about the real world performance of Canon image stabilizer lenses. The EF28-300mm f/3.5-5.6L IS USM would really suit my needs of traveling light, i.e., with as few pieces of equipment as possible, but yet be ready for any situation. After all, one EF28-300 IS doesn't weigh more than carrying a 24-105 and a 70-300 DO. What does concern me, before I invest, is hand-holding 1.6 kilos and getting a really sharp shot. At 300mm, three stops less means shots at about 1/40 sec. At 28mm, three stops less means about 1/4 sec. At 300mm with the EF28-300 IS, the length and weight are similar to any 300mm, but at 28mm the 1.6 kilos and 18cm is an awful lot. Therefore, in the real world, with a zoom with IS, is the real hand-held limit at 28mm actually the same as at 300mm, i.e., 1/40 sec.? The question really applies to all zoom IS lenses; i.e., is the IS hand-held limit at any zoom length actually the same as that at max telephoto because of the extra weight/length of a zoom?

Thanks for the good question! After rechecking my sample of the EF28-300mm L IS lens against my sample of the EF24-105mm L IS, I feel reasonably comfortable in telling you that it is definitely possible to get a full three steps of shutter speed correction throughout the focal length range of either lens during hand-held photography. For best results, it is important to activate the image stabilizer for at least 0.5 second before taking a photo. Also, you'll find that the percentage of sharp photos will improve if you practice good camera handling techniques, like gripping the camera body firmly (but not clenching it) with your right hand, supporting the lens from the bottom with your left hand, and keeping your elbows close to your body and your feet in a comfortable position while composing and shooting. Try to brace yourself against a wall, a tree trunk, or other similar support if possible.

Lighter and smaller lenses like the EF24-105mm L IS and EF70-300mm DO IS are clearly easier to handle than the EF28-300mm L IS lens, but the trade-off in favor of the EF28-300mm zoom is the convenience of using and carrying only one lens instead of two. Choosing between these alternatives is largely a matter of personal taste, but based on real world tests, differences in IS performance are insignificant.

I do a lot of nighttime and low-light shooting, and tend to refrain from using flash as much as possible. Obviously this requires a very steady hand (and subject!) and also the use of Image Stabilization. Many Canon lenses come with this, but I notice that they all seem to be either zooms or telephotos. There are no ultra wide-angle IS lenses. What is the technical barrier, if any, to putting an IS mechanism into the 16-35 2.8L, for example, or the 15mm fisheye?

Here's the barrier: Optical image stabilization requires additional, specialized lens elements in order to compensate for the movement that occurs during image stabilizer operation. For instance, the EF70-200mm f/2.8L IS USM has 23 elements in 18 groups, versus 18 elements in 15 groups for the EF70-200mm f/2.8L USM. The EF300mm f/2.8L IS USM has 17 elements in 13 groups, versus 10 elements in eight groups for the EF300mm f/2.8L USM. Other non-IS lenses like the EF15mm f/2.8 Fisheye and the EF16-35mm f/2.8L USM would have to be redesigned with more elements in order to incorporate optical image stabilization. There's no technical reason why this couldn't be done, but frankly, other lens requests have had higher priority so far. Canon pioneered the concept of image stabilization for SLR lenses starting in 1995 with the EF75-300mm IS lens, and we are still the market leaders with 16 IS lenses in our current line-up. Moreover, we are firm believers in the superiority of lens-based image stabilization versus body-based stabilization in terms of performance, so chances are good that you will see more IS lenses from Canon over time.

My EOS-1Ds Mark II delivers great images but how do I size them for the best display on a 50-inch HD Plasma using a progressive scan DVD player? Of course I wish to fill the appropriate amount of the display with the optimized image. Should I resize in Photoshop and reduce the PPI from 360 to a lower number?

The best way to display images from an EOS digital SLR on your HD plasma screen in terms of image quality is via direct computer input if your display accepts it. For example, most if not all of the current Panasonic and Pioneer HD plasma sets have a 15-pin socket that connects to the external monitor port of a Windows or Macintosh personal computer. If you use this connection, your computer most likely will be able to resize your images automatically, depending on the software you use to display them. For instance, the Canon ZoomBrowser EX (for Windows) and ImageBrowser (for Mac OS X) software that was supplied with the EOS-1Ds Mark II has a slide show function that works very well for this purpose. You could go through the effort of making downsized copies of your high-res originals to match the native resolution of your HD plasma set, but using slide show software on your PC should allow you to bypass that step.

If you use a standard definition DVD player (even a progressive scan version) for input, you will first need to create DVDs that your player can handle. This involves producing downsized JPEG versions of your original images, which are then imported to an authoring program on your computer and eventually burned to DVD. The problem with this approach is that the clarity of your images will be degraded somewhat by the relatively low resolution of the standard definition video format. You could get a sharper image on screen by using one of the latest Blu-Ray or HD-DVD high definition video systems, but you may find that producing compatible DVDs for these new formats is problematic.

PS: An even better way to display high resolution images from an EOS digital SLR instead of an HD plasma screen is to use a Canon REALIS projector with computer input. This method provides better detail and more accurate color than any other non-printed alternative, and it has the further benefit of being able to vary the dimensions of the displayed images according to the size of the screen. For more information, please visit this web site.

When using my EOS-1D Mark II N in Av mode with AI Servo I seem to get exposure differences between shots in rapid fire mode (8 fps). I typically use Av mode for shooting soccer using Custom Function 4-3, as the lighting changes across the field. The exposure problem is fairly consistent with the first shot exposed properly and the second shot under exposed by an increase of shutter speed. This happens a lot and it is always the same with the first shot being properly exposed. I have seen this literally hundreds of times.

For this type of photography, try using center-weighted average metering rather than evaluative. It should provide more consistency to your exposures for two reasons:

1. It's looking at a larger percentage of the picture area for its primary reading.

2. Unlike evaluative metering, it doesn't allow the camera to apply exposure compensation automatically.

When analyzing your sample images, I noticed that there was a slight change in camera angle, making me think that the camera may have been hand-held. Then I overlaid the active focusing point on both shots and noticed that it was fairly close to the kid's teeth, which are brighter than his skin. That's exactly the type of thing that evaluative metering might pick up and try to "compensate," whereas the exposure would almost certainly have remained the same for both shots had the camera been set for center-weighted average metering for the reasons stated above.

Thanks for the reply and your time to look at the pictures. I believe I have used CWA metering with similar results. I will need to test this the next time I'm out in the field. I took a look at the focus points after reading your message. You are correct about the pictures being hand-held. I wanted to emulate a field sports situation (monopod or hand-held). In the shot that had the proper exposure, I see that the focus point is closer to the white tooth than in the underexposed shot. Based on my understanding of the metering system, I think that the shot that has more "white" covered by the focus point would be "compensated" to underexpose picture. I'm seeing the opposite or maybe I have a misunderstanding of the metering system?

As I mentioned, evaluative metering has the ability to execute automatic exposure compensation. This has the following consequences (at least):

1. It cannot be totally controlled by the photographer.

2. It's as likely to add exposure rather than subtract it when confronted with brighter tones.

We're not talking night-and-day differences from shot to shot with the same overall scene, but it's entirely conceivable that a series of evaluative exposures of the same scene could fluctuate by 1/3 stop, especially if there are changes in the brightness of the subject matter being analyzed. Again, center-weighted average metering eliminates automatic exposure compensation, and it is less susceptible to variations in meter readings caused by minor changes in composition with the same scene because it reads a larger area than evaluative as its main emphasis.

I recently acquired CS2 and Adobe Bridge to manage the RAW files from my EOS-1D Mark II and II N. Bridge has a 'Batch Rename' function. I find this very convenient. In a couple of easy clicks of the mouse I can rename a whole day's work by year, month and day with sequential numbers added automatically – i.e., 20060913, 20060913 (1), 20060913 (2), etc., etc. I was wondering if am able to take this one step further and have the cameras automatically naming files by date and sequence so this extra step in Bridge isn't necessary. Not that it's that great a sacrifice, but it would be one less thing to think about and maybe something Canon might want to consider if it isn't already available.

I appreciate the suggestion on customizing filenames in the camera body. As you may be aware, the EOS-1D Mark II N already offers this capability to a limited extent, in that the first four characters can be set on the camera by the user. However, the current file format (i.e., the file naming and directory structure format, as opposed to image recording format like JPEG or RAW) in use by all Japanese digital camera manufacturers, which is known as DCF, strictly regulates the conventions for file naming in digital cameras. The current version of DCF requires in-camera file names to be eight characters plus a three-character suffix (no more and no less).

This is why most current downloading software, including Canon's EOS Utility as well as other independent applications, have recently been strengthened in terms of batch renaming functionality. The bottom line is, fully customizable batch renaming cannot be done in the camera unless or until the file format is changed. There are all sorts of good reasons why digital images should be renamed to facilitate cataloguing and archival storage, but I don't expect the in-camera file naming scenario to change any time soon unless or until DCF is updated.

I spent the weekend shooting with several cameras, including my EOS 30D, at the Grand Prix of Denver. I don't know if it's the altitude and humidity, but I noticed several marks on the 30D's sensor. They look like condensation residue as opposed to dust, and won't blow off with a lens cleaning bulb. What's the best way to clean marks like these from the sensor? Is this something I can do myself, or should I take it to a photo store or Canon service center? Does Canon have a Web site that explains things like this?

Canon's official recommendations for cleaning the image sensor (or more accurately, the low-pass filter in front of the sensor) of an EOS 30D are essentially the same as they are for other EOS digital SLRs. The suggestions are spelled out in the Instruction Manual, with language similar to this: "If the sensor needs to be cleaned directly, have it done by a Canon Service Center. However, if you want to clean the sensor yourself, follow the procedure below...." The instructions never involve touching the low-pass filter in any way.

Realistically, we understand that our customers may use commercially available sensor cleaning products. Moreover, there's no doubt in my mind that at least some of these tools can be effective and safe when used properly. But our customers must realize that Canon will not be held liable for any user-inflicted damage to the low-pass filter or other camera parts. This is why we cannot endorse cleaning tools that are designed to touch the low-pass filter.

Let me cover this controversial topic in a little more depth: Before taking any action to clean a DSLR image sensor, the first thing I would suggest is to carefully evaluate whether the spots on the low-pass filter are actually showing up in your images. If not, I'd advise you to leave well enough alone until such time that your images are significantly affected. Even when dust spots do start to show up consistently, there are various ways to automate retouching procedures in post-processing so that you can eliminate the spots in your finished images.

At some point, though, it will be best to clean the low-pass filter. Plenty of EOS Digital SLR owners have had successful results doing their own cleaning, and there's no reason why you shouldn't be able to do the same. However, it's very important to understand that any sensor cleaning you perform is done at your own risk. In other words, if you end up scratching the low-pass filter, it will void the camera's warranty. You can get a scratched filter replaced, but only at your expense. Replacement costs vary according to the camera, but the going rate to replace (for example) the EOS 30D's low pass filter is approximately $250 including parts and labor.

If you are uncomfortable with that thought, you are welcome to have your camera's low-pass filter cleaned by Canon Factory Service or an Authorized Service Facility for a nominal fee. But I would encourage you to explore the possibility of learning how to clean the filter safely on your own. If you're successful, it will save you tons of time and money, and it will give you a lot of peace of mind. There are several effective cleaning methods, and each of them has its own group of supporters. I do not specifically recommend any single method over another, because all of them can be effective when executed properly. Thus, choosing a method becomes largely a matter of personal taste.

Here are a few options you might want to explore:

Hope this helps!

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

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 2-year old daughter, Anna. As Chuck says, "Bringing up the baby is a blast, and we're enjoying every minute of it."