Tech Tips
May 2009

by Chuck Westfall

Just a quick note before we begin to say that this month's edition of "Tech Tips" marks the 4th anniversary of the column here on The Digital Journalist. A hearty thanks to Dirck Halstead, Cecilia and Connie White, Mark Wilkie, and others who make this Web site possible month in and month out, and as always an especially warm thank you to all of our readers, especially those who have taken the time to send in their questions and comments.

Here's the (slightly comical) problem: I am sliding around in several inches of marshland mud with the EOS 5D Mark II. My feet are slipping, the tripod legs only work by splaying them out wide (as they just slide otherwise), the wind is blowing so my eyes are watering, the camera's at the wrong height to be able to see the top plate which I need my glasses to read but I have to take those off to see through the viewfinder - and the sun's setting fast. I am bracketing and changing modes (Custom to Av or M and back) furiously, and so finally I realize what live view is for! So my question raised by being in this situation is this: How can I get a large display on the back LCD screen of exposure mode, f-stop, shutter speed, metering mode and bracketing amount, ideally without lots of other irrelevant info? I don't mind if I have to get out of Live View to do it but it would be nice to stay in it.

Based on your description, the EOS 5D Mark II's new "Quick Control Screen" sounds like it might be nearly perfect for you. Here's a nice article about it:

You will have to exit Live View temporarily to use this feature, but it's worth it, especially when you're working from a monopod or tripod and find the top of the camera difficult to see.

The EOS-1D Mark III has both global and per-lens AF microadjustment. If they are both set, does that give the net effect of the sum of the two values? Example: global = -2, lens = -8. Is the net effect essentially the same as setting global = 0, lens = -10? If that were true, I would see a huge difference when I set both to -20, netting -40! However, I don't see this. The reason for my question is that I find after using LensAlign, all my lenses require at least -2, so I was wondering if I should globally adjust to -2, and then on a per-lens basis, adjust more if required.

Any AF Microadjustment value set for an individual lens in C.Fn III-7-2 on the 1D Mark III or 1Ds Mark III will override any AF Microadjustment value set in C.Fn III-7-1 when that lens is used. Conversely, any AF Microadjustment value set in C.Fn III-7-1 will be used if there is no AF Microadjustment value set in C.Fn III-7-2 for the lens in use.

I have a question about AF microadjustment on the EOS-1D and 1Ds Mark III. If you find that a lens is consistently front focusing (focus DOF more to the front of subject), do you adjust "+" or "-"?

Apply a "+" adjustment to correct for front focusing with any EOS camera that has an AF microadjustment function.

When looking at all the recommendations in Canon's recently posted online AI Servo AF manual for EOS-1D Mark III and EOS-1Ds Mark III cameras (, I noticed that C.Fn III-8 [using adjacent (1) vs. surround assist (2) points] is changed from case to case. What are the disadvantages of using C.Fn III-8-2 for cases 4, and 6?

As a preface, please keep in mind that the suggestions provided in the online AI Servo AF manual are exactly that: suggestions, rather than absolute commandments. Anytime you're photographing moving subjects, there are always going to be trade-offs between one focusing technique versus another. The optimum combination of camera settings will vary according to the photographer's level of experience and judgment as well as the subject matter, camera-to-subject distance, lens selection, lighting conditions, etc. Generally speaking, when you're shooting fast-moving subjects at close range as illustrated in Case 004, C.Fn III-8-1 will reduce the chances of the camera picking a focusing point that is on a part of the subject that's closer or further than the area being covered by the manually selected focusing point, compared to C.Fn III-8-2. Keep in mind that depth of field is typically quite shallow when working at or near maximum aperture at close range, so the less opportunity you give the camera to pick a focusing point other than the manually selected one, the better off you'll be – that is, assuming you can keep the manually selected point on the subject throughout the shooting sequence. If you do a lot of work on the same kind of subject matter, such as the snow skiing example shown in Case 004, you should experiment with III-8-0, III-8-1 and III-8-2 to see which one works best for you. The main difference between Case 004 and Case 006 is that there are more "obstacles" temporarily obscuring the main subject in Case 006. That's why there are differences in the recommendations for C.Fn III-2, III-3 and III-4 compared to Case 004. But the similarity between the two cases is that the main subject is clearly identifiable and relatively easy to track with the manually selected focusing point. Therefore, III-8-1 may give you more consistent results than III-8-2 for the same reasons I explained in the previous paragraph.

In Case #004, when you have a fast moving subject close to the camera the manual recommends using C.Fn III-4-0. To better understand the logic, why would you not use III-4-1? Seems that the closest subject with the servo speed (-2) set at medium slow and III-4-1 would be the best option.

In Case 004, there are no obstructions between the main subject and the camera, so III-4-0 will make AI Servo more responsive to rapid changes in camera-to-subject distance, especially at close range.

In poor lighting, say an exposure of f/1.2, 1/15 to 1/30 second, at ISO 800 in evaluative metering with an EOS-1D Mark III, selecting the center AF point manually, I'm observing a fairly significant difference in the AF sensitivity between One-Shot AF and AI Servo AF. In AI Servo mode, on an object with relatively decent contrast, the 1D Mark III is unable to lock focus. When I switch to One-Shot AF, the center AF point quite accurately focuses on the subject and gives a confirmation beep and I am able to capture the frame with extremely sharp accuracy handheld. It is almost as if in AI Servo mode, the AF sensitivity has suddenly switched "profiles" to a rather less sensitive "mode," so as to not be able to lock onto the subject in a fairly low-light situation, whereas One-Shot AF mode has absolutely no issues with that same situation and subject. Does my camera need to go back to Service or is the camera performing according to its design?

The light level you describe (ISO 800, 1/15 at f/1.2) is close to the threshold of the EOS-1D Mark III's low-light AF sensitivity. Without the use of flash under these lighting conditions, it would be very difficult to obtain sharp photos at f/1.2 unless the camera was steadied through use of a tripod, and also the camera's reflex mirror should be locked prior to exposure. Assuming that you're prepared to take those considerations into account, then your observation about the difference in focusing capability between One-Shot AF and AI Servo AF for the EOS-1D Mark III is correct. Focus will lock on a subject with readable contrast in One-Shot AF, but AF will fail under the same lighting conditions in AI Servo AF. That is completely normal and to be expected. It's due to differences in the amount of time that light is allowed to accumulate on each pixel in the AF sensor. That period of time, which Canon does not disclose, is longer for One-Shot AF than it is for AI Servo AF, and the result is superior low-light performance for One-Shot AF. This is essentially the performance level that the EOS-1D Mark III is designed to offer in extremely low light, so there would be no benefit in sending the camera in for service on this issue.

I have a question for you on the back button focus on 1D Mark II. The setting is AI Servo single AF point, * (AE lock button) to focus, 8 frame per second continuous mode. What I found is that the first shot is always sharp, while the following is unpredictable. But in most cases the following picture is out of focus. I do have C.Fn set to focus priority for the following shot. Here's my question: Is it possible that the lens element is adjusting focus while shutter is released? In other words, does the focus freeze during shutter release?

The sequence control of the EOS-1D Mark II is consistent with other EOS cameras in the respect that lens drive is temporarily suspended during each exposure in a multi-frame burst. Therefore, to answer your question directly, the camera does not adjust the focus while the shutter is open. However, in a predictive AI Servo AF sequence, lens drive can resume as soon as the shutter closes. It can run from the instant that the reflex mirror is on its way back down until the instant that the shutter opens again for the next exposure.

Thanks for answering my question. It's good to know at least the design philosophy is sound. I'm just a little puzzled by the result. It could be just me. The experiment I've done so far includes using different lenses - 50L/85L/135L - using different aperture, changing AI Servo sensitivity standard/slow/fast, etc. But so far the result is consistent. Here I'll attach eight raw images taken just an hour ago. They're two series of four continuous shots. As I mentioned before, the first shot is in focus; the rest are not. Also I wanted to let you know that the camera performs flawlessly in default combined focus/shutter release mode, either in One-Shot AF or AI Servo AF.

Thanks for sending the shots. Very cute kid, by the way! Congratulations. After looking at these images, I would say that one issue you're facing is that the movement of the subject is too slow to cause the camera to go into predictive AF mode. Also, in the first sequence of four shots, the focus on the eye in the first frame is soft, which indicates that the AF system had not acquired focus before you started shooting. One thing that might improve your results is to start tracking the subject by pressing the AE lock button with the focusing point positioned where you want it for at least 1 second before you release the shutter. Additionally, the position of the focusing point in some of these shots appears to be almost completely on the dark part of the subject's eye, which may make it difficult for the AF sensor to see enough contrast to focus accurately. This is one of the inherent difficulties of using autofocus for close-up portraits, and I'm sure you did the best you could. But be sure to pay attention to the level of contrast that the camera is seeing at the focusing point you've selected if you want to minimize the number of soft photos. You could also improve the odds of getting sharper images for this type of subject by moving back just a bit and possibly selecting a moderately smaller aperture like f/2.8 instead of f/1.8. Each of these techniques would slightly increase depth of field, making it easier to keep the subject in focus without necessarily destroying the mood of the shots.

Could you specify how I can tell the AI Servo feature is tracking a moving subject for an EOS 40D? I am trying to test how well AI Servo works to "track" a subject. I place the center focus point over the subject in the viewfinder and press the shutter button down halfway to lock focus for about 1 second before the subject moves. With focus maintained, if the subject moves from the center focus point to an outer point I expected the highlighted focus point (highlighted points enabled) to move with the subject but the center point I have selected always remains selected, no matter where the subject moves. If I use all nine of the AF points and let the camera select the point then it shows all points highlighted in the LCD review, no matter where the subject moves. I would have expected the focus point nearest to the subject to be the only point highlighted. This does not appear to be the case.

If you want the EOS 40D or any other EOS Digital SLR to track subject movement automatically using more than one focusing point, you must set the camera for the combination of AI Servo AF and automatic focusing point selection. See page 78 in the 40D instruction book if you're not sure how to set automatic focusing point selection. Please understand, if you manually select the center focusing point or any other individual focusing point, then that single point is the only one the camera will use. Assuming the 40D is set for the combination of AI Servo AF and automatic focusing point selection, none of the focusing points in the viewfinder will illuminate while you are shooting. Therefore, you will not be able to verify which focusing point the system is using. But you can tell if the camera is tracking your subject by observing the viewfinder data below the picture area. If the camera is tracking the subject, the focus confirmation light, which is a green dot on the right side of the Max. Burst indicator (see page 19 in the instructions) will not illuminate before you shoot. If the camera is not tracking your subject, the focus confirmation light will blink rapidly while you are trying to collect focusing data before you shoot.

Help me understand how custom white balance works when shooting JPEGs compared to manual color temp settings. On my EOS-1D Mark II, can CWB provide color accuracy not available in a manual color temperature selection or can I always rely on manual as long as I dial in the right K setting?

A custom white balance setting can differ from a manually set color temperature setting in two possible ways:

  1. It can be set to a lower color temperature than a manual setting: The range for CWB in an EOS digital SLR goes down to 2000K, whereas the manual settings go down to 2500K at best (2800K for older models).
  2. It can be shifted (tweaked) in the amber/blue and/or magenta/green axes, the same way that you could do it yourself with the camera's WB Shift menu.

Some EOS models like the 1D Mark III and 1Ds Mark III store up to five custom white balance settings that can be named directly in the camera. Others, like your 1D Mark II, can only store one.

I often use my EOS-1D Mark II in Av mode. If I dial in exposure compensation will my auto flash meter differently?

In the EOS system, flash exposure is measured and controlled independently from ambient exposure. Therefore, the level of flash exposure is not affected when you dial in ambient exposure compensation. Let me know if this answers your question.

I have seen several mentions on the Internet about using Live View to help in setting the exact position of a graduated filter since its position is dependent on the aperture. Yet I see no evidence that my EOS 5D Mark II stops down the lens during Live View. Does it only do it when depressing the DOF Preview button?

The Depth of Field preview button stops down the aperture during Live View on the EOS 5D Mark II camera, but the onscreen image will remain bright unless you activate Live View's Exposure Simulation function.

I have acquired an Ec-S focusing screen for my EOS-1V since I usually work at f/2.8 or wider. According to the camera's instruction manual, Custom Function 0 has to be set according to the focus screen in use. My question is this: Which setting should I use, since the manual doesn't list the Ec-S screen?

Unfortunately, the EOS-1V does not have an explicit custom function setting to adjust the camera's metering sensitivity for the Ec-S Ultra Precision Matte focusing screen because this accessory was developed about six or seven years after the camera. So, although the Ec-S screen is physically compatible with any EOS-1 series camera including the 1V model, you're on your own when it comes to exposure metering with cameras that were designed before the Ec-S was introduced. Since the Ec-S is a bit darker than most other Ec-series screens including the standard Ec-N screen that was supplied with the 1V, I would suggest trying to set Custom Function 0 to option 1 for laser matte screens. You should then take some test shots in AEB mode with the lenses and apertures you plan to use most, to determine if there's any need to apply exposure compensation. As long as the maximum aperture of the lens is f/2.8 or faster, I wouldn't expect much need for exposure compensation, but you may run into some metering issues with slower lenses.

I have been a happy user of the DEP feature on my film SLRs for quite a while; similarly I've been using it on my 20D. Recently purchasing the 5D Mark II, I have been unable to locate this feature; however, I can't believe Canon would take out such a feature, since the lenses don't have DOF markings. So the question is simple: Where and how can I locate a DEP mode (or similar) on my 5D Mark II?

Over the last 22 years, Canon has offered two types of "depth-of-field" exposure modes on EOS SLRs. The first type, called DEP, was originally introduced on the EOS 650 in 1987. The last time it appeared on a new EOS was in 2002 with the original EOS-1Ds. On the lower-end cameras, DEP was eventually replaced by A-DEP, which was a simplified version that required only one press of the shutter button to operate. This mode appeared in the early 1990s on Rebel-series cameras, and it's still available now on all EOS models from the Rebel series up to the EOS 50D. Your EOS 20D had A-DEP too, not DEP. Anyhow, Canon eliminated DEP and A-DEP modes from high-end DSLRs starting in 2004 with the EOS-1D Mark II, and it's not included on either the original EOS 5D or the 5D Mark II. Bringing DEP back is no trivial matter, and it most definitely cannot be done with a firmware update. Your best bet with the EOS 5D Mark II is to use Live View mode when possible, especially when the camera is mounted on a tripod. One nice feature that's available in Live View is the ability to preview depth of field without darkening the image, and another nice feature is the ability to magnify the screen image by a factor of either 5X or 10X to check critical focus.

With reference to the long exposure and high ISO noise reduction features: I use a 1Ds III and 1D III, and regularly make images at either long exposures (landscape) or high ISOs (documentary). Being obsessive about quality and exhibiting prints around 20 x 30 inches, I'm always trying to extract the maximum detail. If I read you correctly, I should shoot High ISO with the noise off, and landscape similarly, to preserve detail, then use Noise Ninja to fix the hot pixels that may arise. Does this then make the dark frame subtraction method used by the cameras less effective than NN? Am I better to leave it off and use DPP?

I'm glad to hear you found last month's column helpful, but you may have misinterpreted some of my remarks. I'm basically recommending the use of the camera's long exposure noise reduction whenever it's applicable. As I explained in one of the comments after the column, there are certain kinds of random noise that cannot be removed as easily in post-processing as they can by using the camera's dark frame subtraction capabilities. However, I feel that the camera's High ISO noise reduction capabilities are not as powerful or flexible as the tools that can be used during post-processing. So unless your workflow requires the convenience of in-camera High ISO NR, you're probably better off taking care of it in post. That said, in-camera High ISO NR is getting a lot better with newer EOS models like the 5D Mark II and the 50D.

I have a question about the Canon 5D (old model) and ISO settings. I heard rumors that ISO 50 is no 'real' ISO setting (not knowing what that means though) and that dynamic range is limited in this setting. ISO 100 is a better choice but still with smaller dynamic range and ISO 200 is the best setting. However, I don't understand what the background is. Which setting produces the best image quality/highest dynamic range/smallest amount of noise? (I, personally, do notice an increase of noise between ISO 100 and 200.)

On the EOS 5D, the ISO 50 setting is only available when the camera's optional ISO Expansion setting is engaged. One reason for this is that ISO 50 is actually captured at roughly ISO 100 and then processed in the camera to achieve an effective sensitivity equivalent to ISO 50. As a result, there is less dynamic range in ISO 50 images compared to ISO 100 images from this camera. Incidentally, this is not "news;" Canon has acknowledged this right from the start. The main benefit of the ISO 50 setting is the flexibility it provides in terms of other camera settings like aperture and shutter speeds. This flexibility can come in handy in studio lighting situations as well as landscape photography. As for your second question, I've personally found that ISO 100 provides the best overall image quality from the EOS 5D in terms of noise and dynamic range. I'm aware of various individuals who feel otherwise, and they're entitled to their opinion, but I haven't seen any pictorial images from the 5D with lower noise or higher dynamic range than ISO 100. In all honesty, though, I find that I end up using much higher ISO settings like 400, 800 and 1600 for many of my images with the 5D because I like the look of those settings, especially for photos of people, even though the images have more noise.

Thanks! Two more questions:

  1. What is the H (ISO 3200) Setting on the 5D? Is it anything different than an ISO 1600 picture with all values doubled? Hence, can I reach the same result regarding dynamic range and noise through raw development on my computer?
  2. Raw data is linear, as far as I know. Increasing the exposure by one stop improves tonal gradation, especially in the highlights. I obtain the best image quality if I slightly overexpose the picture just to the extent that no highlight detail is lost. However, I find it very difficult to decide how much overexposure to apply. The camera's metering functions are not very helpful for this. They are metering for a medium grey in the JPEG's dynamic range which is much lower than Raw. In many situations, I can overexpose by several stops. Can you advise how many steps of 'overexposure' would be a good starting point?

H mode on the EOS 5D is basically an ISO 1600 image that's been intentionally underexposed by one stop and then processed internally by the camera to simulate ISO 3200. It's primarily convenient for in-camera JPEGs, but you could achieve the same effect in RAW mode by shooting at ISO 1600 and then applying exposure compensation in your RAW conversion software.

There is no hard and fast rule on how much overexposure to apply to RAW images for maximum image quality in terms of low noise and dynamic range. This is partially because there are differences between various RAW converters in terms of how much highlight compensation they can handle. And then, once you start comparing RAW converters, there are many other differences to consider not only in terms of image quality but also in terms of speed, workflow, etc. The choice becomes a matter of personal taste. Therefore, my best advice on this question is to perform your own tests using the RAW conversion software you prefer. In most cases, you can safely overexpose by one full stop, but anything beyond that is up to you.

I have an EOS 5D Mark II (wonderful camera) and two questions:

  1. I use a 580EX II Flash, but have noticed that if left to the camera, the picture is generally underexposed. If I set it to +2/3 it is OK, but not always. If the subject is close, I overexpose and if the subject is far I underexpose. For general indoor photography, I have been setting the camera to Manual and using a speed of about 125 (depending on the focal length and the subject motion) along with an aperture usually between 8-11 and ISO 400-800. The flash is set to E-TTL. Is this underexposure common with the 5D Mark II? Is there a better way to set the camera? Is this firmware-fixable?
  2. I try to use a white balance card with custom WB as much as I can, but sometimes I don't have my card with me. In such a case I try to match the WB with the pre-settings, or use AWB. Sometimes it works well, sometimes not. I'd try and tweak it in DPP, but my question is as follows: In DPP (as well as the Kelvin settings in-camera) there are only choices in 100K increments. I was wondering -- when I use the custom WB with the WB card, does the camera estimate the WB in 100 increments as well, or does the custom WB have an even more precise reading of the WB (thus giving me even more incentive to make sure to have my WB card with me at all times)?

Based on testing I've performed with my own samples of the 5D Mark II and 580EX II, I am not seeing any specific problems with flash exposure accuracy as long as the photos are taken within a usable distance range, as determined by camera settings such as ISO and aperture as well as flash settings such as direct or bounce, flash exposure compensation, etc. It is not unusual to hear that some photographers prefer a higher flash exposure compensation setting than the camera's default; it really comes down to a matter of personal taste, assuming that you're using the flash properly. If you're going to shoot at small apertures like f/8 or f/11, it's possible that you might be getting close to the maximum distance range the flash can provide, even at ISO 400 or 800, especially if you're using a diffuser or reflector card. Maximum distance might be reduced even further if you shoot as soon as the ready light appears. You may find that your exposures become more consistent if you use a more moderate aperture like f/5.6, and it might also be worthwhile to consider the use of Compact Battery Pack CP-E4 to speed up recycling time.

Custom WB is the most precise way of setting a white balance in the field, but it's often better to adjust WB during post-processing, especially if you capture most of your images in RAW mode. For that purpose, it's a good idea to shoot a test photo with a known neutral target so you can use DPP's eyedropper effectively while editing your images. To answer your question directly, Custom WB sets WB values more precisely than the 100K increments in Manual WB mode, and it also covers a wider range of K values (down to 2000K for custom WB compared to 2500K for manual WB with the 5D Mark II).

I currently have the EOS 50D and like the Auto ISO function as it keeps the ISO values down. But, when shooting with wide-angle lenses in Av (Aperture Priority) mode shutter speeds can get very low, which is not always desirable (at least for moving subjects) especially with indoor/lowlight photography - like on EF 24mm f/1.4L it will mostly default to 1/30. If Auto ISO is set in Tv (Shutter Priority) mode, shutter speed is as selected but at the expense of depth of field as Auto ISO will always open the aperture to its widest to get the lowest ISO speed possible which again isn't always desirable (due to very thin depth of field) with fast wide-angle primes. So are there any custom functions or modes that I am unaware of that would help me with Auto ISO in this particular situation(s)? Or is there any other EOS camera system that has such options user configurable? I, however, very much enjoy Auto ISO with normal and telephoto IS lenses in daylight.

Auto ISO is a handy function, but as you've discovered, it's not ideal for every possible shooting situation. In the low-light conditions you've described, it might be better to specify the ISO manually and then in Shutter Priority (Tv) mode, set a shutter speed high enough to handle camera shake. Then you could activate Safety Shift (Custom Function I-6-1 on the 50D) to lower the shutter speed if the light level drops beyond the point necessary to maintain a correct exposure at the widest aperture of the lens.

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

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.)

P.S.: The purpose of the Comments section is to allow readers to respond to the content of each month's edition of Tech Tips. New topics or questions should be submitted by e-mail (using the link at the end of each column) in order to support the development of future monthly editions. I appreciate your kind support and cooperation. Thanks!

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© 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 Technical Advisor for the company's Consumer Imaging Group, working out of Canon U.S.A.'s headquarters office in Lake Success, NY. 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 Consumer Imaging Group products including Canon's professional and consumer-oriented digital cameras. Most recently, he has been developing content for online and on-site consumer education projects in Canon USA’s Professional Products Marketing Division.

On the personal side, Chuck enjoys sightseeing, photography, reading, music, and family life with his wife Ying and their beautiful daughter Anna.