Lensblogger

What Lens Do I Want? Part I

This is the question with 1,000 answers. Or at least the question we answer 1,000 times a day. We stock 200 different lens models, each of which is the right tool for some photographers some of the time. Sometimes the question is for subtle differences between specialty lenses: I can wax poetic for half an hour comparing the differences of a Canon 85mm f/1.2,  Zeiss 85 f1.4, and Nikon 85mm f/1.4. But we’ll save that for later. I’m going to focus this discussion on that dreadful moment most of us have faced when after spending a significant bit of money entering the world of SLR photography we find that the kit lens that came with our camera isn’t going to do everything we want.

Focal Length

For most people, the first realization is that they will need a focal length outside of the kit lens. We’re not going to shoot eagles with our 18-55 or 16-85mm lenses and the knee jerk reaction most people have— aided by camera store salesman— is to grab a 70-300 zoom of some sort to go along with the lens their camera came with. For some people this is all they’ll ever need, as demonstrated by the number of “two-lens-kits” sold with introductory level cameras and the fact that most new SLR owners never buy another lens. So focal length is the first factor to consider when asking the “which lens?” question. Focal length is also the simplest part of the which lens equation, it simply is how big or small of a field of view you want.

Given the lens(es) we already own, its usually straightforward to figure out the focal length we’re interested in. There are three possibilities:

1. You already know the focal length. For example, you’re shooting between 70-150mm on your superzoom kit lens and want better quality in this range.
2. You can calculate from shots you’ve tried. For example, 24mm on your zoom only gets half the field of view you want, so after calculations, you figure out you need a 12mm lens.
3. You have to estimate what focal length because you’re about to do a type of shooting you’ve never done before.

This last situation is probably the most common we deal with for LensRentals customers. In this case our first response is always “try to use a zoom in roughly that range”, because a zoom leaves a margin for error. At other times, though, this question comes up when considering telephoto lenses for wildlife and in that situation the answer is usually found by going directly to “how much lens can I afford or am willing to carry?”, because in some situations more length is always better. Supertelephoto lenses increase amazingly in size and cost as you try to get a bit more length or a bit more aperture.

Aperture and Image Stabilization

Before we get too locked in on focal length (because everyone wants to cover everything from 12mm to 1200mm) lets look at the other factors we need to consider. Needed aperture is the second factor to consider. Aperture is more complex than focal length. A wide aperture (small f/ number) lens lets in a lot of light, which is necessary if we’re shooting in low light conditions (indoors) and/or need a fast shutter speed (action shots). The wider the aperture, however, the narrower the depth of field, so larger portions of the picture in front and in back of the subject are out of focus. Done properly in portraits or sports photographs, this is a good thing. But if you’re goal is to get the family group shot at the Thanksgiving table, a narrow depth of field can be difficult to work with. And since the amount of glass needed is inversely proportional to f-number squared, wider aperture lenses cost more— often a lot more— for each extra notch.

One important note needs to be made regarding aperture: the maximum possible aperture of a lens is often not the maximum useable aperture. Almost all lenses get sharper when stopped down a bit. An f/1.4 prime lens may not be acceptably sharp to you until f/2.2 or so. However, this effect varies greatly from lens to lens. Most manufacturers’ top-of-the-line zooms (the f/2.8 constant aperture zooms) are pretty sharp wide open. You can shoot them at f/2.8 and the picture is almost as good as it is at f/4 or f/5.6. Consumer grade zooms (those with variable maximum apertures, like f/4-5.6) usually aren’t quite as sharp wide open and you might really need to shoot it at f/5.6 to f/8 to get the detail you’re after. So, often you might be paying not just for one more stop of maximum aperture, you might be paying for two more stops of useable aperture because the f/2.8 lens is sharp at f/2.8 while the f/4-f5.6 zoom lens isn’t sharp until f/5.6 or even f/8.

This maximum useable aperture varies depending on the lenses in question and its anticipated use though, so a little bit of research is often needed here. The effect is most dramatic on the edges and corners of the lens, especially on full frame cameras, so it may or may not be important. The Canon 24 f/1.4 is quite sharp in the center even wide open, for example, but the edges don’t get maximally sharp until f/4 or f/5.6. A portrait photographer may find the lens is great even at f/1.4, while a landscape photographer may find it unusable until f/5.6. Some online research (or a call to LensRentals) may be needed to find out how much a given lens must be stopped down to reach maximum sharpness. Some general guidelines though are:

• Constant aperture zooms— those that are the same maximum aperture at both the long and short end of the zoom range, usually f/2.8 or f/4— are generally quite sharp wide open.
• Variable aperture zooms— i.e. f/4-5.6— are generally going to perform better stopped down one stop or more.
• Wider angle lenses are more likely to benefit from being shot stopped down, especially in the corners and along the edges.
• Prime lenses, especially those in the 85mm to 200mm focal length are often very sharp wide open. Wide angle prime lenses (35mm or lower) are less likely to be sharp wide open, especially in the corners and edges.
• The widest aperture prime lenses at a given focal length (often f/1.2 or f/1.4) usually have excellent center sharpness wide open, but may not get good edge sharpness until f/2.8 or f/4.

Image Stabilization (or Vibration Reduction, Vibration Control, etc.) will help eliminate camera shake and can allow longer exposures of still images without using a tripod. This will eliminate some of the need for wide aperture for still shots with little motion involved: portaits and group shots, landscapes in low light, etc. Modern image stabilization systems give 2 to 4 “stops” of increased ability to handhold the shot, meaning you might be able to handhold a 1/25 second exposure with a stabilized lens or camera, while you’re only able to handhold 1/150 second without stabilization. This could let you shoot that landscape shot at f/5.6 instead of f/2.8.

However, bear in mind that the IS/VR/VC/OS feature does not break the laws of physics— all it does is combat camera shake at slower shutter speeds, just like bracing against a wall or using a tripod. None of these help at all if your subject is moving faster than your shutter speed, because the long shutter will capture motion blur. If you need a fast shutter speed (say, sports shooting), your options are:

• Wider aperture: capture more light from the scene
• Higher ISO: use less light to capture the scene
• Flash: add more light to the scene at the instant you’re capturing

Stabilization is conspicuously absent. To reiterate: anti-shake features won’t help you try to freeze the action shooting a basketball game or a bird in flight.

Image Quality

Of course, everyone wants the best image quality possible, but there are always trade-offs. Desired image quality is the third factor to consider. Top IQ requires large, expensive prime lenses. Just a slight reduction in image quality allows the better zoom lenses to enter the picture, and a slight further reduction may drop the cost (not to mention size) of the lens in question by half.

It’s best to be practical about what image quality you want, and that generally means considering the what your final output will be. If your goal is to put images up on the internet and print sharp 4×6 inch prints for family members, it’s silly to spend a fortune on the lens with the highest image quality. Most decent lenses (read “most lenses better than a $300 zoom”) will make a reasonably good 8×10 inch print. Again, if you’ll never print more than 8×10, it may not be worth spending top dollar for the top lenses. When you want to make 11×14 inch prints a better quality lens (i.e fixed aperture zoom or standard prime) may be needed to get a good print. And if you want to print big, 16×20 or more, especially on a top-of-the-line 24 megapixel camera, you’ll want the best lens available, generally the ones with the widest aperture.

Cost and Size

Like it or not, for most people, there are limits to how much your back and wallet can manage. Cost and size are the final considerations.Going on a non-photography vacation, I might sacrifice absolute image quality and aperture for a one-lens do it all solution, since I’d rather take a smaller bag and not bother changing lenses. On a photography based vacation like an Alaskan cruise or a safari I might take six lenses and two cameras to catch the different types of shots that might be available.

Finances always are part of the equation, at least for everyone I know. We all have to decide if one stop of increased aperture or a bit of extra sharpness is worth what it will cost. What is true for microscopes and telescopes is also true for camera lenses: “Increasing resolution is increasingly expensive”. A high quality 300mm f/4 lens costs a bit over $1,000, while a 500mm f/4 costs over $5,000. An 85mm f/1.8 lens costs a few hundred dollars, while an 85mm f/1.4 is about $1,000 and an 85mm f.1.2 closer to $2,000. That being said the biggest money waster for many photographers is the not-good-enough lens they bought and threw away because they couldn’t even sell it used. It’s usually better to save for a while and get a decent lens than to buy a piece of junk that has to be replaced.

Get to the Point Already!

To summarize, we’ve got 4 main factors to consider when deciding “What lens do I want?”

• Focal length
• Aperture, modified in some case by the presence of image stabilization
• Absolute image quality
• Number, size, and cost of lenses

The first step in choosing lenses for a given situation is to rank the four factors in order. Actually, that’s the second step— the first step is to take a deep breath and realize you will be making compromises. There is no 18-500mm f/2 lens that only weighs 2 pounds and costs under $1,000. So our second step is to look at the various factors and decide what’s the most important. If you’re shooting wildlife, a long focal length is most important. If you’re shooting action sports, it’s a wide aperture. If you’re going on vacation it may be that only one or two small lenses are needed. For a fine portrait, absolute image quality may be number one. Then, proceed to what’s next in importance. For wildlife shooting, it may be lens size if you have to carry it three miles to the shoot. (Of course, that might not be a consideration if you have an assistant.) For sports, focal length is probably the second most important factor. For vacation with one lens and for the fine portrait, the range of focal length will probably be number two on the importance list.

The third and fourth factors may be of limited importance or nearly as important as the other factors. Before I get to them, though, I generally take a look at what lenses meet my first two criteria. If there aren’t any (say I need a 17-35 f4 image stabilized lens for Nikon), I need to reassess my requirements. Assuming there are such lenses, then it’s time to make sure that they are going to be acceptable in terms of the other factors. In my experience, most people who are unhappy with their lens choice either didn’t take all four factors into account when making a decision, or they failed to face the reality that the lens they needed just isn’t available in their price range. For example, we have at least one renter every month who tells us the 70-300 f/4-5.6 lens gave them blurry pictures. After looking at what they shot we find they were trying to use the lens for indoor sports, the shutter speed given the f5.6 aperture was 1/25 second, and every picture is horribly motion blurred. When we talk to them, they usually say “I wanted an inexpensive zoom to shoot indoors with”. Unfortunately, there just isn’t such an animal and they therefore just went with two factors: focal length and cost. Not considering aperture resulted in them wasting their money and getting no useful shots.

Even if the other factors don’t seem important on our original list, they may be and should at least be glanced at. I can tell horror stories like the five foot tall, 100 pound lady who rented a 400mm f/2.8 lens— which weighs 9 pounds and is 2 feet long— because she wanted the best absolute best image quality available and a wide-aperture telephoto. She never asked how big it was and we didn’t realize she planned on shooting it handheld from the stands at her son’s first football game. Or others who took a 70-300 f/4.5-5.6 to an indoor concert because it was the longest zoom that was small enough to fit in their coat pocket and ended up with 400 shots of motion blurred lights. And we don’t even want to talk about the person shooting their first wedding who rented a fisheye for the group portraits because it was the only wide focal length in stock that day… let’s just say the plus-sized bride was not flattered by what the fisheye did to her in the family portrait.

An Example or Two

Lets walk through a couple of common examples.

“I want one or two lenses maximum for my vacation. I use a crop sensor camera.” Okay. First, let’s refine that, because depending on the person asking the question I can think of 42 different things they mean. Let’s rank our priorities. Probably number and size of lenses is number one on our list (one or two relatively small lenses). Focal length— nearly everything— is probably number two. There are a number of good superzoom solutions that fit our focal length requirements. Each manufacturer has an 18-200mm image stabilized zoom, Sigma offers an 18-200mm in each mount, and Tamron adds 28-300mm and 18-270mm zooms. All are small aperture, so they’re suited for outdoor work primarily, but have image stabilization so they may be okay for brightly lit indoor shots where the subjects are still. Image quality and price are comparable for all of them.

Let’s check off the other factors though, and to do that we need to know what will you be shooting. If its the family at the beach, aperture isn’t an issue so we’re all done— one of the supertele zooms is perfect. If its a week in Rome, with narrow streets, superb wide angle views, and magnificent indoor cathedrals and museums where flash isn’t allowed, that lens will be nearly useless. In this case, we really should go back and adjust our priorities, putting “wide angle” and “wide aperture” as our priorities. A Canon 40D shooter may want a 17-55mm f/2.8 IS and a 10-22mm in that situation, while a Nikon D700 shooter would prefer 14-24mm and 24-70mm f/2.8 zooms.

“I’m going on a wildlife safari.” Here, priority one is a long focal length. Priority two is usually size— it may not be possible to carry a 500mm f/4 lens through three airports and from camp to camp. So lets look at our choices: we have a number of zooms that go up to 500mm in length, and several others that go to 400mm that are reasonable size. There are also prime lenses in the 300mm f/4 (and for some brands 400mm f/5.6) range that are even smaller physically and provide slightly higher image quality than the zooms. A bit larger than the zooms physically are 300mm f/2.8 lenses that could be used with a 1.4x teleconverter to give an effective 420mm f/4 lens.

Before we go any further, please raise your right hand and repeat after me: “I will not try to use a teleconverter on a zoom, or if I do I won’t complain about how autofocus wasn’t accurate and the images sucked.” Thank you, I appreciate that.

The next decision probably requires us to determine if image quality is our third or fourth priority, and if we’ll be shooting much in dawn or dusk low-light situations requiring a wide aperture. The prime lenses will give slightly sharper images. The difference will be visible in large prints, but maybe not too much in 8×10 prints. On the other hand, taking a prime will require us to have at least one other mid-range lens like a 70-200mm for closer work, while the zoom will cover that range and the telephoto range in one lens. Dawn or dusk shooting means we will want at least an f/4 lens, and may make the 300mm f/2.8 an even better choice. Since animals on safari are usually fairly still, and Safari jeeps often rock around as photographers jostle for position, and image stabilized lens may be a high priority too.

So, what’s the right answer? It depends. If a bit of size, carrying a second lens for midrange work, and absolute cost aren’t dealbreakers, and absolute image quality is high on the list, the 300mm f/2.8 with a teleconverter is probably the right answer. If cost, and not carrying a second mid range zoom is a bigger priority, than one of the 80-400mm or 100-400mm image stabilized zooms is probably the best choice.

At this point, too, there’s a lot of different choices depending on the brand of camera equipment you use. Canon shooters have the choice of a 300mm f/4 Image Stabilized, 400mm f/5.6, 400mm f/4 DO, or a pretty decent 100-400mm f/4-5.6 zoom. Nikonians have a wonderful 300mm f/4 (but not vibration controlled) and the 80-400mm, and if they don’t mind a bit of extra weight the amazing 200-400mm f/4 VR. Olympus 4/3 shooters benefit from the 2x crop factor of the 4/3 sensor which makes their 90-250mm f/2.8 the equivalent of a 180-500mm f/2.8 on a full-frame camera and the 300 f/2.8 the equivalent of a 600mm lens. Sony’s choices are bit more limited (read as “only a 300mm f/2.8”) but the Sony in-body image stabilization makes the Tamron 200-500 a reasonable alternative, and the 500mm f8 reflex lens gives a supertelephoto option that none of the others have.

Another common example is covered in some detail in our Shooting Indoor Sports tutorial posted earlier. And in a week or two, I’ll put up another bit discussing how to start choosing lenses for your permanent kit.

Canon's Err 99

This is probably the most boring article I've written for LensRentals. (Personally, I like the Smashed Front Element thing the best.) But, I love a good mystery, and I love debunking DSLR "urban legends". Every so often I run across an online forum where someone makes broad statements about Error 99 which I know are incorrect or at least incomplete. As is my practice, I've boldly charged into these online gunfights devoid of intellectual ammunition (i.e. facts). And predictably, the intellectual level of the discussions quickly spirals down from "Is not", "Is so" into the traditional online-forum sign-offs of "You get Err99 because you're a bad photographer" and "if you've never gotten Err99 you're obviously not taking many pictures". Because Canon Corporate apparently believes that releasing no information about a problem makes it go away, there is little factual information to debunk the online myths regarding Err99 unless you really do a lot of digging. Googling Err99, Canon EOS error codes, etc. brings up several dozen pages of links most of which are the above mentioned "discussions". There are a few nuggets of truth out there, though. The most complete of these is a multi-year 2,300 post discussion of Err99 problems at Richard's Notes. There are also a few thoughtful and factual discussions that have taken place in some of the better forums online. After spending far more hours than I intended looking through these sources to settle an online debate, I thought I'd write a summary of what I found and what we've experienced here-- LensRentals has 700 Canon lenses and 50 Canon bodies, so we have a bit of Err99 experience. The Myths Some of the most common Err99 myths are listed below. Strictly speaking, they are not myths; almost every one is true. The myth part comes from thinking that any one of them is actually *the* cause of Err99. So: Err99 results from an electronic communication problem between the lens and the camera. Err99 results from using third-party (i.e. Sigma, Tamron, Tokina) lenses. Err99 means that electronic circuitry in the lens has failed. Err99 means that electronic circuitry in the camera has failed. Err99 results from using third party batteries. 

Err99 is a firmware issue, and can be fixed by upgrading to the latest firmware.

Err99 started with Canon XT and 20D cameras.

There are a lot more. Almost all of them are true for at least some cases of Err99. The best myth, though, is that Canon purposely created error 99 to prevent the use of third party lenses. As best I can tell, that one isn't really true, but it does make fun speculation. And, of course, Canon's nearly total silence on error 99 and other problems certainly helps feed the conspiracy theorists among us. A Brief History of Error 99 Canon no longer officially comments on Err codes, but if we go back to the golden days when they did, we can unravel a lot of the Err99 mystery almost immediately. Back in 2000 Canon released its first mainstream DSLR, the 3.1 megapixel D30. The manual contained a helpful list of the camera's built in error codes: ERR 09: System Error. This error occurs when the EOS D30's self-checking system processing time has exceeded the specified limit. ERR 22: CF DRIVER. Data cannot be written to the CF card for some reason or another. ERR 23: NO SPACE LEFT ON THE CF CARD. Space remaining is smaller than needed to complete the write operation. ERR 50: CF FORMAT. The CF card cannot be formatted in the camera. ERR 51: PLAY MODE. The CF card cannot be played back in the camera. ERR 80: SHUTTER. The shutter operation sequence has not been completed correctly. ERR 81: MIRROR. Mirror up/down status cannot be detected during shutter release. ERR 82: STROBE. The built-in flash cannot be charged. ERR 83: POP UP. The built-in flash's pop-up operation cannot be detected. ERR 84: LENS COMMMUNICATION. Electronic communication with the lens cannot be established, or the aperture diaphragm cannot be controlled. In 2002, the D60 was released. It had a reduced set of error codes: ERR 01: LENS COMMMUNICATION. Electronic communication with the lens cannot be established, or the aperture diaphragm cannot be controlled. ERR 02: CF DRIVER. Data cannot be written to the CF card. ERR 04: NO SPACE LEFT ON THE CF CARD. Space remaining is smaller than needed to complete the write operation. ERR 05: POP UP. The built-in flash's pop-up operation cannot be detected. ERR 99: SYSTEM ERROR. There is an internal malfunction detected during the camera's self-checking procedure which is executed before every attempted exposure. Key point: Error 99 is a catch-all which can mean almost anything went wrong. As far as we can tell, the Canon error codes have remained the same through the 50D and 5D Mark II camera bodies, at least nominally. The more recent bodies have added an Err 06 code for 'sensor cleaning unit malfunction', and there are now ERR 10, 20, 30, 40 . . . 80 codes on 5D Mk II cameras (with the useful message "Shooting is not possible". Duh!). Also some more recent manuals now define ERR99 as "an error other than one of the above (ERR1-ERR06)" has occurred. The only semi-official statement from Canon in recent years is one from Chuck Westfall in TheDigitalJournalist saying "[ERR99] is a non-specific error code which can be caused by a wide range of malfunctions. [...] a variety of problems can be caused by the use of non-Canon accessories such as lenses, memory cards, battery packs, electronic flash units, etc." Now, Let's Speculate We know from the above that the ERR99 code has existed since the D60, but most of the current ERR99 online discussion and speculation started around 2003-2004. A large part of this is for obvious reasons: the number of Canon SLRs in service exploded around 2003 and 2004 with the introduction of the Digital Rebel and the 20D cameras. There are some other factors that may have contributed to the marked increase in ERR99 reports around this time. Several changes that occurred, but probably did not have much to do with the ERR99 increase include: The EF-S lens mount was introduced in 2003 with the Digital Rebel. Canon flash systems changed to E-TTL II in 2004. E-TTL-II largely incorporates a change in the flash calculations done in the camera body and communicated to the flash unit through the hot shoe. (Some people state ERR99 problems involving flashes have only occurred since this change, but these are rare at any rate.) In 2003 Canon increased the number of autofocus points in prosumer cameras from 3 to 7 (10D) and again to 9 in 2004 (20D). The Digic image processing chip was introduced in prosumer cameras in 2003, and the more powerful Digic II in 2004 with the 20D and Rebel XT. There are a few changes, however, that logic suggests might have had some causative effect on ERR 99 messages. Lens-to-Camera Electronic Communication Although Canon hasn't said so specifically, pretty strong circumstantial evidence indicates that the electronic connections between lens and camera were changed at least once and probably twice since 1998. The first change is probably better documented and seems to have occurred first with the EOS 3 and EOS 1V film cameras, which introduced the 45-point autofocus system later used on the 1D series digital SLRs. A number of third party lenses (mostly Sigma) would not communicate autofocus information with these cameras, and required re-chipping by the manufacturer to regain compatibility. The same problem occurred with the introduction of the 10D digital camera, which increased prosumer autofocus points from 3 to 7 and introduced the Digic processor. Of note, those incompatible third party lenses gave and ERR99 message, not ERR01, when used with the 10D. As best I can find, the first widespread ERR99 reports occurred when third party lenses couldn't communicate electronically with the new 10D camera, and the soon-to-follow Rebel and 20D. This is the source of many people's partially incorrect belief that ERR99 always means a miscommunication between camera and lens. Lens Current Draw The second change is less clearly established. Some sources state that lenses with IS systems have higher electric current transmitted from the camera than other lenses do, which makes sense, considering that they have more work to do. In-lens image stabilization first appeared in 1995 with slight improvements in 1997 and 1999. A major improvement was made in 2001 with the faster IS system used in the 70-200 f/2.8L IS and again in 2006 with the new four-stop system in the 70-200 f/4L IS. The newest IS systems are more powerful and stabilize more quickly (0.5 seconds as opposed to 1 second with older systems), so it's logical to assume they draw more current across the connections, although this is not documented anywhere that I can find. Several lenses with newer IS, including the 70-300mm f/4-5.6 IS (2005), EF-S 17-55mm f/2.8 IS (2006), and 70-200mm f/4L IS (2006) became very popular with photographers shooting EF-S mount cameras. We know that malfunctions in some of these lenses, most commonly reported with the 17-55 f/2.8 IS, cause ERR99 (and not ERR01) on EF-S mount cameras. Cleaning the electronic contacts on the camera and lens will often fix, or at least improve the problem. There are a few reports that the problem is more common with original Digital Rebel and 20D cameras, and less common with newer cameras; our data supports this too. Some knowledgeable people have speculated that there was a change in contact alloy, a thinner layer of gold plating, or other electrical contact issues with the XT and 20D cameras that make it more difficult for these cameras to deliver the required current to the newer IS lenses. On the other hand, the problem may simply be more common with older cameras because the lens contacts are more likely to be worn. In-Camera Voltage Drops Another theory that has some factual basis was reported several years ago on "DPReview":http://forums.dpreview.com/forums/read.asp?forum=1019&message=11025585. A tester found that Canon 20D cameras would display ERR99 if the camera voltage fell below 7.3 volts. The BP511 battery used in all prosumer cameras prior to the 5D Mark II should deliver a bit over 8 volts in fully charged state, but will fail to deliver sufficient voltage in certain conditions: dirty contacts, failure of a cell within the battery, age, rapid power consumption, or some combination of the above. This certainly would explain the ERR99 problems occurring with bad batteries or bad battery contacts. Again, just speculating, but I would suggest that a fall in voltage across just part of the camera circuitry would also cause ERR99-- for example, across dirty or corroded electrical contacts, across a cracked ribbon cable, or perhaps a slightly corroded circuit board connector. I'll come back to this idea later. Common Causes of ERR 99 I'm listing these in my own perceived order of frequency, combining our experience at LensRentals with reading countless online ERR 99 reports. * Lens/camera electrical contact failure * Lens circuit (AF or IS) failure * Camera electronic circuit failure (see below) * Broken or stuck lens aperture diaphragm * Older third-party lens with incompatible electronics * Jammed or damaged camera shutter curtain * Mis-formatted or damaged card * Damaged or corroded cell within camera battery * Corroded battery or camera contacts * Incorrectly mounted battery grip, particularly if it's too loose * Camera/hot shoe electrical contact failure * Moisture condensation within camera or lens Most of us cannot define in-camera circuitry failure more specifically than "it went to Canon for repair", but a few skillful individuals have disassembled their ERR99 frozen cameras and reported things like loosened solder splats that were causing shorts, ribbon cables not firmly seated in their connectors, loose metal shields in the camera that could move enough to short or ground an electrical part, etc. If you've never seen the insides of a digital SLR, there are an amazing amount of electronic connections packed into basically no space in there. Experience at LensRentals.com There are a number of "what to do when ERR 99 occurs" lists that I've summarized below. Before we jump to them, though, I think its important to try to narrow down the ERR 99's cause, rather than to go through the list and hope everything is better. I realize "finding the problem" sounds remarkably obvious, but bear with me for a second. With hundreds of lenses mounted to hundreds of different cameras at any one time, we deal with a lot of ERR 99 problems. Some ERR 99 issues are specific and immediate: suddenly the camera starts giving ERR99 with almost every shot. Resetting the electronics helps for a few shots-- or doesn't-- but the problem recurs and the camera is basically useless. These "catastrophic" ERR 99 episodes usually means there's been a major injury in the camera or lens: shutter failure, circuitry burnout, etc. Sometimes the fix is easy-- new battery, smoothing a jammed shutter curtain, changing lenses, etc.-- but most often a trip back to the mothership for either the camera or the lens is in order. Other ERR 99 problems are more subtle: ERR 99 shows up after a lens change, lets say. Cleaning the contacts makes it go away, but it comes back a week later, getting more frequent over time. It may just be with one lens at first, but may start occurring with other lenses. In these cases I think it important to remember the point about electrical voltage made above: if voltage drops below 7.3V in the camera's circuitry, ERR 99 is likely to occur. Voltage drops across different connectors are cumulative, and batteries produce less voltage as current increases. What may seem a case of dirty contacts may really be a narrow power margin, due to oil on the lens contacts, an old battery that's not producing its rated voltage when fully charged, a lens that's sucking down power to run the IS servos, which finally drops below the lower operating threshold when autofocus is activated. Cleaning the lens contacts might help, but that doesn't make it "the problem". So, be careful when diagnosing intermittent problem. For example, once or twice a month we'll have a customer tell us "the lens is causing ERR 99 on my camera, none of my other lenses do that", so we send them a replacement. We have the luxury most individuals don't get in that situation: the ability to test that lens on multiple cameras, plus the customer who is about to try another copy of the same lens on their camera. In some cases, the customer will tell us the second lens is the same as the first; meanwhile, the first lens seems fine when tested on other bodies. Here, the problem is a weakness in the customer's camera body that became apparent only when a lens with heavier power requirements was used. In other cases, the second lens works fine for the customer and the first lens, when returned, gives ERR 99 on other bodies. Again, problem obvious, the lens had internal damage to the electronics or aperture system. In a lot of cases though, the problem is less obvious. The new lens works fine for the customer, the old one seems to work well on other bodies. At first, we just shrugged our shoulders and said "one of those things" but over time, as we track the problems that occur with various copies of lenses and cameras, something became apparent to us. Unless we found the specific cause of ERR 99 and corrected it the problem, while intermittent, would recur. We've worked on developing an ERR 99 stress test for lenses that only show the problem intermittently: we use an older camera body, halfway charged battery, and take up to several hundred shots being sure to change the aperture, zoom, and focal distance frequently. Doing this we're sometimes able to reproduce the problem in a lens that otherwise seems to have just had some isolated ERR 99 reports. That being said, there are also circumstances where ERR 99 has occurred and then never, ever happened again: * Using older battery (solved after replacing battery) * Bad CF card (solved after replacing card) * After marked temperature change (solved after letting the camera sit for a day or so, probably condensation) * After mounting battery grip (solved after remounting the battery grip) * With single lens only, all other lenses fine (solved by repairing the lens) * Early-revision 50D (solved after firmware update) * Camera used with third party shoe mounted flash (solved after flash removed) * Dirty contacts (solved by cleaning, sometimes that's the only problem) * For no apparent reason, it went away for good after doing the routine ERR 99 protocol. This part reminds me of "any sufficiently advanced technology is indistinguishable from magic"... The LensRentals Error 99 Process This is based on Canon's technical support suggestions, with a couple of additions we've made as we gained experience. First, we pull a "tech support": reboot. 1 Turn camera off. 2 Remove battery. 3 Replace battery. 4 Turn camera on. 5 Try a shot. Sometimes that works. If not: 1 Turn off the camera. 2 Remove the lens, battery, date-time battery (see below), and CF card.

3 Allow the camera to sit without power for approximately 20 minutes with the power switch "on". Recharge the battery during this time. (Full disclosure here: somebody once suggested the 20 minutes and power switch on part, we want to top off the battery anyway, and we've generally got other stuff to do so we do it this way. Waiting 30 seconds and using a different, fully charged battery would probably be just as good, but this is what we do.) 4 Turn off the camera, replace the backup battery, insert the fully charged battery, turn on the camera.
 5 Press the shutter button to check for ERR 99. 6 If ERR 99 occurs, remove the battery, examine and clean the battery and camera connections. If at all possible, try a different battery. 7 If ERR 99 still occurs, use the sensor cleaning function to raise the mirror and open the shutter. If the shutter does not completely open, it is the source of the problem. If a leaf is out of alignment, some people have reported using a soft brush to move the shutter leaf back into place. Personally, I'd send it in for service. 8 If ERR 99 still occurs, the camera almost certainly needs service. You might try reinstalling firmware, but it's unlikely to work. If there's no ERR 99 after the above, the next step is to check the storage system: 1 Insert and format CF card, then press the shutter button as you would to take a picture. 2 If ERR 99 try a different brand and size of card. If no ERR 99, the problem was the card and you should be done. 3 If ERR 99 still occurs with a different card, the problem is with the camera's card connections, and repair will be necessary. Finally, check the lens: 1 Turn the camera back off. 2 Gently clean the contacts on both the lens and the camera (see Note #2 below)

3 Remount the problem lens, set to manual focus, IS off, widest aperture and take a picture. 4 If no ERR 99 with everything off, activate autofocus, then IS, then stop the aperture down, taking a picture to confirm no ERR 99 after each step. 5 If ERR 99 occurs, try a different lens. If only one lens is a problem, that lens needs servicing. You'll get better service results when you can be specific: i.e. "ERR 99 only when IS activated, etc." in your service request. 6 If ERR 99 occurs with more than one lens, and no other cause is apparent, the camera needs to head to Canon for repair. Note #1: Some ERR 99 problems occur only with the camera in certain settings: i.e only in Av mode, or only in AI servo. In these cases, repair is almost certainly needed. Note #2: I know first-hand that Canon Service Techs use the "gently rubbing a clean pencil eraser" technique of cleaning the electrical contacts. I also know that knowledgeable electronic engineers state this is a bad idea, that the friction could wear out the gold plating on the electronic connections, leading to corrosion. Radio shack and other electronics stores sell electrical contact cleaning solution that can be used with a Q-tip or soft cloth to clean the contacts as an alternative. I'm still using the eraser; I figure if rubbing metal contacts across each other every time I change a lens isn't wearing out the coating, the pencil eraser sure isn't. h2. End Game I know this has been an overly long and probably not-very-useful essay, but it's a topic I really got into. I certainly will have made some omissions or mistakes in something this long and complex. I welcome corrections and suggestions from any of you with different experience in this area and plan on updating and upgrading this piece as I get more input.