Puma Ocean Racing’s entrant in the 2011-2012 Volvo Ocean Race, Mar Mostro (Monster of the Sea), sails with the spectator fleet after winning Leg 6 (Itajai, Brazil to Miami, FL, United States). The Volvo Ocean Race is a 39,000-mile, 10 month, regatta that circumnavigates the globe stopping briefly in ports around the world to replenish, race, and make repairs.
I undertook a personal search in an attempt to try and find the limits and conditions where one could expect the EOS 5D Mark 3′s light leak to affect their metered exposure. In the process of making these measurements, I’ve tried to account for and control errors as best I can; however, in many cases I lack the appropriate instrumentation to make precise measurements.
My initial objective had been to build a mathematical model to quantify the problem and then make testable predictions from it. In the process of doing that it became painfully clear that I lacked the precision in test instrumentation to make it count for much. Though it did turn out to be a good point to start from in the empirical tests I ended up doing.
I don’t work for Canon, in some ways I wish I did, as I’d at least have a paycheck coming in for this kind of thing. That also means that I have a completely statistically irrelevant sample size of 1 camera. The one I bought.
That brings me to outliers. I don’t think my camera is one, either good or bad. However, without a statistically relevant sample size, I can’t say for sure. What I can say for sure, is if your 5D mk. 3 shows consistent exposure errors under normal shooting conditions in daylight or otherwise, there’s something wrong with your camera.
One other thing, in this article unless I say otherwise assumes when you see EV I mean EV100, or the EV at ISO 100.
The good news is that, in my opinion, it takes a pretty impressive set of hoops to jump through to get the meter to start being a problem, and especially a more than 1/3rd stop problem. Moreover, in very low light situations you can go quite a bit lower than 1 EV and still not see the backlight affect the exposure, especially with an f/1.4 lens.
In my testing, with a Canon EF 24-70mm f/2.8L USM lens, it took a scene somewhere around -3 and -2-2/3rds EV to induce a backlight error. With a 24-105mm f/4L IS USM, that jumped a bit to around -1-2/3 to -1-1/3 EV.
The difference between the two lenses is a byproduct of their various transmission percentages (the 24-70/2.8L is a t/3.3 lens wide open, the 24-105/4L is a t/5.1 lens at 70mm wide open). The difference in transmission is a bit less than 1-1/3rd stops and that nicely corresponds to the differences in scene illuminances where the error first occurred, as it should.
This brings up an important point, and it applies to more than just the 5D mark 3, but in fact to all camera meters. The speed of the lens, specifically in t-stops, will affect the bottom limit for the meter’s accuracy. A 24mm f/1.4L will be able to meter accurately in a darker scene than a 17-40 f/4L will. This is simply a byproduct of the fact, that the lens always attenuates some light before it can reach the sensor or meter. The light the lens attenuates, the more noise, or in the case of the 5D-3 leaked light, will influence the meter readings.
The problem isn’t strictly related to the backlight, that’s just what prompted its discovery. More generally, the problem is that light on the top LCD or produced by the backlight for the top LCD leaks to the meter. The amount that does is a very small percentage of the actual incident light; however, given the right conditions it can become significant enough to affect exposures in other than just dark situations.
This is the not so good news for some, and a non-issue for others, and much, much, more complicated than just the backlight in the dark.
Because of the nature of the leak, what we’re really looking at is a situation where the meter is fed light from a 3rd highly attenuated source, in addition to the lens and viewfinder. How attenuated I’m not entirely sure yet, but it looks likely to be about 35,000-100,000 times. This works out to something like 15.1-16.5 stops (including the losses of the lens), give-or-take, to show a 1/3rd stop error.
This isn’t necessarily great but it does mean that uncontrolled illumination of the LCD isn’t going to be an appreciable problem for most people. With the camera in direct sunlight, it takes about 10 stops of ND + a t/5+ lens to show a 1/3 stop error in metering. I’ve done 3 direct tests of this, metering a clear blue northern sky as a similarly lit approximately mid toned target.
|
Lens / Filter Combination |
Effective loss in T-Stops (Lens + filter) |
Meter Changes when Shaded |
| EF 24-70mm f/2.8L USM + Hitech Pro Stop 10 + B+W Kaesmann CLP + B+W UV 010 |
15.15 |
Yes |
| EF 24-105mm f/4L IS USM + Hitech Pro Stop 10 + B+W UV 010 |
15.35 |
Yes |
| EF 70-200mm f/4 IS USM + Hitech Pro Stop 10 + B+W UV 010 |
15.05 |
No |
There is a caveat to all of this though, included in that 15-odd stops, is the lens’s transmission as well. In other words, a person using an f/1.4 lens will be able to operate over a wider range of conditions than someone using an f/5.6 lens will. Likewise, using an adapted lens where stop-down metering is necessary will be even further constrained.
In practical terms, you have to place a considerable amount of neutral density in front of the camera’s lens, or have an incredibly slow lens, to prompt a metering error in daylight.
The one real conclusion that I can draw from this is that, as Canon states, the light leak won’t be an issue for most users. Interestingly, the people most likely to be affected are actually ones that are using lots of ND and still expecting the camera to meter though the ND instead of metering and adjusting for the ND manually; especially if they are using adapted lenses that have to be manually stop-down metered.
Moreover, in the time since I started looking at the problem and now, Canon has announced that they’ll fix cameras for people that believe this is a problem for them, as well as having updated their manufacturing to include a better light shield over the meter and prism.
What I can say from my own experience, and I’ve done a considerable bit more shooting with the camera in practical situations since I looked at the problem, is that there’s very little if any reason for most people to run back to Canon to get this fixed, or even bother. While I may have this addressed eventually on my body, I’m in no rush to do so either and will definitely only be sending my camera in when it’s convenient for me.
I’ve been seeing an intermittent but reoccurring issue over the past couple of days with my 5D mark 3 and 8GB SandDisk Extreme III 30MB/s flash cards. I will, on occasion, get an ERR 2 that the camera can not write to the card. Removing and re-seating the card will fix the problem for the duration of the time the card is in the camera.
Now before people start with the Canon fail drama on this, these are old, fairly well used (but not excessively), non-UDMA cards, and that I don’t see the issue in any consistent way. Nor do I seem to have an issue when using my Lexar 16GB 300x UDMA cards, though I’ve not used them enough to be really sure.
Also the issue seems to be both intermittent and dependent on how much writing the cards are doing. I can blow though the entire card several times over, then all of a sudden at the end of an extended high FPS shoot or while recording a video segment, it throws an ERR 2. I can’t do anything on the camera with respect to shooting or what not that prompts the issue. The only thing I’ve noticed is that after heavy use the CF cards are warmer than they’ve ever been for me—I think this is expected due to operating at near maximum write speed—but at the same time it may be contributory to what I’m seeing.
As it stands I’m leaning towards this being a localized card issue but I thought I’d throw this up and see if anybody else was seeing something similar.
If you’re seeing an ERR 2 or a card write failure and have a Canon 5D Mark 3, if you wouldn’t mind please drop a comment in the comments section with the type of card you’re using, what you were doing (i.e. continuous bursting, recording video, etc.), whether the card is UDMA or not, and approximately how well used it is?
The Black Diamond jet team’s L-39 Albatrosses fly in formation at the 2012 Lauderdale Air Show.
With weather taking a turn for the worse backed against storm clouds, the USAF Thunderbirds 1-4 make a pass in a diamond formation at the 2012 Lauderdale Air Show.
Thunderbirds 1 through 4 fly in their diamond formation during a practice run for the 2012 Lauderdale Air Show.
Thunderbird 6 flies overhead during a practice run for the 2012 Lauderdale Air Show.
Thunderbird 1 flies past during a practice run for the 2012 Lauderdale Air Show.
The USAF Thunderbirds overflying a Fort Lauderdale neighborhood during their practice run for the 2012 Lauderdale Air Show.
Update May 1, 2012: I’ve published a preliminary report on the extent of the issue I’ve seen on my camera. Though not as scientific as I wanted it to be, it’s good enough to draw some conclusions about how and what situations could cause metering issues.
Update April 23, 2012: Canon has updated the service notice regarding the light leak situation. Canon will be offering a free inspection and adjustment on a voluntary basis if you feel your camera is operating improperly. I have to say this is about what I expected them to do. In the mean time I’m in the process of trying to put together a write up based on my findings under various conditions. Unfortunately due to limited time and equipment, I was unable to investigate to quite the level of rigor I was hoping to be able to, but even with the wider error margins from what I could do, the picture is vary clearly one of a non-issue at best, and a potential issue for a very small minority of users at worst.
Update April 13, 2012: I don’t know if I should be surprised or not, but Canon has officially acknowledged the top LCD backlight affecting the meter in certain dark environments and that they are working on a fix for it. The official service notice has been posted by Canon USA, and I’m sure if they haven’t already the rest of Canon’s global sites will have similar notices posted soon.
Update April 9, 2012: I have spent some time playing with the range where the back light causes a metering error, and so far as my limited testing shows as long as you’re operating in the EV 1 to EV 20 metering range, the meter behaves correctly. I used a 45W lamp, on an X10 lamp module, and shot at f/4 ISO 3200. The test goes something like this.
For my test, I’ve summarized the the settings and whether the meter was affected by the backlight in the table below.
| Summary of EV, shutter speed, and backlight error at f/4 ISO 3200 | ||
| EV | Shutter Speed | LCD Backlight Effects Metering |
| EV -1 | 1s | Yes |
| EV 0 | 1/2 | Yes |
| EV 1 | 1/4 | No |
| EV 2 | 1/8 | No |
| EV 3 | 1/15 | No |
Even though the meter seems to work correctly inside the designed/specified EV 1-20 range, I still think that Canon should address this.
Update April 8, 2012: I’ve been keeping up with the discussion on Canon rumors forum and my own testing and the thing is there doesn’t seem to be any real impact in metering when actually shooting. Moreover, there are a number of people reporting that they can reproduce the behavior on a huge verity of cameras including Nikon bodies. Given that, and the fact that I see virtually no difference in metering between my 5D Mark 3 and my other bodies in actual use and under conditions that are within the design parameters of the light meter (i.e EV 1-20 with a 50mm f/1.4 lens as ISO 100) I’m even more comfortable in my conclusion that this is even more of a non issue that I had initially believed.
Originally Posted April 7, 2012: Canon Rumors is reporting that there’s a potential light leak in the 5D mark 3 LCD into the viewfinder. Subsequently, at least for some it seams, the world has ended, and we should all send our cameras back to Canon, switch to Nikon, flail our hands over our heads and generally freak out.
That said, there doesn’t seem to be much of a problem in actual practical usage of the camera.
If you have a 5D mark 3, or really any other camera, you can test it for this light leak by following the procedure outlined in the Canon Rumor’s article.
I sat down and ran the test, and yes, turn the backlight on and my 5D mark 3′s meter changes when the backlight is on and both the viewfinder cover and body cap are on. Out of curiosity, I figured I’d test this out on my other bodies as well. My 40D doesn’t exhibit this behavior, even when shining a light on the LCD. However, the meter on my 1D mark 3 does change, though it requires shining a light on the LCD not the backlight.
But the real concern for me, is if the “light leak” is leaking to the sensor during an exposure or just the meter, since this would be a real problem. Fortunately this doesn’t appear to be the case at all.
1 second, ISO 25600, Light shone on top LCD |
1 second, ISO 25600, No light on top LCD |
Both images are uniformly black and have no noticeable localized lightening. Moreover, at ISO 25,600 even a small amount of light, never mind a 3 D-cell Maglight at point blank range if there was a light leak that effected the sensor there would be a something in those images.
So all this has the potential to do is affect the metering in practice in the real world?
Maybe.
Under normal use, I’m having a hard time finding a situation where there’s an change in metering that 1) I can attribute directly to the top LCD leaking and not a change in the composition, subject, eye-placement at the viewfinder, or lighting, and 2) where said error in metering is appreciable enough to affect the captured image in any appreciable way.
So far as I can tell, so long as the light levels at the camera and subject are in the same neighborhood, there’s really no impact what so ever. The only case where I can make an appreciable change by shining light on the top LCD is when it’s basically the only light the camera’s meter is seeing.
In any case, I’m certainly not all that concerned. As I already mentioned, if I shine a light on my 1D mark 3s top LCD under the same kinds of ambient conditions and I can get the meter to change as well. However, in more than two years of using that camera, I’ve never had a single exposure related problem.
So what should you do?
Well that’s up to you, but I’m going to continue to use my camera as I normally would. Moreover, whenever Canon gets around to addressing this—and I’m assuming they will—I don’t expect to be real quick in sending my camera back unless it’s also convenient for me to do so. While this certainly shouldn’t happen and it would be good to have fixed, it also doesn’t seem to be impacting my images either and that matters more than any potential problem that doesn’t quite manifest itself in real world usage.
