For the first time, after using Canon equipment for nearly 20 years, I experienced a mechanical problem with a Canon lens.

I was on a location shoot and, while looking through the viewfinder of my camera, suddenly everything went black. I depressed the shutter and nothing happened. Auto focus wouldn’t work, the camera was locked up. All I could see was darkness in the viewfinder and, although the camera was still powered on, it was completely unresponsive.

At first I thought my camera had packed in. So I removed the lens and depressed the shutter again to see if my camera body had actually failed. Then, without the lens attached, the camera shutter at least fired. Then I thought, if the camera isn’t taking pictures when the lens is attached, then it might be something wrong with my camera settings. At that point it hadn’t occurred to me yet that something actually went wrong with the lens while I was shooting.

But then I held the lens itself up to the light to look through the lens and I discovered that the aperture blades of the diaphragm had closed down into just a tiny little hole. I could barely even see any light coming through the lens, which is not normal. That’s when I figured out I had a real problem and might not be able to continue the photo shoot that day.

But before completely giving up, I tried putting the lens back on the camera and switching it into manual focus, yet nothing changed with the diaphragm. It was still stuck in the same closed down position. I could at least fire the shutter though with the lens set to manual focus, but shutter speeds were way off and the camera showed an error message on the preview screen each time after I depressed the shutter. Of course it still wasn’t capturing any photos either.

As per the error message, I removed the lens again, cleaned the contacts on both the lens itself and the camera body using a micro fiber cloth, but still no change. So obviously it wasn’t a lens contacts issue.

The lens involved with this event was my Canon 24-70mm F/2.8 L, which is a lens I got new and have owned now for about 10 years. I hardly use it though in comparison to some of my many other Canon lenses. From the outside the lens it actually looks virtually brand new.

New Canon lenses (for the last 20 years or more) all have lens apertures that are controlled electronically by the camera body. So there is no way to manually adjust a diaphragm nowadays using the aperture setting ring on the lens like before. So a few days later I decided to take the lens over to the Canon service center to be checked.

While standing at the Canon service counter I met another gentleman who was holding the same Canon 24-70mm model lens in his hand. I asked him what kind of problem he was having with his lens and he explained that he just had to have the diaphragm changed on his after the lens stopped working. A few minutes later, after discussing the symptoms of my lens with the Canon service staff, we came to the conclusion that my lens was having the same problem as his.

Now what are the chances of two people bringing the same exact Canon lens model to Canon in Thailand to be repaired at the same exact moment? Apparently reasonably high with this lens model.

After some further discussions with the Canon service staff, they explained to me that this is a common problem with Canon lenses after 5-6 years of use. This came as a big surprise to me as I have never had any problems like this with any of my other Canon lenses, and some of my lenses are getting close to 20 years old already.

The fact that two people showed up at the Canon service center at the same exact time, with the same exact lens and same exact problem makes me curious if there is simply a design problem with this particular model of Canon lens. Or maybe it is just coincidence?

Canon’s staff also mentioned to me that the other popular Canon 24-105mm F/4 L lens often has this same problem too. I myself also have the Canon 24-105mm lens which I use very regularly (see here), and I have never had a problem with it at all. In fact, I probably use my 24-105mm lens 5 times as often as I do the 24-70mm lens. So it seems likely the diaphragm problem is more prevalent with this 24-70mm lens than the 24-105mm lens.

In Thailand this repair from Canon costs you around US$130 equivalent. In North America, Europe, and other countries Canon may charge more for this same repair. But they made the repair very quickly and the lens was ready for pickup in about 2 days, which is good.

Bear in mind that after manufacturing this lens for ten years, since 2002, that in 2012 Canon stopped production of this lens and replaced it with a 24-70mm F/2.8 L Mark II version of the same lens. The new model is lighter weight and has various optical improvements.

Perhaps this issue with the diaphragm failing is now less common on the newer model, but I regret I wouldn’t know. I think many photographers, like myself that have the older 24-70mm F/2.8 L model, probably have not upgraded to the newer model, which now sells for close to US$2,000. Canon also released a lower cost F/4 version of this 24-70mm L lens which sells for around US$1,000. The price of the new F/4 model is roughly the same price that the older F/2.8 model sold for when I purchased mine for around $1,000. So price has gone up a fair amount for this lens on the new Mark II version. 

If you have had a similar occurrence with this particular Canon 24-70mm lens, or any another Canon lens model, then please kindly post your experiences below. I would be interested to hear about them.