Canon 5d Mark Iii Continuous Autofocus Video

Aug 25, 2019 15:58  |#1 Hello fellow Canon users, I need your help! I haven't used my Canon 5D mark iii in around a month (Everything was working fine). Today, I turned the camera on to take some photos and to my surprise the autofocus doesn't work. Below are the symptoms and also the things I've tried. After 5 hours of Googling I've exhausted all my options. I wondered if anyone out there may be able to help me. 1) The autofocus works (As in the lens starts working) fine when in Liveview or in Video mode. 2) The lens is 100% set to AF and not MF. 3) When in live view and video mode both the half pressed shutter and the AF-ON button both work. Just NOT in normal mode (looking through the viewfinder and half pressing the shutter) 4) I've check the custom button menu (C.Fn2) both the AF-ON and Shutter button are set to Metering and AF start. 5) The firmware is updated to 1.3.5 6) I've tried 5 of my lenses with the same result. 7) When I look through the viewfinder I can hear the image stabilisation working and when I switch the stabilisation the noise stops 8) I've tried all shooting modes A+, P, Tv, Av, M, B, C1, C2 etc I'm completely lost and your need help. I've got everything crossed hoping someone out there might be able to solve this mystery. Thanks in advance guys!

Aug 26, 2019 03:22  |#2 Does the focusing motor run back and forth, then give up without finding focus? Or does it not move at all? If the latter, have you checked the setting "AF drive when focusing is impossible"? Set it to ON, if it isn't already. Anders

gjl711 gjl711 "spouting off stupid things" 56,732 posts Likes: 3401 Joined Aug 2006 Location: Deep in the heart of Texas More info

Aug 26, 2019 06:43  |#3 Since the AF function works normally using contrast detect focusing (live view and video) but fails using phase detect, you can pretty much eliminate everything except for the second mirror and the autofocus sensor at the bottom of the camera. About the only thing you can check is that the mirror functions as it's suppose to. You can very gently lift the mirror and behind the main mirror is a smaller one used to divert the light path to the PDAF sensor. It should look like this when operated. It should move with the main mirror and return when the mirror is let go. It's not easy to see and you need to be exceptionally careful when you move the mirror as you can really screw things up playing around with the mirrors. Here is a video of a guy manually lifting the mirror. I would have used something like a dental pick or watch screwdriver, but a finger works. If the mirrors are working, I believe that there is little else you can do other than sending it to Canon for further analysis. Not sure why, but call me JJ. I used to hate math but then I realised decimals have a point. . ::Flickr:: ::Gear::

Aug 26, 2019 06:45  |#4 Do you have a grip attached? Past Equipment | My Personal Gallery My Business Gallery "Man only has 5 senses, and sometimes not even that, so if they define the world, the universe, the dimensions of existence, and spirituality with just these limited senses, their view of what-is and what-can-be is very myopic indeed and they are doomed, now and forever."

Aug 26, 2019 07:35 as a reply to  @ apersson850's post |#5 Hi, In live view and video the internal aperture and distance ring spins then focuses like normal. When not in live view nothing happens when the shutter is half pressed. It's so weird, why would it work in one and not the other... Thanks.

Aug 26, 2019 07:38  |#6 TeamSpeed wrote in post #18916740 Do you have a grip attached? Hi, theres no battery grip. Would the little silver battery on the side have anything to do with it?

Aug 26, 2019 07:41  |#7 MandeepNayee wrote in post #18916764 Hi, In live view and video the internal aperture and distance ring spins then focuses like normal. When not in live view nothing happens when the shutter is half pressed. It's so weird, why would it work in one and not the other... Thanks. As gjl mentioned, the camera uses totally different methods to check focus in live view vs standard still shooting with the mirror box. PSA: The above post may contain sarcasm, reply at your own risk | Not in gear database: Auto Sears 50mm 2.0 / 3x CL-360, Nikon SB-28, SunPak auto 322 D, Minolta 20

gjl711 gjl711 "spouting off stupid things" 56,732 posts Likes: 3401 Joined Aug 2006 Location: Deep in the heart of Texas More info

Aug 26, 2019 07:44  |#8 One thought, it is possible in the MkIII to set back button focus for PDAF and the shutter for CDAF? I don't think so but thought I would ask as I don't have the MkIII. Not sure why, but call me JJ. I used to hate math but then I realised decimals have a point. . ::Flickr:: ::Gear::

Aug 26, 2019 16:04  |#9 So, I've just checked the second mirror behind the main one and it's fine and free moving. I've been playing around a little more tonight and when my lens is set to MF it takes a picture with no problem. It just doesn't do anything when I switch the lens to AF, but AF works in live view etc. I've raised a ticket with Canon to see if they can crack this.

John ­from ­PA John from PA Cream of the Crop 11,101 posts Likes: 1471 Joined May 2003 Location: Southeast Pennsylvania More info Post edited over 3 years ago by John from PA.

Aug 26, 2019 16:14  |#10 Even though you are up to date on firmware, I'd refresh it. Some strangle things have been reported in the past and resolution was obtained by a firmware refresh.

Wilt Wilt Reader's Digest Condensed version of War and Peace [POTN Vol 1] 45,748 posts Gallery: 1 photo Likes: 4087 Joined Aug 2005 Location: Belmont, CA More info

Aug 26, 2019 22:31  |#11 Using your viewfinder focus, the secondary reflex mirror diverts light downward to the AF sensor in the floor of the camera. Using your LiveView/Video focus, the camera uses the sensor's pixels to determine focus. As someone stated earlier, the mechanism of AF is totally different between the two modes. So if your secondary reflex mirror is truly operational and properly diverting light down to the AF sensor, the AF sensor might have some foreign body blocking the light from reaching the AF sensor, or the AF sensor itself may be non-operational due to some issue in the AF circuit. You need to give me OK to edit your image and repost! Keep POTN alive and well with member support https://photography-on-the.net/forum/donate.p​hp Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention

Aug 26, 2019 23:02  |#12 So it's been explained that it is not weird that Live View Focus works as it uses a different AF system than viewfinder. You mentioned the silver battery. Before sending camera for repair it's worth trying removing the main battery and the silver button battery. Leave both of them out for several minutes. It probably won't fix your problem but it's always worth doing before sending for repair. It does fix some problems, it's like a full reset or factory default reset, even though there is usually a menu item for factory reset, double battery removal does a little bit more. Be patient and leave them out for 10 minutes. I have a 1DS2 that once lost many normal functions. First double battery removal for about 2 minutes did not fix. The 2nd removal for 10 minutes did fix. Dave Image editing OK

Aug 27, 2019 02:42  |#13 Choderboy wrote in post #18917167 So it's been explained that it is not weird that Live View Focus works as it uses a different AF system than viewfinder. Oh yes, it's indeed wrong if it doesn't even attempt to focus, using the normal viewfinder. That's why I asked if the Lens drive when focusing is impossible AF function is set to ON or OFF. No reply to that yet. The OP wrote about "internal aperture ring", but I presume he means the distance scale on the lens, as there is no internal aperture ring. He stated that the ring is moving when using Live view, obviously enough, since that method works. But he also states that it doesn't move when attempting normal shooting with AF. The main question is then why doesn't it start moving. Even if the AF light path in the mirror box is blocked, the lens should drive the AF motor to attempt to get it right. You can put a piece of tape over the AF sensors in the bottom of the mirror box, but neither the lens nor the camera will know that, until it has attempted to focus, by racking the lens' focus setting from closest to farthest and back again. Anders

Aug 27, 2019 03:28  |#14 apersson850 wrote in post #18917221 Oh yes, it's indeed wrong if it doesn't even attempt to focus, using the normal viewfinder. That's why I asked if the Lens drive when focusing is impossible AF function is set to ON or OFF. No reply to that yet. The OP wrote about "internal aperture ring", but I presume he means the distance scale on the lens, as there is no internal aperture ring. He stated that the ring is moving when using Live view, obviously enough, since that method works. But he also states that it doesn't move when attempting normal shooting with AF. The main question is then why doesn't it start moving. Even if the AF light path in the mirror box is blocked, the lens should drive the AF motor to attempt to get it right. You can put a piece of tape over the AF sensors in the bottom of the mirror box, but neither the lens nor the camera will know that, until it has attempted to focus, by racking the lens' focus setting from closest to farthest and back again. I did not know that. I see why Lens drive when focusing impossible setting is now needed. Dave Image editing OK

Aug 27, 2019 04:36  |#15 That setting is there for specific needs. Like if you have a long telephoto lens, and temporarily lose track of the subject. In such a case, a long telephoto lens frequently gets grossly unfocused, due to the very short depth of field. With the normal setting, Lens drive when focusing is impossible = ON, the camera will run the long focus screw in the lens from infinity to minimum focusing distance and back again, in an attempt to get somthing in focus again. But if you just momentarily lost the subject, it would have been better to stay put, and wait until you get the AF point over the subject again. While the lens is approacing minimum focusing distance, you can't, and you can usually not even find the subject visually, due to the extreme blur in the viewfinder. That's when you set the Lens drive when focusing is impossible to OFF. But if you do that, it also implies that if you start with a lens at minimum distance, but aim it at infinity, it will not even attempt to focus, since it's so far off. If something is blocking the AF sensor at the bottom of the mirror box, then the camera will always consider the lens to be hopelessly off, and never attempt to drive the lens to find focus. But with that setting ON, it will make a full stroke attempt, before it gives up and signals that focusing is impossible. Technically the AF sensors are a bit like rulers, with a zero point in the middle, and the a certain range of +/- focus setting. As long as you aren't more off than that the current setting falls within the +/- limit of the sensor, the camera can see in which direction you are out of focus, and by how much. Thus it can quickly correct the problem. This is the state where focusing is considered possible. If your lens is set far from the correct foucs, you'll end up outside the scale of the AF sensor. The camera will consider focusing impossible, as it can't determine neither how far off you are, nor in which direction. If the setting is OFF, you then have to rotate the lens focusing ring manually until you get inside the bounds of the AF sensor. Or aim at something at the appropriate distance. With the setting ON, the camera will turn the ring, whilst checking the AF sensor to see if it can find something coming inside the boundaries of the AF sensor. Anders

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