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5D3 + AF assist beam = slower focus


Hello All,


While I am new on these forums I have been on the Canon Rumors Forums for a few years now, 


I really wanted to bring this too the attention of you and Canon as it is simply a highly important problem, those of you that don't know, the 5D3 suffers serious focus locking issues when a Canon speedite is attached in Low light, the AF assist beam causes lag with the AF from the 5D3, this makes it virtually impossible to achieve focus in low light when the speedlite is attached, I wanted to bring the topic to this forum, so I have pasted a link to all the discussion we have already had about this problem at Canon - see below



Please help in letting Canon know this is a very serious problem and effects the cameras performance in most working environments when a speedlite is attached and working in low light, conferences, nightclub work, weddings etc, and can stop the photographer completing the job or task.




180 REPLIES 180

Just did an evening engagement shoot at Longwood gardens....there were many times the camera would not focus at

all....I was using the 70-200 F4 IS and AF assist light at a distance of maybe 20 ft....will try to post some images later.

I really wish someone from Canon would respond. Can we at least get confirmation that this issue is being looked into?

They will only respond when they know they can fix the problem, it maybe that its unfixable and hense no response ever, Im wondering what happens if it just gets ignored, all the club / event photographers will have to use an older camera instead, how will this effect new models, Im sure this topic will ensure the safety of new models, but it doesnt help us, its very frustrating.

just my take:


If an issue is solved via education, i.e. the problem is perceived to be due to user error or even if there is an attractive work-around, I would expect Canon to jump in enthusiastically, as Mike did.  That is,  I expect,  this forum's most important objective is to  educate and for Canon to respond to product-use questions. 


when there is potential or mounting evidence of a serious product defect or especially if the camera is shown NOT to perform well within the venues it is designed and marketed for (and with officially supported accessories like 600 ex -rt), then I would expect a very conservative response from Canon.  I would expect a sequence of events something like this:


1.  The first step is  immediate withdrawl from the  forums..  They will monitor the forums, imho, but only to collect information, not to respond to it.  The weightier the evidence that the camera is at fault, the less I expect to hear   from Canon in the forums .I am relatively new to this forum, so I could be wrong about this, but I wouldn't expect product defects to be acknowledged here at all, unless accompanied by a press release and official public announcement.  btw,  Its even possible for Canon to have annonymous reps on other forums such as  Thus, the silence here and elswhere  is evidence in favor that Canon really knows about this, but is just not saying anything about it yet. 


2.  Step 2 is where support and R&D teams collaborate and/or study the problem.  I expect continued forum silence during this time.  my personal read is that we are "here"


3.  When/if the issue is known and documented internally, I'd expect additional time spent with internal marketing teams to decide on the response action and associated narrative.  There are a number of possible responses, depending on the nature of the problem,, but until they have an official response and action plan, I'm not expecting any participation in the forums.  Assuming there is an internally-recognized problem and action plan,  here are some possibilities imho of course:


a)  if the problem is hardware design  related, i.e. the AF implimentation on the sensor itself for example,  this would be the most serious.  Yet, I would not expect Canon to recall hundreds of thousands of camera bodies.  Instead, I would expect them begin the process of re-design and to start filling the mfg and repair pipelines with "fixed" parts.  I would also expect them to craft  a suitable narrative from the repair side that allows them to fix issues that are reported (and carefully described)  without any formal  recognition of the problem -- and perhaps update cameras that come into the repair facilities for different reasons.  Even if a camera is sent in for repair, and they end up changing some parts, I would expect  the explanation will be generic enough so that it will be hard to decipher the actual root cause, even if the repair makes the AF issue go away. Canon is already very good at this in my experience (I've gone through two repairs) - you can't get to their repair technicians and you can't talk to anyone except a call center, and you can't influence or discuss the test/verification methods at all, and they provide very little detail in their repair orders.  All you can do is obtain status, and "camera is performing within specifications."  That process works very well, and arguably one of the smoothest repair processes you could ask for -- BUT it just does not provide any detail.  Remember that Canon has to balance the cost of repair against their reputation and the installed base.  They could decide to repair selectively or they could decide to update all cameras that come in for repair -- all depends on what the bean counters tell them.


b) if the problem is about parts quality, then I'd expect Canon to hold their supply chain responsible, and to quietly fix things in much the same way as in (a) above, only quicker -- and if the repair cost is not expensive then chance are greater that all cameras coming in for repair will get the update. 


c)  If marketing approves of the right narrative, its possible that Mike or someone else may be authorized to suggest or recommend a repair (here in the forums), using some carefully crafted language that no one can reproduce the issue inside Canon, etc,  and that maybe the full functional test at the repair center might diagnose something that needs repair  But there will be, imho, no formal recogntion of a wide-spread class-related problem. 


d) if the problem is firmware related, then I would expect Canon to fix the problem along with the announced April feature list (which includes f/8 focusing for example).   It would be unusual, but its posssible (if the issue becomes widely known and there is market pressure) that Canon could release a bug fix firmware release before the April feature enhancement. 


of course, I hope all of the above is wrong, and that Canon suddenly announces either a reacall/repair process or that a firmware fix is coming soon! 

oh -- I forgot to mention one other response, that I saw over at canonrumors:  Canon ignores the issue in the 5D3, produces a 5D mark iv at an elevated price, and continues to sell 5D4s  along side 5D3s! 

I wonder why at both DPreview and Fred Miranda there is little mention of this particularly DPreview that one of the most volatile forums around. They usually sniff these things out veyr quickly and and the shredding begins.    

If we are able to present this issue as something Canon technical support can systematically test, maybe we'll get a response through their "Contact Us"?  I had a good experience with tech support when dealing with a quirk I was seeing on the 5DM3 and 7D (unrelated to the issue we're talking about here): through emailing tech support, clearly explaining the issue and steps to reproduce it, they were responsive and admitted it was a firmware bug that they'll try to fix with the next update.

good suggestion jfo.  the test scenario is very specific:  go into a dark room so that AF depends on the assist-beam from an approved Canon accessory atop the hot shoe mount.  From what I glean over on canonrumors, this is a marriage problem between the 5D3 and the 600 ex rt, 580 ex ii, and perhaps others I'm not aware of.  Its trivial to reproduce and consistent among most if not all examples using these products.


oh - and by the way if Mike had posted the detailed opinion piece  that I did he would probably be relieved of his Canon responsibilities :-).  That was just totaly my opinion, flavored by a certain sense of Canon arrogance and my experience with Canon service over the years.   

I don't think its that simple....the af in low light isn't as great as they you still need af assist in those scenarios

and it just doesn't work on the 5d3 as well as it does on the mark2...I tried all options on my last evening outdoor shoot and

the camera just sucks.

Digital....I did start a tread at FM forums....mostly it was denied and poo pooed by their posters....made me wonder if there

are variations among the bodies