5D MkIII. 5D triggers flash or shutter inconsistently on static scene.

[fsamuelson]

Testing out my new ABF-800 flash with my 5D MkIII. 5D settings on M, flash sync through cord. The 5D arbitrarily decides to trigger shutter & flash or not, and will not even trigger shutter at times, with no changes in the scene. Any ideas of what is happening?

[amfoto1]

Just a guess. It's possibly the sync cord. Those can be problematic. You might want to try one of the radio trigger setups.

I don't know the sync speed with that particular strobe, either. With my 5DII and some Norman monolights I use, I have to use 1/160 tops.

***********
Alan Myers

San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM 

[fsamuelson]

perhaps sync cord for the flash, but not the issue with the shutter.  Press the button, nothing happens.  I'm thinking maybe something with AF setting but do not know what to look for. Beam sssist in low light situation?

What are the normal settings for external flash, not Speedlight?

[Skirball]

If you're having trouble and trying to trouble shoot the very first thing I'd do is turn it to full manual - exposure and focus.  Turning off auto-focus should be the first suspect, pretty much always.  And if you're shooting a static scene you don't need it anyway.

I'm not too familiar with studio flashes, what is a ABF-800?  You're not referring to an AB B800 are you?   If you're using studio lights and want to use autofocus then use the modeling lights.

[TCampbell · Accepted solution]

On a 5D III you can override a lot of stuf that you can't control on other camera bodies.  But in general... if the camera is in One Shot mode and the if the AF is enabled on the lens, then the camera will NOT take the shot until it can confirm that it was able to lock focus on at least one AF point.

If a Canon dedicated speedlight flash was in the hot-shoe, it would fire it's AF-assist beam (again... by default but this can be disabled) to help the camera focus (it projects a light pattern onto the subject that the camera can easily lock on and focus.)

Since you have a 5D III (so those who might be reading this who do not own this same camera body -- ignore this because your camera will not have this setting) do the following:

Press Menu

Navigate to the magenta colored "AF" tab page 3 (there are 5 sub-pages in the AF section... you want the 3rd one)

Navigate down to the selection which reads "One-Shot AF release prior." (this is the release priority setting) and press the "Set" button.

It will show two options... "Release" and "Focus" - change it to "Release" and press the "Set" button (and whatever you do... DO NOT FORGET THAT YOU CHANGED THIS or you'll regret it later.)

What you have done is changed the camera from "Focus priority" to "shutter release priority".  Here's what this means:

Normally when you are in One-Shot mode (and most Canon bodies work this way), the camera is in "Focus Priority" mode.  That means when you fully press the shutter button to take a photo, the camera computer is told that the most important factor is to ensure the image is FOCUSED ... BEFORE taking the shot.  The camera doesn't actually take the shot the moment the shutter button is completely pressed -- it waits until it can confirm that it locked focus on at least one AF point.  In plenty of light this all happens very quickly.   However... if the camera is unable to lock focus at all (lack of contrast, not enough light, no focus-assist beam to help, etc. etc.) then it will actually refuse to take the shot... it'll be like the camera is malfunctioning (only it's not... it's doing what it was told to do which is not take a photo until it can confirm focus first.)

When a Canon camera is in AI-Servo mode (other Canon bodies -- not your 5D III) the camera is changed to shutter "Release Priority".  This means the computer in the camera is told to take the photo as soon as you FULLY press the shutter button... and it will do this, whether it was finished focus or not (and it's VERY important that you remember that.  In that mode it's up to you to only half-press (or if you've reassigned the focus button to a back button) to ensure focus is completely before you fully press the button.  There are reasons why you'd want a camera to behave this way -- often in a situation you may have pre-focused the camera anticipating the action and the most important thing is that it take the photo at that "decisive moment".

On your 5D III, you can actually change the release priority between shutter or focus by menu settings and it'll work regardless of whether the camera is in "One Shot" vs. "AI Focus" mode.

Just don't forget that you changed it... or the next time you're out somehwere and fully press the button, you'll end up with blurry shots because the camera will think you just decided to skip focusing because you knew what you were doing (and that can be embarrassing when you come back with a whole bunch of soft shots.)

[Skirball]

Why would you go through all that trouble when you could simply make sure there's sufficient light for the camera and let the 5d3's legendary AF system do its job?

[fsamuelson]

off camera flash is the key element here. Even legends fail when commanded to do so :).

[fsamuelson]

Thanks.  That's what I suspected after I thought about it more.  I will learn how to do a custom setting for off camera flash so I do not have to remember the changes I made.  Like any tool, the more bells & whistles, the more chances possible for success or failure are compounded.

[amfoto1]

I am assuming that "ABF800" is refering to an Alien Bees monolight. If that's the case, regarding the problem with focus and being unable to trip the shutter, there is no AF Assist beam possible. But as someone else mentioned the monolight should have a modeling light mode you can use to help with focus. Alternatively, you could fit a Canon ST-E2 module in the camera's hot shoe and that can emit a Focus Assist beam. Most Canon portable flash also can emit a Focus Assist, but are much larger than the ST-E2 module. Note that the ST-E2 communicates with Canon flash off-camera via near IR light, so it will not be able to trigger the monolight. So it's only purpose would be to assist with focusing. Also note that the newer ST-E3-RT does not have the Focus Assist feature. As a radio controller for off-camera flash, there might be some way to get it to trigger a monolight, but it's not designed for that purpose and you won't be able to control the monolight remotelly with it, the way you can Canon 600EX-RT flash.

If I'm incorrect and "ABF800" is refering to some third party portable flash, I have no idea. Most Canon portable flash and some third party portable flash have a Focus Assist feature. Others don't .

You need to have the camera set to One Shot focus mode to use Focus Assist. The 5DIII is able to focus in unusually low light (Canon rates it to -3EV, which is about the brightness of the moon on a clear night), but even it has its limits. If your working space is pretty dark, enough that the camera is unable to achieve focus, then that can prevent you from tripping the shutter (depending upon how you have the camera set).

Another thing with monolights... perhaps the reason the flash isn't firing sometimes... Depending upon their output settings, monolights take a while to recycle after each shot. If you try to shoot too fast, the strobe may not be able to fire after the first one or two "pops". Recycling can take 2 to 5 seconds at max output (varies depending upon the particular monolight). To get faster recycling you might  try a reduced setting (half power or quarter power), combined with increased ISO or other exposure setting adjustments as needed on the camera. I use five Norman monolights and usually try to keep them set to 1/2 or 1/4 power for exactly this reason. I have "ganged up" two of my monolights as my primary light source, so that they can be used at 1/2 power or lower, and thus recycle much faster. Look up the specs on your manufacturer's website, to see how fast yours recycles.

Portable flash will do the same thing, also need some time between "pops" to recycle, altho they are usually faster than monolights and if used at reduced power may be able to fire a short series of flashes, before needing to stop to recharge... Plus might even "communicate" with the camera, tell it they aren't ready, and prevent the shutter from tripping before recycling is complete... 

With portable flash, you might be able to override this with some camera settings. But in general you don't want to force too fast recycling or you could overheat and damage the flash or strobe. Many strobes and flashes have a limit on how many "pops" they should do in a given period of time, to aviod risk of damage. Again, check the specs on your particular unit.

***********
Alan Myers

San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM 

[fsamuelson]

Thanks for all the replies.  The flash mentioned is an Alien Bee B800.  I have the commander trigger & receiver but was connected with a cord for the first attempts to use.  I am aware of recycle time for flash.  I have had the 5D for only 3 months, and the flash & remotes are new.  A lot to learn here.  I used the custom setting function & created a setting for studio flash.  I am sure I will tweak it further. I think my query has been sufficiently answered for now.  Will continue to follow the posts on this forum, and will most likely have a lot more questions to come.