5DM2 won't AF when using just a modeling light

bobbyz wrote in post #15452534
Sorry you took it wrong way. Your issue is the trigger but now where it is clearly mentioned. Title says 5dmk2 can't focus in low light. Now if you click on the shutter button in same light in focusses fine, so camera/lens or the light is not an issue. Ia m just trying to help. Don't want to take it, so be it. Enjoy.

When I started the thread I didn't know that it was the trigger that was the cause of the problem. Nevertheless no worries...water under the bridge.

john_galt wrote in post #15452520
i think i have this same problem with my yongnuo 602 triggers. it will not auto focus when pressing the trigger halfway when im in manual mode.

but, if i switch to auto mode green box and half press the trigger, it will auto focus leading me to brlieve its not my trigger. of course, in a studio setting u dont want green box. does yours focus in greenbox?

so i end up just manual focusing. id love to figure out why it does that also but i dont do many studio shots so i learned to live with it. i use center focus also, one shot.

Interesting...I will attempt this later tonight. I'll try the Av and Tv
modes as well.

coeng wrote in post #15451189
Me sitting on a stool, front and center, in front of a backdrop.

You see, when I do my photography work very late at night, I have no one in the house to pose for me as I experiment with the position and power settings of my 4 strobes. What I do (or should I say "used to do when I had my 40D") is start by setting up the key light, take a seat, pose for a few shots, and see how the shadows fall across my face (I can see the images on a tethered laptop that is on a table adjacent to me out of frame).

Then once I am happy with the key light, I postion my fill light and adjust its setting as needed. Then in a similar manner I add my hair light and then finally my background light.

So I am constantly taking sample shots of myself during the process. With the 5DM2 I can no longer do that it seems, but at least I narrowed it down to the fact that it only happens when using the remote trigger.

In the troubleshooting process (when I had only the key light's modeling lamp on and nothing else), I placed a large stuffed animal on the stool and pressed the camera's shutter button. It achieved AF right away. When I instead triggered the shutter with my remote (while looking through the viewfinder) I saw the center focusing square flicker red (while the lens was rapidly focusing back and forth) and sometimes it achieved AF after a few seconds and sometimes it gave up.

When I turn on my ambient lights, there is no problem. Except that in my studio environment I don't want ambient lighting affecting my shots, especially since they're flourescent bulbs.

To answer a few other questions:

- I started out using liveview, but stopped using it because I wanted to rule it out as the culprit.

- I am not using back button for focus

That doesn't entirely answer the question, but it does put us down the right path.


There is one of 3 things happening:

1: The remote is not allowing the camera to find focus before it tries to trip the shutter. This is a common problem and related to lack of feed back from the camera.
You could try a different remote (I suggest Phottix or Canon).

2: The AF system needs an area of contrast UNDER the SELECTED AF point. This becomes more and more important as light levels drop, and the area of contrast needs to be better defined.
It maybe with the beer on the chair, and you looking through the viewfinder your putting an area of contrast under the center point.
When you sit in front of the camera yourself, or even take your finger off the shutter button and use the remote, the focus point is moved to an area of low contrast and the camera is unable to find focus.

3: A combination of all of the above.

Changing the exposure mode will have NO effect on the auto focus, they are effectively independent of each other for your purposes.

The 5D2 has a very simple AF.
Put it in one shot, show it an area of contrast and it will find focus.

coeng wrote in post #15452663
Interesting...I will attempt this later tonight. I'll try the Av and Tv
modes as well.

curious if the trigger auto focused in other modes like greenbox?

apersson850 wrote in post #15452072
I don't know what works for you. I don't have any radio trigger. I use the TC 80-N3 wired remote controller or the RC-6 IR remote. Haven't seen any need for any radio remote for what I do.

Somebody else here will hopefully be able to guide you.

Hi PLUS 1!
I bought the RC-6 IR remote trigger - really cheap £10 or £15 . It was not listed as a supported product on my 7D documentation. On a canon support page somewhere, it said worked with the 7D. Assume OK on. 5DII as a similar age.

I was interested to see if it would mimicking the 1/2 push to focus. Not sure about the 1/2 push, but it seems to focus dirt then fire. This then fires my 7D, and in turn the Bowens Pulsar radio trigger, which sets off the strobes with the radio receivers - or those with the optical sensor cell turned on. I just use the receiver cards as it allows me to set the others in groups of flashed, and then I can remotely control the groups

Works every time and allows me to focus using the constant modelling light, on either low, max or relative to strobe power settings, or user set - on minimum.

Works 100% - think it will solve your problem

I would suggest simply resetting all custom functions just to guarantee there isn't some setting that was adjusted that could be the culprit. Remote shutter devices are very, very simple. They don't talk to the camera and tell it what to do, all they do is jump across any one of 3 wires in the N3 connector, to mimic the buttons on the camera being pressed.

In fact, it is quite easy to build your own wireless RF transmitter if you know circuits and can get your hands on a N3 plug.

IR remotes could indeed work differently because the camera has logic to accept IR signals and fire off camera functions from those signals.