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

I would use Liveview. 5DII does not have the best AF system, and I too had quite a few problems with what seemed like simple focusing tasks. In a studio setting it is possible to use Liveview and results will be excellent.

bobbyz wrote in post #15449091
OP problem is not low light and read he is using studio strobes with modelling lights. He is using a radio trigger to activate AF and then take the shot. Problem is trigger is not doing AF. It is not low light, nor camera, nor lens issue.

I agree. I can get full focus locked on easily using centre point in pitch black with only a small phone illuminating the subjects face. This was on my 5D2.

coeng wrote in post #15445788
I am a fairly new owner of a 5DM2 and am having an issue with low-light focusing, particularly in my home studio.

What are you focusing on, as in, what is in front of the lens that you are you putting the focus point over?

Does the 5dii have an AF assist beam? If so, can someone point me in the right direction to it? I need this for low light shooting too.
Wouldn't that solve this problem as well...

Moppie wrote in post #15451006
What are you focusing on, as in, what is in front of the lens that you are you putting the focus point over?

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

here is my suggestion, nothing to do with your current problem.

1. forget stuffed animals
2. find a human being for the test subject
3. if 2 is not possible the atleast get a mannequin.

why make it harder. you need to be at camera position to see that modelling light falling on face. no stuffed animal is like a human face. get real folks. offer free test if you have to for learning. IMHO harder part of potrAits is interacting with clients, seeing how to handle different face/body shapes etc.

BTW you can prefocus on your chair you sitting and put lens in manual mode. remeber you shooting at f11 so no need to focus all the time.

And your problem with AF, it is trigger issue. Does that same trigger does AF at other times?

bobbyz wrote in post #15451433
here is my suggestion, nothing to do with your current problem.

1. forget stuffed animals
2. find a human being for the test subject
3. if 2 is not possible the atleast get a mannequin.

why make it harder. you need to be at camera position to see that modelling light falling on face. no stuffed animal is like a human face. get real folks. offer free test if you have to for learning. IMHO harder part of potrAits is interacting with clients, seeing how to handle different face/body shapes etc.

Stuffed animal was only for troubleshooting as I clearly indicated but thanks for the sarcasm.

Disregarding those making fun of you, it seems you've found the root cause of your problem. Get a trigger which properly operates the equivalence of half-press on the shutter button, and you'll be all set.

apersson850 wrote in post #15452023
Disregarding those making fun of you, it seems you've found the root cause of your problem. Get a trigger which properly operates the equivalence of half-press on the shutter button, and you'll be all set.

And that would be??

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.

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.

Okay thanks. At least you summarized the root cause for me.

If you are in front of your camera and not more than 5 m away, then the RC-6 may work just fine. It's so cheap that you could get one just to try it out. I'm pretty sure the 5D Mark II has an IR remote receiver, but just to be sure, take a look at the front of your camera's grip. There would be a small window there, just a few mm i diameter, if it has the receiver. Don't mix it up with the self timer indicator lamp.

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.

coeng wrote in post #15451837
Stuffed animal was only for troubleshooting as I clearly indicated but thanks for the sarcasm.

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.