Focus control with long lenses

[Diane Miller]

It's not the usual use here, but I want to use the software for focusing on stars for astrophotography. I'm using the Canon 7D Mk II. With the new Canon 400mm DO II, I can drive the focus motor with the chevrons. But when I attach a 1.4X III or 2X III teleconverter there appears to be no drive, or possibly it is very slow and the steps are very small.

Is the lens unresponsive to the software in those conditions?

Thanks!

[Stas Yatsenko]

If it's the issue of steps being too small, you can make them bigger in the settings: Shooting -> Big / Medium step size. Also make sure the step type is set to "Big" on the Canon tab.

But it could also be that the extension rings are of the simpler kind and don't correctly preserve the connection between camera body and the lens. Some tubes have all the contacts and retain the functionality perfectly, while others simply don't patch some of the communication lines through - leading to issues like what you described.

[Diane Miller]

I'm using the newest Canon teleconverters, 1.4X III and 2X III, and the lens is a new model. Everything works with them in normal daylight shooting and there should be complete communication between them.

But now I'm trying focusing with the same body and a 100-400 II lens -- no teleconverter -- lens attached to body. Camera attached to computer directly -- no hub.

I just sent a big report but noticed too late that I am in the system with an old email address. It is now dianedm@sonic.net.

I'll try to change to in my pref's.

[Diane Miller]

Problem solved. The camera was in manual focus mode while I was trying to focus, and I assumed that was all I needed to do. But before I switched it to MF it had been in AI Servo. I went back and changed that to One Shot, and then went to MF and now the chevrons work, even with the teleconverters.

[Stas Yatsenko]

Also note that most of the time you need to set both the camera and the lens to AF (single shot). It is only some Canon bodies with some lenses that can work even in MF.

[Diane Miller]

OK -- thanks. I mis-spoke when I said the camera was in manual focus -- that's a switch on the lens for the mid- to high-end Canon SLRs. The body is where you set One-Shot focus mode.

If I have trouble with the chevrons not working in the future I'll try the lens in AF. In the past with the lens in AF, I've had the camera trying to override the chevrons and focus on its own. That may be because of the Live View mode that Helicon Remote puts it in. But maybe as long as long as I'm in One-Shot mode it wouldn't be trying to focus on its own. I use back button focus for regular photography so before I was always in AI Servo, assuming that was OK as long as I went to manual focus on the lens. Obviously not.

I'll remember to switch to One Shot now.

Thanks!

[Stas Yatsenko]

That's definitely a servo / continuous focus problem, has nothing to do with live view.