Do I leave my Canon 5D MkIII on AutoFocus at all times?

[mikepaling]

Hi ... I am very new to BYE and currently carrying out testing in the comfort of my office. Currently I am using a Canon EF 135mm to try things out. When the weather allows I want to piggy back this set-up in my scope&mount at the earliest opportunity.

 

After reading the "focusing section" of the manual I have a question ....

 

Do I leave the camera in Auto Focus mode at all times or do I have to switch it to manual mode when I end up pointing at the stars?

 

Does BYE automatically stop my camera from trying to re-focus when my lens has been left in AF Mode?

 

In the past, when I have taken shots of the sky (before I came across BYE), I had to switch off AF Mode because it could not find anything to focus on so the lens failed to find the focus point.

 

Regards Mike

 

 

[mikepaling]

Hi Rick ...

It works

I now have separated my shutter and Auto Focus operations on my Canon 5D MkIII .... so there is no danger of autofocus happening when I take any images when using BYE.

 

It was a bit of a convoluted process to program the 5D as the camera manual was not very clear .... but I got there in the end after finding some very useful info on the web about doing this which helped a lot.

 

Now I can start using BYE and my camera ... if and when I get some clear skies!!!

 

Mike

[mikepaling]

Sorry if my question was possibly a bit convoluted ...

 

But what I am basically asking is ..... does BYE override the Auto Focus control on my Canon EF lenses when taking shots ... or not?

 

Mike

[admin]

No it does not.

 

You need to set you camera to manual focus and focus manually.  This is because the AF is designed to focus on daytime images and a single star in the field of view is simply not sufficient to Canon's AF to work becasue it was not designed for this.

 

Regards,

[astroman133]

Mike,

 

It may be a bit more complicated than should autofocus be on or off.

 

I can tell you what I do and why.

 

First I have a T6i so it may work differently from your camera.

 

Using the default settings and operating the camera manually but with the shooting mode in one of the automatic modes, pressing the shutter halfway down causes the lens to focus and to choose an exposure. That may not be what you need, even for terrestrial photography. Fortunately there is a setting in the camera that allows you to change that behavior.

 

Custom Function 6 controls the Shutter/AE lock button behavior. The default is 0: AF/AE lock. This setting does what you would expect. That is it allows you to focus AND meter by pressing the shutter button halfway down. Changing this to 1:AE lock/AF moves the focus operation to the <*> button, but you still press the shutter halfway down for setting the exposure. However in Manual mode the camera does not adjust the exposure.

 

Now, to answer your question about the AF/MF switch on the lens...You can basically work in either position. In MF you must physically rotate the focus ring to bring the image into focus. However, if you set the switch to AF the camera, then you can use BYE to adjust the lens to bring it into focus. I doubt that you will be able to use LiveView to do this because LiveView is not very sensitive and stars will not be large enough or bright enough through the lens to focus with LiveView. The workflow is to use a short Snapshot image to focus from. The manual describes this as well as how to use the "chevron" buttons while the lens is in AF to adjust focus of the lens.

 

I hope this helps.

[mikepaling]

OK ... thanks for this.

 

Looking again at the focussing section of the manual (Pages 54 to 64) ... it says that the BYE "Camera Lens Drive control" can only be done if the camera has been set to Auto Focusing.

 

So ... after doing this and then using the various focusing methods, described in the manual, I then need to disengage the Auto Focus (carefully without knocking anything) on the camera before I start taking any images to stop it from changing the focus on its own?

 

Mike

[astroman133]

No, not if you change the Shutter/AE lock button behavior as I described in my post. That change uncouples focus changes from the shutter functionality.

[mikepaling]

No, not if you change the Shutter/AE lock button behavior as I described in my post. That change uncouples focus changes from the shutter functionality.

Hi Rick ...

Thanks for your suggestion .... however, after looking through the manual for my 5D MkIII, I can't spot how to alter the Shutter/AE lock button behaviour that you suggest. Maybe the are big differences between our two Canon cameras?

 

Mike

[astroman133]

I downloaded the manual for your camera.

 

Page 321 (Custom Controls) describes how to reassign the AF function to a different button.

[mikepaling]

I downloaded the manual for your camera.

 

Page 321 (Custom Controls) describes how to reassign the AF function to a different button.

Hi again Rick ...

Well spotted !!!!

I will give this a try out tomorrow.

 

Mike

[admin]

Cool 

[1DegreeN]

Re the AF/MF switch position on the lens: I find that, using a 700D, I can set the switch to MF but still use the chevron controls on the Frame & Focus screen to adjust focus. This is the case for a number of Canon lenses e.g. the 400 f5.6, 200 f2.8, 70-200 f4 and 100 f2.8L. However it wasn't true for my nifty fifty - BYEOS could only adjust the focus with the lens set to AF. I do have the camera set for back button AF i.e. pressing the shutter release does not trigger autofocus but I'm not sure that makes a difference. Best to test out your own lens & camera combos to determine which ones allow BYEOS to focus with MF. 

[admin]

Re the AF/MF switch position on the lens: I find that, using a 700D, I can set the switch to MF but still use the chevron controls on the Frame & Focus screen to adjust focus. This is the case for a number of Canon lenses e.g. the 400 f5.6, 200 f2.8, 70-200 f4 and 100 f2.8L. However it wasn't true for my nifty fifty - BYEOS could only adjust the focus with the lens set to AF. I do have the camera set for back button AF i.e. pressing the shutter release does not trigger autofocus but I'm not sure that makes a difference. Best to test out your own lens & camera combos to determine which ones allow BYEOS to focus with MF. 

 

Good point.

 

The thing is the actual lens has a motor and the lens must response to the SDK command fir it to work.

 

As you saw, this is a hit and miss.  Some lens to respond and others do not