Hi! A little background, I'm fairly new to DSLR cameras but I have taken several online courses and so I'm progressing. My weak point is understanding the autofocus system (you'd think that would be the easy part!) I shoot on manual. I recently set up back-button focusing and I'm confused. This is what I do -- select my subject --- set focus by pressing the button dedicated to back button focusing (the asterisk) recompose and take the picture. As I understand it, once I set the focus I should be able to recompose to my heart's content without losing focus. That being the case, when I look at the photos in the Canon software and check the focus point, you'd think the focus point would always remain in the same position even though I've recomposed the photo. It's not at all though? It's never in the same spot! lol. Can someone tell me what I'm doing wrong or what I'm missing? I'm definitely set up correctly for back-button focusing and I have it set to AI SERVO AF.
I believe that what you are seeing is exactly how AI SERVO AF works. Have a read of this for more detail: https://www.canon.com.au/explore/glossary/ai-servo
is this the same as using af to focus on your subject then switching to mf and re-composing to take the picture? I usually will hit exposure lock before moving to re compose also
No, for me it is using spot focus to focus on a particular point, hold focus with BBF and recompose the image. If that is what you want to achieve then AI SERVO AF is not the focus mode that you would be using. I would always use ONE SHOT AF as that mode won't try to focus on something else.
what i meant by this was would Tatlyned be better off achieving what he wanted using this method rather than using BBF?
Caladina, I think you will find that a lot of new photography people hear about BBF form magazines and you tube and don't realize there are other ways to skin a cat. Come to think of it I don't use exposure lock much either , might start pushing it a bit more in my class.
My apologies, Caladina. I misread your post. Recomposing is not related to AF or MF and the purpose of BBF is to move the AF function to another button rather than the half press of the shutter button. If you use single point AF to focus on your subject and if that subject needs to be moved to a better position in the frame then you hold your BBF button and recompose and then press the shutter button. BBF is meant to be used for static subjects in conjunction with ONE SHOT AF mode. Using AI SERVO AF mode defeats the purpose of using BBF and then recomposing as in that mode the camera continually refocuses if it senses that the focus distance changes. The purpose of AI SERVO AF is to keep moving subjects in focus.
