Back button focus (Cfn 04) - advantages?

[chris_shawn]

Hello,

 

one simple question: In what kind of situation is the back button focus (custom

function 04) useful for me (I am using the EOS 1Ds MKII)?

 

Can someone just name the advantages please?

 

Thanks

Chris

[ronaldo_r]

Situation #1: Shooting landscapes on a tripod. Easiest thing in the world - focus with the * button and fuggeddabodit:) Just like with manual focusing, only AF:)

 

Situation #2: Portraiture. Focus on the model's eyes or what have you (press the * button). Recompose and relax, talk to the model, wait for that moment - you don't have to refocus - then badabing: press the shutter and voila!

 

Situation #3: Street photography. Focus on the nearest garbage bin (* button), set your exposure. Then walk around, relax, point and shoot if you see something - no need to re-focus!

 

All in all, it feels like a manual focus camera with all the benefits of AF. Good luck

[yakim_peled1]

http://www.photoworkshop.com/canon/EOS_Digital.pdf

 

Search for "C.Fn 4".

 

Happy shooting,

Yakim.

[michael_ziegler2]

NE1 know if there is a pdf available for the 5D like the one above?

[jon_austin]

Be careful about focus and recompose as recommended above, regardless whether AF is assigned to the [*] button or the shutter button. Recomposing after achieving focus *can* in many instances lead to out-of-focus images. (Same goes for achieving AE lock and then recomposing ... can lead to poor exposures.)

 

I have AF assigned to the [*] button, because I often find myself in many situations where I'm focussing on the same spot and taking multiple images, often in rapid succession. Example: graduates receiving their diplomas during commencement. The camera captures the images more quickly if it doesn't have to achieve focus first before each image.

 

After a very short while, using the [*] button to achieve focus became 2nd nature for me, and even though it's easy to move AF back to the shutter button at will, I leave it where it is.

[dave_hoffmann]

You are shooting sports and an official or someone else enters the frame in front of your subject. Release the back button (*) to avoid focusing on the improper subject -- and once the obstruction moves out of the way -- hammer back on the (*) button.

[robin_sibson1]

CF-4-1, or the fairly similar CF-4-3 which I prefer, is something of a cult - once you're hooked, you won't go back. The only circumstance in which CF-4-0 seems to me to be actually preferable is if you are shooting a moving subject like a bird in the air, using AI Servo, and prefer to hold down one button rather than two. Otherwise CF-4-1/3 has many advantages over CF-4-0. I describe it as offering AF-on-demand rather than AF-by default. Here are just two advantages.

 

1. Once you have taken your thumb off the * button, there is no risk that the camera will suddenly change its mind about what it is focused on, whereas it is very easy to release the shutter button far enough to let it have another go at AF when you take the picture.

 

2. If you need AI Servo intermittently, it will operate only when you have your thumb on the * button, and you avoid the possibility that it will hunt when you don't want it to.

[michael_ziegler2]

Is Cfn4-1 automatically disabled when using the self timer or remote controller?

[john_schwaller]

"Is Cfn4-1 automatically disabled when using the self timer or remote controller?"

 

No...you are expected to focus first.

 

john