Wanted: Composition tips when limited to central AF point with 2x

[Jamie Douglas]

Hi folks,

Does anyone have any good compostion tips for working around the often limiting feature of being stuck with the central AF point when using a 2x convertor (in this case a 500mm with 2x)?

I was photographing an eagle on sunday using a 2x convertor and due to the skittish nature of the birds in that area I had to stay wide and struggled framing it with only the central AF point. Going in tight wasn't an option so I want to see if anyone has any tips besides having to crop the end result, or heaven forbid... go to manual focus ;) ?


Cheers

Jamie

[Diane Miller]

I use back button focus and once focus is obtained placing the center point on the subject, come off the focus button and you are in MF and you can recompose and shoot. Of course, if the bird is moving, you have to move faster.

[Dan Brown]

Back focus button. Use it almost all the time. It takes a little getting used to but it is very versatile. Supposedly it also speeds up your AF a tiny bit to focus without activating the metering system until you actually press the shutter button.

[Daniel Cadieux]

Back focus button all the way! I switched to that after a few months shooting digital and have never looked back. I have also never touched the AF mode button since too!

[Jamie Douglas]

Hmm maybe I overlooking something obvious here so forgive me if I am being a muppet. I have been using back button focus for about two years now but just never had to work with/around only having the central AF point until now and struggled with composing the image. Basically the subject was in the middle of the frame and I had to crop at the end of the day to balance the composition. Am I missing something about back button focus? I thought about AF lock but then if I swing the lens a few degrees left or right to move the subject off centre etc. that will likely throw the AF? :bugeyed:

Thanks for chipping in guys and if anyone can explain further I'd really appreciate it.

Cheers

Jamie

[Diane Miller]

Push the back button and focus is quickly acquired. Then release it and you're in MF and free to re-compose. Hitting the shutter button (if you have it set NOT to focus, only to meter) will not re-focus.

On the 5D3, in Custom Controls set the top left item, Shutter button half-press, to Metering Start. Then the Star button (third one down) to Metering and AF start. Or you can set the AF-On button to this, also, if it is a more comfortable reach. I think it would be fine to set both of them, in case you get excited and hit the wrong one.

Although it wasn't necessarily center point only, I shot about 700 candid portraits at a friend's birthday party a few days ago, with the 70-200, using this method. I left it on center point just for consistency in a constantly-changing situation (no time to move the selected sensor around) and I only had about 5 where I missed focus. It takes some training not to hit the focus button again after you recompose, or to let go of it to lock focus before you start recomposing. (I'm always in AI Servo so the latter can be a pitfall.)

[Jamie Douglas]

Push the back button and focus is quickly acquired. Then release it and you're in MF and free to re-compose. Hitting the shutter button (if you have it set NOT to focus, only to meter) will not re-focus.

On the 5D3, in Custom Controls set the top left item, Shutter button half-press, to Metering Start. Then the Star button (third one down) to Metering and AF start. Or you can set the AF-On button to this, also, if it is a more comfortable reach. I think it would be fine to set both of them, in case you get excited and hit the wrong one.

Although it wasn't necessarily center point only, I shot about 700 candid portraits at a friend's birthday party a few days ago, with the 70-200, using this method. I left it on center point just for consistency in a constantly-changing situation (no time to move the selected sensor around) and I only had about 5 where I missed focus. It takes some training not to hit the focus button again after you recompose, or to let go of it to lock focus before you start recomposing. (I'm always in AI Servo so the latter can be a pitfall.)

Thanks Diane, that is how I have my 1D Mark IV set up for rear button focus. The shutter button only meters and takes the image. I need to go try your method out during the day but it sounds very like AF lock, similar principles i.e. acquiring focus, locking focus, and then recomposing before taking the shot.

I'll experiment at the weekend and get back if I canny make sense of it :e3.

Cheers

Jamie

[Jim Longworth]

Back button focussing is available by default for all cameras, however it only becomes useful for these situations if front button focussing is removed by customisation (so that AF isn't triggered when shooting) - that is the difference that Jamie is perhaps missing? So focus on subject (using back button) then STOP focussing when focus obtained (take thumb off!), then recompose and shoot without refocussing.

[Jamie Douglas]

Back button focussing is available by default for all cameras, however it only becomes useful for these situations if front button focussing is removed by customisation (so that AF isn't triggered when shooting) - that is the difference that Jamie is perhaps missing? So focus on subject (using back button) then STOP focussing when focus obtained (take thumb off!), then recompose and shoot without refocusing.

Cheers Jim, I have my camera set up not to AF with the shutter button and only the back button. I think I am just overlooking the fact that once focus is locked you can move the lens and the AF will stay locked? Not something I have had to consider before in the past from not using the 2x on a f4 lens before and being able to adjust AF points while composing the image.

A rookie question maybe that I should have raised off-line LOL :e3

Jamie

[Steve Canuel]

Jamie,
Does One Shot Focus and recompose not work for you? Assuming you're shooting from a tripod at a somewhat stationary subject (perched eagle), it would seem that acquiring focus using the center point, turning off the AF button on the lens, then moving the lens to the desired composition will do what I think you're asking. That's how I do it anyway. When the subject moves, I repeat the process. Obviously doesn't work for something moving around too much though.

[Doug Herr]

Does One Shot Focus and recompose not work for you? Assuming you're shooting from a tripod at a somewhat stationary subject (perched eagle), it would seem that acquiring focus using the center point, turning off the AF button on the lens, then moving the lens to the desired composition will do what I think you're asking.

I find this technique to produce a high rate of mis-focussed images because even something as small as the bird shifting its weight from one foot to another will shift the optimum focus plane. This is the primary reason I prefer manual focus (and a camera optimized for manual focus) because it allows me to focus as-composed no matter where the bird's eye is in the image area and reduce or eliminate the need for cropping.

[Daniel Cadieux]

I think I am just overlooking the fact that once focus is locked you can move the lens and the AF will stay locked?

Jamie, just to make it easy...after achieving desired focus with the back button just let it go before moving the lens...it is now locked and you are ready to re-compose. Press and let go = One Shot, press and keep pressed = AI Servo.

[Jamie Douglas]

Jamie, just to make it easy...after achieving desired focus with the back button just let it go before moving the lens...it is now locked and you are ready to re-compose. Press and let go = One Shot, press and keep pressed = AI Servo.

Cheers for the summary Daniel and to all the others who chipped in. Thank you.

My primary concern with this approach was that if I lock focus and then swing the lens on a gimbal even ever so slightly to recomp the image after acquiring focus and letting go of the back button, that the image would then be just a little soft but from what you say this is the best approach for recomposing an image. I started this thread to get a sense of what others do as I haven't had much practice in the field and it's not the best time to experiment when the subject is in front of you. It looks like this is the most adopted approach so I'll go with the majority :)

Cheers everyone. I am heading out to the garden to experiment.
Jamie :cheers:

[Diane Miller]

If you're quite close to the subject, that would be an issue -- you are changing the distance a little. But even in the example I gave above with the 70-200, where I was maybe 10-15 ft from the subjects, the focus was still tack sharp after recomposing, and I was at f/6.7.

[Jamie Douglas]

If you're quite close to the subject, that would be an issue -- you are changing the distance a little. But even in the example I gave above with the 70-200, where I was maybe 10-15 ft from the subjects, the focus was still tack sharp after recomposing, and I was at f/6.7.

Cheers Diane, this is comforting to know and I'll practice a little before heading out in the field again. Was caught unprepared last time out and went for the conservative approach of AF on the head and then cropping.

[Don Lacy]

At the distance you are shooting there will be enough DOF to cover a slight change in the focal plane if any from re composing the image

[Jim Neiger]

Another option is to use the AF Lock button to lock the focus while you recompose and shoot.

[Jonathan Ashton]

This is something I have been wrestling with for quite some time. I have always used AI Servo and the AF ON Button re set to AF STOP, it seems more intuitive to have focus by default on the shutter button and to stop it by pressing the AF ON button. I have revisited this several times over previous years and thought that this amounted to the same thing as rear button focus, but it is not. I am stating the obvious but using rear button focus makes focusing independent of shutter activation so if you press the shutter button it will fire. When using the shutter button to focus and fire the shutter the shutter only fires when the camera thinks it has achieved focus, so sometimes when I expect the shutter to fire it does not. I know the argument could be made that using rear button AF could result in some non images not being properly but it does mean the shutter will fire when I choose and not when the camera decides. I am still trying rear button AF and have to admit only yesterday I became frustrated because the camera didn't focus when impressed the shutter button but I am going to persevere. The point concerning continual focus as the shutter fires seemed to make a little bit of sense to me I think having focus and shutter activation as two distinct processes is the way forward.

[John Chardine]

Hi Jonathan- IMO Back-button focus is successful when you commit to it and develop the "muscle-memory" needed to activate it without thinking. I am sure you could get used to a setting where the back-button STOPS AF but for me the act of focusing and pressing the shutter button do naturally go together so I find it easier to START AF with the back-button as I actuate the shutter, rather than stop AF.

[Charles Glatzer]

Jamie,

Use either back button focus or setting the AF On as AF Off... to focus lock and recompose (FLR). That said, when maintaining in-camera composition is a priority I will manually tweak focus.

Chas