Back Button Focus
Dec 19, 2020 10:51:01 #
bleirer wrote:
If you focus exactly on an eagle's eye, then lift your thumb to recompose left right or up down, you put the plane of focus behind the eagle's eye. In that case it does impact sharpness negatively.
Not restricted to BBF (as some people will infer), this happens with any other focus button also.
Dec 19, 2020 11:18:17 #
bleirer wrote:
If you focus exactly on an eagle's eye, then lift your thumb to recompose left right or up down, you put the plane of focus behind the eagle's eye. In that case it does impact sharpness negatively. Of course if you are using it right you will keep the servo focus active and move the af point or turn on tracking in situations that call for it.
Assuming that you have removed AF from your shutter button, I am not sure why that would occur.
Dec 19, 2020 11:34:41 #
will47 wrote:
Can using back button focus improve sharpness in your photos.
The main reason I use BBF is to separate the focus point from the metering zone. Taking landscapes I will usually look for something a third of the way into the scene as a focus point and that is often going to be something to the side of the scene, but may not be what I want to meter on. I have BBF set on the focus joystick button and use point or small zone focus so it is all one operation.
Dec 19, 2020 11:41:13 #
will47 wrote:
Can using back button focus improve sharpness in your photos.
Any feature or idea that you find helpful or is more convenient to your focusing endeavor can improve sharpness.
If you take well to BBAF then it’s helpful. Likewise for MF using LV focus magnifier. Likewise peaking. Likewise illuminated AF points in the viewfinder.
Acoarst don’t let this one reply stop you from opening up new separate threads about each of those helpful features !
Dec 19, 2020 11:43:17 #
For me, BBF is perfectly natural now. Took some self training, however. It is how I take all photos
Dec 19, 2020 12:02:41 #
repleo wrote:
The main reason I use BBF is to separate the focus point from the metering zone. ..........
Great point. I never analyzed it like that, but I use BBF as my only form of AF. And I refocus constantly yet seldom re-meter. So that separation is a good thing.
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Changing viewpoint, or reframing, tends to require constant refocusing.
Unfortunately, changing viewpoint, or reframing, also changes your in-camera meter reading even when the light level is constant such that camera exposure controls ought NOT to be continuously adjusted in response to those changes.
Dec 19, 2020 12:08:17 #
User ID wrote:
Great point. I never analyzed it like that, but I use BBF as my only form of AF. And I refocus constantly yet seldom re-meter. So that separation is a good thing.
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Changing viewpoints or reframing requires constant refocusing.
Unfortunately changing viewpoints or reframing changes your meter reading even when the light level is constant such that camera exposure controls ought NOT to be constantly adjusted.
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Changing viewpoints or reframing requires constant refocusing.
Unfortunately changing viewpoints or reframing changes your meter reading even when the light level is constant such that camera exposure controls ought NOT to be constantly adjusted.
Doesn't that depend on the metering mode you are in? If Evaluative (full frame) I am not sure that changing focus point changes metering values. Certainly it does if you are using spot metering.
Dec 19, 2020 12:20:04 #
bajadreamer wrote:
Doesn't that depend on the metering mode you are in? If Evaluative (full frame) I am not sure that changing focus point changes metering values. Certainly it does if you are using spot metering.
Why are you asking that ?
What has been your experience ?
You raise an interesting point. If your meter can be locked to your AF focus target, will it fully ignore other bright or dark areas that grow or shrink within the larger frame as you reframe the shot ? (assuming either auto object tracking, or the user, keeps the AF target reliably on the same object).
If a system does a pretty good job of that, pretty good is not always good enough. But maybe such a system can do a near perfect job ? If you’re using such a system, please find out.
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My solution without object tracking has been AEL Toggle, which locks out any further AE response to the meter, until the toggle is unlocked. EV is frozen, same as full manual operation, until the user unlocks it. (FWIW TWIMC Olympus cameras disable AEL when using BBAF.)
Dec 19, 2020 12:29:57 #
User ID wrote:
Why are you asking that ?
Just responding to the attached quote in your post. I am not sure if you quoted someone else or not.
Dec 19, 2020 12:45:41 #
bajadreamer wrote:
Assuming that you have removed AF from your shutter button, I am not sure why that would occur.
Releasing the thumb in BBF is similar to focusing then turning the switch on the lens to manual focus to recompose. No problem if the change is slight and within your acceptable depth of field. But maybe you don't have much DOF or maybe focus on that eye is really critical.
If you lock focus on one spot in the scene the plane of sharp focus is right there flat and parallel to the sensor (ignoring possible curvature of field which you can't control) If you lock focus by removing the thumb and tilt the camera the plane of sharp focus stays at that same distance from the camera and still parallel to the sensor. But your subject is back in the same original spot now in front of the plane of sharp focus.
Dec 19, 2020 12:51:28 #
bajadreamer wrote:
Doesn't that depend on the metering mode you are in? If Evaluative (full frame) I am not sure that changing focus point changes metering values. Certainly it does if you are using spot metering.
Even in evaluative metering can change when you tilt the camera to recompose. What if there is a bright or dark patch that comes into the scene or leaves the scene when you tilt the camera?
Dec 19, 2020 12:59:37 #
bajadreamer wrote:
Just responding to the attached quote in your post. I am not sure if you quoted someone else or not.
Sorry. It’s got ambiguous or confused. Seems a dead end now. Just keep on keepin on !
Dec 19, 2020 14:42:23 #
User ID wrote:
Great point. I never analyzed it like that, but I ... (show quote)
A. That's why I separated them - hated both focus and metering on the same button.
B. Why would changing the viewpoint or re-framing require constant refocusing? If i have something I want in focus but want it in a different location in the frame, I won't re-focus when I re-frame. Unless I find something else I want in focus, as an alternate shot.
C. I focus on what I desire, lock the meter on what I desire, then compose and click. I don NOT have to continually adjust everything if I move the camera.
But I suppose it all depends on how one shoots, eh?
Dec 19, 2020 14:49:41 #
bleirer wrote:
Even in evaluative metering can change when you tilt the camera to recompose. What if there is a bright or dark patch that comes into the scene or leaves the scene when you tilt the camera?
I lock the metering so it doesn't change when I re-compose.
Dec 19, 2020 14:52:38 #
bleirer wrote:
Even in evaluative metering can change when you tilt the camera to recompose. What if there is a bright or dark patch that comes into the scene or leaves the scene when you tilt the camera?
True. You would have to aware of that. Because metering is still on the shutter button I would assume that would automatically take care of that. I shoot M with auto ISO so the only thing that should change would be ISO.
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