There isnt a problem with the focus but when i hold the shutter and move to the composition i want the focus always gets off is this natural? Im using a 6d and sigma 85f1.4
Should make like a way to track the object you set the focus, recompose and then auto refocus on the tracked object again before it fires off
camera can track stationary object provided its moving relative to camera view.
just swing your camera.
Depends on what camera you're using. My 60D will re-focus on whatever is at the AF point immediately, it will not track. 60D does not have an option to set the delay before AI servo picks another focus target, so it happens immediately. I believe 70D can, but it is still unreliable from my experience. Swinging the camera will make the camera switch the AF point to something nearby, but not exactly what you initially focused on.camera can track stationary object provided its moving relative to camera view.
just swing your camera.
Stopping down would of course make it not so much of an issue, but then you don't buy a f1.4 lens to shoot at f5.6 anyway.Based on James Brandon's illustration on the dart board, he was shooting wide open at f1.4. The focus recompose method was off due to DOF much shallower. If we were to step down to f5.6, there will not have such issue, or at least not that obvious. Of course other factor is for the photographer to consider.
Does a camera with 51 focus point more accurate than the 39 pts if given the same wide opening setting?
Accuracy is not related to the number of AF points a camera has. Sometimes each AF points performs differently from others. But the more AF points means u can get more precise at the point u want the focus to be.Based on James Brandon's illustration on the dart board, he was shooting wide open at f1.4. The focus recompose method was off due to DOF much shallower. If we were to step down to f5.6, there will not have such issue, or at least not that obvious. Of course other factor is for the photographer to consider. Does a camera with 51 focus point more accurate than the 39 pts if given the same wide opening setting?
Should make like a way to track the object you set the focus, recompose and then auto refocus on the tracked object again before it fires off
+1 You're buying an f1.4 lens to shoot at f1.4Stopping down would of course make it not so much of an issue, but then you don't buy a f1.4 lens to shoot at f5.6 anyway.
Nikons can do this with the combination of AF-C and 3D tracking, but it isn't very reliable. If you focus on the eyes and recompose, it will focus somewhere on the face but not necessarily the eyes. Canons can do this with AI servo and automatic af selection I believe, but it's even more unreliable.
Those 2 cases that I mentioned above are meant for tracking subjects that are actually moving across the frame, not static subjects that "move" because you move your camera. In general, cameras can't track stationary subjects (at least they don't do it very well)
Sorry, my understanding was based on older Nikon cameras, like the D90. I'm using Canon system now so I don't know which AF area modes (on Nikons) are used for what purposes now.For the purpose you mentioned 3D tracking is not the af mode to use. you should be using dynamic tracking. You need to go back and understand what each tracking mode does and how they work. In the end it comes down to how well the photographer understands his/her equipment.
Dynamic area AF:In AF-A and AF-C autofocus modes, user selects focus point using multi selector. If user changes composition after focusing, camera uses 3D-tracking to select new focus point and keep focus locked on original subject while shutter-release button is pressed halfway. Use to recompose photographs while shooting relatively static subjects.
In AF-A and AF-C autofocus modes, user selects focus point manually, but camera will focus based on information from surrounding focus points if subject briefly leaves selected point. Use with erratically moving subjects.
Maybe Nikons can, but my Canon 60D definitely cannot. I have tried both combinations of AF area modes (single point and automatic area) in conjunction with AI servo mode on my 60D. None of them are able to retain focus on the subject after recomposing. I can only do it (unreliably) by focusing (back button AF), snapping the camera very quickly to recompose, releasing the AF button immediately, and then shooting. If the AF button is held down after recomposing, the camera immediately switches to focusing on the selected AF point (or the middle AF point if automatic area AF is used)And you are mistaken, cameras can track a stationary object quite well with the frame moving. Again it comes down to you understanding how your equipment works and react.
However, in practice, this only works if the subject is actually moving. If the subject is stationary and I move my camera, the camera will re-focus at the centre AF point (where I normally have it on)When the AF point selection (p.78) is automatic, the camera first uses the center AF point to focus. During autofocusing, if the subject moves away from the center AF point, focus tracking continues as long as the subject is covered by another AF point.
Sorry, my understanding was based on older Nikon cameras, like the D90. I'm using Canon system now so I don't know which AF area modes (on Nikons) are used for what purposes now.
From Nikon D90 manual:
3D-tracking AF:
Dynamic area AF:
Maybe Nikons can, but my Canon 60D definitely cannot. I have tried both combinations of AF area modes (single point and automatic area) in conjunction with AI servo mode on my 60D. None of them are able to retain focus on the subject after recomposing. I can only do it (unreliably) by focusing (back button AF), snapping the camera very quickly to recompose, releasing the AF button immediately, and then shooting. If the AF button is held down after recomposing, the camera immediately switches to focusing on the selected AF point (or the middle AF point if automatic area AF is used)
From 60D manual (using AI servo in conjunction with automatic AF point selection):
However, in practice, this only works if the subject is actually moving. If the subject is stationary and I move my camera, the camera will re-focus at the centre AF point (where I normally have it on)