Questions about the Canon G1 X's AF Flexi Zone and maximizing DOF

Started Jan 12, 2013 | Discussions thread
Rod McD
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Re: Questions about the Canon G1 X's AF Flexi Zone and maximizing DOF
In reply to Sgt_Strider, Jan 12, 2013

Hi,

I understand what you've written and why, but I don't think it's going to work for you.  Let's say you place the point of focus one third of the way up from the bottom vertically on the LCD.  I think you're then assuming that this also places the point of focus one third of the way into the composition (from the nearest point in the scene to infinity).  This may be true on some occasions, but I don't think it will be true on all occasions.

What you're trying to do is engineer a way of placing the point of focus one third of the way between the closest point in the image and the farthest point.  There are several variables which will have an effect on whether such a point is also displayed one third of the way up the LCD screen.  The angle of view determined by the zoom setting may have an effect.  Your choice of where you place the horizon may have an effect.  The rise or fall of the land may have an effect.  To cite an obvious example, if the land falls away very quickly, like a cliff or a gorge, it's quite possible that the point displayed one third of the way up the LCD may in fact be quite some distance away, even at an infinity distance, from the camera.  The opposite is true if the land is rising steeply away from you - the point one third of the way up the LCD may be proportionally quite close to the camera.

I suspect that the photographer has to train their eye to recognise a suitable point at which to focus.  You then have to either move the focus frame to that point and allow the AF to do the work within the chosen composition, or select centre focus, then AF on a suitable distance and recompose.  People do use both techniques.  I got sick of changing AF points years ago and now only use centre-point-and-recompose technique if I'm using AF.

Another issue to think about is that if you move the focus frame off centre, you will have to consider where it is every time you shoot.  That will include taking a vertical shot.  If it was in the centre and one third up when the camera was horizontal, it would be to one side or the other when you took a vertical shot.  Another reason (for me)  to use centre-point-and-recompose technique, but that's just personal preference.

Hope this helps.  Cheers, Rod

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Canon PowerShot G12 Canon PowerShot G1 X Pentax K-5 Fujifilm X-T1
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