Tom Reichner wrote in post #18395868
Ok, so the way I see it is:
With phase detect, you do your best to put the little red square where you want it to focus, and hope that it really does focus exactly
where you put the red box. .
This could be problematic because the camera or lens could be off by an extremely slight bit, and I won't even know that it is missing my exact mark. .
Even perfect micro-adjustment won't solve the problem, because cameras miss focus by wee little bits in challenging conditions, even if they are calibrated perfectly. .
This is particularly true when the thing I want to be in absolutely perfect focus has very little contrast, and an area extremely close to it hs a lot of contrast. In these situations, the camera often picks up on the area with a lot of contrast and focuses on it, even thought it isn't exactly
in the center of where I put the tiny little red box.
With touchscreen focus (DPAF), you touch the part of the image that you want to be in perfect focus, then you wait a second to see what, exactly, is highlighted. .
Then you touch it again to see if exactly
what you want is highlighted. .
Repeat and repeat and repeat until exactly
what you want is finally highlighted. .
This seems to be extremely precise and accurate, albeit slow to achieve the degree of precision that I am demanding.
If what I have described above is the way things really are, then I can see a huge advantage to using dual pixel AF with a touchscreen, because I will know exactly what parts of which feathers are in perfect focus when I photograph birds. .
With the phase detect, I could be off by 2 or 3 millimeters and I wouldn't even know until I got home and viewed the images on my big 5K monitor. .
This is a very big real-life problem for me because I often miss focus by the very tiniest of margins..