On the 5DM3 what is the difference

[RGF]

Hi,

Not a rumor but a question about different settings on the 5D M3.

On selecting the AF area, there are two settings which seem to be identical

  - Single Point Spot AF
  - Single Point AF

Description in the manual does not help. Is the difference the first mode, link the Spot metering to the AF point and in the second case the spot metering is always at the center AF point (whether or not it is the active AF point).

Thanks

[neuroanatomist]

Spot AF reduces the effective size of the AF point. With single point 'regular' AF, the actual AF point is quite a bit bigger than the little box in the VF (basically, the real points on the AF sensor almost touch).  Spot AF restricts the AF point size to only very slightly larger than the little box that represents it in the VF. Spot AF is useful for macro shooting, I also use it with small birds in thickets. It's bad for moving subjects.

On the 5DIII, spot metering is always in the center (only 1-series bodies can link spot metering to the selected AF point).

[Mt Spokane Photography]

Spot AF reduces the effective size of the AF point. With single point 'regular' AF, the actual AF point is quite a bit bigger than the little box in the VF (basically, the real points on the AF sensor almost touch).  Spot AF restricts the AF point size to only very slightly larger than the little box that represents it in the VF. Spot AF is useful for macro shooting, I also use it with small birds in thickets. It's bad for moving subjects.

On the 5DIII, spot metering is always in the center (only 1-series bodies can link spot metering to the selected AF point).

+1
There are also some limitations to using spot AF so only use it if you really need it.  Its great for focusing on a bird in a situation where the AF might pickup the wrong thing to focus on, but in low light, AF is slower.
 
Here is a situation where spot AF can help, you do not want the camera to focus on the branches or flowers, just the bird. The focus is sharpest on the wing, but depth of field is enough so that she is pretty much all in focus.
 

[RGF]

THANKS

[gbchriste]

When you look through the view finder, the array of focus points is a matrix of small squares.  But each of those small squares also has an even smaller square in the center of it.  When using Single Point AF, you are using the larger, outer square for that point.  When using Single Point Spot AF, you are using the tiny square in the center of each focus point.

[crasher8]

and I was using it to get out stains!

[AlanF]

When you look through the view finder, the array of focus points is a matrix of small squares.  But each of those small squares also has an even smaller square in the center of it.  When using Single Point AF, you are using the larger, outer square for that point.  When using Single Point Spot AF, you are using the tiny square in the center of each focus point.

I had assumed that when just the central spot has the dot in it, the single point spot AF was activated for that central spot. But when each of the array of squares has has a dot, it is an indication that the whole of that array is active, and not the centre of each component.

[neuroanatomist]

When you look through the view finder, the array of focus points is a matrix of small squares.  But each of those small squares also has an even smaller square in the center of it.  When using Single Point AF, you are using the larger, outer square for that point.  When using Single Point Spot AF, you are using the tiny square in the center of each focus point.

Just to be clear, with Spot AF the actual AF point is still slightly larger than outer square.  The area being used for AF isn't nearly as small as the little inner box, that 'double' box is just the indication that Spot AF is being used.

[RGF]

Spot AF reduces the effective size of the AF point. With single point 'regular' AF, the actual AF point is quite a bit bigger than the little box in the VF (basically, the real points on the AF sensor almost touch).  Spot AF restricts the AF point size to only very slightly larger than the little box that represents it in the VF. Spot AF is useful for macro shooting, I also use it with small birds in thickets. It's bad for moving subjects.

On the 5DIII, spot metering is always in the center (only 1-series bodies can link spot metering to the selected AF point).

Thanks.  This explains some things to me.  I had always been using spot AF and at times having a hard time getting focus.

I was canon manuals were this clear.

[RS2021]

I was canon manuals were this clear.

I guess you are from a time after the Japanese company VCR manuals and the Millions of American households with blinking 12:00 LEDs. This is par for the course.

[Mr Bean]

When you look through the view finder, the array of focus points is a matrix of small squares.  But each of those small squares also has an even smaller square in the center of it.  When using Single Point AF, you are using the larger, outer square for that point.  When using Single Point Spot AF, you are using the tiny square in the center of each focus point.

Just to be clear, with Spot AF the actual AF point is still slightly larger than outer square.  The area being used for AF isn't nearly as small as the little inner box, that 'double' box is just the indication that Spot AF is being used.

Ah, that clarifies why I have trouble getting focus on some of the smaller birds. I was aware of the difference in the two settings, but not aware of the AF coverage

[FatDaddyJones]

Never knew that spot AF was slower in low light. Thanks for the tip!