First Time FF User - 5DM3 or D600?

Started Oct 1, 2012 | Discussions thread
bobn2 Forum Pro • Posts: 58,087
Re: Please elaborate on the "vastly" better AF

Press Correspondent wrote:

sandy b wrote:

Reports show the AF of the D600 as excellent and much improved over the D7000, indeed users are reporting as good as the higher body AF modules.

A couple points to get you started on your own research:

D600 has cross points only at the center requiring to focus and recompose that does not work well in some situations, such as with extremely shallow DOF.

No focus recompose is required because D600 has functional linear AF points towards the edges, where cross type points become less effective. I'm not aware of any well conducted tests of the relative efficiency of the D600's linear points and the 5DIII's cross points towards the edges.

5D3 and 1Dx utilize a new AF system with high precision sensors in the latest lenses (2010+).

However, the high precision sensors are in the middle of the frame, requiring focus and recompose (losing that extra accuracy) if the subject isn't in the middle.

As a result, the standard deviation of the focusing error is reduced twice compared even to the earlier pro models that had already excellent AF. Read Roger's report from

On the other hand, D600 can AF at f/8, useful for using long lenses with TC's, which you might end up doing if your lens budget is limited.

The truth is this: both AF systems are complex. Both are what their designers thought was a good compromise between functionality and the physical limitations of AF. Nikon chose to concentrate on sensitive linear points towards the edges, where cross points don't work very well, and the extra space they use can be utilised to making better linear points, Canon decided on more cross points, presumably in the hope that the residual two axis sensitivity still outweighs the disadvantage. You can really only work out which is better by trying - cherry picking features when you don't understand the underlying technology doesn't give a good clue to which AF is better.

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