wilfredsdad
Well-known member
EOS 450D - Auto Focus "Cross Type at F2.8 at center" er ... me no understandee
Hello
Could somebody clarify this for me: looking at the spec of the EOS450D (which I am considering buying) it states that the auto focus system has 9 points and has a "cross type at F2.8 at centre"; the spec for the EOS1000D has "cross type at F5.6 at centre" - I'm not clear what this means and how significant it is when using a telephoto lens for bird photography. Does it mean that the centre focusing point only functions as a cross type (ie detecting focus on both the vertical and the horizontal axis) when the lens is set to the (big) apertures stated? At smaller apertures it only functions as a single axis focus point?
Is it absolute - ie it really won't work as a cross type focusing point on anything less than the apertures stated? or is Canon just playing safe and there is some latitude? Does it make a lot of difference with focusing speed, reliability, and accuracy?
There are two reasons why I am asking: 1)The problem I have with my current set up is that the camera (Olympus E510) often struggles to focus my Sigma 50-500 lens (it hunts for ever and I miss a lot of shots), and this is one of the reasons why I am considering upgrading my kit. 2)The EOS1000D centre point will work as a cross type at F5.6 (or so the spec says) and a 500mm lens that goes to F5.6 is going to be a lot more affordable than one that goes to F2.8.
The fact is that 90% of the time that I am photographing birds I am using the centre spot for focusing - so any improvement there might make a big difference (or maybe not 'real world' difference at all?)
Could anybody put me straight on this. Also - I am looking at the Sigma 150-500 lens to go with the EOS450D (or EOS 1000D) - anybody got any experience with that combination? particularly with regard to autofocusing efficiency and reliability. I am discovering that in bird photography focusing is more than half the battle - a very high percentage of the pictures I take (and it seems other people take) are useless because they are not quite in focus, regards Pete
Hello
Could somebody clarify this for me: looking at the spec of the EOS450D (which I am considering buying) it states that the auto focus system has 9 points and has a "cross type at F2.8 at centre"; the spec for the EOS1000D has "cross type at F5.6 at centre" - I'm not clear what this means and how significant it is when using a telephoto lens for bird photography. Does it mean that the centre focusing point only functions as a cross type (ie detecting focus on both the vertical and the horizontal axis) when the lens is set to the (big) apertures stated? At smaller apertures it only functions as a single axis focus point?
Is it absolute - ie it really won't work as a cross type focusing point on anything less than the apertures stated? or is Canon just playing safe and there is some latitude? Does it make a lot of difference with focusing speed, reliability, and accuracy?
There are two reasons why I am asking: 1)The problem I have with my current set up is that the camera (Olympus E510) often struggles to focus my Sigma 50-500 lens (it hunts for ever and I miss a lot of shots), and this is one of the reasons why I am considering upgrading my kit. 2)The EOS1000D centre point will work as a cross type at F5.6 (or so the spec says) and a 500mm lens that goes to F5.6 is going to be a lot more affordable than one that goes to F2.8.
The fact is that 90% of the time that I am photographing birds I am using the centre spot for focusing - so any improvement there might make a big difference (or maybe not 'real world' difference at all?)
Could anybody put me straight on this. Also - I am looking at the Sigma 150-500 lens to go with the EOS450D (or EOS 1000D) - anybody got any experience with that combination? particularly with regard to autofocusing efficiency and reliability. I am discovering that in bird photography focusing is more than half the battle - a very high percentage of the pictures I take (and it seems other people take) are useless because they are not quite in focus, regards Pete