40D's new AF experience......

^^Gord^^

^^Gord^^

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First post of Talk so I'll start off by saying, hello all! :wave:

Got a chance to play with my 40D tonight and the AF is a different beast to my previous 20D and current 30D.

I used my 50mm f/1.8 as it would allow me to use the double sensitive centre point at f/2.8, the cross point at f/5.6 and it's also has slow AF.

I've been playing it low light conditions mostly and the AF is quicker and hunts less than the 30D but hits the centre point a lot less. At first this confused me and I started to wonder if I have a bad copy until I worked out the more sensitive outer AF points were locking onto things that my 30D wasn't picking up.

For example, shooting down a corridor my 30D would almost always go centre point, even if I had an outer AF point on a high contrast item like a door frame. With the 40D if I don't have anything in the centre point and the outer point is touching a door frame it will lock that point.

This is going to take some adjustment for me as I've got lazy and expect the centre point to lock on.

I'm going to try to get out tomorrow and see if this behaviour only occurs in low light conditions or not.

Have other 40D owners noticed this?
 
No I've not noticed as I've not bought one yet... but will do.

Keep up the good work of informing me/us/the masses
 
Not noticed with mine, but you can set different AF.

In the basic zone &adep you can't change it, but you can with the joystick or wheel. The manual does list examples of when AF can have problems.
 
Byker28i said:
Not noticed with mine, but you can set different AF.

In the basic zone &adep you can't change it, but you can with the joystick or wheel. The manual does list examples of when AF can have problems.
Click to expand...

I'm aware of the AI Focus, AI Servo, One shot AF settings and the ability to select individual AF points but I'm more interested in the sensitivity of the outer AF points in comparison to previous xxD cameras.

All my testing has been done in One Shot AF with all nine AF points. I have tested both selecting the centre AF point and AI Servo and both produce focusing similar to my 30D.
 
Ah - I'll keep an eye on it and see if I can report back. I guess I'll see some of it on Sunday when I use it in anger at the first football match of the season.

I've upgraded from a 300d so at the moment I'm loving it :D
 
Finally found time to get out and give my 40D a test on a moving object to see how the AF faired. RAF Cottesmore was night flying so I could shoot over there after work. The light was pretty poor but I got to pan a couple Harriers as they landed.

The AF worked well, especially at f/5.6, locking multiple points and keeping them locked even when I purposely panned it through static objects.

The custom function (Lens drive when AF impossible - C.Fn III #1) also worked well stopping the lens hunting around when heat haze enveloped the Harriers (take offs).

So, in summary the AF looks good to be, an improvement over the 20/30D, but it also means I now need a 300mm f/4 L so I can take better advantage of the AF! :D
 
A quick shot from the evening....

IMG_0090.jpg
 
I was at Prescott Hill climb yesterday with no AF problems at all.

I have noticed on two quick exposures it writes the second exposure to the CF before the first. Quite funny when reviewing the pics as they appear to go backwards :D
 
^^Gord^^ said:
I'm aware of the AI Focus, AI Servo, One shot AF settings and the ability to select individual AF points but I'm more interested in the sensitivity of the outer AF points in comparison to previous xxD cameras.

All my testing has been done in One Shot AF with all nine AF points. I have tested both selecting the centre AF point and AI Servo and both produce focusing similar to my 30D.
Click to expand...

Cant comment on the 40D as dont have one, but the other new Canons have cross point sensors across the AF elipse and these are almost as sensitive as the centre FP used to be - ergo the AF system will lock onto anyone of the AF points as they are almost as sensitive.

So no, there is nothing wrong, your AF system is working exactly as it should (y)

Hello & Welcome BTW ;) :wave:
 
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