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>  forums  >  All cameras  >  Canon 70-200 F4L focusing issues
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The Maven  [admin] 
Canon 70-200 F4L focusing issues
7 Jul 2004 at 13:43 GMT
number of posts: 330
member since: 13 Jan 06
location: uk

status: offline

I've had this lens for a few months now, and have been quite happy with it. However, I have heard a lot of people complain about it back focusing. Once in a while I do have a photo that was front or back focused, but I'd usually attribute it to the focusing point being bigger than the subject (e.g. photography of small birds).


Has anyone else experienced focusing problems? If you haven't please post to say that you haven't, so that we can get an idea of how common or uncommon the problem is.

The Maven  [admin] 
re: Canon Gear
8 Aug 2004 at 20:06 GMT
number of posts: 330
member since: 13 Jan 06
location: uk

status: offline
Back focusing is when the camera doesn't focus on what you are aiming at - but instead focuses slightly behind the subject (usually off by just a couple of cm). There is also something called front focusing - in this other case, the camera focuses slightly in front of the subject.

On the Canon 10D, there are 7 AF points in the viewfinder. These are shown as squares. The complaint I have is that these squares are rather large. Sometimes I want to focus on the head of an animal (for example). But the square is 2x or 3x the size of the animal's head. In such a case, it's hard to know what the camera will lock onto.

What's worse, the 10D's AF sensors are actually even larger than the squares you see in the viewfinder. So you might point the square at the animals eyes, but it might lock on to the nose instead. Canon seriously needs to redesign the focusing system on their low and mid range DSLRs.
Carl Kirstein 
re: Canon 70-200 F4L focusing issues
9 Jan 2007 at 07:01 GMT
number of posts: 6
member since: 8 Jan 07
location: za

status: offline
I had focussing issues with this lens when I had the 300D, I don't have them anymore with the 30D... I don't think its the lens that causes focussing issues
Plagiarist 
re: Canon Gear
10 Jan 2007 at 01:30 GMT
number of posts: 50
member since: 20 Jul 06
location: Australia

status: offline
Maven that is exactly my problem on the 300d. The af is so unreliable which is why when i recently shot some stuff with a d80 i was blown away by its responsiveness. I have been manually focussing to try and compensate. I think however the newer sensors in the newer canons are probably improved remarkedly. i see that the 400d now looks similar to the nikon in the af point placement.
Plagiarist 
re: Canon Gear
10 Jan 2007 at 01:32 GMT
number of posts: 50
member since: 20 Jul 06
location: Australia

status: offline
dont you hate it when you forget to sign in . Nev
Carl Kirstein 
re: Canon Gear
5 Feb 2007 at 12:09 GMT
number of posts: 6
member since: 8 Jan 07
location: za

status: offline
Don't you mean that the 400D is now similar to the 30D placement? The D80 is simlar to the D200 (11 AF points)

apparently the 300D and 350D was not accurate with the focus because the focus point is larger than the block you see in the viewfinder. Therefore when you require accurate focus, it does not necessarily focus exactly on the block.

The 20D/30D is much better by having its focus point as large as the block. Yet I have found that the focus does miss a couple of times. These days I mostly use my centre AF point, as it is the most reliable in obtaining an accurate focus.

apparently the 1D series has remarkable focus... sigh, but I cannot afford those bodies

ergo: it is not the lens that is responsible for focus accuracy or reliability. It is merely responsible for focus speed.

post replying to 's post:

>  Maven that is exactly my problem on the 300d. The af is so unreliable which is why when i recently shot some stuff with a
>  d80 i was blown away by its responsiveness. I have been manually focussing to try and compensate. I think however the
>  newer sensors in the newer canons are probably improved remarkedly. i see that the 400d now looks similar to the nikon in
>  the af point placement.


 
re: Canon 70-200 F4L focusing issues
7 Feb 2008 at 14:30 GMT
number of posts: 4
member since:
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status: offline
Hi Gang, I've used this lens with a 20D and found no problems, tack sharp and focus spot on.


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