BUTTON ON THE SIDE OF 70-200.2.8?

<p>hi all just one more quickie......i have the canon 70-200 2.8 l IS lense , now on the side is a few switches, and i know one is IMB stableizer etc but the other is a button which you can switch for focus legnth, but when im doing busy photoshoots i forget to move it, should i leave it on one or the other, as last time i look at shot at 200mm i noticed it wasnt as sharp as it could be? was this due to that....<br>

Hope u people who use this lense can shed sum light on this for me as i have a wedding coming up.<br>

many thx again</p>

Simple. Set your focus range switch at the beginning of your shoot.

If you're going to shoot stuff far away (racing, sports, wildlife, etc.) then set it to 2.5m-∞ and leave it

there.

If you're going to shoot stuff up close (wedding, portraits, etc.) then set it to 1.2m-∞ and leave it there.

If you're going to be shooting a mix then either remember to change the setting mid-shoot or just leave

it at 1.2m-∞ and don't worry about it.

The sharpness of your shots is not dictated by that switch...the switch only lets the lens know the

base distance from your subject and gives it a head start on focusing. For lack of a technical

explanation, it takes less time to focus from 2.5m to 5m than to focus from 1.2m to 5m...so if you're

shooting stuff 5m away for an entire photoshoot then set it to 2.5m-∞.

<p>The rationale for the switch is for fast moving events where QUICK Auto focus is paramount and necessary.<br>

<br>

As Sean has mentioned, it is all about time taken to focus: at a sporting event (for example) if following midfield action from the sideline and player moves across the lens at 2mtrs it could cost you the shot by the time the AF works in and out - so most sporting shooters always have the AF set to the longer distance.<br>

<br>

When I use my 70 to 200 for portrait, wedding or events work I usually set the closer distance - for the hockey field / swimming pool I usually set the longer distance, for the reasons above.<br>

<br>

WW </p>

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