ST-E2 Transmitter & 70-200 F2.8L

<p>Using a 1DS 3, or a 1Dll, I can't seem to get my 70-200 F2.8L to focus easily in low light, despite using my ST-E2 transmitter. Is this to be expected with the 70-200 together with the addition of the ST-E2, or am I not doing something right? The set-up works a dream with my 24-70 F2.8L, no problem focusing in low light with help of ST-E2. No flash is used.<br /> Thanks for advice.</p>

<p>Sorry folks,heading should read ST-E2 Transmitter & 70-200 F2.8L<br>

Thanks</p>

 

<p>It probably has to do with the longer distances that you are shooting at with the 70-200. I don't believe that the focus assist grid projected by the ST-E2 changes as you move through the zoom range, so at some point it's just going to be too far away/too dim for it to benefit the camera.</p>

 

<p>My ST-E2 Transmitter works a treat as AF focussing aid in low light with my 70-200 F/4.0L IS and 7D or 5D2.</p>

<p>The ST-E2 AF is designed to be used at typical flash distances. So if your subject is 50 feet out it just ain't gonna work. Also, the outer edges of the projected horizontal line AF pattern are fainter than the middle, leading to focus difficulties with outer AF sensors beyond 20 feet. However, I can usually snag focus with the center cross sensor with objects at 30 to 35 feet.</p>

<p>I read there is a clone of ST-E2 with longer distance</p>

<p>I read the trigger range was slightly better, but longer AF assist distance too? </p>

<p>Thanks for the responses so far. However, In a dark room (no lights at all), with the subject no more than 10 feet away, the 70-200 with the ST-E2 and central focusing point seems to hunt/struggle to focus. as i mentioned above, my 24-70 has no problem at all with this set-up.</p>

<p>It could be the length of the lens is getting in the way. Have you tried putting the ST-E2 on a flash bracket ? </p>

<p>Harry may have nailed it. I recall my EF 300 4L partially blocked the AF assist light for the rare times I needed to shoot close enough I could use AF assist. It's easy to test: with eye off camera, half depress the shutter button with camera pointed at a blank wall. If the lens blocks the AF light, you can see the shadow. And, yes, the ST-E2 can be used on a OSCII. I've had to do it a few times and it worked better.</p>