Close up filter on zoom lens

[expositer]

Hi Guys,

Trying to use a Hoya +4 filter (52mm with a 58 -> 52 step-down ring) on a Sigma 70-300 Super II Macro lens on a Canon 350D

However, i always have problems autofocusing. Image in viewfinder always appear blur (i.e. very soft on the edges.) before i take the shot, thus the camera cannot autofocus based on that image. I understand i must set the smallest aperture available, thus i'll use the depth-of-view preview button and manual focus with it.

Any idea how to use auto-focusing in such a scenario?

Thanks.

[Goldenstars08]

I using the Canon 75-300mm. Zoom to 300mm a close up +4 is too close.
Try the close up +2 or max +3...

For MF walk to the correct distance & then turn the focus ring until you see a sharp image...

[expositer]

Hi Goldenstars,

Thanks a lot! I'll try it out to see how it goes (I realised that a +4 allows me only very very little distance to play with to get the focusing sharp).

cheers,

[Navyblue]

Originally Posted by expositer Hi Goldenstars, Thanks a lot! I'll try it out to see how it goes (I realised that a +4 allows me only very very little distance to play with to get the focusing sharp). cheers,

That is how a diopter works, be it +3 or +2, the focusing distance become very limited. Their difference being, +4 enables you to focus closer than a +3.