100mm macro F2.8 USM & Sigma EX Multi-Coated UV filter

[peterlee]

Hi All,

 

I shot this picture with my 300D,100mm macro F2.8 USM lens & Sigma

EX Multi-Coated UV filter and was surprised by the pattern the

lights created. I thought you needed a special filter for this

starlight effect? Any ideas why this happened?

 

Cheers,

Peter<div></div>

[hugh_crawford1]

You are seeing the diffraction from the aperture blades , it looks like there are eight of them on that lens.

[awindsor]

You can get star patterns caused by diffraction at the angle where the blades meet. This occurs typically when you shoot with a small aperture. That picture wasn't taken with f16 or so by any chance ?

 

Incidentally my 17-40/4L, which features Canon's nearly circular apeture gives a faint but many pointed star.

[awindsor]

That is a nice shot Peter.

[peterlee]

Alistar and Hugh - Thanks for the quick response! What you're telling me makes total sense.

 

Since this train caught me by surprise I really didn't have time to get organized for the shot and had a shutter speed of 30 and my apture was set to 22. I was working on another shot that required DOF and forgot how my camera was setup. Lucky it turned out:-)

 

Thanks again!

[bsd230]

Nice shot and yes this is cause by the aperture blades.