How did I create this effect?

[Davo3960]

Anyone know whether the 6 pointed star effect in the attached photo is the result of something I have done or just a nice by-product?

[[1ponders] (Paul)]

That is from the iris of you camera lens Davo. What lense and f ratio were you using?

[RB (Andrew)]

It's from the aperture blades inside your lens.
Beautiful image BTW !

[h0ughy (David)]

thats the stops in the camera lens, they must have been bright and tracking on them to get that effect.

[Davo3960]

When I took the image I had only just got the camera (350D) and it was mounted on top of the LXD and I hand guided for about 15 mins. The lens was a canon 55-200 and I didn't know anything about f-stop at that time. So I have no idea what it was set on. So do high (20) or low (5.6) stops create the effect? (I'd like to repeat it)

[[1ponders] (Paul)]

As the aperture gets smaller (higher f stop - longer exposure time needed) by restricting the iris the effects become more noticeable. The number of spikes you get will depend on the number of blades in the iris.

[33South (Chris)]

Originally Posted by Davo3960

When I took the image I had only just got the camera (350D) and it was mounted on top of the LXD and I hand guided for about 15 mins. The lens was a canon 55-200 and I didn't know anything about f-stop at that time. So I have no idea what it was set on. So do high (20) or low (5.6) stops create the effect? (I'd like to repeat it)

If you open the original image with something like IrFanView then from the menu select image / information then click show EXIF information it will tell you lots of good stuff about the image, exposure time and stop number.

There are plenty of free image viewers that will show the EXIF info such as

http://www.irfanview.com/

This has been around along time and is one of my favourite freebees

[Ric]

Hi Davo, great looking effect.
I get the same as well when I forget to take the Hartmann mask of the front of the scope when imaging.

Cheers