Question on Sunrise Star effect

This morning I was out early and happened on this sunrise and snapped a couple of shots. There wasn't much subject matter, just the sun, clouds and reflections.

The star effect around the sun did surprise me though.

I've taken many sunrise/sunset pictures over the years but have never encountered this six pointed star effect before. I didn't notice it through the viewfinder but there is was in the finished product.

I went through most of the content in the member portfolios and while there were several with simular water reflections I only found 1 or 2 with a simular star pattern.

I was wondering if it was caused by some type of prism effect since there was some fog rising up from the water.

Can anyone shed more light(no pun intended) on the cause of this pattern.

Thanks

The 'star' effect is a function of the lens you use - the number of points depends on the leaves of the aperture. The effect is typically maximized by using smaller aperture values, such as f/22. You also get thinner, sharper star points at wider angles - this looks like it was taken with a slightly longer lens, so the points are not as defined.

Thanks Floris, it was shot at f22/65mm on a 28-135 Canon zoom. The image I posted was cropped about 75% of original. I have taken other sunrise/sunsets at f22 before(Sigma lenses) but hadn't gotten this effect. This is probably the first time I've used the Canon 28-135mm on a sunrise. Sounds like I need a few controlled tests with this lens so I'll know better what to expect. Thanks again.

Thanks Floris, it was shot at f22/65mm on a 28-135 Canon zoom. The image I posted was cropped about 75% of original. I have taken other sunrise/sunsets at f22 before(Sigma lenses) but hadn't gotten this effect. This is probably the first time I've used the Canon 28-135mm on a sunrise. Sounds like I need a few controlled tests with this lens so I'll know better what to expect. Thanks again.

Floris/Ed, I usually get the star pattern once my exposure hits a ½ second or longer, especially when it's a full second or longer. I don't ever shoot past f14 to avoid diffraction issues. When I use my 3-stop Singh-Ray and thus the longer exposure time, I REALLY get a star pattern going, even from streetlights when I'm shooting 10 seconds or longer.

Just my $.02! (Pre-tax before 401K deductions...)

Ed - One thing you might notice is that even numbers of aperture blades produce the same number of star points, and odd numbers of blades produce double the number. For instance - 6 blade aperture = 6 point star, 7 blade aperture = 14 point star.

As an aside, if you can afford to, you should use apertures larger than f/22, in order to avoid diffraction softening effects. In shots like the one above, I'd think you could use something like f/11 or maybe f/16 and get better results.

I found this shot that our HR rep wanted me to take of our MFG plant in the snow... that sun has rays all over the place! I did shoot this at f18 for 1/5 second. This was a couple years ago with my 5D and 17-40. I switched to tehe 16-35mm and get way less flare and sharper star rays now, lol!

I personally like the rays. I saw them in Marc Adamus' shots 4 years ago when I first came across his work and always liked the effect.

OK, nuff babbling, I'd better git back to work!

Thanks Floris, Paul and David. great info. That's the great thing about this forum. If you ask a question you get a wealth of knowledge and experience. Thanks again.