Are these starbursts a side-effect of shooting at f/22?

[TheBiles]

IMG_0701enhanced by Quentin Biles, on Flickr


IMG_0714enhanced by Quentin Biles, on Flickr

This was the first time that I'd ever done long exposures at night, and I was pleasantly surprised at the starbursts in some of these shots. Is this due to shooting at f/22 or something else with the lens? I always thought you needed a filter to get that effect.

 

[analog.universe]

You will get those any time you shoot a bright light against a dark background and you're not wide open. The more you stop down, the more intense the effect, caused by diffraction. There are also star filters, which will allow you to get a starburst effect at any aperture, and in lower contrast scenes.

 

[480sparky]

And the number of 'rays' you get will always be double the number of aperture blades in the lens.

 

[analog.universe]

And the number of 'rays' you get will always be double the number of aperture blades in the lens.

This is technically true all the time, but only true in practice with lenses that have an odd number of blades, since the resultant polygon has no symmetry. Designs with an even number of blades are symmetric on half as many axes as there are blades, meaning the diffraction spike from each blade overlaps exactly one other spike (from the blade directly opposite it). So a 6 bladed aperture has 6 spikes, 7 blades make 14 (as in the OP's photos), 8 has 8, 9 has 18, etc...

 

[MLeeK]

Yes. If you shoot at a very narrow aperture and a long shutter speed it creates the refraction off the blades of the aperture and the lights causing that starburst effect.
Think about when you squint your eyes tiny at the Christmas tree or similar. You get the same effect.
Same thing going on in your camera

 

[analog.universe]

Yes. If you shoot at a very narrow aperture and a long shutter speed it creates the refraction off the blades of the aperture and the lights causing that starburst effect.
Think about when you squint your eyes tiny at the Christmas tree or similar. You get the same effect.
Same thing going on in your camera

I don't mean to be nitpicky... but I also don't want inaccurate information to spread...

This effect is entirely independent of shutter speed (take a picture of your bare flash firing to prove it). And also it's diffraction (the bending of light around a solid object) causing the effect. Refraction is the bending of light as it enters or exits a transparent object (like a lens element).


edit: Technically, I should say that Refraction is caused by a change in the speed of light. In photography, that only happens at surface transitions (glass to air, air to glass, etc). In more general terms there are other ways to change the speed and cause it to bend... curvature of space due to gravity comes to mind.

 

[DiskoJoe]

YES

 

[BBBlack]

I just recently ran into this "starburst" effect as well, but in my case it's rather undesirable. Would an f-stop of 1.7 (that's the widest my lens will go) eliminate the effect? If not, then in what way will it tone it down? Will the rays be shorter, or will it just not be as bright? AND, will I need to expose the shots for less time in order to offset in the increase in aperture size, or can I keep the same exposure time that I used with f5.6/f8?

 

[Big Mike]

I just recently ran into this "starburst" effect as well, but in my case it's rather undesirable. Would an f-stop of 1.7 (that's the widest my lens will go) eliminate the effect? If not, then in what way will it tone it down? Will the rays be shorter, or will it just not be as bright? AND, will I need to expose the shots for less time in order to offset in the increase in aperture size, or can I keep the same exposure time that I used with f5.6/f8?

If you shoot with the lens wide open, light sources (like the sun) are more likely to appear with their natural shape (or round, as per the wide open lens)...but you will probably still get some diffraction and/or flare, it just won't have the same star effect.

And yes, if you make the aperture larger, you would be letting in more light, so to keep the same exposure, you would need to change the shutter speed (and/or the ISO) to compensate for that.