Star Effects : Can someone explain this ?

I have noticed that my pics taken with a compact powershot s30 produce a better star effects than my pics taken with the digital rebel.
Is it because of the size of sensor ? Does it depend on the lens ?
Can someone explain me why ?
I know I can always use a star effects filter with the DRebel but just want to know what's the cause of the difference.
Here are an example. The first one has been taken with the S30 and the second one with the DRebel+18-55. Both taken at f8.

Yacine.

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The number of blades on the aperture detrmin the the shape of the stars.

Though it's a pleasing effect at night in Paris, elsewhere it is image degredation. Similarly, I am able to minimize my flaws by being out in Paris at night. Makes everything better.

The smaller the aperture, the more pronounced the effect.

Cokin has several "star filters" as well, if you like the look.

Like what was mentioned, the smaller aperture make the effect more pronounced and because of the smaller sensor on the S30, F8 is about equal to F16 or so(guessing) on your Rebel.

Maybe you should get some star-effect filter?

That is the correct answer....

Best regards,
Andy

I know it has been mentioned already on this thread but for me the best way to achieve the stars easily is to set the camera on aperture priority mode and then set the aperture to its smallest setting (should be around f/22).

Or if you find it really irritating (like I do in my photos), use a smaller f/stop (4.5, 5.6) and you'll end up with beautiful round orbs of light that dont suck all the attention away from the rest of your photo.