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Argh! How do I get rid of the stars on lamp posts?


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Michael,

 

If you don't want star-patterns around point light sources then you have to use a large aperture. The pattern you are seeing is a direct result of using a small aperture; the number of arms in your star is related to the number of aperture blades in your lens.

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another way that you can fix them if you want to buy, get a star filter. it cames with lines in a two piece glass and they have line in them. whelm you align them in certain position after rotating the front of the filter it will get rid of the stars but a better way is to use a bigger aperture and use a tripod and a faster shutter speed.
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Michael,

 

You can't have both, shooting at f16 will always give you that star effect from a bright light source combined with a long exposure, nature of optics and physics I am afraid!

 

The only way to alleviate this problem is to use a larger aperture even try something like f5.6 but depending on the number of iris blades in your lens, the effect will still appear but to a lesser degree than at f16.

 

The fewer number of iris blades in the lens coupled with a shorter exposure and larger aperture is the only way to reduce the effect, a star filter will not counteract but will add additional false light streaks.

 

You can't unfortunately have a direct light source in a long exposure at night with a good lens and not have this effect to one degree or another.

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You could make multiple shots and then merge them with the HDR (high dynamic range) feature in Photoshop. If you give short exposure for the lights in the scene in one of your shots, that might take care of the situation.

 

But yeah, it's true, it's physics, and it's not going away.

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A lateral solution which comes to mind ... never done it but I think it is logical:-) Open your lens to it's widest aperture** and then organise yourself a 'Waterhouse stop' of the required value.

 

A Waterhouse stop is simply a circular hole to stop too much light entering through the lens. Used in the 'old days' before adjustable iris were invented.

 

**at least a bit larger than the WS you are using so the light is not affected by the aperture's leaves.

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JC is right, but that's tough with modern glass--getting at the aperture is no longer just a

matter of unscrewing the front (or rear) group like you can on LF and some MF lenses. A

stop in the wrong place (in front of the lens) may help a little with the spikes, but it'll give

you massive vignetting too.

 

One of the reasons I love my old Mamiya 50/6.3--I can shoot it wide open and still have

decent DOF and great image quality.

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You could cut out a perfect circle out of a piece of black paper and tape this to the front of

your lens, or use a lens with a perfectly circular aperture, or, as others have said, shoot wide

open.

 

Irises with even amounts of blades will show that number of star streaks. Irises with odd

amounts of blades will show twice as many. So a 5 bladed aperture will give you 10 star

streaks, but an 8 bladed aperture will only show 8.

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>>A stop in the wrong place (in front of the lens) may help a little with the spikes, but it'll give you massive vignetting too. <<

 

I don't suggest yopu take your gear apart unless you are technically qualified. Waterhouse stops do not cause vignetting when used on prime lens close to front or rear elements. Used on a zoom lens where effectively we have two lens, one a prime back close to the sensor and a modifying lens up front to change the angle of view anything on the front is likely to cause vignetting. In my early penurious days I used waterhouse stops made out of coins* with holes drilled in them to control light entering a war surplus aircraft guncamera lens I fitted to my movie camera ... not convienient but it worked AOK :-)

 

*half-pennies c.1952

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