Dracula's Castle

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I have one lens hood for a 28-105mm lens that is petal shaped. I have another lens hood for a 50mm lens that is fully round. If the purpose of the lens hood is to block stray light, then wouldn't fully round always block more?

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6 Answers 6

up vote 11 down vote accepted

As Chills stated, petal shaped hoods are designed to better take into account the wider shape of a camera's film or sensor.

This article on Lens Flare has a good description of lens hoods and how they function.

enter image description here

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This doesn't really answer the question, just link to a article / page that might. Would be better if the answer contained the information, like @Reid's answer. –  Håkon K. Olafsen Jul 13 '12 at 11:37

The petal design is more effective. Think of what you can see through your lens: it is a pyramid-shaped chunk of space that falls within your view, one that has a rectangular rather than a square base. Now imagine placing a round lens hood atop that pyramid - there will be a large gap on each side, because the corners bump into the round opening first. A petal-shaped hood fills in these gaps, excluding more stray light.

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Here's an image that may help people to visualise why lens hoods are petal-shaped.


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For wider angle lenses the optimal design is the petal shape. This is because of the rectangular sensor and wide field of view.

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The optimal design for all lenses is petal shaped, but I suppose for longer lenses it would be quite a petal. –  Reid Jul 16 '10 at 2:20
@Reid Preidhorsky As you say, because of the narrower FoV for telephoto lenses, the hood would have to be seriously long before it became necessary to petal-shape it in order to avoid vignetting. –  Edd Jul 22 '10 at 15:55
For some fisheyes expected to produce a circular image, I would assume that a round shape is optimal. But in most cases we are using a circular lens to take rectangular pictures on a rectangular sensor or film. –  Markus Mikkolainen Apr 27 '13 at 12:46

Short answer: Yes, a round tubular lens hood will always block more stray light than a petal-shaped lens hood.

BUT, that's only half of the answer, however. The part that is missing is, "without cutting off (vignetting) the corners of the image at the widest angle used, in the case of a zoom." (an important omission, no?)

The petal shape is one compromise solution unless designed specifically for a particular fixed-focal lens.

Another solution is used by some manufacturers who make an over-size tube lens filter and then cut a rectangular window in the end for the light blocking.

Motion picture cameras have such a thing attached to the camera mount in some way. It is also called a matte box and allows various inserts to mask the shot from various things and for various effects. It is a pleated accordion-fold affair that allows it to be changed for various set-ups.

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Petal shaped hoods are better (because they fit better the rectangular size of the negative/sensor), but they can only be used in cameras which have a non-rotating front element.

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