Whats the benefit of a lens hood?

[manaheim]

hmmm...

I'm curious if anyone will disagree with me on this.

My understanding is that lens hoods are intended to reduce the amount of light from sources other than the subject off of the film/sensor. (Imagine if you look through the hood--- what do you see? Mostly the subject your lens would be focused on) This has the indirect effect of keeping the sun off your glass, reducing lens flare to SOME degree, etc.

In some cases, the lens hood will also be shaped to deliberately allow more light in at strategic locations, most notably with wide angle lenses where you will find a shaped hood with "cutouts" at the corners... this allows more light in at the corners to reduce the vignetting effect on wide angle lenses.

 

[Fiendish Astronaut]

Also, someone told me that the lens hood on Canon L series zoom lenses helps keep dirt and dust from getting into the lens via the bit which extends when you're zooming back and forth. I'm not sure how true this is... but thought I'd share.

 

[nynfortoo]

As per negatives. I would say they are expensive. Canon does not include lens hoods with their non-L series lenses, which is pretty cheap of them.

Which is pretty annoying. Spend £700 on a lens and, just because it isn't an 'L', I have to fork out an extra £35 for the hood.

*slaps Canon*

 

[Helen B]

hmmm...

I'm curious if anyone will disagree with me on this.

My understanding is that lens hoods are intended to reduce the amount of light from sources other than the subject off of the film/sensor. (Imagine if you look through the hood--- what do you see? Mostly the subject your lens would be focused on) This has the indirect effect of keeping the sun off your glass, reducing lens flare to SOME degree, etc.

In some cases, the lens hood will also be shaped to deliberately allow more light in at strategic locations, most notably with wide angle lenses where you will find a shaped hood with "cutouts" at the corners... this allows more light in at the corners to reduce the vignetting effect on wide angle lenses.

A properly designed lens hood should not obstruct the image forming rays, so it shouldn't really be able to reduce the 'vignetting effect' - it simply shouldn't add to it.

As you say, a properly designed lens hood should obstruct as much of the unwanted light as possible, not just the direct rays from a source. Light is coming from everywhere and any stray light can reduce the contrast of the image, particularly in the shadows. If you want good shadow detail, use a good lens hood.

Best,
Helen

 

[TamiyaGuy]

Using a lens hood makes other people think that you have a clue what you're doing .

But on a serious note, lens hoods can block out "glare" from having the lens at a certain angle to the sun. A bit of light enters the lens at a funny angle, bounces around in the lens a bit, and shows up on your camera sensor or film as a weird glare look, kind of like the hexagonal things you see on computer games when you look into the game's sun (it emulates this). In order to stop the light entering, a lens hood blocks out light entering almost perpendicular to the lens, and makes glare much less apparent, if it still gives any glare at all. Also, a lens hood provides great protection for the lens.

Downsides, though? Hmm, these are really nitpicky, but they make the lens bigger and perhaps more cumbersome, you might have to buy them seperately, and they make filters harder to rotate. But IMO, the advantages blow the disadvantages outta the water.

 

[Mary-Beth]

Hey guys! For those who need a lens hood at short notice – for FREE – looky here! Also get your spare lens hoods here!

 

[Dubious Drewski]

Also, as mentioned above, lens hoods get in the way of filters and other devices that you may want to attach in the front of the lens.

*ahem*, not if you use Pentax glass :greenpbl:. They usually have that removable hatch for access to your polarizers, etc.

I personally use the lens hood whenever possible simply because I don't use filters for protection and I want every bit of protection from impact that I can get. Hoods are great for that.