hood

ok this is kinda a dumb question i think.

im kinda new to photography and I just wanted to double check is the purpose of a hood to block out extra overhead light?

orrr...? what is the purpose?

Two things...to block extraneous light entering the lens causing flare and physical protection of the lens.

And it makes the lens bigger ; )

you mean "flare" as in those like red dots or lines that appear in a photo sometimes?

babos02 wrote in post #6330168
you mean "flare" as in those like red dots or lines that appear in a photo sometimes?

Yup.

ok thanks. it has just been bothering me for a while. ive seen some that arent completly even all the way around like...............

http://www.nikonusa.co​m …HB-35-Lens-Hood_FRONT.jpg

what is the purpose of this one versus one that is completly full?

babos02 wrote in post #6330247
ok thanks. it has just been bothering me for a while. ive seen some that arent completly even all the way around like...............

http://www.nikonusa.co​m …HB-35-Lens-Hood_FRONT.jpg

what is the purpose of this one versus one that is completly full?

Because the sensor isn't circular some bits of the hood aren't needed so they can be cropped away to make what's known as a 'petal' design. The amount that can be cut away depends on the focal length of the lens. With long lenses the excess hood is negligible, so they don't bother.

Courtesy of NK Guy at www.Photonotes.org

The part below is part of his Canon EOS Beginners FAQ which can be found here http://photonotes.org/​articles/beginner-faq/


What does a lens hood do?

Aside from making the lens look longer and bigger and thus more impressive to non-photographers, lens hoods (sometimes called shades) serve two basic functions. First, they help reduce the amount of stray light hitting the surface of the lens. This is a good thing, since non-image-forming light coming into the lens at an angle results in lens flare. Lens flare can result in lower-contrast images or, in extreme cases like light from the sun, can result in big glowing blobs in the final photo. Second, lens hoods serve as physical protection for the lens - the plastic or metal tube can absorb blows that might otherwise hit the glass itself.
Lens hoods come in a number of basic forms. The two types sold by Canon today are tube-shaped hoods and petal-shaped (notched) hoods, made of hard black plastic. The petal-shaped type are sometimes called “perfect” lens hoods and shield the lens more effectively than simple tubes of the same weight. This is because the notches are cut out to match the rectangular shape of the imaging area (think about it).
Some hoods clip onto the lens, some twist on bayonet-style and some screw onto the end. Some are lined with black light-absorbing flocking and some are not. You can also buy flexible adjustable rubber hoods from third party makers, but Canon do not sell any such hoods themselves.
Unfortunately, lens hoods are hugely overpriced. Camera makers somehow feel justified in charging massive sums for simple moulded plastic tubes. Ah well.

How are lens hoods named?

Canon lens hoods are identified by a confusing and cryptical alphanumeric code. There is a system to the hood naming, though it’s only somewhat informative. Still, if you understand how the hood naming works you can usually figure out which hoods can be interchanged with other lenses.

• 
  
• The first letter in a hood name is E, indicating that the hood fits a Canon EF mount lens.
  
• The second letter is either W, S or T. W stands for Wide, S for Standard (probably) and T for Telephoto.
  The letter refers to the type of lens to which the hood fits. W is for any lens wider than 50mm, S is for a 50mm lens (with a couple of odd exceptions) and T is for any lens longer than 50mm.
  
• The two letters are then followed by a number which indicates the size of the hood mounting ring in millimetres. Some hoods fasten to the very end of the lens barrel by means of a bayonet (rotating and locking) mount and others clip further down the barrel to a small ring by means of small spring-loaded plastic clips in the hood. Generally newer lenses use the former style and older lenses the latter.
  
• The hood size is sometimes followed by a letter from A through D. This letter indicates the hood style, and unfortunately there’s no real way of knowing what style fits what lens without looking it up, because the hood style appears to be chronological depending on when the lens was released and whether there happened to be any lens hoods already in the lineup with otherwise identical specifications but with a different shape. There is no way to tell if the hood is a standard tube or a petal shape (“perfect”) lens hood just by looking at this letter.
  For example, the original EW-78 fits the 35-350 3.5-5.6L USM, the EW-78B fits the EF 28-135 3.5-5.6 IS USM, the EW-78C fits the EF 35 1.4L USM and the EW-78D fits the EF 28-200 3.5-5.6.
  
• Finally, the hood name sometimes ends in a Roman numeral - typically either II or III. This indicates the hood version.
  Generally speaking, mark II and III hoods are flocked on the interior with black anti-reflective material, like velvet. Hoods with no Roman numeral designation are typically painted flat black, but since this depends in part on when the hood was released this is not a guarantee. Some mark II hoods also have slightly more clearance around the end of the lens so that polarizing filters fit better if their predecessors didn’t.

Some hood naming examples:
ET-65 III

E indicates that the hood fits an EF mount lens.
T indicates that the hood fits a telephoto lens.
65 indicates that the hood mount is 65mm in diameter.
III indicates this is the third hood of the ET-65 series, and means in this case that the hood is flocked to reduce reflections.
This particular lens hood fits a number of Canon EF telephoto lenses - the 85 1.8 USM, the 100 2.0 USM, the 135 2.8 SF, the 70-210/3.5-4.5, the 75-300 4-5.6 and the 100-300 4.5-5.6 USM.

EW-78B

E indicates that the hood fits an EF mount lens.
W indicates that the hood is for a wide angle lens.
78 indicates that the hood mount is 78mm in diameter.
B indicates that it’s a hood of type B.
This particular hood fits the 28-135 3.5-5.6 IS USM.

ET-160

E indicates that the hood fits an EF mount lens.
T indicates that the hood fits a telephoto lens.
160 indicates that the hood mount is 160mm in diameter.
This gigantic hood fits the 600mm 4L USM IS.

Knowing this system you can figure a few things out. For example, the EW-65, ES-65 and ET-65 can all clip onto the same lenses - the only difference is the length. The EW-65 is the shallowest lens and the ET-65 the deepest, so putting an ET-65 onto a 28mm 2.8 lens is a bad idea as you’ll get vignetting unless you have a cropped image sensor on a digital camera. But you can put an EW-65 onto a 100-300 4.5-5.6 USM if you like. It won’t shield your lens as effectively as the longer hood, but it’s better than nothing. Or if you can’t find the discontinued ES-65 you can always use the EW-65 instead.

ok thanks

One more thing: you should ALWAYS shoot with the lens hood on.

How much do hoods usually cost?

canonnoob wrote in post #6334331
How much do hoods usually cost?

it ranges from about 30-60 bucks (expensive! i know..) depending on your lens model.
you can try to look for hoods for your lens model from third-party manufacturers on ebay or around the internet. But obviously, the material and quality may be cheaper than the genuine Canon ones..

I see... would it depend on the size of the lens? say... a 28-135mm is a 72mm lens, while i have a 50mm?

canonnoob wrote in post #6335037
I see... would it depend on the size of the lens? say... a 28-135mm is a 72mm lens, while i have a 50mm?

Filter size is not the same as hood size on every lens. My 85mm f/1.8 takes a 58mm filter, but an ET-65III (65mm) hood.

Take a look at Canon's pages for the lenses you own or are thinking of owning. The correct lens hood is typically listed under the "Supplies and Accessories" tab. (Not every hood has a picture, be sure to check the descriptions.)

http://www.usa.canon.c​om …tIndexAct&fcate​goryid=111

canonnoob wrote in post #6335037
I see... would it depend on the size of the lens? say... a 28-135mm is a 72mm lens, while i have a 50mm?

Just check amazon. Search for the lens and the hood should come up too.