Why do cropped DSLRs need "special" lens hoods?

[nabman - montreal, canada]

Hi,

 

Why are hoods designed for EF lenses not useful on "cropped" sensors?

 

A cropped sensor captures a smaller area within the FF image. This area (and

more) is captured by a full frame. So if a hood is effective on this area

within a full frame, why can't it be effective on the same are on a cropped

frame?

 

I don't get it.......please to me in layman's terms.

 

Thanks,

Nab

[denisgermain]

because the image is cropped... you could use a longer hood than on a ff sensor.

There is nothing wrong with using the "normal" hood with a cropped sensor camera - a longer one could help even more but - I would say: don't worry about it!

[amol]

"Why are hoods designed for EF lenses not useful on "cropped" sensors?"

 

I have never heard this before... Where did you hear this?

[keith_lubow]

"Why are hoods designed for EF lenses not useful on "cropped" sensors?"

 

This statement isn't really true. Lens hoods do indeed help on any format. They are "useful", just not "optimized" for the smaller formats.

 

The ideal hood design is one that has the same aspect ratio as the frame (meaning that it is rectangular), and goes out as far as possible without cutting into the picture.

 

As to why the hoods are not ideal for the smaller format, it all has to do with field of view. With the same lens, a hood can be longer on a smaller format camera without vignetting the image. However, since the hoods are designed for the large format, they are not as long as they could be, and thus not as effective as they could be. It doesn't mean they are useless. It's kind of like using a toy spare tire.

 

Keith

[tien_pham]

A lens hood should be influenced primarily by its lens, not the sensor size. So if a lens with its hood has been used on a FF sensor, it should perform in a similar way on a "cropped" sensor, as long as you don't intend to use a quite different hood on the lens. Even though a hood can be fit for one lens and another, e.g., 24-70mm/2.8L and 70-200mm/2.8L, using the hood of one can cause optical abnormalities on another. For example, the hood for 70-200mm/2.8L can cause optical abnormalities, although small, if used with a wide-angle 24-70mm/2.8L. I mention "small" because the length of the two hoods are about the same, and because the 24-70mm/2.8L lens extends out under the wide-angle end. When this happens, the hoods becomes relatively shorter with respect to the lens. So if the the length of the hood of the 70-200mm/2.8L lens is about the same as that of the 24-70mm/2.8L lens, using the hood of the longer lens in this case would cause minimal affect.

[mars c]

A FF lens will have a FF lens hood, A cropped lens will have cropped lens hood.

 

I dont see anytihing special about the lens hood on cropped lens.

 

But if you're using the ef 17-40L on a cropped body, It would be better to use the hood for efs 17-55 2.8 IS , cause it's narrower, It offers more protection , cause it's deeper And I dont find the orig. hood of the 17-40 to be practical on a cropped body cause it is to large in diameter, difficult to put in a bag.

[mark u]

I think you'll find this article on hoods very informative:

 

http://www.vanwalree.com/optics/lenshood.html

[gdanmitchell]

The EF hoods are "useful," just not as useful as hoods that more closely match the angle of

view of the lenses. These hoods can do a better job of protecting from flare since the area

they block will be closer to what is actually required for the lens on crop.

[sravan]

It is a bit true only if you are using a lens for full frame camera on a cropped sensor camera.

In the croped sensor you do not see the full view of the lens. So there is a tendency to cut nearer to the bright source of light which then brings the source of light within the field of view of the lens but not the field of view of a crop sensor. This then causes flare which is expected if the source of light is not blocked off. That is why putting a different hood on the same lens which is longer than the normal hood is useful as it now brings the FOV of the lens to be the same as the camera and so the bright lights you are trying to cutoff are rally cutoff when you see through the view finder.

[kelly_flanigan1]

Using a narrower lens hood when 35mm still camera lens are used on smaller formats was mentioned 1/2 century ago or more in Pop Photo; I think in the Feiningers Workshop column by Andreas Feininger. In this era one was using a 16mm cine camera for home movies; one could use a 16mm cine C-mount to say Exakta slr or Leica thread mount. A 50mm normal lens thus becomes a long telephoto lens; and a lens hood of a 135mm could be used ; since one is not using the lens on a full frame camera; but with a smaller format.<BR><BR>When I use my 50mm F1.4 Nikkor on a 16mm camera; one can use a 200mm lens hood; or one for a 105mm lens.<BR><BR>One really doesnt have to use a lens hood; or a hat in the desert; or that deal/shade on you car that blocks the sun when driving into a sunset.:) take them off; you get less contrast; have wrecks more; get sunburned:)

[mendel_leisk]

Likely you're misled by all the threads on this subject. Canon (as far as I know) makes one hood per lens. The EF lens/hood combo's can be used on either full frame or crop bodies. It's just that some people are thinking, logically enough, that you could have a "tighter" hood on a crop body, say by swapping hoods. But, there's not much to be gained, not worth the hassle. And if you switch to full frame, you'd be chasing after another hood.

 

FWIW, I rarely use hoods, find they impede getting so many shots that I'd rather live with out them. I know they could help some of my shots, but as often as not, they cause me to miss shots.

[m3rdpwr]

I have a 17-40L on my 20D and I don't like the large hood.

 

I had read the same that you could use the Hood from the 17-55 which is smaller and would offer more protection.

I like the smaller hood better as I can keep it attached inverted in the camera case without removing like I have to do with the original 17-40L hood.

 

Here is a site that offered some comparison's.

http://www.burren.cx/photo/alternate_hoods.html

 

-Mario

[nabman - montreal, canada]

Thank you all. Mark's article, especially the pyramid example, explains it very well.

[conraderb]

they don't really need special lens hoods - you can use any sort of lens hood. you can just use more aggressively designed hoods on cropped bodies since some of the area of the lens isn't used to make the image.

 

as well, some hoods will work on more than one lens. for instance, the hood on the 16-35mm works the same on a full frame as it does on the 10-22mm on a 1.6 body, since the latter lens on 1.6x is equivalent to the former.