Lens Hoods And The Crop Factor

I am wondering if the angle difference that results from the crop factor would justify a different size hood. Has anybody out there done any research on this? Now that Canon has entered the consumer DSLR market there may be enough call for them to come out with different hoods for digital, or identify an alternate existing hood for each lens that is right for digital.
Have Fun

I have a lens hood from a 70-200mm telephoto (? I think thats what its from ? ) on my 17-40mm f/4 L

So yes,. it definately is worht look.

Are you sure you don't get vignetting at 17mm???

--Jens--

The Vignetting was tiny... so small I could not beleive how little I needed to trim off the hood to get it perfect at 17mm....

but yes,. I did have to trim it a little,. The hood I got was used,. it is an EW-83B which is much longer and narrower than the stock hood. I had also tried the 70-200mm and it was almost exactly the same size with similar vignette,. but yes it too would have been neede to be trimmed. That is why I bought the used one.

The pont is this hood is so much longer and narroer than the stock 17-40mm hood it illustrated how totally useless the stock hood really is.

Here is the post I had on the subject.

http://www.photography​-on-the.net …wthread.php?t=1​4986#78115

FWIW, I have a Sigma 15-30 wide zoom. It comes with a removable hood.

On a 35mm film body, the vignetting is terrible at 15mm. You get a big black circle around the image. You *have* to remove the hood to shoot at 15mm.

On my 10D, I can shoot at 15mm with the hood on. There's a slight darkening in the corners of the shots, but you really have to look for it.

So yes.. Obviously you can use larger hoods when using 35mm lenses on a Digital camera with an APS sized sensor.

You can use whatever hood your lens came with. And if it didn't come with a hood and you want one, you can just get the hood that was made for it. No need to complicate matters by over analysing what effect the crop factor has on the relationship of the hood and the lens because there ain't anyting to analyse.

PacAce, Thanks for the reply. Your statement would be true in the 35mm film world, but in the case of 10D and Digital Rebel the crop factor changes the angle that the lens captures. Therefore, the hood should be longer to prevent flare while avoiding vignetting. The question is, how much?
There is an extensive reply and reference to a solution for the 17-40. That is a good one. The lens that started me down this path is the 28-135 IS. Has anyone found a solution for that one?
Have Fun

That doesn't make sense to me. If a hood prevents flare when used on a full-frame camera, it will prevent flare on the 10D. The 10D simply uses the center portion of the view and crops away the perimeter.

It would be better to say that a hood "COULD" be longer since vignetting is less of an issue.

Right? Or am I missing something here?

Here we go again.
The problem with reasoning that the crop factor makes a difference to the hood which can be used is ignoring one important point.
The WHOLE of the lens forms the image, not just the centre portion.
Whilst there may be no vignetting PacAce and DonCoon are therefore correct in their replies.
Why mess about buying differnt lens hoods when the one which is made for the lens is either supplied or will usually be the cheapest anyway?
Those of us who may have to swop lenses between different bodies and crops - even onto full-frame digital or (God forbid!) film bodies can't even think about swopping lens hoods as well...............!

Paul

You're not missing anything. That's right.

I have a 17-40. The included hood is a joke when used on a 10D. It barely provides any additional shielding. I purchased the EW-83DII which is the hood for the 24/1.4L and it's much better.

The easiest way to make a selection is to think about the FOV at the widest end. For the 28-135, the wide end is equivalent to 44mm on a 35mm camera. So, you want a hood that won't vignette a theoretical 44mm lens. The 28-135 has a 72mm filter diameter. If you look Canon's offering of lens hoods in a 72mm diameter, you won't find much. The only two choices seem to be the E-72 and the E-72U. The E-72U is spec'd for the 28-135, so that really only leaves the E-72, which is spec'd for the TS 24mm and 45mm lenses. I doubt that the E-72 will provide any improvement at all.

That means you'll have to buy a 3rd party hood. I think Hoya makes a screw-in, collapsible hood that won't vignette at 35mm. That might be a reasonable choice.

geez, it seem like a straightforward question, but... so if you have already made up your mind on this then thanks, but for those of you that may still be interested -
The way I see it, the hood should protect against all light that enters the lens at a greater angle than the angle of view of the lens. Now the perfect hood would be rectangular, and the scalloped hoods for the wide angles approach that, but I want to try and keep it simple (may be too late)...
I have not done the research, but I'm pretty sure the Canon hoods are designed for the angle of view (AOV) of the lens when used for the 35mm film format. For the lens that got me going on this (28-135) the maximum AOV is listed as 75 degrees. Okay, fine, but when I put that lens on my Digital Rebel, the maximum AOV becomes 51 degrees. So for best results (granted it will only be best results when zoomed all the way wide), the hood should block all light coming in at greater than 51 degrees. That's a lot of difference, and I just thought it might be worthwhile to see if I can get there.
Now, am I missing something?
And one thing to keep in mind is that even though the 28-135 has a 72mm filter size, the specified hood is EW-78BII, because the bayonet portion of the lens where the hood attaches is larger than the filter diameter (probably 78mm), so the options mght be the EW78C or the EW78D. Has anyone tried either one of them on the 28-135?
I'm sorry if I started a firestorm, but inquiring minds want to know - geez, any time you mention the words 'crop factor'...
Have Fun

Canon, and everyone else, makes lens hoods that are not nearly long enough to be effective for the given focal length of the lens that will use them. The problem is that an effective hood would be too damn big, especially on telephoto lenses, or it wouldn't look cool enough. They all make hoods that are "better than nothing".

The shape of the lens hood is open to debate. My feeling is that a rectangular hood/shade just on this side of vignetting is what you want. The longer the shade (without vignetting) the more effective it's going to be in controlling flare. Once again a bellows lens shade does both. With the review you don't have to worry about vignetting and you adjust it to fit it to each lens.

Yes, but the 10D sensor doesn't see the WHOLE image made by the lens, it only records a portion from the centre. Since bright lights in that portion of the image that the viewfinder doesn't show, and won't appear in the final image, can still cause flare it makes perfect sense to mask those lights out using a lens hood that suits the actual FOV of the lens and not the FOV that the lens would have on a different camera system.

Lens hoods are relative to FOV not focal length. If you had a 6x6 camera with a 50mm lens and a 35mm camera with a 50mm lens would you expect the lens hoods to be the same shape?

Actually ,. the "flower petal" shape IS the "perfect" shape,. a lens hood that was engineered to block all light that hits the front of the lens EXCEPT the light that goes in to the rectangilar film plane/CCD will in fact look exactly like the "flower petals" we are used to. But with the smaller film plane of the 10D etc.. the petals are not long enough to do the job.

The lens elements bulge outward,. so a perfect ractanglar hood would result in a vignette shaped like a collapsing rectangle with sides like this ) ( and the same for the top and bottom,.. by using the curves of the petal,. the shadow that us cast on the bulging convex elemnts is in fact a virtually straight rectangle,. that is exactly why they are shaped that way.

O-kay super lame diagram time