Question: I have a Canon EF 24-105mm f/4L IS USM lens and its hood EW-83H. I also have an EW-83J lens hood intended for EF-S 17-55mm f/2.8 IS USM. I don't have a full frame camera; my camera is a crop sensor one.

If I'm using the 24-105mm lens on a crop sensor camera, it's equivalent to 38.4mm-168mm. The 17-55mm lens is equivalent to 27.2mm-88mm.

I'm thinking of using the 24-105mm lens with the EW-83J lens hood intended for another lens, because the 24mm lens hood (EW-83H) needs to be relatively small due to the wide angle, and therefore, it doesn't offer as much protection as the EW-83J hood. Of course, using the lens on a full frame camera really requires the EW-83H hood so I'm not planning to throw that away.

I have been looking at the lens hood mount, and the diameters (81mm inner, 84mm outer) are the same, and the number 83 in the model number (whatever that means -- I couldn't find any 83mm dimension in the mount mechanism) is the same too. The lens hood mount mechanism seems to be identical. However, I'm afraid that if I try mounting the EW-83J hood on the L lens, it could get stuck due to some difference in the mounting mechanism I couldn't see.

So, my question is: can I use the EW-83J lens hood on the 24-105mm lens intended to be used with the EW-83H lens hood (when using the lens with a crop sensor camera)? Is it a good idea to use the EW-83J hood on a crop sensor camera or can it cause some bad effects on the image quality?

Answer: 
Yes, because you are using a crop camera, you can use the EW-83J hood on your 24-105 without any vignetting or other effects. 

Here is a chart that shows many other alternate lens and hood combinations.

[Alternate Hoods](https://khromagery.com/2006/11/16/alternate-canon-lens-hoods/)
[![enter image description here](https://i.stack.imgur.com/2qA6r.jpg)](https://i.stack.imgur.com/2qA6r.jpg)
For the vast majority of Canon lens hoods, if the number part of the name of the hood is the same as the number part of the name of another hood then the hood will mount on lenses for which the other hood was made.

There are a few exceptions for hoods that do not use the typical bayonet style attachment. For instance, the ET-65III made for the EF 85mm f/1.8, EF 100mm f/2, and several other discontinued lenses that presses straight on with release buttons is not interchangeable with the bayonet twist-on style ET-65B for the EF 70-300mm f/4-5.6 IS.