Protective lens hood for fish-eyes

[nail33]

I have a canon xti with a canon 50mm f/1.4 USM of which I am quite pleased.

Unfortunately, I didn't have the knowledge when I bought it regarding the 1.6

crop factor. I like to take indoor pictures occasionally and this lens is

terrible for tight quarters. I wish I had purchased the kit lens with the camera

when I had the chance. Hind sight is always 20/20. I prefer prime lenses, and if

I had the kit lens I would be able to figure out what focal length would satisfy

me. I went ahead and ordered the Zenitar 16mm f/2.8 fish-eye, which many people

on this site, as well as others, rant and rave about because of it's low price

and fairly good optics. This should produce a focal length of 25.6mm if I'm

correct. I realize that it has to be used as a manual lens, but I'm used to that

with all my FD lenses for my A-1. One of the problems I've read about this lens,

and most other fish-eyes', is the inability to put a protective filter on the

front. It comes with a very short lens hood; too short to do any good as far as

protection is concerned. My question is: Because of the 1.6 crop factor,

shouldn't I be able to make a larger lens hood that would better protect the

lens? Because the image projected is larger than the sensor, the lens hood

shouldn't show up in the picture as a dark ring on the outer edges. I'm assuming

I'll have to d-fish and/or crop some of the pictures anyways. Plus, the larger

lens hood should help reduce flare, which I guess is notorious with fish-eyes.

Am I making any sense, or am I way off with this line of thinking. Thanks in

advance for your help.

[j_smith6]

Are you sure you want a fisheye lens? Removing distortion on every picture will take lot of time + results won't be good.

[steve_dunn2]

<p>Even with the crop factor, the lens has rather a wide angle of view, so any substitute hood will still have to be rather wide (and therefore quite open) and won't offer a great deal of protection, either from stray light or from stray objects.</p>

 

<p>De-fishing the shots can be done in software, yes, but remember that it involves stretching some parts of the picture. You'll end up with decent resolution in the centre of the picture, but <a href="http://www.bobatkins.com/photography/reviews/wide-angle-lenses-2.html" target="_blank">you'll lose some resolution towards the corners and edges</a>. See <a href="http://www.bobatkins.com/photography/reviews/fisheye.html" target="_blank">Bob Atkins' review of this lens</a> for an example which shows that de-fishing isn't always necessary on a 1.6-crop body. He also mentions that the FOV of this lens on a 1.6-crop body is about equivalent to that of a 20mm lens on a full-frame body. I guess the discrepancy between this and the expected 1.6x factor is just another of the weird things that crop up in the world of fisheye lenses.</p>

[bobatkins]

I cover issues of the field of view of normal (rectilinear) lenses and fisheye lenses here - http://www.bobatkins.com/photography/technical/field_of_view.html.

 

You can calculate the FOV due to various amounts of cropping from the equation given there.

 

On the subject of lens hoods, you could make a hood with a little better shading, as others have said it may not be worth the effort.