How to design the perfect lens hood (for 35mm format)?

[Chan Tran]

You also need to make sure that the hood doesn't protrude into the image area at different focusing distance.

 

[Ian Grant]

The best lens hood I have ever seen is the werra: -

Metal Super LENS HOOD 30.5mm 30.5mm 30.5 screw for Werra pentax ? rollei 35 ? | eBay UK

Fully Functional. I always take a lot of pictures. ✧ ✧ - Usable. ✧ ✧ ✧ - Good. ✧ ✧ ✧ ✧ ✧ - Excellent.

www.ebay.co.uk

That is not a Werra lens hood.

This is a genuine Werra lens hood

Ian

 

[snusmumriken]

I don't know what you mean by "edges reflexed inwards". Didn't Ravilious use tape to get a flat rectangular opening in his hoods? To make a rectangular hood, locate the entrance pupil, then compute the openings according to the chosen length and using 24 and 36mm as the image sides. Formula is in post #12.

Yes, thanks, I completely understand your post #12. Before I go down that route, though, I also want to understand lens hoods like these:

Yes, James Ravilious taped his lens hoods to make a flat rectangular opening with its corners at the edge of the original round opening. (I’m not trying to ape Ravilious, but I do like to shoot against the light, especially when the sun is low.) When I tried this tape trick with my generic hood, I got vignetting in the corners. That still puzzles me.

 

[Ian Grant]

I agree.

Ian

 

[Don_ih]

I also want to understand lens hoods like these:

I think the attempt is to make a lens hood that doesn't flare out, which will protect the edge a little (and eliminate a sharp rim from the front of the camera). The rectangle could just as easily be the outside of a cone. The shape may also help eliminate flare from light reflecting off the inside of the hood.

 

[OAPOli]

Yes, thanks, I completely understand your post #12. Before I go down that route, though, I also want to understand lens hoods like these:

Yes, James Ravilious taped his lens hoods to make a flat rectangular opening with its corners at the edge of the original round opening. (I’m not trying to ape Ravilious, but I do like to shoot against the light, especially when the sun is low.) When I tried this tape trick with my generic hood, I got vignetting in the corners. That still puzzles me.

To block out stray light, you just need to place the rectangle at the right distance. How you get there doesn't really matter I think. Those hood may be configured like so for aesthetics, but they also offer a little less frontal area for internal reflections as @Don_ih suggests. I would paint the inside matte black anyway.

You also need to make sure that the hood doesn't protrude into the image area at different focusing distance.

If the hood is correct for infinity, it won't vignette for closer focusing distances because the effective FOV decreases a little bit.