Do you
have a lens, but no lens hood for it,
have a broken lens hood you want to repair,
want to check if your lens hoods may be improved,
have a zoom lens, but only a lens hood for the shortest focal length,
use lenses and their lens hoods from the 35 mm film era on a digital camera with a smaller sensor than the original film format?
So read on.
I have made two Excel worksheets that calculate all the dimensions needed for constructing lens hoods with circular or rectangular fronts and for petal lens hoods.
Descriptions of how to construct the different lens hoods are included.
How to make drawings for constructing petal lens hoods are also shown.
If you are interessed in receiving these worksheets, send me a PM with your mail address.
You will then receive a zip file (approx. 2.8 MB) free of charge containing an Excel workbook and some additional material.

[AggieDad]

What generous offer. I will be sending a PM.

Thanks.

[CristiC]

To calculate a DIY cardboard hood you need:

• focal length
• distance from film/sensor plane to the nodal point
• sensor/film frame diagonal ~ 43-44 mm (actually SQRT( 24*24 + 36*36) )
• max aperture (you divide focal length by the max aperture) ---> 50mm lens / 1.4 = 35.7
• filter diameter (where you attach the DIY hood)

See lenshoods.co.uk and here for some Pentax lenses or 3D-print one yourself.

[Wingincamera]

Years ago I made a hood out of rubber so I could place it against aquariums glass and not jar the lense.

[sigurdhu]

Wingincamera,

Good idea.

Sigurdhu.