Originally posted by Barresian Hello!
On my reasearch to get proper hoods for my lenses I've found the lens hood calculator which looks awesome... but I don't know how to use it.
Could somebody help me?
I want to calculate the hood for my Pentax-M 28/2.8.
So, Film Format Height and Film Format Width should be 15,70 and 23,60 right? (APS-C Sensor). Focal length is trivial. Now Hood Front Inner Diameter and Lens Front Outer Diameter are confusing to me. What are these values and where can I get them? I guess hood front inner diameter would be the "filter" diameter of the hood (so if I find a hood that needs a 58mm cap, the value for Hood Front Inner Diameter would be 58mm?) and Lens Front Outer Diameter the diameter of the front element of the lens? If so, do you know a ressource to find this piece of information?
Thank you very much!
if you are using HoodCalc i can offer some help
For format, you are correct, although i generally roound it up to 16 x 24
Lens diameter is the diameter of the actual lens, inside the beauty ring. It is easy to calculate, especially for older primes, because diameter and maximum lens aperature are related. remember F Stop = focal length / diameter. It is the actual diameter of the front element.
Hood inner diameter is exactly that the diameter of the hood, (NOT the threads, which are usually smaller.
ALso, be careful on length. the length is the distance from the centerline of the front element, not the physical length of the hood.