ricleo
Senior Member
a bigger filter thread doesn't mean better light gathering abilities, note that the canon 50mm F1.2 has a 72mm filter thread, incidentally the canon 35 1.4L also has a 72mm filter thread.
Images from Sigma 35mm f1.4 dg
- Thread starter subzero
- Start date
a bigger filter thread doesn't mean better light gathering abilities, note that the canon 50mm F1.2 has a 72mm filter thread, incidentally the canon 35 1.4L also has a 72mm filter thread.
jun550D
Deregistered
ManWearPants
Senior Member
bigger front lens opening, more light pass into the lens, no?
Blur Shadow
Senior Member
ManWearPants said:
Yes, there is more light enters the lens due to the larger front lens element. However, the amount of light per unit area, is the same for a lens with a larger and smaller front lens element.
A simple counter example is - is the 600mm f/4, with the really large lens element, faster or brighter than a small 50mm f/1.4? If so, why is one rated at f/4 and the other, f/1.4, a 3 stop difference?
a bit OOT.. f stop is give based on focal length / diameter. so to maintain a small f number (i.e bigger opening) the longer the focal length the bigger the diameter needs to be.
So thread size typically have nothing to do with light entering, and why longer focal length need bigger thread size is due to the diameter it needs to provide the smaller f-stop number.
Make sense?
So thread size typically have nothing to do with light entering, and why longer focal length need bigger thread size is due to the diameter it needs to provide the smaller f-stop number.
Make sense?
tsaieh
Senior Member
Big glass element in front does not meant it's f stop is smaller. It the glass construction inside the lens is the key element. ( i hope i'm right)
Smaller lens have lower f stop eg. 0.95 is able to achieve is because during manufacturing, It's easlier to achieve and cheaper.
It's all come to how light passes though the glass element.
Google about the fundamental of how light pass and you understand more.
Smaller lens have lower f stop eg. 0.95 is able to achieve is because during manufacturing, It's easlier to achieve and cheaper.
It's all come to how light passes though the glass element.
Google about the fundamental of how light pass and you understand more.
SilentSeth
New Member
Basically it's true (focal length / diameter), but I am not sure how to calculate it properly, because even a simple prime lens can have multiple optics elements inside, with different diameter and different focal length
ageha
Senior Member
SilentSeth said:Basically it's true (focal length / diameter), but I am not sure how to calculate it properly, because even a simple prime lens can have multiple optics elements inside, with different diameter and different focal length
It can be fun to talk to an unicellular organisms.
Last edited:
