Basically the corners are getting less light because of the tunnel that is created.
Step up down ring.
Step down rings do the exact opposite of a step up ring.
The exception to this rule is when using lenses and filters designed for larger format cameras i e.
A stepping ring is simply a thin metal ring with a male filter thread of a certain size on one side and a female filter thread of a different size on the other side.
Pile of step up and step down rings.
Step up step down rings don t work well with lens hoods so you ll likely have to do without the hood.
To solve this you can use stepping rings.
Step down rings are also available that connect filters with diameters smaller than the lens.
If you do there s a good chance you ll damage the lens s thread.
Step down rings are not as widely used as step up rings because in most cases the smaller filter sizes result in vignetting.
Use step up and step down rings to swap between different.
When using step down rings and filters one can notice a lot of vignetting.
Lens filters offer many aesthetic options when it comes to taking pictures or videos.
Full frame on smaller format cameras i e.
Things worth knowing about step up step down rings.
As with regular filters don t over tighten them.
Aps c and micro four thirds.
They attach filters that are too big.
They adjust a larger lens thread to accommodate a smaller filter.
The male side screws into the end of the lens and the filter screws into the female side.