wide angle corner sharpness

Before you say "here we go again"...

How about we develop a set of criteria for testing out these wide lenses?

Seems to me so far it's pretty ad-hock as to subject distance, focus points, subject to sensor planes, charts, etc etc dioptres and their quality blah blah.

Folks jump in the pool and bang away... and the results tend not to be that repeatable. Don't get me wrong I do this for myself but refrain from posting results as I feel they would not stand up to critique.

Maybe some tripods, consistent distances, subject/sensor planes and common subject matter.

Maybe we could make up a test chart file that could be printed large on a wide format printer and laminated.

If we could make such a chart, what sort of things do you guys think it should contain?

Is a flat field chart really useful to us? and if not, what else could be included, and where, to make it a more real-world test?

Before you say "here we go again"...

How about we develop a set of criteria for testing out these wide lenses?

Seems to me so far it's pretty ad-hock as to subject distance, focus points, subject to sensor planes, charts, etc etc dioptres and their quality blah blah.

Folks jump in the pool and bang away... and the results tend not to be that repeatable. Don't get me wrong I do this for myself but refrain from posting results as I feel they would not stand up to critique.

 

Maybe some tripods, consistent distances, subject/sensor planes and common subject matter.

 

Maybe we could make up a test chart file that could be printed large on a wide format printer and laminated.

 

If we could make such a chart, what sort of things do you guys think it should contain?

Is a flat field chart really useful to us? and if not, what else could be included, and where, to make it a more real-world test?

I agree Darren; and I don't think it would be that difficult to do. One of the main advantages would be that different people could then test different lenses at diffferent times, and results would be comparable. A more useful database could also be compiled for port / extension / dioptre / lens combinations. I propose we come up with 3 simple identical test patterns that could be downloaded say from WP and laminated. These laminated patterns would take up no space for travel etc. The tested lens would be set up to it's widest setting and say 2m from the wall. Test patterns would be placed with one at center, one at a widest corner at the same distance, and one at a widest corner set say 30cm forward off the plane. That would allow comparison for most shooting purposes in all critical areas. Another benefit of this approach is it would help people make choices according to what they need, corner sharpness vs central sharpness etc. There are some pretty smart people here on WP who could compile these standards. (Not me)

I've copied Fred's reply to a different thread, as I felt it was helpful to this discussion

(.... edited by photovan for relevance to this discussion)...

 

To get a really valid comparison of the lens with the different diopters, EVERYTHING else needs to be consistent. It would be better to simply hang the slates along the edge of the pool, not have them held by people who are clearly changing position from picture to picture. And when taking the pictures, make sure that you keep the center of the image really centered on the "center sharpness" slate and the far edge of the "corner sharpness" slate at the very same position in the corner of the frame.

 

Fred