FoCal Database for Lens Quality of Focus

[AlanF]

Another set measurements that tell you just about the lens is for zooms where you can see the relative performance at different focal lengths. Rich posted wide, medium and tele for the 100-400mm II and Sigma 150-600mm. Now, both photozone and lenstip have MTFS for wide and tele very similar for the 100-400mm II, but ephotozine has a drop at 400mm from 100mm. The FoCal results suggest ephotozine results are more typical. My lens has very similar values at 100 and 400mm. FoCal has a sytematic decrease from wide to tele, like the two website. My own copy of the lens is really good at 400mm, rivalling the 100-400mm for resolution from charts, and the FoCal scores for mine are the same at 150mm and 400mm.

Otherwise, as you say, the scores are indeed generally camera-dependent. But, they do tell you something about how well a particular camera and particular lens go together.

 

[takesome1]

It was mentioned earlier, but with the data Reikan collects it wouldn't be a stretch to add a comparison tool geared specifically at determining lens sharpness.

Imagine a new poster asking about his new lens that is soft. We tell him to buy Focal and run a lens sharpness test.
He does and it tells him his lens performs in the top 10 percent (or where ever it falls).

Then the best part, Reikan sends all of us in this thread a royalty check for our brilliant idea and helping expand their customer base.

 

[Mt Spokane Photography]

It was mentioned earlier, but with the data Reikan collects it wouldn't be a stretch to add a comparison tool geared specifically at determining lens sharpness.

Imagine a new poster asking about his new lens that is soft. We tell him to buy Focal and run a lens sharpness test.
He does and it tells him his lens performs in the top 10 percent (or where ever it falls).

Then the best part, Reikan sends all of us in this thread a royalty check for our brilliant idea and helping expand their customer base.

There are companies that do this, their software is expensive and the setup is critical. http://www.imatest.com/

A amateur trying to run a lens sharpness test would likely come up on the low end, and keep exchanging lenses and complaining about how bad they are. We have plenty of that around the internet now.

One test that most users can run (but don't) is for the biggest issue by far to affect zoom lenses, and that's centering. A person can purchase or download and print a star chart. As long as you are squared up with it, it can tell you if you have a problem.

http://www.edmundoptics.com/test-targets/

Example: https://www.bhphotovideo.com/c/product/717671-REG/Zeiss_1849_755_Siemens_Star_Test_Chart.html#!

 

[takesome1]

Both good tests.

I would think an armature that doesn't follow FoCal instructions will most likely botch the other tests as well.

There are things Focal could monitor to insure comparable results, and fail errors. But no matter what safeguards and instructions you give, you can't prevent stupid.