Lens tests for the REAL real world: Why LensRentals are the only people in the world who can do this

by Dave Etchells

posted Sunday, June 28, 2015 at 12:25 AM EDT


Our friends at LensRentals have a pretty special operation. They not only rent a pool of thousands of lenses to photographers all over the US, they have some of the most sophisticated lens-testing equipment on the planet. One incredible machine ("OLAF") was custom-built to their specifications by an optical test equipment manufacturer. OLAF alone cost them $500,000, but they felt the investment was worth it, not only to be able to ensure that lenses are in proper condition when they send them out to customers, but also to be able to adjust and repair lenses themselves. (In some cases to specs tighter than the manufacturers themselves test to.)

This puts them in the absolutely unique position of not only being able to test lenses with a speed and accuracy found in very few places around the world, but also being able to test dozens of samples of the most popular lenses, which allows them to see how performance varies from sample to sample.

Sample variation is the bugbear of lens reviewers and photographers everywhere. Some lenses are fairly consistent from sample to sample while others can vary quite a bit. In our own tests (as with those of any other lens-testing organization we know of), there's always the question of just how representative the sample we tested is of the general run of lenses out in the market.

These graphs show aggregate MTF curves for multiple samples of two lenses. The central line in each colored band shows the average MTF performance while the bands themselves show the range of variation for each lp/mm test condition. (Of course, in comparing lenses, you may not care so much about variation, if the worst performance of one lens is better than the best performance of another.)

Leveraging their massive investment in computerized test equipment and the massive array of lenses that pass through their hands, Roger Cicala and his team at LensRentals have announced plans to measure and publish sample-variation results for many popular lenses, based on real data from multiple copies of each. They've even come up with some clever math that lets them produce a meaningful score for variation.

This is pretty revolutionary for the photo industry; other than subjective anecdotal reports from different photographers, nobody's ever had overall idea of how much variation was actually out there.

Now, thanks to Roger and company, there will be ratings based on actual, objective measurements, published for all to see. It's a whole new dimension of lens quality, and we believe one that will encourage manufacturers to up their game.

As usual, Roger's published an article describing their methodology that'll satisfy even the most uber of uber-geeks; you can read all about it here.