August 10, 2017

Lensrentals is Changing How Cine Lenses are Evaluated

The popular online lens rental company will be applying its famously thorough still photo tests to cinema lenses.

It's hard for filmmakers to remember this, but 4K isn't actually that much resolution to a photographer. 4K video is something like 8 megapixels, which is nowhere near top of the line resolution for modern photography. 1080p, which many still shoot and most networks still broadcast, is only 2.3 megapixels. Compared to photographers who regularly shoot 30-50 megapixels, these are tiny numbers. While there are a lot of demands on a cinema lens (light weight, consistent focus, parfocal zoom), high resolving power has never been the top priority.

8K and other high resolution cameras are becoming common enough that rental houses have to accommodate that market with more detailed information.

When Lensrentals developed its own proprietary set of MTF tests to determine the resolving power of its lenses, the company focused its testing on still photo lenses. This makes sense since a still photographer is way more likely to notice slight resolution issues on a 50 megapixel image than a filmmaker on their 1080p 2.3 megapixel image. The low resolution will hide any defects of the lens. This makes Lensrentals' announcement that it is going to apply its testing to their cinema library all the more important. 

More thorough lens tests will help filmmakers make better decisions about renting equipment. Have a shoot coming up requiring highly sharp glass for VFX on an 8K sensor? Better evaluations of a wide variety of glass can save you time testing yourself. 

Increased lens variety as resolution increasesCredit: Lens Rentals
The more interesting information is that it is happening at all. Lens testing takes time for any large inventory of glass, especially as retesting is required regularly for lenses that are frequently shipped and used by a variety of filmmakers. Lensrentals didn't bother testing before because it wasn't needed and, presumably, because it saved a tremendous amount of time not to.

For a rental house to acknowledge that it now thinks its users require that level of testing—that the market has gotten there—is a good indication that it is seeing its actual users in the field need this information. This tells us that 8K and other high resolution cameras are becoming common enough that rental houses have to accommodate that market with more detailed information.

The same lenses matching when measures to 10lp/mmCredit: Lens Rentals

One key takeaway that Lensrentals shared is that it is observing great variety from lens to lens as you increase resolution. At their lowest resolution setting of 10 line pairs per millimeter, all nine lenses of the same type they tested looked pretty similar. Taking the resolution to 50 lines pairs, there was tremendous difference from lens to lens, as seen in the image above. This means that you need to do more testing to make sure all the lenses you have match each other, and that you are getting the best lens available from the rental house. It also means that lens reviews might have less meaning, since the lens that the reviewer tested on their 8K Helium might not match at all with the one you buy.

This is a major change from the days when a review of a lens on a 1080 camera would generally hold up just as well on your similar 1080 camera. If you are a RED Helium owner, or anyone considering upcoming 6K or above production, check out the Lensrentals blog for more info. The company is in the middle of a big push into the motion market, with new 360, VR and Drone gear added to its inventory,  but even if those new technologies aren't interesting in you, the changing resolution needs of new film formats will affect you soon. Lensrentals would say it already does.      

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