By Matthew Jeppsen, May 28, 2008
Letus has been producing flipping lens adapter systems for years, and the Extreme is their most recent update to the line. While previous versions used a mirror-flip design, the Extreme is built on a much higher-quality prism optical array. The adapter is constructed of milled aluminum with a hard anodized black finish. It attaches to your camcorder’s filter threads and juts downward to a lower level imaging tube. This lower portion houses the ground glass diffuser element and 35mm lens mount.
The Extreme could be flipped over and used in a upper configuration, but the size of the flip unit causes it to come in contact with the built-in camera microphone on the Sony EX1 and FX1. (This may not be the case on other camcorders.) On one side of the unit is a removable plate that exposes two standard AA batteries used to power the unit. This plate is secured by four strong magnets and simply pops on and off when you need to swap batteries. On the camera side of the flip unit is a lighted on/off power switch.
The Letus Extreme utilizes an oscillating ground glass diffuser design. This imaging element is the image plane of the 35mm adapter. The unit arrives with the oscillation frequency and intensity pre-configured and is not user-adjustable. Adding and removing different style still lens mounts takes just a few minutes and really opens up the option of using a many different still lenses in your projects. Letus offers a variety of lens mount options. For instance, if you own an obscure wide lens with an M42 mount, you can probably use it on the Extreme.
Collimating the lens of the adapter is a fairly simple task that involves loosening the lens mount and moving it incrementally in or out to attain proper focus on a backfocus chart. Once you are satisfied that the measurement marks on the 35mm lens correspond to the distance to the chart, you simply lock down the lens mount. This procedure is relatively easy to accomplish and takes just a few minutes. I would, however, like to see it improved so that the collimation could be retained when swapping lens mounts. If you add a different style lens mount to the Extreme, you are forced to re-collimate if you want the lens distance markings to be accurate.
Letus states that the adapter exhibits about a half stop of light loss. Using a Sony PMW-EX1 camcorder along with the Extreme adapter, I tested resolution and sharpness using a DSC Labs Multiburst chart
. With the same 50mm lens at f/4 I noted about 700x650 lines of resolution. This was with the camcorder set at an optimum zoom-in level of Z75. The Letus Extreme allows you to zoom the camera in all the way to Z99, but image detail and edge sharpness tends to suffer as you increase the camera’s focal length.
To determine how evenly light was distributed across the frame I shot an evenly lit white background. I connected a waveform monitor to the Sony HDR-FX1 test camera and noted IRE percentage levels from left to right with various lens configurations. I found that vignetting is most apparent when the camcorder’s lens is wide, and least visible when it is zoomed in to the Z99 max. With a 50mm lens at f/4 and the FX1 set to Z73 I noted a 6-percent dip in left edge brightness, and a 17-percent drop on the right edge of the frame. Wide lenses tend to exhibit more edge falloff, telephoto less. To virtually eliminate vignetting, you must zoom the camera into Z94, where on the 50mm I noted just a 2% drop in edge illumination over the stock lens.
One might conclude that the simple answer to vignetting is to just zoom in as far as you can. But consider that camera zoom-in has a negative effect on image sharpness. It also limits the effective field of view for composition. So the process of setting up and configuring the Letus Extreme becomes a balancing act between enough sharpness and an evenly illuminated frame.
While the Extreme is technically light enough to be used without a rod support system, I would not recommend it. Users should budget for a complete 15mm rod support system and the optional Extreme support bracket. LetusDirect does in fact offer its own rods and base plate solution, and have also partnered with Zacuto to create a full-featured handheld support rig.
Letus Extreme 35mm Lens Adapter
$1,199
DV Score:
Pros:
Excellent resolution and edge sharpness and virtually no vignetting when properly configured. Uses AA batteries.
Cons:
Unit size limits configuration options on certain camcorders. Lens collimation is not retained across lens mount changes. Attaining perfect sharpness and zero vignetting at the same time is virtually impossible. Bottom Line: Great item, but a balancing act of functions. MSRP:$1,199 Contact: www.letusdirect.
Bottom Line:
Great item, but a balancing act of functions
| COMMENTS (1) | | 10/13/2009 | | http://www.club6666.com |
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