Lumix G 12.5mm f/12 3D lens review

The Lumix G 12.5mm f/12 3D lens, launched in 2010, was marketed as the world's first interchangeable 3D lens. It is currently available at a discounted price in some markets:

Physical

This is probably the simplest lens available for the Micro Four System so far. It is very small and light, and also, it has no moving parts whatsoever.

There is no focus mechanism. This is a so called fix focus lens. Fix focus lenses are typically seen in disposable cameras, cheap web cameras, and cheap mobile phone cameras.

Also, the lens is fix aperture, meaning that there is no aperture mechanism at all. There is only one aperture, f/12, and the lenses cannot be stopped down further.

At the fixed focus and aperture setting, the lens is in focus from 0.6m to infinity, according to the specifications.

There are two separate lenses, each of which has four lens elements in three groups. The stereo base, i.e., the distance between the lenses, is 1cm. For comparison, the stereo base of a typical human is around 8cm, which is the distance between the eyes. Hence, using this lens will give you significantly less 3D effect than what you are used to from your daily perspective.

Focal length and field of view

This lens is stated to have a focal length of 12.5mm. However, you should not let that fool you into thinking that this is a funky wide angle lens. Each of the two lenses project much smaller image circles onto the sensor, hence, there is another crop factor to take into consideration.

On the GH2 camera, the images created are 1920x1440 pixels, out of a total sensor area of 4608x3456 pixels. Hence, the crop factor of each projection is 2.4, and the field of view corresponds to a lens with a focal length of 30mm, e.g., the Sigma 30mm f/2.8 EX DN. So the 3D lens is actually a short tele lens.

This diagram illustrates the sensor sub areas used by the 3D lens:

The lens only uses 35% of the total sensor area, which helps to explain the limited resolution of the resulting 3D images, more about that later.

You can also choose to cover the electrical contacts of the lens, and use the full sensor output. Them you need to convert the image to 3D manually, but the advantage is that you get a much larger resolution to work with, around 2000x3000 pixels for each of the stereo pair image. Your image will be in portrait format.

Compatibility

As this lens was launched after the first wave of Micro Four Thirds cameras, it cannot be used on all of them. The first generation of Panasonic cameras can't use this lens, i.e., the G1, GH1, and GF1. Newer cameras can use the lens, however.

The Olympus E-P1, E-P2, E-P3, E-PL1, E-PL2, E-PL3, and E-PM1 cameras cannot use this lens. The OM-D E-M5 can, however.

Video

Contrary to what you might expect, you cannot record video using this lens. Not with any of the current cameras available, anyway.

Although it does not officially support video, there is nothing stopping you from covering up the electrical contacts of the lens, and then recording the video the camera sees through the 3D lens. I have demonstrated that here.

Use of the 3D images

When taking pictures using this lens, you get two image files. The first is an ordinary JPEG file, with the image from one of the lenses. When using a GH2 camera in the ordinary 4:3 aspect ratio, these images are 1920x1440 pixels, and are generally around 1.5 megabytes in size.

The second file has the .MPO suffix, and is a container file with two JPEG images, one from each lens. Both images are 1920x1440 pixels (when using the GH2 camera), and is around 3 megabytes in size.

If you have a Panasonic 3D TV set, it is pretty easy to display the MPO images on it, and there is indeed a 3D effect to them.

On other TV sets, this might be more difficult. Honestly, I don't have much experience with this.

On a PC, you could choose various different ways to display 3D images, depending on your hardware and preferences. I've chosen to use the Gimp plugin script-fu-make-anaglyph, which takes a pair of images, and turns them into a cyan/red image to be viewed using anaglyphic glasses. See the "Example images" section below.

Example images

This image was taken outdoors on the Intrepid Carrier Flight Deck. It was taken with the GH2 at ISO 160, f/12, 1/400s. The images are straight from the camera with no processing. Click for larger images.

left image	right image

And here is the anaglyphic version of the same image:

Another example, this image was taken indoors, at ISO 320, f/12, 1/60s, and with the onboard flash. The image depicts a LEGO model of the Intrepid carrier, inside the carrier itself. There is a large window letting in light from the side, but the lightning is still quite dim.

left image	right image

And here is the anaglyphic version of the same image:

In the last example, the 3D effect is more dominating, due to the shorter distance to the subject. For the best 3D effect, it is good to leave some items in the foreground, preferably around two feet out from your position, or thereabouts.

Close up use

According to the specifications, the lens can be used from 0.6m to infinity. At 0.6m focus distance, you can photograph items that are about 33cm by 25cm, which is not very impressive. Most lenses can photograph smaller items than this.

As this lens has no focus mechanism at all, there is no way for the camera to know at what distance your subject is. So you may very well ignore the 0.6m close limit, and photograph items that are closer. The disadvantage is that any items closer than 0.6m will be somewhat out of focus.

This is demonstrated here, where I have a focus distance of 0.2m to the central LEGO figure. For lightning, I used the Panasonic FL360 flash unit with a large diffusor.

left image	right image

And here is the anaglyphic version of the same image:

As you can see, the image is rather out of focus. It is probably best to avoid going this much outside of the lens focus distance specifications.

Conclusion

This lens has a short stereo base, hence, the stereo effect is rather limited. Also, it has a very small aperture at f/12. This restricts the lens to being used outdoors at daylight, or with a flash at a short distance.

The short stereo base could have made more sense for close up images, but the lack of a focus mechanism limits it to a distance of 0.6m and more. Even when used on a camera with a good resolution, the resolution of the 3D images is quite small.

And it is not possible to record 3D videos with this lens.

So is there anything positive to say about this lens? It can be an easy way to create some crude 3D images to show on your television. But my conclusion remains:

Don't buy this lens. Even at the discounted price you can find in some markets these days, it is not worth it, in my opinion.

If you are genuinely interested in 3D imaging, it is better to get one of the 3D compact cameras. Both Panasonic and Fujifilm market some compact cameras with two separate lenses, and two separate sensors, at a more sensible stereo distance of around 5-10 cm. These cameras give a better resolution, a zoom, a larger aperture, and can be used to record 3D videos. So they are better in every conceivable way than using the 3D lens on a Micro Four Thirds camera.