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Another independent review for ProMa King Tablet

At the beginning of the crowdfunding campaign of ProMa King Tablet, we sent a prototype to ThirdDimensionSociety. This is a review from one of his members.

NOTICE: This review is from an early prototype. Since then software features have been updated and modified, and new features added (like using the tablet as 3D PC monitor). Information about software capabilities might not be accurate.

The package

The ProMa is an Android tablet that arrives in a silver coloured box with the necessary accessories.

Well protected by foam padding, the tablet comes ready charged for instant use. To prevent accidental switch-on in transit, the foam around the on-switch is recessed to prevent any pressure being exerted that would activate the tablet.

The AC/DC adapter is a 2-amp unit that has wide voltage Euro two-pin input feed (that will need a common UK adapter), and a standard USB 5 volt output. Included is a USB3-C cable that fits into the charger’s USB output socket, and the other end fits
into the USB3-C socket on the tablet. The single USB3-C socket on the tablet is a universal connector that acts as a 2-amp current charger, file data transfer, and video HDMI input/output connector with suitable accessory cables.

Finally, a SIM extractor tool is used to pull out the SIM card holder for the tablet to accept any network SIM card and gain access the internet via the user’s mobile network. As with any Android tablet, built-in wifi can be used to do the same via the user’s usual broadband provision.

This latest hi-resolution Android tablet is a new dawn for 3D enthusiasts who have been asking for a portable digital 3D display for ease of use to view 3D photographs and 3D videos, combining a pixel density that the human eye cannot resolve into dots, long battery life, and glasses-free usage in daylight. The ProMa King tablet achieves these aims admirably, with its compact design that incorporates a 10.75 inch diagonal digital screen with a pixel density of 280 pixels per inch in both horizontal and vertical directions. The tablet has a lenticular screen in front of the image plane, allowing the left and right elements of the image to be viewed by a pair of human eyes at a suitable distance from the tablet. In 3D, the vertical axis has 1600 pixels, and the horizontal axis has 2560 pixels. In use, the effective horizontal resolution is reduced to 1280 pixels because the 3D image is split into vertical pixel strips Left-Right-Left-Right etc. across the entire screen. Counting only the horizontal density, that would represent 140 pixels per inch, which would be much better than the 70 pixels per inch of most lenticular 3D prints. But remember that all vertical resolution is preserved in 3D, so 1280×1600 pixels per eye on a size of 10,75″ gives 190.6 pixels per inch.

The vertical lenticular lenses are carefully arranged to ensure that the vertical image strips that are placed across the entire screen are visible to the correct eye at a well-defined distance from the tablet surface.

The below schematic diagram illustrates this effect by showing the viewing angles of the middle and both edge pixels of three left image strips. All three pixel positions across the screen can be seen by an observer’s left eye if the eye is placed in the green kite-shaped area where the viewing angles all overlap each other at the same time. (Not shown here is a similar layout of angles for the right eye’s viewing of the right image strips).

This green area is known as the “sweet spot” for 3D viewing, where both eyes are in their best viewing positions, and the entire screen has no image breakthrough (or ghosting) where no parts of the left and right images can be seen by their unintended eye. Moving the observer’s eyes away from the “sweet spot” area will cause ghosting.

The usable “sweet spot” distance from the tablet screen to the observer lies in the range 14 to 18 inches. Also shown is the point “X” which lies about 15.7 inches from the screen, where there is the least chance of the observer moving out of the best 3D viewing position.

The screen quality is first class in that neither in the vertical plane of 1600 pixels, nor on the horizontal plane of 1280 pixels for each of the two eyes, can any trace of pixelation be seen. The result is a smooth 3D experience with very detailed features clearly visible in still and moving 3D presentations.

In practice, as with any lenticular system, there are other “sweet spots” of varying quality to the left and right of the central “sweet spot” where the principal viewing person is situated. It is possible, with careful positioning, to have two more people experience a near perfect 3D presentation at the same time as the centrally placed viewer. Obviously there is some small degree of horizontal compression of the image in these situations, just as in watching any TV screen from the side, but the overall tested experience of such secondary observers is one of satisfaction.

Viewing personal 3D videos from internal storage

Users can store their own 3D content onto the tablet’s internal SSD by transfer from their PC. Just plug in the supplied USB3-C cable into the tablet’s singular USB3-C socket (unlike other USB sockets, the USB3-C socket accepts the cable either way up), and plug the other end into a standard USB socket on the PC. The ProMa tablet will appear as a standard disc drive device with the name P10. Data transfers in either direction can be easily performed in the usual manner of Drag/Drop or Copy/Paste features.

There are two video players readily available from the main screen. They both act in the same way, by loading video files from the tablet’s internal SSD storage device, and playing them in one of three ways.

  • traditional 2D for ordinary videos
  • side-by-side usual 3D videos
  • over/under or up/down 3D videos
    Just tap the desired icon to launch the chosen program.

Here on the right, the 3DPlayer video format menu is selected by tapping the top right corner of the screen, then tapping the required video format to suit the loaded video. Usually this program acts in the desired manner, but occasionally a video may be too large or be in an unusual format and crash the program.

The Sight3D program has the same features for displaying 3D content, in this case by tapping anywhere at the top of the screen and choosing the desired option.

The following activities are illustrated using the Sight3D program. The following pictures of the live videos showing on the tablet were taken using a standard DSLR camera in 2D mode.

From the internal storage device, a full sized 3D video of FullHD stereo dimensions of 3840 x 1080 pixels was loaded. Each of the left and right frames is sized at 1920 x 1080 pixels, exactly as projected on two Full HD DLP projectors in Society meetings.

Shown here in 2D layout

When indicating that video is SBS, Sight3D is showing a very horizontally stretched version of the locomotive. This is due to the software being capable of showing just half-width stereo images and videos, the standard layout for commercial TV 3D stereo. For that reason, the sView Media Player is also included on the device. There’s an option on the sView Media Player’s menu to avoid stretching of the video.

Finally, many video file types were tested successfully on the ProMa tablet, such as .MP4 .MOV .MPG .AVI
However, when testing .WMV videos, there seems to be a missing audio codec.

Viewing 3D videos from external sources

With the ProMa tablet linked to Broadband by Wi-Fi, or using 4G capabilities, any website or streaming service can be accessed and have 3D videos streamed in all their glory. Commercial sources have their films correctly HSBS formatted and parallax corrected, so straight streaming to the ProMa tablet is just as straightforward as streaming to a 3D TV. However, YouTube 3D videos are frequently badly parallax controlled, leading to 3D window violations or excessive forward projection of material content in the scenes.

Web based sources are opened with any Chromium based browser or directly with YouTube. Opening any of them, automatically activates the earlier mentioned 3DVF video playback selection method and parallax control overlay that is essential for comfortable viewing in most cases.

The tablet will playback 4K video quality.

Once a video is played from YouTube or a streaming service, it will play back on the ProMa screen in 2D format by default.

Midway down the left side of the screen is a small blue bar with a white arrow head on it. Tapping this bar will bring up this overlay in the middle of the screen.

This will allow selection of the 3D video original transmitted format as:

  • a squashed half width HSBS video
  • a full size FSBS video
  • a squashed TOP-BOTTOM video

The 3D screen grab sample shown below was captured from the ProMa screen on a hand held Fuji W3 stereo camera. Since it was snapped from a moving image, the quality is not very clear due to motion blur, but it does convey the extreme depth in the 3D video. The red ball is way out in front of the screen. This video has been selected from the above panel as HALF width and zero parallax change. The side by side 3D image is easily viewed in 3D by Free viewing or with a 3D lorgnette viewer.

Note the aforementioned tiny blue and white 3DFV chooser half way down the left side of the image.

Another 3D video grab using the Fuji W3 stereo camera, this time exhibiting extreme protuberance of a saw blade through the screen.

To avoid such extreme effects, the 3DFV selector allows the user to change the parallax setting.

The following screen grab of the turtle was taken after the HALF width video was adjusted by 23 % parallax by pulling the white dot along its slider bar. What this does is to move the two images in the 3D display further apart. This action moves the whole scene backwards for easier viewing or to correct stereo window violation.

Viewing 3D photographs from internal storage

As previously noted, the ProMa tablet can be linked via the tablet’s single USB3-C port with the suitable cable supplied in the box to any USB socket on a PC. Hence photographs can be copied onto the tablet’s internal storage area.

Almost everyone saves their 3D photographs as full sized FSBS format stereo files. Their aspect ratios and pixel dimensions may vary enormously. Cropped stereo images may have any aspect ratio that suits the subject, at any size from tall portrait through square to super wide panoramic. On top of that, any pixel counts may be encountered from just a couple of hundred pixels wide to ten thousand pixels wide. 3D photos can be opened with sView Image Viewer (the other App included on sView bundle). If you have stretched pictures, you should use Sight3D for that pictures.

Another way of displaying 3D photographs is to download the 3DSteroid app from the Google Play Store. This app is from the makers of StereoPhoto Maker, famously used by everyone in the PC and Mac worlds to make, edit, display and print 3D images.

This stereo image is shown in 2D. It is a 4:3 ratio shot in FSBS at 2800 x 1050 pixels. It will displayed correctly by the 3DSteroid app when selecting 3DLCD on Stereo options.

Any aspect ratio of 3D photographs will be displayed as intended, with no distortion. To view the 3D picture in full-screen mode, just tap the image.

Comparison of four 3D glasses-free viewing devices

A selection of 3D digital viewing devices was arranged. They all had the same 3D image installed, and all displayed that image using the 3DSteroid app, and all four were photographed as a set with a DSLR.

At the top left is the ProMa King 3D Android tablet, with 2560 x 1600 pixel screen size. The colour is just the same as seen on my colour-corrected PC display. Brightness and contrast controls are set exactly as the shipped tablet was received. At the recommended “sweet Spot” distance the 3D image experience is first class.

At the bottom left is a Rokit Pro 3D mobile phone with 2160 x 1080 pixel screen size. The image is substantially the same image quality as that shown on the ProMa tablet, but at a reduced definition due to its small screen size, so very fine picture detail is not resolved as well as on the ProMa.

At the top right is a Freevi Flightdeck Commander tablet with a screen size of 1920 x 1080 pixels. There is a colour cast on the image display, and slight pixellation is evident when viewed from the “sweet spot”.

At bottom right is a SuperD C1001 mobile phone, whose screen size is 1920 x 1080 pixels. The image is slightly off-colour, and the fine detail definition is lacking due to its small size.


The ProMa King and the Rokit Pro are equally good on image display quality in terms of brightness, contrast and colour rendition, but the ProMa King shows more detail. The Freevi and SuperD devices have inferior colour rendition.

Although not discernable from this small image, the ProMa has far more fine detail in its display than the other three devices. Hence the smallest items in a 3D full-HD image are readily appreciated.

Coupled with its smoothness in display of fine image detail (no pixellation visible) and its rock-steady video playback, the ProMa tablet is the best glasses-free 3D viewer available in the amateur market place. Users of this tablet will enjoy nigh on full-field-of-vision stereoscopic 3D entertainment of the highest quality available in both the spheres of 3D photography and 3D video playback.


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