In earlier experiments taking slide-bar pictures with a Polaroid PDC640 digital camera, I was very impressed by the quality of the stereo images, despite the fact that the camera was limited to VGA (640 x 480 x 24-bit) resolution. Quite apart from general convenience, there were several things that made the digital camera very attractive:

• No film
• No processing of negatives or prints
• No scanning of film or prints
• The digital format assures almost perfect image registration
• The image aspect ratio is essentially 4 : 3, almost identical to a 35 mm format, and much easier to work with, in terms of composition, then the Realist-format.

• the camera often requires an extended time to boot
• it seems to go through batteries at an alarming rate
• the Smart Media memory cards would require an upgrade as the card that comes with the camera only accommodates 12 images at 640 x 480 resolution.
• the PDC640 uses a standard serial port for image uploads to the PC and the process is slow.

I ran across this camera while researching basic digital cameras on the Internet. The camera has a 640 x 480 CCD image sensor and can be used to create 640 x 480 or 320 x 240 still images. List price is about $150 but street prices run in the $110 to $130 range.

It is a very versatile camera and can also be used to shoot bursts of images or short video sequences. In addition, connected to your PC, it can also function as a web-cam. Image transfer to the PC is via a USB interface, which means you must be running Windows 98 or later as your operating system. Image transfer is very fast.

The camera does not have an LCD display for viewing or reviewing images, which greatly reduces power consumption. There is a small LCD status display at the top of the camera, which covers most of the operational features of the unit:

 (B) The camera has an audio transducer that, among other things, tells you when you have triggered the shutter release.

(C) Image quality, where HQ is the 640 x 480 mode. No icon shows in the 320 x 240 mode.

(D) A nice touch is that the camera has a 10-second self-timer function.

(E) This display shows how many pictures have been taken. The camera has 4 Mb of RAM and will hold 128 images at 320 x 240 resolution. The capacity at 640 x 480 resolution, based on relative image size, should be 32 images but is listed as 64! This suggests a very high level of image compression, later confirmed with actual tests.

(F) Battery condition - the unit operates on four AAA cells, with a "starter set" of batteries included with the camera. When connected to the computer, the USB interface provides the operating voltage.

(G) The icon for the video mode.

(H) The focus setting. In the stand-alone mode, the camera is fixed-focus with a specified range from 30 inches to infinity.

The camera is very compact (3.5"W x 2.75"H x 1.0"D) and extremely easy to use. This is definitely not a camera for a serious photographer, but rather is intended as a rugged "knock-about" camera for generating colorful snapshots - pretty much what I was looking for.

The images were considerably "softer" than I had expected, based on experience with the Polaroid PDC640. This seems to be a function of a very high level of JPEG compression which is required to get the high image capacity out of the 4 Mb of camera memory. Colors are well saturated and the camera is a no-brainer when it comes to operation. Since my objective was a stereo snapshot camera and not a fine-art project, I decided to press on and tie a pair together for shooting stereo.

Twinning the Cameras

The two 5/8 inch holes provide access to the USB port connector on the rear of each camera. This permits the images from the right and left cameras to be uploaded to the PC without removing the cameras from the mounting bracket. The cameras do have to be removed to change batteries (4-AAA cells per camera), but it looks like the cameras have good battery life compared to most digital cameras I have used. The small holes were placed in the upper corners to anchor a neck strap, but that idea was abandoned due to a lack of clearance between the rear of the camera bodies and the support bracket and the holes are not included in the drawing of the bracket.

First Tests

For the first pass I decided to try triggering the two shutters manually. This turned out to be very easy. The shape of the camera makes for easy handling and the shutters have an easy-to-feel intermediate position that requires just a slight amount of additional pressure to actually take the pictures. Since both cameras provide audio feedback when the shutter is triggered, a clean shot results in the inability to differentiate the sound from each of the two cameras. Even when simultaneous triggering was not achieved, the pictures were often fine as long as there was no rapid motion. When in doubt, I simply took a second or even a third picture, but that was rarely required. With a capacity of 64 images per camera, you didn't have to worry about wasting film or processing less-than-perfect photos. The shape and weight distribution turned out quite nicely, and it is very easy and natural to hold the camera precisely horizontal when taking pictures.

For the first tests, I simply shot some pictures in the garden and then walked down into town to take additional shots. I shot a total of 34 stereo pairs on this little expedition. A few of the images are included in the EZ200 Gallery at 1/4 resolution (320 x 240) to speed download time.

Even at the reduced resolution used for these samples, it is obvious that the camera does nicely for generating pictures for display on the computer or distribution via the Internet. What was really amazing was how quickly you can go from shooting your pictures to actually having them set-up in stereo format. With my Realist-format cameras I had to make sure I had film on hand and, once the film had been processed there was still a lot of work left to scan the negative, correct for image size and registration, and then get them into Depthcharge image sets. It was not uncommon to spend an evening setting up pictures from a single 24-exposure roll, so you aren't likely to take pictures on a whim.

With the digital twin-rig, film wasn't needed and pictures could be taken at any time. Since there is no need to "fill-up" a roll, you can shoot one or two pictures or dozens! Besides the cost of the film, you also save time and money by being able to skip the processing step. With the high-speed USB image transfer and no need to do any scanning or formatting for frame size or registration, the "digital darkroom" time was minimal. I shot 34 pictures on the first outing and the complete set was ready to view in about an hour! Yes, the film pictures are sharper, but, for casual photography, the time and money saved with the digital cameras is a real plus.

When shooting with my Kodak Realist-format camera, I am always conscious of the limited number of exposures available on each roll of film. One consequence is that I tend to be conservative in my selection of subjects, but that means that I also pass up subjects of uncertain potential or which might just be fun. With the digital twin-rig I don't have to be a photographic miser! If I shoot something that doesn't work out, I just delete the pair later - no real loss of time or money. In short, the digital twin-rig is a lot of fun with tremendous potential for candid photography.

Holmes Views?

My favorite format is Holmes stereoviews, so the final test was whether the twinned EZ200 cameras would produce useful views. I could have masked the frames to the nearly-square format for normal Holmes views, but they were composed for a 4 : 3 aspect ratio and I didn't want to compromise the pictures, snapshots or not. Rather than employ the classic Holmes format (see my page on Making Your Own Holmes Stereoviews), I used my basic procedure to create a modified format that would let me preserve the original image aspect ratio:

I must say that I was pleasantly surprised at the quality of the final views and delighted to see that the camera would work with all of my favorite approach to stereo image viewing.

Conclusions

My goal was to create a casual stereo snapshot camera that would eliminate all the hassles associated with film loading, processing, and scanning. There is no need to set focus, shutter speed, or lens opening and, if held carefully, the camera will produce good results indoors, even without a flash. All-in-all, I am quite pleased with how the project worked out. The camera is extremely easy to use and most people like the slight exaggeration of the stereo effect created by the hyperstereo lens separation.

The manual triggering of the two shutters has worked so well and is so easy that I will not be rushing to slave the shutters electronically. I may get to it eventually, but for now I simply want to take more pictures! The project is a very useful addition to my stereo camera inventory and I expect I will end up using it most of the time, reserving the additional hassles of film for the most demanding or critical applications. Later Notes: I am really surprised at how often I have used this camera. It is so easy and convenient that I take it places I wouldn't want to be bothered with a conventional camera. It is a "snapshot" camera and basic "Brownie" rules apply. The most important of these is to try to shoot with the sun at your back. If the scene is very contrastly, the camera will not render deep shadow detail to any great extent. I'm sure more sophisticated cameras, with greater dynamic range, would have less of a problem.

Problems Unique to Digital Cameras:

When you are twinning two film cameras of the same model/type, alignment of the film/mask is pretty much assured if the camera bodies are aligned. This is not necessarily the case with digital cameras, particularly ones with small image sensor arrays. The orientation and alignment of the sensor is not fixed with respect to the camera body, since the sensor is basically a small chip installed behind the lens. Even with robotic assembly of the cameras, some misalignment is to be expected:

• On the two cameras I used, the vertical alignment was off by about six pixels and that requires a routine realignment of the stereo pairs when using the stereo software (Depthcharge Developer Studio in my case).
• There is probably some horizontal misalignment as well, but that is a very small percentage of the total lens separation and can be ignored in practice.
• Finally, there appears to be a very small rotational mis-alignment that is not enough to generate any eye-strain in merging the two views.

The following galleries are made up of pictures shot with the EZ200 twin rig: