It pays to read the fine print

Almost every digital camera is measured by the megapixel count or by the resolution of the sensor used. iPhones and other smartphones also use this standard. Today’s document cameras are no exception. They typically use CMOS sensors and the resolution matters. It is important to remember that resolution or megapixel count alone do not determine how good the camera is. The number of colors, color fidelity, size of the sensor, optics, and other aspects of the sensor are also important. Megapixel count is most frequently used as a quality indicator because it is the easiest metric for consumers to understand.

 

Full Sensor Resolution

This is the total number of pixels in a sensor. Five million pixels equals five megapixels or 5MP,   which is the resolution of HoverCam T5 and Solo 5..  8MP is the sensor resolution of HoverCam Solo 8 and the HoverCam Ultra 8.  The HoverCam range have an 8 megapixel sensor resolution and a 4:3 aspect ratio that is equivalent to the new 4K Ultra HD standard.

 

Effective Sensor Resolution

This is the actual maximum number of pixels used by the camera. For example, some cameras have a spec sheet stating “3.0 MegaPixel Effective Resolution” using a 5.0 Megapixels sensor. That means 2.0 megapixels have been cropped or scaled out. The 5.0 megapixel spec used is a misleading number.

In many cases, “Effective Resolution” is only the still image capture resolution, with video resolution even lower. It is almost an indicator of how ineffective some camera resolutions can be.

 

The HoverCam range (Solo 8 and Ultra 8) have an 8.0 megapixel full sensor resolution and effective resolution of 8.0 megapixel.

 

Video Display Resolution

This is the maximum number of pixels used by the camera. For example, some document cameras have a spec sheet stating “3.0 MegaPixel Effective Resolution” using a 5.0 megapixel sensor, which means 2.0 megapixels have been cropped or scaled out. The 5.0 megapixel specification used in this case is misleading. Further, in many cases, “Effective Resolution” only takes into account still images, while the resolution for video is even lower. “Effective Resolution” is almost an indicator of how “ineffective” some cameras are if you read the fine print.

 

The HoverCam Solo 8 and Ultra 8 have  an 8.0 megapixel sensor with an effective resolution of 8.0 megapixels.

 

Still Image Capture Resolution

This is the number of pixels in a still image you can capture with a document camera. Some cameras claim a sensor resolution of 5.0 megapixel but only allow you to capture a 3.0 megapixel still image.

HoverCam Solo 8 and Ultra 8 allows you to capture true 8.0 megapixel still images using a 8.0MP sensor.

Sensor size is often a number manufacturers do not want you to know. When they cram many megapixels into a small physical silicone chip, each pixel is lower quality in terms of color. A lot of junk pixels crammed together result in a junk image. So look for a bigger sensor size. 1/6” is considered very small for even 2.0 megapixel. ½” is very big for a CMOS sensor.

 

The Solo 8 and Ultra 8 sensor size is 1/3.2”,  giving the pixels plenty of space for a high-quality image.

 

Frame rate specifications should only be given together with resolution readings. For example, 30fps @ 1080P, 30fps @ 720P. The higher the resolution, the more difficult it is to achieve 30fps. When a vendor claims “Max 30fps”, the fact is most likely they can only achieve 30fps at a very low resolution, such as 640x480 (or 0.3MP). For document camera use, because you need to show small objects and text on a large screen, the lowest usable resolution is about 800x600.

 

When 30fps@1080P is achieved, you have a much better chance to see clear video with smooth motion without blurriness.

On the other end of the spectrum, some cameras claim a high resolution/pixel count, such as 10MP, but fail to achieve a high enough frame rate (i.e., lower than 7fps). This is like getting a “pixel junk pile” and is not practical for teaching, training, presentations or recording video.

 

 

Uncompressed video, most often in YUV format, has the highest fidelity image in each frame. There is no quality loss and it is the best video you can get. You should look for specs for YUV video, and ideally at 30fps @ 1080P or higher resolution.

 

Technologically, it is exceedingly hard to achieve YUV video at 30FPS speed with ultra high resolution, such as 4K or 8MP resolution.

 

HoverCam Visualisers (Ultra 8 and  Solo 8) are the only document cameras in the market that can deliver YUV video at 8MP resolution @ 30fps over USB3.0.

We discussed the impact of having more pixels, the size of sensors, frame rate and compression. The final image quality, however, depends also on other factors. These factors are, focusing, white balancing, exposure, lens shading, and colour adjustment.

 

Focus

Your camera should be able to auto-focus or manual-focus for the whole field of view quickly and accurately to achieve the sharpest image possible. Once focus is achieved, you should be to lock focusing so that hand movements under the camera does not go in and out of focus repeatedly.

You should be able to perform “select focus” or “touch focus” (when there is a touch screen), which means you can select a small region of interest within the whole field of view and make objects in that region to appear sharp. This is helpful when there are multiple 3D objects with different heights in the scene or when shooting at a thick open book.

 

Flex 10 software, used with both the Solo 8 and Ultra 8, includes auto focus, auto focus lock and select focus functions.

White balance is “the method by which digital cameras adjust the colours of a scene to accurately represent them. Because different sources of light -- such as a candle versus sunlight -- emit different colours of light, it's important for the digital camera to adjust its colour scheme to match human vision, which can interpret all white objects as white, no matter what colour of light they're reflecting. Think of white balance as the base line for creating colours using a digital camera.

Digital cameras can automatically determine the proper white balance settings by finding a white object in the scene and measuring all other colours from it. Manual white balance allows the photographer to choose a white object in the scene, and the camera then adjusts other colours from that object. With preset white balance, the user can tell the camera the type of lighting conditions that the photograph will experience, such as fluorescent or sunlight, and the camera bases its white balance settings on the expected lighting conditions.” – quoted from about.com

HoverCam has built-in software and hardware controls that allow you to auto white balance (AWB), manual white balance (MWB), and lock white balance (WB-L). You can also perform “Select WB” or “Touch WB”, which is a handy tool when the scene is composed of multiple objects with multiple colours. While the default full frame AWB takes the average of the whole scene, Select WB lets you accurately white balance on the object of the most interest.

 

“In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film, as determined by shutter speed, lens aperture and scene luminance. In digital photography "film" is substituted with "sensor". Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region.” – quoted from Wikipedia.org

Normally, auto exposure is based on the whole scene. When a scene is composed of high contrast objects, auto exposure often produces an inaccurate middle-of-the-road image.

 

In the example of a small business card sitting on top of a dark background, such as a desk, auto exposure shows a totally over exposed business card.

 

“Select Exposure” controls on the Flex 10 software can easily correct the exposure level by measuring exposure only of the business card, making the text appear clear.

Optical Zoom: 90% of the time, people paid more than necessary for a document camera that looks “substantial”. What’s not known by most customers is that these expensive cameras look substantial due to the addition of an optical lens assembly with 6x to 12x telephoto zoom capability along with a control panel. - The manufacturing cost for adding the optical zoom capability and controls can double the retail price of the product. In the case of a high quality Austrian-based manufacturer, their opitical zoom capability can increase the camera cost by 10-fold.

 

ASR Optical Equivalent Zoom.  

HoverCam has pioneered the patent-pending ASR Zoom technology which achieves the equivalent of 8x optical zoom. This eliminates the need for expensive and bulky lenses while making the zooming and panning operation highly responsive and easy to use. ASR stands for Adaptive Sensor Resolution.

 

Digital Zoom

Digital Zoom is another misleading specification used by some vendors. In fact, “Digital Zoom” is no more than a euphemism for “enlarged pixels”. When implemented in the most commonly known document camera brands, the pixel enlargement is often done with rudimentary techniques; you can easily see irritating pixilation effects. At 8x digital zoom, users must step back and watch the image from a distance

 

HoverCam Enhanced Digital Zoom. 

 HoverCam cameras all have a USB connection that allows the digital zoom to be performed on a PC or a Mac computer. The processing power of a computer enhances the digitally enlarged pixels by applying certain “smoothing” type of image processing in real time. As a result, HoverCam’s digital zoom is far less pixilated and more eye pleasing.

 

Traditional document cameras emphasize direct VGA output to projectors. Many don’t have a USB connection to PC or Mac computers, or even if they do provide a USB connection, the video is too slow to be useful.

Recording of lessons or capturing video clips for the purpose of “flipping the classroom” will benefit from a camera with the capacity of recording many hours of HD video. Recording directly onto a PC will save hours of transfer time and it is easy to share the video straight from your desktop.

 

HoverCam software and hardware work together to let you record in 1080P at 30fps or 720P at 60fps (Ultra 8) for 100s of hours without using up all your storage. Even live annotation marks are captured along with audio and video, making HoverCam the most easy to use video recording tool for teachers.

 

The limitations caused by low processing power of the embedded device used by the traditional document cameras goes away once a HoverCam is connected to a PC or Mac. The full modern Graphical User Interface (GUI) on a computer makes annotation simple, easy, and even fun, using Flex 10 software.