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A quick guide to document cameras

Introduction

 

The first thing that people always ask is "what the difference is between a document camera and a visualiser?".  Well the answer is that they are the same thing.  Overhead projectors used to be used to display clear plastic sheets onto a projector screen.  You used to have to take a piece of paper with information you wanted to show, such as a page out of a science book, and photocopy it onto an acetate sheet to display it.  Document cameras allow you to put pieces of paper, or "documents" under them to then be displayed on either a projector screen, TV or large LCD monitor instead.   All a document camera really is is a digital camera or video camera mounted so that you can put your items underneath it.   The term "visualiser" (or "visualizer" with the American spelling) seems to be a term we have imported from the US which is now used interchangeably with "document camera".

 

The first document cameras our company dealt with was over 10 years ago and many were just standard 640x480 pixel video cameras with component video (you know the ones from video cameras with 1 red, 1 white and 1 yellow cable).  You just plugged them into a projector or TV and whatever you put under them was displayed on screen.  Now document cameras are like digital cameras in that they can take still images as well are displaying and recording video.  They are all designed to be connected to computers via a UBS port or wirelessly and connect to software on your computer so that snap shot pictures can be taken as well as showing live video.  The software will record the images or video if required.

 

Types of document cameras

 

Gooseneck visualisers, like in the picture below, have the camera mounted on a flexible neck so that it can be positioned over an object by adjusting the neck.

 

The two little arms on the picture above are lights so that you can illuminate the object and with two lights you can position to avoid shadows as well.  This means that the image captured is clear.  It also means that if you are projecting an image in a darkened room, that you can still use a visualiser.

 

Flatbed visualisers, like below, have a bottom area for putting objects or paper on.  The white surface gives a nice white background as well when taking pictures of small objects placed below the camera.

 

 

 

Ceiling document cameras are either installed in a suspended ceiling, or embedded within a ceiling.  Usually there is a table below where the presenter will be placing objects to be displayed.  These tend to be very high specification units.  The picture below shows this in a corporate environment:

 

 

These are also used in medical operating theatres to allow cameras to zoom in on areas being operated on to take pictures and to show live video feeds to consultants that may be viewing the operation remotely.  Being in the ceiling they are out of the way and from a medical point of view there is no contamination as the camera is nowhere near the patient.

 

Pixels

 

A digital picture taken with a document cameras is made up of a number of pixel (dots).  The higher the number of pixels, the better quality of image.  A high number of pixels also means that if later, you want to crop the image so that you are just left with part of it, you still end up with a nice quality image.  Common sizes are:

 

800x600 - This is a non-widescreen normal shape.   This is OK for low quality image capture and display of objects.  Ideal use would be in a school class room where a basic display of something small on a projector screeen is required.  If you compare this to digital cameras, then this is less that 1 megapixel.

 

1024x768  - Non-widescreen again.  Better quality images that 800x600, but again this is less that 1 megapixel if you are trying to capture high quality images.

 

1280x1024 - Non-widescreen. 

 

1280x720 - This is a widescreen format.  1280x720 is the number of pixels for HD ready, so if you are recording video with this then the quality is going to be very good.

 

1920x1080 - This is a widescreen format and is also known as True HD.  When recording video this will give you the perfect quality video.

 

3296x2460 - These are the new 4K HD TV format for Ultra High Definition Telvision. There are just coming onto the market in 2016.

 

 

Optical zoom

 

This is how far the camera can zoom in before displaying the image with the full number of pixels that your document camera supports.  This is different to digital zoom, where zooming in just focuses one area of the image and you end up with less pixels being displayed.

 

Auto focus

 

When you put an object under a document camera, depending on the size and height you would have to adjust the focus using wheels or buttons.   The more expensive visualisers include auto focus so that when an object is placed under the visualiser the focus is automatically adjusted to give a clear image.   The ceiling document cameras tend to have this feature as standard.  If you are using the document camera to take pictures of small objects then we would recommend you choosing a camera with this feature as it will save you a lot of time.

 

Paper size

 

This is the maximum size of documents that you can put under to display.  Common values are A4, A3, and B4 sizes.  A4 is the standard paper size for letters in the UK, with A3 being double A4 size.  

 

Wireless

 

Some visualisers can send their images to a computer wirelessly using your existing wireless network.  Make sure you read the manufacturer's PDF datasheet first to familiarise yourself with how this works.