Going Digital: Camera Basics

The easiest way to tell cameras apart is by cost.  But higher price doesn’t always mean better performance – especially if you don’t know what kind of performance matches your microscope.  Knowing the jargon is the first step to determining what camera is best for your application.

Camera Specifications

Here are the basic terms and specifications to know about cameras in order to get the most bang for your buck.

          Pixel: A pixel is the smallest individual unit of the camera sensor.  When you zoom very far into a digital picture, each square dot that makes up the image is one pixel. 

       Pixel Size: The physical size of one pixel, typically a square ranging from 1-10um.  A bigger pixel collects more photons but takes up precious space.  A smaller pixel can increase resolution but also adds noise and limits dynamic range.

          Resolution: The number of pixels a camera has, often reported as Horizonal Pixels x Vertical Pixels.  It is important to note this is not the same term as microscope resolution, which is a measure of the smallest thing that can be seen.

          Megapixels: Literally meaning one million pixels, this is the total number of pixels a camera has.  It is often used as a shorthand reference for resolution.  But without knowing the pixel size or aspect ratio (height compared to width) of the camera, this specification does not give very much information by itself.

       4K: A term that comes from TV and broadcasting.  While it would be logical to assume that 4K means 4,000, it technically refers to an image that is 3840 x 2160 pixels. Sorry, not all jargon makes sense.

       Sensor Size: The physical dimension of how big the imaging area on the camera is.  Too small means a limited field of view, but too big causes vignetting (black edges) and wastes valuable imaging space.

       Frame Rate: The speed that the camera can send out pictures, typically measured in frames per second at full camera resolution.  Sometimes the limit is based on the sensor, and sometimes the computer connection (USB, GigE, etc.) is a bottleneck.  No fast frame rate will help speed things up for samples that require long exposure times.

       Bit Depth: The difference between the highest and lowest readout that a pixel can report.  8-bit means 256 levels (2^8) from the brightest to darkest signal seen from a camera.  12-bit means 4096 levels, and 16-bit means 65,536.  Low bit depth may lose information, but too much bit depth can result in unnecessarily large picture files.

       Sensitivity: How efficient a camera is at picking up light.

           Noise: The opposite of sensitivity but just as important, this refers to how dark a camera can read with no light present.  Many different types of noise exist, including read noise and dark current.

Let Us Help

Don’t fall into the common trap of just picking the camera with the most megapixels.  That’s a simple number to look at, but it never gives the full story of what makes every camera special.  At I Miller, we’re happy to talk you through the specs of any of our cameras to make sure it’s actually the right fit for your microscope and application.

For more information contact us at sales@imillermicroscopes.com or call 215-925-2285.

Look for Part 4 "Shutters and More" Coming Soon