What is "Full Frame?" Its Like Asking "What time is It?"

What time is it?  (click to enlarge)

What is "full frame" when it comes to photography? Without context, there is no right answer.  It is like asking "What time is it?"  You have to have context, such as location in order to know what time it is.  As with time, to understand what "full frame" is you have to have some context.  Read on.

There are many misconceptions when using the term "full frame," or "crop factor."  First of all, the term "full frame" is meaningless without some reference.  Second, the same goes for "crop factor" when used in and of itself.  We all use these terms in isolation because supposedly it is understood as to what we are referring.  But to individuals who are just getting into photography, it may not be understood.  We need to use those terms in context so we all have a clear understanding of what we are speaking.

What is full frame?  Is it the 11" X 14" film format?  Is it the 8" X 10" film format?  How about the 5" X 4" film format?  Hasselblad sized 6cm X 6cm size?  Might it be the size of 35mm film? There is no such thing as full frame when it comes to defining photographic formats. In fact, when using the entire sensor or film surface to produce an image, you are using the "full frame!"  So why the confusion?

Commonly, we refer to the size of a 35mm film image as full frame.  That size is 24mm X 36mm or about an inch by an inch and a half in dimension.  Not very big for being "full frame!"  Cropped frame (or crop factor) is commonly used for any digital imaging sensor dimension smaller than our "full frame" as just defined.  For example, APS-C or (as Nikon calls it) DX sized sensors are approximately 1/2 the size of a full frame sensor, thus creating a crop factor of 1.5.  Canon's sensors are slightly smaller than Nikon's and have a crop factor of 1.6.  Micro 4/3 (or I as advocate Mirrorless 4/3) sensors are about 1/4 the area (26%) of a 35mm film frame.  They have a crop factor of 2.

Note:  Speaking of crop factor, always keep in mind that any specific focal length lens will produce the same size image, no matter what sensor size (or film size) the light going through it falls upon.  In other words, a 100mm lens will produce the same size image whether it is attached to a 5" X 4" film camera or an APS-C sensored camera.  The difference being the sensor (film) size determines how much of the projected image is intercepted and recorded by the receiving medium.  For a 5" X 4" camera, a 100mm lens would be very wide angle.  For an APS-C sensored camera, it would be moderate telephoto.  Same size image but different sized recording medium.  The actual size of the subject in the image is the same.

In thinking about why the 35mm film dimensions are considered full frame, I suspect because it was the most popular size for imaging around the world when the shift to digital imaging occurred.  When Kodak first made their digital cameras, they made them using 35mm film camera bodies with the sensor and electronics grafted inside.  Thus 35mm size became full frame.

What difference does all this make?  Really none to most of us who have been involved in digital imaging for some time.  But it may make a difference to newcomers in digital imaging who are thoroughly confused by the terminology.  It is good to use context when defining something in every endeavor so everyone is clear on meaning.

Thanks for looking.  Enjoy!

Dennis Mook

Many of my images can be found at www.dennismook.com.  Please pay it a visit.  I add new images regularly.  Thank you.


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