Alpa Focal Equivalents

Alpa Lens focal length comparison chart.

By Paul Slotboom  Summer 2010.

This chart is designed to help the user determine how a particular Alpa lens will behave in terms of angle of view, perspective, etc. on a given digital back.

This is intended to be a practical guide.  As such, I have combined certain digital backs together, even though their respective sensor sizes may be very slightly different.  For example, a P25+ sensor is 37x49mm, while an Aptus II 7 sensor is 36x48.  But for the purpose of keeping this chart as concise as possible, I have grouped them together as one.

How to read this chart.

I am using the full frame 35mm format as the reference for use of this table, since all users will be familiar with focal lengths when thought of in these terms.

To use this table you simply find your digital back or film size on the left, then locate the Alpa lens that interests you along the top row.  Where these two intersect on the table will show you what the equivalent view of that combination would look like in terms of a 35mm full frame camera.

For example, if you have a Phase One P65+ back and are interested to know how a 70mm Alpa lens would look on it, you would find the P65+ on the left column and then find the 70mm lens on the top row.  These two intersect at 45mm, so a 70mm Alpa lens on a P65+ will have the same basic look as a 45mm lens would look on a 35mm full frame camera.