Recently, I asked the question:  How large a print can you make from a Leica M9 file?

For my purposes (portraiture and simple element scenes), the answer turns out to be 36 x 24 inches:

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I thought about this some more, and realized that it would be interesting to see how much of a magnification over the Leica M9 sensor those prints above represent.  If you want to skip the math below, the answer turns out to be 645!

Here’s the math:

The Leica contains a so-called “full frame” sensor that is exactly 36 x 24 mm in size (that’s where the 36 x 24 comes from).

The area of this sensor

= 36 x 24 mm

= 864 mm²

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The prints I made were 36 x 24 inches.

In the equivalent (metric) mm, this translates to

= 914 x 609.6 mm

=557, 174.4 mm²

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The magnification of print-over-sensor area, therefore

= 557,174.4/864

= 645

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This is remarkable when you think about it.  The digital sensor (about the size of a stamp — remember those?) produces an image which is then magnified 645 times to produce the prints you see above.

Proportionally, this is what is going on:

All of the above underscores the importance of technique, lens quality, etc., when photographing with the aim of producing large prints: any “error” will be magnified 645 times!

Of course, you always have the option of turning to the much larger and more forgiving medium format sensors, but that’s another story…

—Peter.