The background
In 2004 DxO released DxO Analyzer. It pioneered a new measure of lens resolution that it called BxU or Blur Experience Unit. Luminous Landscape reported on it (DxO Explained) and Imatest commented on it (Blur MTF)
More information about the product can be found here (DxO Analyzer).

It is a form of SFR Slant Edge test that uses solid circles instead of 5 deg slanted edges. Like the SFR Slant Edge test it calculates edge blur which it presents in units of BxU (Blur Experience Units). The SFR Slant Edge test though uses the edge blur to calculate MTF.

An argument for this measure is that it is a concept that is easy to grasp and seems natural. Essentially it measures sharpness by the number of pixels that an edge is blurred.
The principle argument against this measure is that DxO never disclosed their algorithm, keeping it proprietary.

But, I now see very few references to this method, though DxO still sell their product. To make it even more confusing, on their web site DxO Mark, they report resolution in standard MTF20 lp/mm.

So my question is this: Is the BxU measure of lens resolution still used by anyone? Has it been discontinued, has it fallen into disuse or is it simply ignored?


SLRGear.com publishes what they call "blur units" (and sometimes "Blur index") in their tests. These seem to be DxO BxUs (aren't TLAs wonderful?)

  • Yes, that does seem to be the same thing, THX
    – labnut
    Mar 28 '11 at 21:06

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