Distance Index & Scale on 100mm f/2.8L

[lwalker]

When manually focusing the EF 100mm f/2.8L IS USM macro lens (or any lens, for that matter), is best practice to align the distance index | with the periods on the distance scale (e.g. 0.30 m) or with the magnification ratios' central colons (e.g. 1:1)?

The difference may seem subtle, but it matters when imaging (and then calibrating scale bars and measuring) tiny subjects.

- L

[Tim · Accepted solution]

Hello lwalker, 

The infinity position on that lens where the vertical line of the 'L' mark is aligned with the distance indicator on the scale.  For best focus it should always be checked either through Live View magnified or through the viewfinder.   

[TCampbell · Accepted solution]

Don't put too much stock in the position of each distance on that scale.  Factors (in particular the physical temperature) can affect the precision of those distances.