An important feature of any macro lens is the distance it allows between its front element and your photographic subject at maximum magnification. This distance is called the working distance. If it is too short, it may not only scare away your subject, but also cast shadows on your scene.
The working distance w is always shorter than the minimum focusing distance dmin (between sensor and subject) of your lens. It can easily be calculated if you subtract the flange focal distance k (between sensor and flange) and the length of the lens barrel l (between flange and front element) as
|w||=||dmin – k – l||(W1)|
Note that if your lens extends for macro photography, you will have to use its maximum length.
The following table lists the macro lenses for the Micro Four Thirds system (figures rounded to full mm):
|lens||minimum focusing distance||flange focal distance||length||working distance|
|Olympus 30 mm f/3.5||95 mm||19 mm||60 mm||16 mm|
|Lumix 30 mm f/2.8||105 mm||19 mm||63 mm||23 mm|
|Leica 45 mm f/2.8||150 mm||19 mm||62 mm||69 mm|
|Olympus 60 mm f/2.8||190 mm||19 mm||82 mm||89 mm|
Obviously, a longer focal length allows for a much longer working distance. So does a longer focal length make a better macro lens?
If you are after butterflies in the wild or want to take pictures of coins in a studio, it is certainly a good idea to use a long focal length. Note that a telephoto lens with an extension tube may also work well in these cases.
However, if you have various subjects of different sizes, as in medical photography, a short focal length may be the only practical way to also capture larger subjects. So it depends on what you want to do.