Olympus 12-100 For Macro. It Focuses Closer Than You May Think.

Many of the Olympus zooms are nice for closeup work, and the 12-100 is no exception.

First, the 12-100 works beautifully with the manual focus ring. Like all (most?) of the Olympus PRO lenses, there is a snap-back focus ring that lets you operate the ring with the feel of a real mechanical focus ring.  It has hard stops on both ends of the distance scale and the travel distance from one side to the other (close focus to infinity) is 90 degrees. That’s a smooth one-quarter turn from minimum distance to infinity. It’s a bonus that the focus distance will stay right where you leave it.  Turn the camera off and then on, and your focus distance is right where you left it. All that being said, auto focus works great too!

Second, focus peaking works well at short distances.  I am not a fan of using peaking at landscape distances because it appears to me that everything is in focus, and I'm suspicious of that.  But for closeups, peaking works brilliantly.  It enables you to see a ribbon of sharp focus (I like the yellow option for the color of the area in focus) across the viewfinder or screen.  For example, if you are focusing on flower stamens from the side and from a 45 degree angle, you will also be able to see which petals are in focus to the left and right of the stamens. Because the ribbon of focus peaking has some width to it depending on your F stop, it gives you a sense of your depth of field as well, so you will also be able to judge how much is in focus in front of and behind the stamens.

Third, the relatively short minimum focusing distance designed into the lens at all focal lengths, gives a very nice magnification of about 1:2.4 (35mm equivalent), over the range of 18mm to 100mm.  At 12mm the magnification is actually better (about 1:1.7 equivalent) but to accomplish this you must be right on top of the subject and the image will be somewhat distorted (see example further below).

Minimum focus distance versus working distance:

What is interesting is how close you can get to your subject with the end of the lens.  The advertised minimum focus distance is 6” at the wide end and 18” at the long end.  But I quickly realized that this is the distance between the subject and the sensor.  The “working distance”, which is defined as the distance between the front lens element and the subject, is much less.  I found at 12mm I could fill the frame with a 2” wide object, but the actual working distance was about 1/2”.  On the other end, at 100mm I could fill the frame with a 3-3.5” subject at a working distance of 9”.

Here are samples shot “as close as I could get” at 12, 18, 25, 35, 50 70 and 100mm.  

12mm.  Lens element is 1/2" from the ruler. Major distortion obvious.
Perhaps I could have focused better, but there seems to be some field curvature here,
as the edges seem sharper than the center.
The dark corners in the upper right and left are merely from the wide angle seeing
past the edges of the white paper I used behind the ruler.

18mm.  Working distance is 1.25"

25mm. Working distance is 3"

35mm. Working distance is 4.5"

50mm. Working distance is 5.5"

70mm.  Working distance is 7.5"

100mm.  Working distance is 9".

At first it seems that it makes no difference what focal length you use, from 18mm to 100mm.  However, not considered in this experiment is the background and depth of field.  The relationship between the subject (the ruler) and the background (of which there is none here) will change depending on the focal length.  At 18mm there will be more background visible (or blurred) from left to right because of the wide angle nature of the lens and larger depth of field.  At 100mm there will be less background from left to right and it may be blurred (often a good thing) due to the smaller depth of field. Distractions in the background are expected to be more prevalent at 18mm than they are at 100mm.