Well, first let me explain my use of the term "macro". I believe the technical definition of a macro lens is that it creates a 1:1 magnification, typically based on the specifications of a full frame camera (i.e. a 35mm film camera or a digital camera with a 36mm wide sensor).
I remember understanding this meaning only after visualizing a 35mm Kodachrome slide. Look at the image on an old slide, not what the image looks like in a slide viewer or when projected on a wall or screen. The actual slide image is 36mm wide, but the cardboard mat reduces it to 35mm, or about 1.4”. So, if a lens is able to capture, for example, a 1.4” caterpillar in such a way that the caterpillar fills the width of the slide, then this is 1:1 magnification, sometimes written as 1x magnification.
Interestingly, old macro lenses were often unable to achieve this magnification, by themselves. They could only fill half the frame with the above mentioned caterpillar. This is 1:2 magnification or .5x. To accomplish a full 1:1 these old lenses usually were sold with an extension tube of about 1” in length. It was attached between the lens and the camera body, to provide 1x magnification when desired.
The capabilities of the Olympus 12-100 do not approach 1:1, except at 12mm wide angle. At 12mm, the equivalent magnification is about 1:1.7. In this case a 2.4” caterpillar would be needed to fill the screen! But on the 12-100, the lens would need to be about 1/2” away from the caterpillar to get this magnification, which is not exactly practical. Even if you could get that close, the lens would likely block most of the light.
At 18-100mm, the magnification is less, at about 1:2.4. It would take a 3.4” caterpillar to fill the screen. So, the 12-100 isn’t really a good option for true macro work. But for general close up photography it’s pretty awesome. Coming to mind is food photography, butterflies, and flowers.
Maybe the 12-100 is more of a quasi-macro. At any rate, this is why I put macro in quotes in the title of this post.
So let me get on with why I think there are six “macro” (note again the quotes around macro!) lenses within this one zoom lens. In my prior post I showed that the 1:2.4 magnification was basically available at all marked focal lengths greater than 12mm. Those markings are for 18, 25, 35, 50, 70 and 100mm. So there you have it. Six macro lenses starting with the 18mm (35mm equivalent) focal length and ending with the 100mm (200mm equivalent) focal length.
Which one to use?
With six focal lengths providing similar magnification, which one should you use? The obvious answer is that it all depends and what you are trying to do. I realize that the image examples given in the prior post were not too helpful in showing the differences realized at each focal length, as there was no background or foreground in the shots. That’s because I was only showing how much magnification could be obtained at various focal lengths and at minimum focus distances.
Below are examples that show some background. All were hand-held. Flash at 1/32 power. Aperture at F8. Ambient light at -2 EV. The focus point was the orange head of the fly. I tried to maintain the same camera angle by using the electronic level. All are at minimum focus distance.
|18mm. Note how stretched-out the scene is, front to back|
and how wide the scene is in the background.
I see an orange pen and food shopping list in the background.
|25mm. The background is beginning to fade away.|
|100mm. This is a good example of the compression|
of the foreground and background that is achieved with longer focal lengths.
It almost looks like the striped dishtowel was held up vertically
behind the fishing fly.