I guess two of the most common ways to get close up capabilities with common lenses are: Using a macro extender ring between the lens and the camera, and using a macro ring on the front of the lens. I am comparing these two approaches here.
For the test, I am using the Lumix G 100-300mm f/4-5.6, which is a reasonably priced, very long tele zoom lens. It is commonly used for birds and wildlife photography, as well as sports. By using macro accessories, one would be able to use it also for photographing small objects, e.g., flowers and insects.
Here are the two accessories I have tested:
|Macro extension rings: Meike/Neewer/Skyblue||B+W 67mm NL-4 close up lens|
|The macro extension rings go between the camera and the lens||The close up filter goes on the front of the lens|
A big advantage of both these methods, is that the autofocus still works, and also the aperture control. This makes it very easy to use the lens while photographing small items.
These rings go between any Micro Four Thirds lens and camera, however, you generally get the most useful combination with reasonably long focal lengths. If you have a kit zoom lens, use it at the max (usually 42mm) when using the macro rings.
The shorter the lens, the shorter the extension you need, and vice versa. So with the Lumix G 100-300mm f/4-5.6, I combined both for a total of 26mm extension.
Using the extension rings shifts the usable focus range closer. Hence, you can focus closer, but you can no longer focus at infinity. Here is a summary of the effect:
|Lens||Focal length||Extension||Working distance||Magnification|
|Lumix 100-300mm||300mm||None||1.3m - infinity||Max 0.21x|
|Lumix 100-300mm||300mm||26mm||1m - 3m||0.36x - 0.12x|
From the first row in the table, you see that the maximum magnification at 300mm is 0.21x. This means that you can photograph objects which are the size of the sensor divided by 0.21, i.e., 82mm by 62mm. So at the closest focus distance at 300mm, you could use the lens to photograph a large insect, like a butterfly.
Using the extension rings extends this focus range towards you, so that you can photograph items 48mm by 36mm. The working distance is still quite generous, you have a distance between the front of the lens and the object of 1m. Hence, using the macro rings should make the lens much more useful for photographing insects, which tend to be a bit camera shy.
Here is an example image taken at maximum magnification using the extension. Lumix 100-300mm with 26mm macro extension, f/8, the autofocus area was placed on the eyes of the figure:
|Full image||100% crop|
I think this approach works quite well, and makes the lens more versatile. Bringing the macro rings in your bag means the lens can double as a macro lens for insect or flower use.
Some are concerned that the insides of these macro tubes is too glossy. To assess this effect, I tried to sand down the insides to make them more matte, but I did not see any significant before/after effect. So I think this concern is exaggerated. If you are worried about this, you could go for sanding the glossy insides like I did, or get more expensive macro rings with matte insides.
When putting the macro front lens into the lens threads, you can only focus on quite close items. The lens was not able to focus on anything in the long end of the focal range, so I used the lens at 150mm. In this setting, I was only able to focus on items with a working distance of about 0.25m. This makes the lens less versatile, as you need to be at only one specific distance to the subject. Hence, a tripod is clearly needed.
At this focus distance, I could photograph with a magnification rate of 0.6x, meaning I could photograph items 29mm by 21mm. Here is an example image, taken at 150mm, f/8:
|Full image||100% crop|
We see that there are quite some chromatic aberration artefacts, making this combination less useful.
In this test, I think it is quite clear that using the macro extension rings gave the best results. Using them with the Lumix 100-300mm at 300mm enables you to use the autofocus for distances between 1m and 3m, good for photographing, e.g., insects or flowers.
Using the B+W 67mm NL-4 close up lens, on the other hand, limited the usefulness of the lens a lot: The area covered by the autofocus shrank to almost non-existent, and the image quality deteriorated a lot.
Some have had better luck with snap-on macro lenses from Raynox, and claim to get images less tainted by chromatic aberration artefacts. I have not tried them myself, but based on the example images I have seen, this appears to be true.