Q&A: Macro Lenses and other Solutions

Recently we got the following questions from a reader.

I have a Nikon D3100 with a 18-200mm VRII lens.  Is there any add-ons to the lens to make it/give it the “macro” ability?

Since this is not the first time such a question has come in we thought we could answer it here to help other who may be having similar questions.

Macro Lens

There are 3 main ways to get macro ability out of almost any camera and lens combination. By asking if one can get macro out of your existing lens you kill the one solution which is getting a macro lens, however we would not suggest ruling it out completely just yet. Many of the camera manufactures are now making affordable entry level macro lenses. Sigma make a 50mm macro that retails for under R4000,00 and in addition to being a macro lens it can do double duty as a great portrait lens with a fast f/2.8 aperture.

What Is True Macro

I am getting ahead of myself. True macro is having a 1:1 (or lifesize) magnification ratio this means a subject measuring 10mm in size should be projected on you camera’s sensor by the lens as 10mm. Most zoom lenses only offer 1:4 or 1:3 (quarter to third lifesize) meaning in our before mentioned example the subject will only be projected on your camera sensor as 2.5mm or 3.33mm respectively.

A Macro lens achieves its magnification because its focus closer than it’s equivalent non focal length lens that is not a macro. For example, the Sigma 50mm f/2.8 macro focuses at 18.5cm opposed the 45cm on the normal 50mm f/1.4. It is only at the closest distance that the lens gives you the maximum 1:1 (lifesize) magnification ratio. For this reason a telephoto macro like the 150mm will give the same magnification but at a further working distance – 38cm to be precise. Why is that important? The closer you are to the subject the more your shadow etc impacts your lighting. Also if shooting a snake or other dangerous creature – or just not wanting to frighten off butterflies etc – you may want more working distance.

How to make your existing lens focus closer

Now how do you make your existing, non-macro lens get better macro magnification? Simply you have to get the lens to focus closer than it currently allows. The two ways to do that is to use either a close up filter that screws on the front of you lens or by using extension tubes that go between you camera body and the lens.

Close up filters are like screw on magnifying gasses. They come in different strengths and often come in sets of three. They are the cheapest solution however they can be of poor quality if purchased too cheap or in a no name brand form. Even the best ones will have some impact on the image quality your lens can achieve but not much more than using a good quality UV filter to protect your lens does. Like many things in photography, you will get what you pay for.

Extension tubes are simply hollow tubes that fit between your camera and lens which makes the lens focus closer and lose its ability to focus on infinity. They usually cost more than most close up filters do but are optically better. The trade off of these is that you loose light passing from the lens to the sensor. Most cameras will compensate for this but be aware to use a sturdy a tripod – a must for macro photography in most situation really.

Depth of Field

It is important to remember that the closer you get to a subject the less depth of field you have and to get a sharper image with sufficient depth of field to get say the whole butterfly in focus, or flower etc, will require you to stop down to smaller apertures than you may be accustomed to. You will have slower shutter speeds so look for a good tripod, camera shake will be your greatest enemy in this situation.