A Guide to Working with Different Focal Lengths for Macro Photography

At some point in your photography journey you may be fascinated by pictures capturing living creatures in great detail, flowers close-up, and in general intimate vistas, which may go unnoticed in our daily viewing habits. Such shots are commonly described as macro photography.

The purpose of this article is to provide you with theoretical and practical insight, to help you select lenses for macro photography with focal lengths suitable for your style.

What is macro photography?

The Collins English Dictionary defines macrophotography as: extremely close-up photography in which the image on the film is as large as, or larger than, the object. Extending this definition into the world of digital, the word “film” can be replaced by “sensor”.

The terms magnification and reproduction ratio (RR) are two ways of quantifying this definition. They describe how big the capture on the sensor is as compared with the subject you are photographing.

• “As large as” means that whatever object is captured it is the same size om the sensor as it is in real life (magnification of 1x or x1 and RR of 1:1).
• “Larger than” means if the image on the sensor is N times the actual life size of the subject, the magnification is then Nx and the RR is N:1.

An important distinction has to be made between the image on the sensor and the printed image. 1cm of object captured on 1cm of sensor may appear on a typical 10x15cm print as much bigger than 1cm.

It is important to note that not all lenses are capable of reaching 1x (1:1) magnification, even if they contain macro in their name. So it is important during your gear selection to know what is a true macro versus a marketed as a “macro” lens. This does not mean that you cannot and will not make breathtaking close-up pictures with that lens, it just means that you will only able to reach lower magnifications and RRs (e.g. a 0.25x magnification = RR of 1:4)

Now that we have established the realm of macro photography, there are a couple of other terms that are essential in this article.

Other definitions

Minimum focusing distance (MFD). This is a lens’s construction characteristic. According to Nikon, MFD is the shortest distance at which a lens can focus. In the case of DSLR Cameras, the focus distance to the subject is measured from the focal plane mark on the camera body, not from the front of the lens. MFD is important because 1:1 or life size RR only happens at the MFD of any true macro lens.

Minimum working distance (MWD). This is the distance from the subject to the front of the lens barrel (excluding the lens cap if used), while the lens is set to its maximum magnification (i.e its MFD).

On the web, there are various tools to help calculate MWD. This is a lens and camera combination characteristic, as different cameras contribute differently to the MWD (even if minimally so). A simple graph illustrating MFD and MWD is shown below.

The purpose of this article is to practically demonstrate the difference in Minimum Working Distance between two lenses of different focal lengths, as well as some implications that arise from this difference.

Gear and settings

For the examples used in this article, two macro lenses, the Tokina 35mm f2.8 and the Sigma 150mm f2.8 were mounted on a Nikon D750. This will demonstrate the MWD difference between two considerably different focal lengths (short versus long).

The supporting platform (all-important for macro photography) consisted of a SIRUI T-025X carbon-fiber tripod, a Manfrotto 410 Junior Geared Tripod Head and a Velbon Super Magnesium Slider Macro Rail. A Nikon ML-L3 remote was used to trigger the shutter to avoid adding additional vibrations.

Quick comparison

Let’s start with a 1:1 macro shot of an everyday item like a coin. In the photographs below the coin was shot 1:1 with both the 35mm and 150mm lenses. Rulers were placed to show the sensor size of 35.9 x 24.0 mm. The difference of a few mm is probably ruler set-up error on my part.

I measured an MWD of 19.5cm for the 150mm and only 1.8cm for the 35mm!

To see how this big difference affects a real-world shooting scenario, the owner of a close by flower shop allowed me to use his grounds and beautiful flowers. Continue reading for more info on this.

Doing macro photography of flowers with different focal lengths

To obtain the 1:1 photo shown below, the 35mm lens needs to actually be on top of the bulb as shown in the second shot.

Focal length matters even more in macro photography

Macro photography is exciting. In the words of Roman Vishniac, “In nature every bit of life is lovely. And the more magnification we use, the more details are brought out, perfectly formed, like endless sets of boxes within boxes.”

However, in my experience, macro has more gear and technical considerations than other popular subjects (e.g., portrait or landscape), especially as magnification goes up. One primary point of concern is the Minimum Working Distance of the lens used (true macro or not). This will determine significantly, in my view, the ease of use of the lens and the subsequent willingness you may (or may not) show towards doing macro photography.

Working distance issues

Apart from static subjects, where you may be okay to handle a short MWD. But if at some point you want to shoot bees or other living critters, then most probably you will want a longer MWD. This will help you to not scare away your subject and also to avoid being bitten/stung by it.

Additionally and importantly, a longer working distance will allow access to more light (natural or flash). You can imagine the limitations trying to introduce extra light to the 35mm setup shown above. Things will get even more cramped if you introduce closeup lenses or do lens reversal to reach even higher magnifications.

A rough proposed working classification of focal lengths in macro photography could be as follows:

• Focal lengths up to 60mm – Useful in product photography (e.g. jewelry) and small objects that can be approached and lit in a controlled environment.
• 60-150mm – Usable with caution for insects, flowers, and small objects from a greater distance.
• Above 150mm – Ideal for critters where additional working distance and additional lighting options are preferred.

Finally, there are other considerations, such as perspective differences due to varying focal lengths. These are more aesthetic than technical and not in the scope of this article.