Macro photography is probably my favourite genre of photography. Allowing us to focus (HA!) on details and objects that we don’t take much notice of in our daily lives.
Macro lenses come in many different focal lengths, ranging from the wide angle Sony E 30mm f/3.5 Macro all the way up to the Nikon 200mm f/4 AF-D monster and everything in between. This article will discuss what difference the focal length of a macro lens makes and will help you decide on which one to buy.
Elephant Weevil taken with a 180mm macro lens
What is a macro lens?
Before we dive too Deep into this article it is important to know what I am talking about when referring to a macro lens. A macro lens is one that allows us to take a photo at a 1:1 magnification ratio (or greater). There are many zoom lenses out there that have a ‘macro mode’ but these lenses rarely get down to a 1:1 level. This article discusses ‘true’ macro lenses that can focus to at least 1:1.
1:1 magnification means that, when focused as close as it can, a lens will be able to fill your photo with something that is the same size as your camera’s sensor. If you use a full-frame camera this means you can take a photo of something 36x24mm. A cropped sensor will be around 22x15mm and a micro 4/3s camera 17x13mm. The focal length of the lens does not change the maximum size of the image a macro lens can produce.
So if all macro lenses at 1:1 make the subject the same size in the photo, why bother with different focal length macro lenses? Put simply, longer focal length lenses have a larger working distance. Read on to discover what that is and why it might matter.
What is the working distance?
You have probably heard that every lens has a minimum focusing distance – the smallest distance from your camera’s sensor to the subject that the lens can focus on. Working distance is very similar, but the distance is measured from the front of the lens. Essentially it is the size of the gap between your camera and what you are taking a photo of.
Working distance of popular macro lenses at 1:1 Magnification:
- Sony 30mm f3.5 Macro = 24mm
- Tamron 60mm f2.0 Macro = 100mm
- Nikon 105mm f2.8 Macro = 155mm
- Sigma 150mm f2.8 Macro = 186mm
- Nikon 200mm f4.0 Macro = 260mm
Due to different optical tricks that are employed with each lens, the working distance between two lenses of the same focal length won’t be exactly the same – please make sure you check your exact model before purchase!
Why working distance matters
If you are chasing macro photos of shy insects they are going to be a lot more tolerant of you if you don’t need to get right up close. Some insects will fly away as soon as you cast a shadow on them – it is much easier to avoid this if you don’t have to get as close
Jumping Spider taken with a 60mm macro lens
On the contrary, if you are taking photos of documents or jewellery in a studio you might not have the space required to be so far from your subject (and jewellery cares less about how close you are to it).
Another consideration to take into account is that a wide angle lens will capture more of what is behind your subject. If you work in tight spaces where busy backgrounds can be a problem then a longer focal length lens will help to capture less area behind what you are taking photos of, potentially minimising distractions and giving a ‘smoother’ look to the out of focus areas in your photo.
Black and Red ant taken with a 180mm macro lens
The Depth of Field Myth
Despite what you may have read, the focal length of a macro lens will not affect the depth of field of a photo taken at a given magnification value. Let me explain:
When starting out in photography we are taught that the depth of field of a photo depends on three factors:
- Aperture value (the f-stop at which your lens is set)
- The focal length of your lens (bear with me!)
- The distance your subject is away from the camera – further distances give more depth of field – (the important bit)
To achieve the same magnification with a longer focal length your lens will be further away from your subject than with a wide-angle macro lens. Points two and three above combine to give the magnification factor of a photo. Thus, the depth of field depends on just:
- Aperture value (the f-stop at which your lens is set)
- The subject magnification factor (how big the subject is in your viewfinder)
As you can see above – the focal length of a lens does not affect the depth of field, the amount of magnification of your subject is what matters (this applies to all types of photography.
Lizard taken with a 60mm macro lens
So Which Focal Length Macro Lens Should You Buy?
As mentioned above, it will depend on what you are trying to shoot. My recommendations are as below:
- Jewellery, Coins and Similar:Usually done in controlled environments and large working distances aren’t generally required. Recommended focal length = 40mm – 100mm
- Flowers, Plants & Similar:Large working distances aren’t usually a requirement, but longer focal lengths help control distracting backgrounds. Recommended focal length: 60mm+
- Insects, Spiders and Similar: Any alive creature will usually require longer working distances so you don’t disturb them. Recommended focal length: 100mm+
- Documents & Artwork: Not usually done at 1:1 magnification but macro lenses are often used. You will want a short focal length lens for this type of work so you’re not too far from the subject. Recommended focal length = 40mm – 60mm
- A bit of everything: If you want a macro lens that will be a good ‘all-rounder’ that can handle just about anything. Recommended focal length = 90mm – 105mm