Sunday, 19 April 2015

Macro Diffusion for the Mirrorless Camera system

.... Continuation from my previous post on the types of Equipment I use.

The truth is, most modern cameras and lenses that are available out there in the market, regardless of the system, are more than capable of achieving good if not great macro images on its own merit. Having said that, then why are our photos failing to deliver desirable results, time and time again? More often than not, it probably has to do with Lighting, or to be more specific, the lack of Proper Diffused Lighting. This is the one most important aspect of (macro) photography that would be the differentiating factor between mediocre, good, and great photos.

Before I begin, I would like to gently remind that there is no one-size-fits all solution when it comes to lighting - Every subject matter and shooting environment comes with its own set of inherent challenges and it is up to us to manipulate the lights to create the most pleasing results, so do not be afraid to experiment. Just to be clear, henceforth, I will be discussing solely on TTL fill-flash and not natural-light photography, and since this is a site dedicated to the mirrorless system, I will approach this topic from that angle, although I can assure you that most of the points that I will be covering stand true for DSLRs as well.

1) What is considered a Properly Diffused Lighting?

An ideal diffusion of the fill-flash would result in the even distribution of the light from the flash to the subject, minimising any hotspots or shadow spots by wrapping light around the subject matter(s).

A clear illustration would be:

Imagine that you are photographing a ping pong ball. A properly diffused lighting would be able to
reach all if not most of the surface area of the ball with the right and even exposure.

A properly diffused lighting should also be able to solve or alleviate these problems:

a) Subject matter with odd shapes and shiny, reflectives surfaces.

This Cosmophasis sp. jumping spider would be the ideal example of a difficult subject to photograph. It is tiny (5mm) and highly reflective, especially the eyes!

b) Poor distribution of light; Focused on just one or more scattered spots.

Pls excuse the extremely graphic use of Microsoft Paint but you get my point.
2) What are some of the considerations to take note of when aiming for a Proper Diffusion?

a)  The design specifications of your mirrorless system (Mirrorless systems have a much shorter distance between flash head and front of lens as compared to a regular DSLRs, due to its smaller size)
b)  The Guide Number (GN) or power of the flash
c) The types of materials that you can use as diffusion and the appropriate amount of layers.
d) Wastage of light due to light leakage.

Lets us dwell deeper into point (a) and (b) for a bit before moving on to the other points in just a while. It seemed like what lured me to the mirror less system in the first place was also a source of my initial problems - its  size. As we all know, most mirrorless systems are tiny and if you recently made the switch from a DSLR where the mantra seems to be 'the bigger the flash, the better', it takes a lot of getting used to. Just remember that this is not the case when it comes to a mirrorless system, as a matter of fact, it is the exact opposite!

3) How to choose the right flash for your type of macro work.

Factor of exponents and Guide Number

When choosing a flash for your mirrorless camera, resist the temptation to go with the biggest flash you can find. Instead, choose a flash based on its Guide Number that is appropriate for the length of the lens in terms of providing the right exposure when shooting a subject at your preferred shooting/working distance. In general, the higher the Guide Number of the flash, the more powerful it is. The question is then, what would be the minimum GN needed for my close-up shots? The answer is in this formula:

GN (guide number) = f-stop number X Distance (flash to subject)

So let's say that the distance (flash head to subject, not front of lens to subject) of my macro lens (M. Zuiko Digital ED 60mm f/2.8)  for my 1:1 magnification shots is approximately 30cm at a f-stop number of 11 (full format equivalent of f22 due to X2 crop factor) and with an ISO of 100. So by applying the formula, the minimum Guide Number needed for a correct exposure at these settings is:

GN (guide number) = f22 X 0.3meters
                                = 6.6metre or 21.6 feet

What does these numbers above means to you and me? To give you a point of reference, my smallest flash, the Olympus fl-LM2, that comes with free with the OMD EM1, has a guide number of 7 meters (22 feet) so what this simply means is that, technically, this flash is sufficient for my 1:1 magnification shots - the bare minimum GN needed to correctly expose my subjects at a distance of 30cm. Of course, this is not ideal especially when I am shooting larger subjects at a much lower magnification, and that is why I decided that the default flash simply won't cut it for my type of macro work.

The Olympus fl-LM2 with a GN of 22 (feet). Sorry for the lousy IQ, taken with a mobile phone.
Probably not ideal flash for larger subjects like this Agamid, due to the low GN.
In a nutshell, the main points that I want to bring across are:

a) Be aware of your preferred settings for the usual group of subjects that you photograph often (eg. f11 for beetles smaller than 5mm at a working distance of 10cm or f5.6 for a large lizard at working distance of 50cm, etc).

b) Choose a flash with the appropriate GN. The larger the GN, the larger the flash usually is in terms of size and relative power. Remember; you are shooting close-up photos of insects and not birds high up on trees so don't overkill it.

The Olympus fl-14 with a GN of 46 (feet). I decided on this flash due to its relative high GN and low-profile design.
The Olympus fl-50r with a GN of 146 (feet)! Too big and powerful for my type of work.
I figured that the Olympus fl-14 (GN 46) has more than sufficient power for my type of macro work. Putting on the Olympus fl-50r (GN 146) would be an overkill for me, plus it is way too big for my liking. I prefer to keep it small and light!

4) Suitable materials for Diffusers

There are many materials out there that would be suitable for macro work although I have my preference. Some of the more common materials:

a) Tissue towel
b) styrofoam
c) Packing foam
d) tracing paper
e) Thin translucent sheets of plastic

I have experimented with all the above, even layering some of them in creating some of my own diffusers. Most of them are pretty good in terms of the overall results although realistically, some would not last 30 minutes out in the field, given the wet climate conditions where i live. The other considerations apart from durability would be the flex-rate and of course, the actual light-distribution capability of the material. After taking into account all of my pre-requisites, and after months of testing, I finally decided to settle on packing foam as the base material for my diffusers.

5) How many layers is appropriate?

This depends on the Guide Number of your flash. The stronger your flash, the thicker the diffuser must be. I personally engage just one main diffuser, fitted around the lens, for less reflective or larger subjects. For rounder or very shiny, reflective subjects, I would insert another layer in between the flash and the main diffuser. The idea here is to spread the light as much as possible so the further the diffuser is away from the light source, the better. Remember, the purpose of the diffuser is not to cut out the light but rather to spread it across a larger surface area.

Main Diffuser with 4 layers of thin packing foam spray-glued together.
Phaeacius cf. malayensis with single diffuser.

For more reflective subjects, I insert an additional layer of foam between the reflector and the main diffuser.
A pair of Dipterans with dual layer diffusion.
7) Reflectors

A reflector is basically any flat object, preferably made from a durable lightweight material that is placed directly over the flash head to direct the light towards the diffuser.Having a good reflector would prevent the leakage of valuable light, especially if you are settling for a smaller flash with a lower GN. I have experimented with various store-bought and DIY designs and I find that the store-bought ones are pretty much useless in terms of light distribution and usability so I prefer to make my own.

Some considerations when making your own reflector.

1) Choose a dark coloured reflector, preferably black and avoid translucent or tinted materials as it would end up throwing coloured lights onto the subject and the surrounding scene.

2) Line the inside of the reflector with aluminium tape. Avoid making the mistake of scrunching up the aluminium tape before applying it - this would only scatter the light. You don't want to scatter the light but rather direct it.

3) Think about how you can minimise light-leakage.

Version 2.0 - It can be completely flat-packed for easy storage!

Ready to roll!

There is certainly a lot of to talk about with regards to the topic of diffusion but I reckoned this short tutorial would be more than sufficient to assist you in designing your very own diffusers for your mirrorless set-up. Feel free to contact me here or on my personal Facebook Page should you have any further questions or suggestions for my future posts. Have fun experimenting and do remember that a larger flash does not necessarily mean that it the better choice, especially not for our tiny machines!

UPDATE (1 Nov 2016) : Click here to for a tutorial on how to make your very own Concave Diffuser!

Interested to learn backlighting and how to re-create shots like the one shown below? Click here to find out more!