The flash zoom setting on speedlights can confuse a lot of people and there’s a few things to consider to make sure you are using it correctly.
Let’s go through the important things that you need to know to get you comfortable in using it correctly.
What Is The Zoom Setting For On My Flash?
The zoom setting on your flash describes how wide or narrow the light from the flash will be.
For example, a 24mm zoom setting for flash zoom is quite wide so the flash will be dispersed quite widely and illuminate a wider area of your scene.
On the other hand, a 105mm zoom setting for flash zoom is narrow so the light from the flash will be quite narrow and illuminate a smaller area of your scene.
How Does The Flash Zoom Work?
The zoom setting changes based on where the position of the flash head is within the unit. If you are using a narrow angle / high zoom like 105mm then the flash head will be further back in the unit. This means that the light rays are more directed in a straight and narrow fashion.
On the other hand, if you are using a wide angle / low level of zoom like 24mm then the flash head is closer to the front of the unit so the light immediately gets dispersed in a wider angle as it leaves the unit.
Why Do I Need Flash Zoom?
Since it works alongside focal length, the flash zoom is necessary so that you don’t waste light from your flash.
Let’s look at an example:
If you are shooting a scene with a lens with 50mm focal length then you would probably want your flash zoom to be set to 50mm too. Let’s assume you have the flash set up on the camera and it is facing directly at the subject.
If you used a longer flash zoom like 105mm then the light from the flash will be more concentrated and you will have more of a spotlight effect. The edges of the scene will be much less illuminated and this can look unbalanced – unless that’s the look you want to go for.
If you used a wide flash zoom like 24mm then you would be illuminating an area larger than the area captured by the lens so you will be wasting some of the flashes power on illuminating things which are not in the scene. This isn’t so much a problem if you have enough light, but this can be important especially if you are only just getting enough light in your scene with the flash.
How Do I Select The Right Camera Zoom For Crop Sensor Cameras?
The flash zoom setting is described in 35mm equivalent focal length terms, so you will need to take this into account if you are using a set up where you have a crop factor.
For example, a Canon 200D (an APS-C body) with a 50mm lens will have a crop factor applied of about 1.6x. This means that the actual equivalent focal length will be closer to 80mm.
So in this case you would want to manually set your flash zoom to 80mm instead of 50mm. This will keep the flash dispersion more in line with the scene that the camera will be capturing.
Luckily some speedlights will recognise the right focal length automatically using an auto zoom feature.
Auto Zooming Speedlights
Some speedlights have an auto zooming function which basically allows the speedlight to automatically detect the correct zoom level based on the camera set up that it is attached to.
This can be useful especially if you have a zoom lens attached to your camera and you will be using different focal lengths throughout the shoot. Rather than manually changing your zoom level on the flash you can just let the speedlight do the work itself.
Not all speedlights have this feature so you will need to check if yours has this feature. Make sure to also check that your camera is compatible too.
Off Camera Vs On Camera Flash
You only need to match the focal length to your flash zoom if you are using the flash directly on the camera hot shoe since it will be illuminating the exact same scene that your lens is capturing.
If you are setting up the flash on a separate stand then it is less important since it becomes a judgement call based on where the flash is positioned and where it is pointing. For example, if your flash is positioned quite far from the subject then you might want to use a high level of zoom like 105mm even if you are shooting with a lens that is 24mm. This is because the higher the zoom, the further the light should travel to light up the subject.
With off camera flash a lot of it comes with practice and getting a feel for what fits your style.
Just remember that the higher the zoom the more concentrated the flash will be and the lower the zoom the more widely the flash will be dispersed.
What If My Focal Length Is Longer Than My Maximum Flash Zoom
If your focal length is longer than your maximum flash zoom then you will be ‘wasting’ some of the flash as some of it will be dispersed beyond the scene that your camera is capturing.
For example, if the maximum flash zoom is 105mm and your camera lens is 200mm then your camera will be capturing a scene with a narrower field of view compared to what is being illuminated by the flash.
Of course there is not much you can do about this since you can’t make the flash zoom any narrower, but don’t worry about this too much.
Speedlights are small flash set ups which are designed more for studio setups or outdoor shots where the subject is not too far away from you. In these situations you won’t be using lenses that are extremely long in focal length (e.g. 400mm) since the subjects are closer to you.
In fact, if you are using something like a 400mm lens then you are probably photographing a subject which is a considerable distance away and you are most likely not using flash in this case.
If your subject is too far away to light up with a speedlight you will probably be using other types of off camera artificial light which are set up closer to the subject.
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