A grid is a pattern of black fabric that you mount typically on the front of the softbox instead of the usual white fabric. The grid will effectively stop or dampen all light that tries to travel sideways relative to the direction the flash is pointing, and hence make most of the light travel in the same direction.
The grid seen from the side when the flash fires. Most light that tries to “travel” sideways will be stopped or dampened.
Although the softbox itself is coated with a reflective fabric on the inside and and hence designed to send all the light forward, the forward direction is still much wider than the front of the softbox itself. The grid helps limit the sideways travel by only allowing the light moving straight forward to continue, the rest is blocked or dampened.
The grid in action to the left, and the softbox without grid to the right. Notice how much wider the light is cast to the right.
I use the grid to give more specific direction to the light, if for example it is important that the light bouncing from the floor or the ceiling is minimized. Notice that the grid dampen the effect of the flash all things equal quite significantly, so especially if you shoot the flash in manual mode, you need to factor in the effect of the grid when setting the flash power.
So a softbox is a device that gives soft light, right? Well, yes and no. A soft box is a light modifier, intended to make the size of the light source bigger. And all things equal, when the light source gets bigger relative to the subject, the light gets softer. And then the softbox also helps making the best use of the light by redirecting the light that would otherwise not have hit the subject.
Softbox example
Softboxes can be used for both steady light and flash light, but in the following I will assume that we are talking flashlight.
A softbox from Godox. The front fabric is all lit up when the flash fires.
Bigger softboxes are often made as a umbrella like construction, where a set of wires defines the shape of the box. And just like an umbrella, the softbox can be folded to take up very little space when not in use. In my case the softbox is square, but many other shapes can be found.
The front fabric is half open so you can see the diffuser fabric inside and and all the reflective material on the sides of the inside of the softbox.
Inside the softbox the sides of the softbox is fitted with reflective material to make the best use of the light. On the front of the softbox a white fabric is mounted and this is all lit up when the flash fires.
A look inside the softbox. Notice the reflective material to the right. The metal pole in the middle is part of the umbrella like construction that defines the shape of the softbox.
My softbox from Godox is also fitted with a diffuser fabric in the middle so the flash fires straight into the first layer of fabric than then diffuses the light and makes sure the light is distributed evenly within the softbox to make the final light on the front as even as possible. The ideal softbox gives a evenly lit up surface on the front of the softbox – if your softbox does a bad job here, you will see that the light is stronger in the centre than in the corners.
Mounting the softbox to the stand.
The rear of the softbox typically has a Bowens interface that allows you to mount the softbox directly to most light systems. In my case I used the supplied holder shown above, that connects with the softbox via the 3 pins in the Bowens interface and to the stand via a locking mechanism. In the centre of the ring above, the flash is mounted and of course it needs to be radio controlled (or in optical slave mode).
Why a softbox
As mentioned the softbox is intended to make the lightsource bigger and hence give more soft light. Relative to shooting through an umbrella, the soft box gives much more direction to the light and the light is also more evenly distributed.
Most pro photographers will tell you that getting the flash off camera will be a much better option that having it on camera, as the options for positioning the flash grows to infinite. But to do so, you either need a cable between the flash and the camera (not recommended – limited reach + cumbersome) or you will need some sort of radio communication between camera and flash.
Many modern flashes like the Godox V860III comes with radio receivers, but you may not have a transmitter to put in the hot shoe of the flash, or you may want to use an older flash as fill light and don’t want to invest in a receiver. What to do?
Optical slave mode
To the rescue comes optical slave mode. Not all flashes have this feature, but many do: in the flash there is a small unit that looks for other flashes firing and when they see one firing, they follow suit. Of course, if you have set it up to do so.
You may ask how this is possible? Well, the time the shutter is open, say 1/100th of a second, is a barn door of time for a flash, so it is plenty of time for one flash to fire, another to see it and fire shortly after, and still stay within the time when the shutter is open. Flashes are unbelievably fast!
The optical slave mode on the Godox flash is found in manual mode. Notice the S2 to the right in the LCD: It will work with a TTL controlled flash and ignore the pre-flash.
Built in flash
If you have a camera with a built in flash like the Nikon D750, you can use the built in flash to trigger the off camera flash. If the camera shoots in TTL mode (the automated flash mode), it will fire a pre-flash to measure the light and immediately after fire the flash for exposing the image. It happens so fast you won’t notice the two flashes, but your slave flash will! Therefore, you need to tell the slave flash to ignore the pre-flash and only fire when the main flash fires.
The built in flash of the Nikon D750.
On my Godox V860III the flash has two slave modes: S1 – will fire every time a flash is seen, S2 – will fire at the second flash and hence ignore the pre-flash. So when I control the built in flash manually, I set the slave flash to S1, and when I shoot TTL, I set the slave flash to S2.
Limitations
Some say that the slave flash needs to have line of sight to the main flash, but I have been able to get the slave flash to fire even without direct line of sight. But you will need to try this out and see what works with your combination of flashes. I will say though that the slave flash will need to see a lot of light in order to be able to react, so direct line of sight is probably the safe way to go.
Another thing to notice is that the strength of the optical slave flash can only be set manually. There is no communication between the camera and the slave flash at all – only a visual signal saying: please fire! This is one of the main limitations of optical slave flashes relative to radio controlled flashes. On that note, if the camera with a built in flash is in TTL mode and the optical slave flash is set to S2, then the camera will not be able to factor in the optical slave when it meters the scene with the pre-flash, so remember to factor in the additional light using flash exposure compensation or set the strength of the optical slave flash low.
A flash in optical slave mode is hiding in the bowl!
Several flashes
If you have a trigger on the camera and a radio controlled (off camera) flash, it is still possible to use an additional flash in optical slave mode. It just reacts to the radio controlled flash. This way you can bring the radio controlled and the optical slave flashes closer to each other and hence be more sure the optical slave flash will fire.
When you shoot with a flash, there are two exposures going on at the same time: one originating from the ambient light, the other to the flash firing. The pop in “pop and blur” is the flash firing, and the blur is the shutter being open for sufficiently long time to let in the ambient light. So pop and blur is combining flash and ambient exposure in one and the same image.
Behind the cow here I am waving a stick of light like a pendulum. The long exposure makes it look like a white background. The flash lights up the cow – had it not been for the flash, the cow would have been a black silhouette. EXIF: 0.8 Second at f/22 and ISO 100.
If something in the frame gives off light, like the headlights of a car or a flashlight, any movement made will be captured by the long exposure. This is in stark contrast to objects only being lit up by the flash. It is this combination of things moving and things standing very still that makes pop and blur so fascinating, if you ask me.
Here I am moving a constant light in a circular motion captured by the ambient light. My hand is lit up by the flash and is hence absolutely still despite the movement.
If you let your subject be lit up by both the flash and the ambient light while moving, then you get a “trailing” look – you may have seen photographers use this for catching people dancing as this gives a very sharp image and illustrates the movement at the same time.
If your subject is moving and is hit by both ambient light and the flash light, you get this trailing look – the pop and blur classic!
Your cameras default setting is most likely to activate the flash at the beginning of the exposure – also known as first curtain synchronisation. Most cameras allow that you change this to be flipped upside down, so the camera now fires the flash with second curtains synchronization. This way you can control the order of the flash and blur. With first curtain sync the flash fires at the beginning of the exposure, with second (or rear) curtain synchronization, it fires at the end of the exposure.
The guide number is an indication of how powerful the flash is, i.e. a high guide number indicates that the flash can illuminate a subject far away when shooting at a closed down f-stop. But you may not need all this power, if your subject is close to the camera (product shoots for example). So there is an element of marketing hype involved in the guide number, a bit similar to the marketing hype related to megapixels.
Back in the days when you were shooting film, the feedback cycle from shooting to seeing the result was pretty long and involved a darkroom and lots of chemicals. Back in those days, it was pretty important to calculate how far away from the camera the subject could be and still be illuminated by the flash firing. And hence the guide number was very much needed. Today, where the feedback is instantly available in the rear screen on the camera, the math involved in setting the flash power is less relevant and has been replaced by simply trial and error. Or automation in terms of TTL.
However, the guide number (often abbreviated GN) gives an indication of how powerful the flash is. Unfortunately the way to measure it differs from vendor to vendor – some shoot at ISO 100, others at ISO 200, some use reflectors, others not, and then it is not comparing apples and apples. And to confuse matters more, some give the guide number based on feet, others on meters, and this gives some significant differences obviously. But within spec sheets from the same vendor, the numbers can be compared. And as such this could be a parameter in your choice of flash, subject to your needs and preferences.
Flash Exposure Compensation (FEC) is very similar to exposure compensation that you may know already from shooting with ambient light.
When you use a flash, the flash is typically the dominating light source and if you find that the flash light is either too strong or too weak, the remedy is to adjust the light via flash exposure compensation.
Why not set the flash power manually? Indeed, that is an option, but if the lighting conditions change, then the manual settings need to be adjusted accordingly, and that requires a bit of adjustment. If you have the flash exposure compensation engaged and the light conditions change, the automated reading of the light will factor in the change. Just like exposure compensation, FEC pushes the automated reading of the light either above or below the automated reading.
The FEV on my Godox V860iii is here set to 1.3 stops of light.
You set the flash exposure compensation in stops of light. My Godox V860iii allow that up to 3.0 stops of light are added or subtracted.
You will typically use FEC when you are not happy with the automated exposure, but don’t want to switch to manual flash power. It can also be that you are happy with the exposure or find that it is just right, but want to make say a high key image where the exposure is deliberately adjusted.
Most cameras have a mechanical shutter consisting of two curtains. One that exposes the sensor and another that covers it (rear curtain).
If you go to a theater and see a show, the first thing you will see is also the last thing to see: the shoes of the actors (provided they are on stage!). That is not so smart in photography, as one end of the sensor would be more exposed than the other. By having two curtains – one that goes up like the curtain in the theater, and another that – in this metaphor – comes up the floor, you are certain all of the sensor gets the same amount of light.
The curtains move fast, but no matter how good technology you apply, it will take a bit of time to move the curtains. When we are talking shutter speeds at 1/8000th of a second for example, it takes – in relative terms – a long time to move the curtain. So to secure that the shutter is fast, the second curtain starts moving before the first curtain has revealed all of the sensor. And the faster the shutter speed, the closer to each other the two curtains will move. At very high speeds the curtains cover most of the sensor at any point of time and only a small crack of light is between them.
The max sync speed is the highest speed at which the camera at some point in time during the exposure reveals all of the sensor. Beyond that, the second curtain starts to move before the first curtain has revealed all of the sensor.
The max sync speed is a vital part of a cameras spec sheet if you want to use it for flash photography. When you go beyond the max sync speed, the flash needs to fire a series of flashes as the two curtains move across the sensor., also known has High Speed Synchronisation (HSS). If you shoot beyond the max sync speed without using HSS, you will get black bars or black areas in the image. The black areas are caused by the curtains on the move. HSS is very taxing on the flash and its battery as the flash has to fire several times in a very short while.
You can use your flash in stroboscopic mode to get several exposures in one image in one go. The flash fires a series of flashes while the shutter is open and this can capture motion and change in a way that illustrates how the subject is moving across the frame.
Here a pair of scissors are moved vertically while the shutter is open at 1/10th of a second and the flash fires 5 times.
Flash setting
The setup of the flash involves two parameters: the number of shots and the frequency of the shots, i.e. how quickly after each other they are fired. This needs to match the shutter speed so all the flash bursts are used in capturing the image.
Top left “RPT” is Nikon language for stroboscopic. The flash will here fire 5 times at a frequency of 50 flashes per second. And the flash power is set to 1/128th of full throttle.
Your flash will typically ask for these two parameters as “Times” and “Hz”, where the first is the number of times the flash is to fire. The Hz is less intuitive, but means the number of flashes fired in a second. So 50Hz would mean 50 bursts of the flash in a second. You can find the appropriate shutter speed by dividing “times” with “Hz”: In the example in the image above, the flash is instructed to give 5 flashes at 50Hz: 5/50 = 0.1 second shutter time.
Stroboscopic photography requires the flash to be in manual mode, so you determine the flash power. In terms of how much power the flash is to give, my advice is: as little as possible – around 1/128th is a good starting point and then you can work a bit up or down from there.
Camera settings
I usually shoot with my camera in manual mode and have camera settings so that the ambient light does not add to the exposure. In other words, if it was not for the flash, then the frame would turn out completely black. My camera settings are:
Base ISO, typically 100, but subject to the camera
Shutter speed: 0.1 – 1 second (but you can go much longer if you want to)
Aperture: Well closed down, say f/8 or higher.
You need to experiment with the settings – I typically adjust the aperture to get the right balance between eliminating ambient light and the power of the flash. Mind you that if the subject is far away from the flash, then the flash power needs to be increased significantly. My advice is to start out with simple cases like the examples I have shown in this post and then work your way towards more advanced scenes. You will find that shooting stroboscopic involves a lot of trial and error and that you will see a lot non-keepers. But keep going – it is a great feeling when you succeed!
Take care of your gear
Shooting stroboscopic is very taxing for both the flash and the flash battery, so you may find that the flash will stop working because a overload safety mechanism starts to engage. I recommend you consult the manual for your specific flash to see how many strobes it can handle before it needs to rest. And stay well below that limit just to protect your gear. Better safe than sorry.
Intentional Camera Movement
Many use the stroboscopic effect to capture motion, but as a twist you can also use it to capture intentional camera movement. In the example below I move the camera while the subject is very still!
Maybe difficult to see, but here the coffee mug is very still on my table while I move the camera during the burst of flashes.
High Speed Synchronization (HSS) is an automated feature whereby the flash fires a series of bursts to expose a single image. It is rather taxing for the the flash to work in HSS mode, as several bursts are needed per image and this puts a big demand on the battery in particular.
In many cases HSS is not necessary. If you are shooting at shutter speeds up to around 1/200th of a second or slower, then all is good. The problem comes when you go beyond the camera’s flash sync speed. You need to check the flash sync speed for your specific camera, but it is typically around 1/200th of a second.
Top red arrow: HSS is turned on as the transmitter shows. Lower red arrow: 1/6000th of a second shutter speed is only possible because HSS is turned on. When shooting with a transmitter, my Nikon Z6ii blocks shutter speeds beyond 1/200th if HSS is not activated.
When you shoot beyond the flash sync speed, the mechanical shutter in the camera will not expose the entire sensor at any point in time. The camera has 2 curtains, one that exposes the sensor and another that covers it (rear curtain). For slow shutter speeds, there will be a point in time when the first curtain has exposed the full sensor, but the rear curtain has not started to move yet. When you go beyond the flash sync speed, the rear curtain starts moving before the first curtain has revealed all of the sensor. So the first and rear curtain move in parallel across the sensor, and only expose a small fraction of the sensor at any given time.
If the flash is fired only one time when shooting beyond the flash sync speed, the light of the flash will only make it through to a fraction of the sensor and you get black bars in the frame. HSS makes sure to fire the flash several times as the two curtains move across the sensor and this way all of the frame gets light from the flash.
My Nikon Z6ii blocks me from going beyond 1/200th of a second in manual exposure mode when using a transmitter mounted on the camera, even when shooting in TTL mode. Only if I switch on HSS on the transmitter, will it allow me to go beyond 1/200th of a second. When the flash sits directly on the camera, the flash and camera based on the shutter speed figure out if HSS is needed and turn it on/off as appropriate without involving me in the decision.
Not all flashes has the ability to zoom, but some do, like speedlites from Godox or Yongnuo. The point is to send the light in the same direction as the lens is “looking”. Sending the light wide if the lens is zoomed in at a narrow field of view does not make much sense, and vice versa.
Here the flash is zoomed in at 200mm and the light only covers a small area of the wall.Here the flash is at 24mm and the light covers a good part of the wall.
The flash can follow the lens on the camera if in TTL mode and adapt the same zoom as the lens, provided it stays within the range the flash can follow (typically 20-200 mm). Notice that if the flash has the built in wide angle diffuser engaged, then the zoom is locked in its widest position.
You can also set the zoom manually just like you can set the flash power manually – in the images above I did just that to illustrate the difference between the two flash zoom positions without changing the zoom on the lens (the Nikon 24-70/4 S by the way).
