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Setting up your DSLR for the studio flash.



                                                    By Eugene Struthers

Studio flash set up.


The concept which I will try to outline in this months article relates to all studio flash units and digital cameras. As a guide and reference also consult your user manual that came with your newly purchased camera.


So where do we start? Well, the metering system of your camera of cause. The metering system within your digital camera is designed to work only with continuous lighting. So we need to apply a set of procedures for the photographer to use a flash.


These are the basic requirements to show the difference between continuous light and a studio flash.


1. Lens aperture

2. Shutter speed

3. White balance

4. Measuring light

5. Trigger the flash

The aperture


The aperture is the main control of your exposure. So you will need to set this to the appropriate f-number to produce the correct exposure. The larger the f-stop number, the smaller the aperture, the smaller the amount of light reaching the camera sensor.The smaller the f-stop number, the larger the aperture, the greater the amount of light reaching the camera sensor. The depth of field varies directly with the f-stop. The larger the f-stops number the deeper the depth of field, the smaller the f-stops number the shallower the depth of field. But you can also control and reduce the power in other ways. The most common method is by putting neutral density gels over your lights or a neutral density filter over your camera lens. The ISO on your camera can also be changed. By moving the lights further from your model you will reduce the effective power as well, but this can be a bad decision as changing the distance will affect the quality and the effect of the light.

The Shutter Speed


In continuous light, the shutter speed will be detrimental as the choice of shutter speed controls or prevents subject blur. It works in conjunction with the lens aperture to determine the correct exposure.By choosing a faster shutter speed, at about 1/2000, you will then be able to capture a topless model running through a castle. In this shutter speed in "Shutter priority" or "Aperture priority" mode, the digital camera will measure the light and set a wide aperture to create and ensure a perfect exposure.


When we use the studio flash, the main purpose of the shutter is to be fully open when we fire the flash. This can alter of cause if there is an extra light, or continuous light mixed with the flashlight. This won't affect the exposure, you will need to set your camera to manual mode and by setting the shutter speed to a speed at which the shutter will be fully opened.


A digital DSLR camera has a focal plane shutter, meaning a shutter plate right in front of the sensor. Simlar to two blinds, which open and close at different intervals. Just as the first one opens up and uncovers the sensor, the second blind lowers and closes. This tells us that at a slower shutter speed, the sensor is exposed to the light for a few seconds. But when we use a flash, the flash will need to fire at this precise moment to be in sync.


But this is where you will probably experience some problems. At faster shutter speeds the second "blind" plate starts to close way before the first one has reached the end of its full function. The affect of this is a moving plate "blind" that moves across and in front of the sensor, and this exposes a part of it at the time of taking the picture. As the plate "blind" has not fully performed its function correctly, part of the image will be covered by the shutter plate "blind" and your image will have a black line covering a section of it.


So without stating the obvious. The shutter speed will need to be slow enough and fully open at the time you trigger the flash. In order to capture a perfectly exposed image. Now, this varies from camera manufacturer and most manuals will advise you to input settings of about 1/250. Consult your user manual that came with your camera to verify the max sync speed for your camera. Once you know your cameras max sync speed, you will notice that your camera and flash units can't sync up properly if you are trying to shoot at a higher shutter speed. That is if you are using a dedicated hotshoe flash and not a studio flash. I would recommend setting your camera to a lower shutter speed of around 1/125.


It is important to remember that when shooting with a studio flash. You control the exposure by adjusting the aperture, not by adjusting shutter speed. Changing the shutter speed changes the ambient light exposure and this isn't exactly what we want. It is also worth remembering that the shutter speed has no effect on the subject blur either. In a studio set-up situation, the flash of light is very brief and it's the flash that freezes the movement, not the shutter speed.


The White balance


If you are using continuous lighting, you should set your white balance to auto, but this won't work with a studio flash as the camera can't measure the colour of the brief flash of light. It therefore is unable to measure the light from the flash or any other light from the surrounding area. You will need to then set the white balance manually. All digital Camera's will allow you to set a "custom white balance". Please consult your Digital camera manual on how to do this. When we set the white balance on our digital camera's we are in fact inputting the colour temperature of the light source and this will set the balance needed to obtain neutral colours.


Measuring light


If you are going to use your camera with continuous lighting in any of the camera settings other than manual. You will notice that your camera will measure the light reflected from the subject and will automatically set both the aperture and shutter speed if we had chosen the programme mode and the aperture that suits the shutter speed in "TV" Shutter-priority. The shutter speed that suits the aperture "AV" Aperture-priority. But these settings won't work with a studio flash because your camera's meter just can't measure for the brief flash of light. By changing your camera to Manual mode we are then able to input both the given shutter speed and aperture. We get both these figures by measuring for them with the use of a flash meter. We could keep checking the LCD preview screen or by checking the histogram to get the correct exposure. But this is time consuming and usually ends with poor results.


When we are ready to shoot with a studio flash, the most important things to do are to set the camera to manual mode and then the correct flash sync speed. Now each camera manufacturer has its own specifications on how to do this. To save time I will give you a generic setup. Apply this to your given camera model, and you should be fine. First set your main control dial to M to select the manual mode. Then turn the input dial behind the shutter button and set the flash sync speed to (1/200sec canon/ Nikon/ Olympus), set to (1/180 sec Pentax), set to (1/160 sec Sony). Once you have taken a flash metering reading press and hold down the +/- button then turn the input dial to set the aperture you require.

Trigger the flash


What do we mean by trigger the flash. This basically means a method by which a signal tells the flash to fire at a given time when the shutter blind plate is open. Now there are various ways in which this can be done. There is the traditional method. Whereby a photographer will plug a synch cable into both the camera and one of the flash heads. If your camera does not have a synch socket, you may choose to use an adapter that fits into your camera's hot shoe via a synch socket.


The next step beyond the flash synch cords is the infra-red transmitters. They are convenient and simply plug into the hot shoe of your camera and emit a low powered infra-red flash when fired. This signal is picked up by the slave sensor on your studio flash. It is advisable to purchase the some manufactured make for both the slave and transmitter. As they may not work if you mix different makes of products. There are however a few drawbacks to these. As long as you are in approximate distance in the line of sight between the transmitter on the camera and the sensor on the flash, as long as you are not too far from the studio flash, they won't work if the flash is behind the photographer or subject.


The most preferred method is the radio trigger. The radio trigger consists of a small transmitter which is plugged into the camera hot shoe and a receiver which is plugged into the studio flash. The transmitter will then emit a signal which is intercepted by the receiver. This signal is very strong and may trigger other flashes some distance away. Purchase one which offers a choice of about four channels. So that you may be able to change to a different channel if you are experiencing problems or interference. I won't go into too much detail in this article. As I have already covered this topic in-depth in previous issues here on Glamour-Photography. But in case you missed that issue please click on this link to read up on it.

         See you all

next month

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