Should Continuous Light or Flash Be Used in Your Photography?
Differences in Photography Lighting
I realize that for many photographers, it is not an either or for having these two items in your photography kit. Continuous lights have their place as well as flash light for various scenarios. Certainly if you do videography you will be using constant lighting as a flash will not be very useful for those projects.
I find each has their place in my photography kit. For instance, I like to do stop motion photography. That is only going to happen adequately with flash. However I like continuous lights for product photography because it allows me to see exactly what the image is going to look like before I snap the photo. It's frankly a minor distinction but I like the convenience of always-on lighting in those instances.
The basic difference in flash and continuous light for photography is that what you see is what you get with continuous light. What you see is not necessarily what you get with flash lights.
Flash typically provides more power and the ability to more accurately freeze high speed motion. We will discuss these differences and more below.
Continuous lighting in many cases does not give the power necessary to allow for a small aperture like f/11 or f/16. It would require lowering the shutter speed down or raising the ISO up to levels that would introduce grain into the image.
With a studio strobe you have the ability to overpower the ambient light. This will allow the photographer to effectively use a small aperture if desired.
To freeze motion when using a continuous light a very fast shutter speed is necessary. In order to get that fast shutter speed it will require a bright light.
A typical continuous light just won't have the power to allow for aperture, ISO and shutter speed values to stop the motion, particularly indoors. The image that is shot in this scenario would likely be blurred. You could increase the ISO which would allow for a faster shutter speed. Unfortunately the aperture would still be quite large. It just would not allow for enough motion freeze with the typical continuous light.
With a typical flash that is easily affordable for most photographers even just starting out, a camera setting of 200, with a shutter speed of 100 and an aperture of f/11 is quite sufficient to freeze an object in a studio.
Why does the flash produce better results? Because the only light the camera sees is the light from the flash. The short duration of the flash is the only thing the sensor collects of the image. The flash is turning on and off quickly, producing only the tiniest instant of a second from the motion.
There are continuous light units that are extremely portable. Some even sets upon the hotshoe of the camera. Many LED rind units are great for portrait photography. However, no continuous light unit will match a flash unit for portability AND power.
In fact to get even a fraction of the power of a flash the rind light has to be rather large even if it is considered portable. A flash unit can basically sit in the palm of one's hand.
A flash unit is going to require a couple of extra accessories to make the most of the unit. An external light meter will need to be used. With a constant light source you can easily use the camera's built-in light meter to set the shot.
A flash will need something to tell it shoot unless you are firing it from the hot-shoe of your camera. Typically off-camera flash provides the best results, particularly for portraits. Of course the continuous light is always on and does not need anything to tell it to generate the light.
One thing that photographers may not consider when deciding between strobe and continuous lighting is the cost of operation. Flash units are generally powered by batteries. The cost of batteries vary but are generally rather affordable.
Continuous lighting uses the power grid. Perhaps a lucky photographer's home is powered via wind or solar but typically there is a cost to using electricity. Continuous lights will need to be plugged into a power source. Additionally many of these units heat up considerably. There are many cool unit available, which can be costly. However the more light power it provides, the more it heats up the photography space requiring air conditioning to cool off the equipment as well as to keep the subject cool.
Changing the shape size and hardness of your light is easy to do with light modifiers. There are more options in this regard for strobes that there are for continuous lights. With flash systems you have the flexibility of everything from large umbrellas to using gels to change the color. Reflections and the like are better modified via a flash than with constant lights.
Continuous lighting that is less expensive tends to get very hot. These days most people prefer to go with LED but they are more costly and end up costing as much as a good flash unit. In general, flash gear is more expensive than always on lighting, but like everything else it really depends on the quality of the unit of choice.
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Choosing between continuous lighting and flash light is really a matter of taste and for what purpose the lighting is needed. Beginners tend to gravitate toward continuous lighting as it is easy to learn for those new to studio lighting. What you see is what you get. An advantage too, is the possibility to use it for videography. If freezing action is of photographic interest then a set of flash units will be required. Portability should be taken into account as a couple of flashes are easy enough to toss into a camera bag.
Either light source will enable the photographer, beginner or professional, to create good studio images. Eventually most photographers end up with a set of both sometime during their career of taking photos.