The first reason someone thinks they need a speedlight is typically a low light situation where you‘ve hit the limits of iso/aperture/shutter speed. Either because your gear is hardware-limited, or because you may need to stop down and use a high shutter speed (e.g., macro shooting for DoF/camera shake).
In respect to this, what is the difference between a speedlight and flash?
A speedlight, also called a flashgun or hot shoe flash, is an add-on flash. It can act as an on-camera flash and then as off-camera lighting. Like a strobe, a speedlight emits a short burst of light. The photographer can control the intensity of that light.
Secondly, do I need flash for outdoor photography? The majority of the time, shooting outdoors doesn’t require firing a flash, even in the shade, as the sun does most of the hard work for you. If you have a subject that you can move, try to get them to change their positioning so that the sun hits them from the side rather than from behind.
Keeping this in view, do I need a flash?
Why You Should Own an External Flash. Almost every modern camera comes with an on-board flash, even the higher-end DSLRs. The onboard flash can also be used in situations where you can’t turn the ISO up high enough (especially if your camera produces grain at high ISOs). But that’s where its usefulness ends.
Should I buy a flash for my DSLR?
Outdoors flash isn’t as essential. Its good for backlight subjects and can be used to create interesting effects, stop motion in less than great light outdoors, but the range of the light is rather limited. You don’t NEED and external flash but if you want your images to stand out you will probably want one.