Arguments for Using Flash:
* Better Image Quality (Generally): Flash provides a burst of bright, consistent light, allowing you to use lower ISO settings. This results in less noise (grain), sharper images, and more accurate colors.
* Controlled Lighting: You can directly control the direction, intensity, and color temperature of the light, allowing for creative effects and better exposure.
* Freezing Motion: Flash has a very short duration, effectively freezing movement, even in dimly lit environments. This is especially useful for capturing active subjects like children or pets.
* Reduced Blur: Using flash eliminates the need for slower shutter speeds, which can lead to motion blur from camera shake or subject movement.
Arguments for Using High ISO:
* More Natural Look: Avoiding flash often produces a more natural-looking image that preserves the existing ambient light.
* Faster Shooting: You don't need to wait for the flash to recycle, allowing for quicker shooting and capturing candid moments more easily.
* Less Obtrusive: Flash can be disruptive and draw attention. Shooting with high ISO is more discreet.
* No Harsh Shadows (Potentially): Direct flash can create harsh shadows, while relying on ambient light avoids this issue.
* No Special Equipment: You don't need an external flash unit; you can rely on your camera's built-in flash or, even better, natural light.
Factors to Consider When Deciding:
* Subject:
* People/Pets: Flash can be great for freezing motion and providing better light. However, direct flash can cause red-eye and unflattering shadows. Bouncing flash or using a diffuser can improve results.
* Still Life/Landscapes: High ISO may be sufficient, especially if you can use a tripod to eliminate camera shake.
* Available Light:
* Brightly Lit Indoors: High ISO might be sufficient, especially if the light is evenly distributed.
* Very Dark Indoors: Flash is likely necessary for decent exposure and image quality.
* Desired Aesthetic:
* Natural, Ambient Look: High ISO is preferred, even with some noise.
* Clean, Well-Lit Look: Flash is often the better choice.
* Equipment:
* Good External Flash: An external flash unit with tilt/swivel capabilities and the ability to control power output offers far more flexibility than a built-in flash.
* Fast Lens: A lens with a wide aperture (e.g., f/1.8, f/2.8) allows more light to enter the camera, enabling lower ISO settings.
* Image Stabilization: Image stabilization in your camera or lens can help you shoot at slower shutter speeds without motion blur.
* Comfort Level: Some photographers are comfortable using flash and understand how to control it effectively. Others prefer the simplicity of high-ISO shooting.
Practical Tips:
* Balance Ambient Light with Flash: Don't just blast your subject with full-power flash. Reduce the flash power and let some of the ambient light contribute to the exposure for a more natural look.
* Bounce Flash: Aim your flash at a ceiling or wall to diffuse the light and create softer, more flattering illumination.
* Use a Diffuser: A diffuser softens the light from the flash and reduces harsh shadows.
* Edit Your High-ISO Images: Use noise reduction software to minimize grain while preserving detail.
* Consider Prime Lenses: Prime lenses (fixed focal length) often have wider apertures than zoom lenses, allowing for better low-light performance.
* Use a Tripod: A tripod allows you to use slower shutter speeds without camera shake, enabling lower ISO settings.
In summary:
* Start with the ambient light first. Try adjusting your aperture, shutter speed, and ISO to see if you can achieve a satisfactory exposure without flash.
* If you need more light and want the best image quality, use flash (with diffusion or bouncing). Learn to control your flash for optimal results.
* If you want a natural look, don't want to be intrusive, or can't be bothered with flash, use a high ISO (and a fast lens if possible). Be prepared to accept some noise and potentially softer images.
Experiment with both approaches to find what works best for your specific situation and preferences. There is no single "right" answer.