1. Distance to Subject:
* Closer Distance: Smaller beauty dishes are ideal. They produce a more contrasty, focused light, which can be great for close-up portraits and beauty shots.
* Farther Distance: Larger beauty dishes become necessary to maintain a soft, flattering light. As you move the light further away, the smaller dish's light becomes harder and less flattering.
2. Type of Portrait:
* Headshots/Beauty: Smaller to medium-sized beauty dishes (16-22 inches) are often preferred. They provide the focused light and can emphasize features, especially when used with a modifier like a sock diffuser.
* Waist-Up/Full-Body: Medium to larger beauty dishes (22-32 inches) are better suited. They create a wider spread of light, covering the subject more evenly. For full-body shots, you might even consider using a large beauty dish in conjunction with other lights to fill in shadows.
3. Desired Light Quality:
* More Contrast/Definition: A smaller beauty dish, or a larger one used without a diffuser, will give you more defined shadows and a more dramatic look. It's excellent for emphasizing bone structure and textures.
* Softer, More Flattering Light: A larger beauty dish, or a smaller one used with a diffuser (sock or grid), will produce softer shadows and a gentler light, generally considered more flattering for portraits.
4. Studio Space:
* Small Studio: A smaller beauty dish is easier to manage and position.
* Large Studio: You have more flexibility in terms of size and placement.
5. Power of Your Strobes:
* A larger beauty dish will require more power from your strobes to achieve the same light output as a smaller one. Make sure your equipment can handle the increased demands.
General Size Recommendations (Keep in mind these are starting points and can be adjusted based on your specific needs):
* 16-22 inches: Great for headshots, beauty shots, and close-up portraits. More contrasty light.
* 22-28 inches: A versatile size for waist-up portraits and headshots. A good balance between soft light and definition.
* 28-32 inches+: Best for full-body portraits or when you need a wider spread of soft light.
Key Considerations and Additional Tips:
* Diffusers: Using a diffusion sock (the fabric cover that goes over the beauty dish) softens the light and reduces contrast. This is often a good choice for portraits where you want a more flattering look.
* Grids: Grids control the spread of light, making it more directional and preventing spill. They can be useful for isolating your subject and creating more dramatic shadows.
* Silver vs. White Interior:
* Silver: Produces a slightly harsher, more specular (mirror-like) light with higher contrast.
* White: Creates a softer, more diffused light with lower contrast. More forgiving on skin. White is generally preferred for beauty dishes.
* Testing: The best way to determine the right size is to experiment with different sizes and modifiers. Take test shots and evaluate the results.
* Budget: Beauty dishes can range in price. Consider your budget when making your decision. Quality of materials impacts the lifespan and light output.
In summary, there's no single "perfect" size. Start with a 22-inch or 28-inch beauty dish if you're unsure, as it's a versatile size that can be modified with diffusers and grids. Think about the type of portraits you'll be shooting most often and the style of light you want to achieve. Good luck!