Guide Numbers and the FJ80Updated 6 days ago

Why don't the FJ80 and FJ80 II report a guide number?

Similar to other roundhead flashes, the FJ80 and FJ80 II flashes do not list a guide number in their specifications. This is because regular speed lights and round head flashes deliver light in different ways. Standard speedlights with rectangular Fresnel lenses focus light into a beam that corresponds to

How do standard speed lights use guide numbers?

Using a Fresnel lens, standard speed lights concentrate light into a rectangular frame that resembles the form of the film plane or sensor on a camera. The guide number shows the effective range of the flash, which is determined by its focussed beam and rectangular light shape. It is useful to compare the power and effectiveness of different standard speed lights.

How does the FJ80's round head affect light output?

With 80W of power (as opposed to the usual 65W of high-end OEM speed lights), the round head of the FJ80 distributes light more evenly over a circular region. This shape simulates a smoother, more natural light distribution, more in line with real-world lighting situations, and is perfect for use with spherical modifiers. Because of this, guide numbers do not directly compare to round head flashes like the FJ80, even if they can be helpful for comparing regular speed lights..

What advantages come with using a flash with a round head like the FJ80?

Improved Light Quality: 

Round heads are great for round or octagonal softboxes. The FJ80's round head design creates a more natural and even light distribution. As a result, the subject is illuminated in a more consistently.

Greater Output: 

The FJ80 is an 80ws speedlight and will produce more light than a conventional speedlight due to its higher watt-second power, especially when combined with round modifiers.

Versatile Use:

The round head can be modified with a long throw reflector to deliver more light over longer distances, making it suitable for a variety of shooting scenarios.

When should I use a standard speed light over a round-head flash?

Without the need for extra modifiers, standard speed lights may be more effective at producing maximum output at longer distances due to their longer Fresnel focusing range and rectangular light pattern. They are an excellent option when you need to distribute light in a targeted region, particularly when the light needs to go farther.