FAQ'S

What is the difference between professional & broadcast lenses?
There are two areas to consider, the lens barrel and the servo Package.

Lens barrel
• The broadcast lens has better quality coatings resulting in reduced flare and ghosting.
• Higher quality of mechanical components.
• Improved corner resolution in broadcast lenses
• Reduced corner resolution and chromatic aberrations on broadcast lenses.
• Reduced Minimum Object Distance on broadcast lenses.
• Ramping of the F No. when zooming in, will start later and finish at a lower F No. on a broadcast lens.
• 2x extenders are normally standard on broadcast lenses.
• Typically broadcast lenses are much wider.
Servo Package
• Higher speed servo motors (ie pro lenses are about 3 seconds end to end and broadcast lens are about 0.7 seconds end to end.
• Accuracy of the servos is higher in broadcast lenses, in other words the ability to zoom in extremely small steps so no stepping can be seen.
• Electronic end stops on the broadcast lens on zoom & focus.

How do I correctly back focus my lens?
It is best done using a Siemens Star Chart and the iris full open. It may be necessary to use the ND filters to achieve this.
1. Place the Siemens Star Chart at the distance recommended by the manufacturer. Typically for Fujinon ENG style lenses this distance is 3 meters and for box lenses it is 7.5 metres.
2. Zoom to the tele end and adjust the normal focus.
3. Zoom to the wide end and adjust the flange focus.
4. Repeat steps 2 & 3 a number of times until there is no difference.

What is ramping and why do lenses ramp?
Ramping is when the diameter of the lens glass is not larger enough for a lens to maintain the minimum F No. and therefore it will increase in a linear function. As a result you will see in a lens specification some thing similar to “1:1.8 (4.5 to 41mm), 1:2.6 (59mm)” which means that this lens will hold the F No. of 1.8 until 41mm and than ramp to F 2.6 when the lens is zoomed to 59mm. When lenses are designed there is a compromise between size and weight and performance. There are lenses which do not ramp, like the Fujinon Cine lens HAe12x9.5 which has a flat F1.6 across the whole range but the weight is 10kg.