Stevedevil
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Ok So I am looking at purchasing some studio flash equipment, I have posted a thread before and had some really good responses, but the thread kinda lost its way.
SO I started reading up a lot on studio flash equipment and most equipment have references to Guide Numbers
And found some usefull reading
Understanding Flash Guide Numbers
The guide number of a flash is a measure of its light output. The higher the guide number, the greater the intensity of the flash. Guide numbers are determined experimentally. A flash unit and subject are set up and exposures are made at a variety of f-stops. When the best exposure is determined, the guide number is calculated from the distance and the f/stop used as follows:
Guide numbers are usually given for ISO 100 speed film. Faster ISO settings will require less light so you can shoot at a greater distance. For this reason, you need a different guide number for each ISO setting. Increasing the ISO film speed by a factor of 4 will double the guide number. When film speed doubles, the guide number changes by a factor of 1.4X; when film speed is halved, the guide number changes by a factor of 0.7X.
In addition to being an indicator of a flash’s power, guide numbers also can be used to calculate aperture settings and subject distances when using the camera and flash on manual mode as when you are using a flash not designed to work with the camera.
n It is the flash-to-subject distance that you use, not camera-to-subject. This is the same when using on-camera flash but not when using flash on a cable or a slave flash.
n Guide numbers are usually given for both feet and meters so be sure you use the right one in your calculations. The differences can be substantial. For example, a guide number of 12, when using meters as a unit of measure, is the same as a guide number of 39 when using feet. Conversions between a guide number for feet and a guide number for meters are:
If so Are the higher Guide Numbers "BETTER" than lower when it comes to choosing which equipment.
Also would lens f stop be an advantage with lower Guide Numbers as have just got a 50mm f1.8
SO I started reading up a lot on studio flash equipment and most equipment have references to Guide Numbers
And found some usefull reading
Understanding Flash Guide Numbers
The guide number of a flash is a measure of its light output. The higher the guide number, the greater the intensity of the flash. Guide numbers are determined experimentally. A flash unit and subject are set up and exposures are made at a variety of f-stops. When the best exposure is determined, the guide number is calculated from the distance and the f/stop used as follows:
GN = f/stop x Flash-to-subject distance
More powerful flash units with higher guide numbers have a greater range, have faster recycle times, and make bounce flash more effective.Guide numbers are usually given for ISO 100 speed film. Faster ISO settings will require less light so you can shoot at a greater distance. For this reason, you need a different guide number for each ISO setting. Increasing the ISO film speed by a factor of 4 will double the guide number. When film speed doubles, the guide number changes by a factor of 1.4X; when film speed is halved, the guide number changes by a factor of 0.7X.
In addition to being an indicator of a flash’s power, guide numbers also can be used to calculate aperture settings and subject distances when using the camera and flash on manual mode as when you are using a flash not designed to work with the camera.
- To calculate the f/stop needed, divide the guide number by the distance to the subject.
- To calculate the maximum flash range, divide the guide number by the selected or largest f/stop.
n It is the flash-to-subject distance that you use, not camera-to-subject. This is the same when using on-camera flash but not when using flash on a cable or a slave flash.
n Guide numbers are usually given for both feet and meters so be sure you use the right one in your calculations. The differences can be substantial. For example, a guide number of 12, when using meters as a unit of measure, is the same as a guide number of 39 when using feet. Conversions between a guide number for feet and a guide number for meters are:
From meters to feet: GN(ft) = GN(m) x 3.3
From feet to meters: GN(m) = GN(ft) x 0.3
The 995 has a guide number of 10 (m) or 33 (ft) at ISO 100. Its lens has a maximum aperture of f/2.6. Its ISO range is from 100 to 800. Using these characteristics of the camera, you can calculate the following:From feet to meters: GN(m) = GN(ft) x 0.3
- The maximum flash range in feet at ISO 100 and f/2.6 is: 12.7 feet
- The maximum flash range in feet at ISO 800 and f/2.6 is: 34.8 feet
- The maximum flash range in meters at ISO 100 and f/2.6 is: 2.6 meters
- The maximum flash range in meters at ISO 800 and f/2.6 is: 7.1 meters
If so Are the higher Guide Numbers "BETTER" than lower when it comes to choosing which equipment.
Also would lens f stop be an advantage with lower Guide Numbers as have just got a 50mm f1.8