jar­gon buster

NPhoto - - Gear Zone -

Guide num­ber (Gn)

This is a mea­sure­ment of flash power, usu­ally quoted in me­tres at ISO100. Di­vid­ing the Gn by the aper­ture value gives the dis­tance the light will reach and still Il­lu­mi­nate the sub­ject suf­f­i­cently. At ISO100 a flash with a Gn of 60 will be able to il­lu­mi­nate a sub­ject 15m away at an aper­ture of f/4 (60÷4=15).

Ex­ten­sion cord

To en­able TTL flash me­ter­ing, a flash ex­ten­sion cord needs to be Nikon-ded­i­cated. Ex­am­ples in­clude the Nikon SC-29.

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