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1 Available flash modes
118
v Aperture to set on the lens and effective f-number
Effective f-numbers of close-up lenses such as Micro-NIKKOR lenses vary, while brightness
of image on film decreases when reproduction ratio increases. The relationship between the
reproduction ratio and the effective f-number is:
Fe = F (1 + M)
where Fe = Effective f-number (actual lens speed)
F=Aperture to set on the lens
M=Reproduction ratio
In TTL auto flash operation, the aperture value appearing on the LCD panel or in the
camera’s viewfinder is the effective f-number when a Micro-NIKKOR lens is mounted on the
camera.
M (manual) mode
In Manual flash photography, you select the aperture and flash output level. In
this way, you can control the exposure and flash shooting distance when
shooting subjects where the correct exposure is difficult to obtain in the TTL auto
flash mode.
Available flash output level
In close-up flash operation: M1/1 to M1/64.
In Commander flash operation: M1/1 to M1/128.
In Repeating flash operation: M1/8 to M1/128.
Determining the aperture and flash output level in the M (manual) mode
In the Manual mode, use the following guide number and the equation to
calculate the aperture, flash output level, and shooting distance to obtain the
correct exposure.
• The guide number (GN at ISO 100; m/ft) indicates the amount of light generated by the
flash. The larger the number, the greater the flash output.
To calculate the correct aperture
Calculate the correct aperture by using this equation:
f/stop (aperture) = Guide number (GN at ISO 100; m/ft) x ISO sensitivity factor ÷ Shooting
distance (m/ft)
• Set the same aperture for both the SU-800 and the camera or lens.
Guide number of the SB-R200 is 10/33 (ISO 100, m/ft)
ISO sensitivity factors
For sensitivities other than ISO 100, multiply the guide number by the factors
shown in the table below.
ISO 25 50 100 200 400 800 1600 3200 6400
Factors 0.50.7111.422.845.68
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