1Available flash modes

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) 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

0.5

0.71

1

1.4

2

2.8

4

5.6

8

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