Modern Classic SLRs Series :
Nikon SB-15/SB-17 - Operational Manual - Part IV

3) Determining the exposure For Through-the-Lens (TTL) Operation

With the SB-15 attached to the Nikon FA, FE2 or FG or the SB-17 onto the Nikon F3 bodies, you can utilize the TTL mode of operation for completely automatic through-the-lens exposure control. After setting the correct film speed, setting the mode setting knob at either N or W, and adjusting the shooting mode selector to TTL, use the exposure calculator dial to determine which f/stop to set on your lens. On the dial there are 8 f/stops ranging from f/2 to f/22. Each f/stop determines the usable distance range in which you can obtain the correct automatic exposure. These ranges are indicated by a series of color-coded lines above the distance scale.

Note: Nikon advised the usable film speed range for TTL flash photography Is restricting within film speed of ASA/ISO 25 to 400 which I think there should have more workable room than this.

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Example: If you are using ASA/ISO 100 film and select f/4.0, the auto shooting range is indicated by an orange line.

Thus, you can take pictures of subjects located between 1 and 6.2m (approx. 3 and 20 ft.) away from the camera. However, if you choose f/8 (indicated by a blue line, the auto shooting range is 0.7 to 3.1m (approx. 2 to 10 ft.).

The larger the aperture you select, the greater the maximum shooting distance and the smaller the aperture the less the maximum shooting distance. So, when choosing an aperture, make sure that your subject is within the auto shooting range. If the subject distance remains the same, the larger the aperture you select, the less the depth of field in the final photograph; however, the recycling time is shorter. On the other hand, the smaller the aperture, the greater the depth of field, but the longer the recycling time. Therefore, in choosing an f/stop, all these factors should be taken into consideration. If a short recycling time is preferable, use f/2.0; if greater depth of field is desired, use f/16 or f/22.

The auto shooting ranges for TTL photography are shown in the following table. If the flash ready-light blinks after you shoot your picture, this indicates that the flash has fired at full light output. In this case. check your flash to subject distance by referring to your lens' distance scale and the flash calculator dial. If your subject distance was farther than the maximum range indicated for your selected f/stop, then you should move closer or use an f/stop appropriate for your subject's distance.

TTL AUTO shooting range with Nikon SB-15/SB-17 flash:

f-stop

Film sensitivity (ASA/ISO)

AUTO shooting range
m (ft) second values is attached with SW-6

400

200

100

50

25

2

-

-

-

-

4-15 (13 -49); 2.8-15 (9.2 -49)

2.8

2

-

-

-

3 - I 5 (10 - 49); 2-12 (7 -39)

4

2.8

2

-

-

2-12 (7-39); 1.4-8.8 (4 -29)

5.6

4

2.8

2

-

1.4 - 8.8 (4 - 29); 1.0-6.2 (3 -20)

8

5.6

4

2.8

2

1.0 - 6.2 (3 - 20); 0.7-4.4 (2.6 -14)

11

8

5.6

4

2.8

0.8-4.4 (2.6- 14.4); 0.6-3.1 (2.3 -10)

16

11

8

5.6

4

0.7-3.1 (2.3- 10.2);0.6-2.2 (2 -7.2)

22

16

11

8

5.6

0.6 - 2.2 (2.0 - 7.2); 0.6-1.5 (2 -4.9)

-

22

16

11

8

0.6 - 1.5 (2.0 - 4.9); 0.6-1.1 (2.0 -3.6)

-

-

22

16

11

0.6 - 1.1 (2.0 - 3.6); 0.6-0.8 (2.0 -2.6)

\Note: Because the voltage of batteries decreases with use, the guide number might also be reduced slightly The flash output of the SB-15/SB-17 depends on the shooting situation and the reflectivity of the subject Because of these factors, the ready light may blink even if the subject is within the auto shooting range.

ttlexpose.jpg
TTL exposure compensation. When shooting TTL auto flash pictures with the Nikon FA, FE2 or FG (Or in the case of F3/SB-17 or SB-15 with AS-17 coupler on F3), you can use the camera's exposure compensation dial to make intentionally over- or underexposed photographs.
dialasa25.jpg

Turn the dial in the + direction to make an overexposed picture and turn it in the opposite direction ( - ) to make an underexposed one. The TTL auto shooting range changes according to the amount of exposure compensation. Exposure compensation can also be set and fooled the camera meter (Or sensitivity circuit) by altering the Film speed ASA/ISO setting ON YOUR CAMERA

For example, if you are using ASA/ISO 100 film with the exposure compensation dial set at +2 (overexposure), reset the exposure calculator dial of the SB-15 to ASA/ISO 25 as shown in the following table. Then the correct TTL auto shooting range to match the compensated amount will be shown on the exposure calculator dial.

Film speed in use /Exposure compensation value

+ 2

+ 1

0

-1

-2

25

-

-

25

50

100

50

-

25

50

100

200

100

25

50

100

200

400

200

50

100

200

400

-

400

100

200

400

-

-

For Automatic (A) Flash Operation

With Nikon cameras, including the FA, FE2 and FG you can obtain the automatic exposure by setting the SB-15's shooting mode selector to A and the A1/A2 switch to either A1 or A2. As soon as the SB-15 is turned on, the appropriate LEDs light up on the flash unit indicating your selection. You'll notice that on automatic, there is a choice of two f/stops which are indicated by the blue and red aperture indicator bands at the bottom of the calculator dial. Nikon advised the effective working range for film speed in AUTO mode is from ASA 25 to ASA 880, one stop higher than the TTL mode.

autof4.jpg autof8.0.jpg
Example: If you are using ASA/ISO 100 film, you can select either f/4 or f/8. Just as in the TTL mode, the depth of field, maximum shooting distance, and recycling time depend on the f/stop selected. Regardless of the film speed and the corresponding f/stop available at A1 or A2, the auto shooting range is fixed and is shown in the following table:

Auto shooting range Unit: Unit in m (ft)

Selector mode

Normal usage

Using wide-fiash adapter SW-6

A1 (blue index)

0.6-3.1 (2 - 10)

0.6-2.2 (2-7)

A2 (red index)

0.6-6.2 (2-20)

0.6-4.4 (2-14)


For Manual (M) Flash Operation

Example: With ASA/ISO 100 and a subject 6m (approx. 20 ft.) away, the aperture is approx. f/4.

After setting the ASA/ISO film speed onto the exposure calculator dial, focus on the subject; then look at the lens and read off the focused distance to determine exactly how far away the subject actually is. Now, read off the f/number which appears directly above the camera-to-subject distance on the dial. Then, set this aperture on your lens.

Without referring to the exposure calculator dial, you can also determine the f/stop by using the following old trusty equation that has worked for one century since the advent of flash unit... i.e. :
f/stop = guide number of the flash in use divided by flash-to-subject distance. For an example, with ASA/ISO 100 film and meters, the SB-15's guide number is 25. If the subject is 3m away, divide 25 by 3 to get approx. f/8. With ASA/ISO 25 film and feet, the guide number is 41. Therefore, if the subject is 10 ft. away, divide 41 by 10 to get approx. f/4.0.

Shooting distance Unit in meter (ft.)

Aperture

Normal

With wide Flash adapter (SW-6)

f/2

12 (39)

8.8 (29)

f/2.8

8.8 (29)

6.2 (20)

f/4

6.2 (20)

4.4 (14)

f/5.6

4.4 (14)

3.1 (10)

f/8

3.1 (10)

2.2 (7.2)

f/11

2.2 (7.2)

1.5 (4.9)

f/16

1.5 (4.9)

1.1 (3.6)

f/22

1.1 (3.6)

0.8 (2.6)


To determine the guide number at various film speeds, use the following table:

Guide Number at Various Film Speeds: meter (ft.)

Mode Selector

N (Normal)

W (With wide Flash adapter SW-6)

M (Manual)

MD Mode

M (Manual)

MD Mode

ASA/ISO

880

71 (233)

20 (72)

50 (164)

14 (46)

400

50 (164)

14 (46)

35 (115)

10 (33)

200

35 (115)

10 (33)

25 (82)

7 (23)

100

25 (82)

7 (23)

18 (56)

5 (16)

50

18 (56)

5 (16)

13 (41)

3.5 (11)

25

13 (41)

3.5 (11)

9 (30)

2.5 (8.2)


For motor drive (MD) operations

Be sure to set the shooting mode selector as well as the mode setting knob at MD. Then you're ready to shoot continuously with a motor drive firing at up to 3.8 frames per second for up to four flash pictures in sequence. Because the light output is manually controlled at this setting, you must compute the exposure manually using the exposure calculator dial or the guide number formula. But remember the guide number is now 7 (ASA/ISO 100 and meters) or 11 (ASA/ISO 25 and feet). When taking rapid sequence flash shots in this way, use the freshest possible batteries and don't begin the continuous sequence until the ready-light has been lit for approx. 30 seconds. (If you start to shoot just after the ready-light lights up, it may be impossible to take four pictures in succession.)

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Note: When using the Wide-Flash Adapter SW-6, you cannot read off the correct f/stop from the exposure calculator dial. In this case, calculate the exposure manually using a guide number of 5 (ASA/ISO 100 and meters) or 8 (ASA/ISO 25 and feet)

Example: With ASA/ISO 100 film and the subject located 1.3m away, the correct aperture is approx. f/5.6. With ASA/ISO 25 film and a subject 2 feet away, the correct aperture is f/5.6. Warning: As the power output will be greatly reduced in this mode, it is always advisable to use higher speed film type and within proper flash working range, too distance of a subject usually will resulted in poorly exposed negatives.

Flash Ready Light/Open Flash Button

Built into the back of the SB-15 is the combination ready-light/open-flash button which is labeled "FLASH." After the ON/OFF switch is turned on, this button lights up to indicate that the SB-15 is recycled and ready to fire. At the same time, the ready light inside the viewfinder of the Nikon FA
*, FE2*, FG*, FM2, FM2n models, F3-series, FE, FG-20, or EM camera also lights up. Thus, without removing your eye from the eyepiece, you can tell when the flash unit is ready for the next shot. Both ready-lights also blink to warn you when the flash unit fired at its maximum output, indicating that the light was insufficient for correct exposure.

* The meter must first be turned on by lightly depressing the shutter release button.

SB-17back.jpg
User tips: The same button can be used to fire the flash unit manually without having to trip the camera's shutter. In this manner, you can create multiple-exposure "stroboscopic" effects or paint the scene with light by firing the flash unit repeatedly with the camera set at "B." (or "B" or "T" in the case for Nikon F3).

The open-flash button is also useful for test-firing the SB-15 to determine whether the illumination from the flash is sufficient for proper exposure in the regular (non TTL) automatic mode. With the shooting mode selector at A and the A1/A2 switch set to either A1 or A2, push the "FLASH" button; if it starts blinking, then you know the subject is too far away.

In this case, switch to A2 if you were using A1 or move closer to the subject. Please note that it is impossible to ascertain beforehand the correct TTL automatic exposure when using the Nikon FA, FE2 or FG with the SB-15 (Or F3 with the SB-17, SB-15 with AS-17 on F3 body) set at the TTL mode.

Notes: 1) With alkaline-manganese or manganese batteries, if the ready-light takes more than 30 sec. to light up, you should replace the batteries with a fresh set. If you're using NiCd batteries and the ready-light takes more than 10 seconds to come on you should recharge the batteries. 2) The ready-light will light up when the SB-15/SB-17 is recycled to approx. 80% full capacity. Therefore, it is a good idea to wait for a few more seconds when shooting subjects located at the far limit of the auto shooting range. 3) The white plastic card found inside the Nikon FM, FE2 or FG camera not only serves to protect the shutter curtains, but also can be used when making test shots with the SB-15. Without film or the white plastic card in place, the ready-lights blink even if the camera and the SB-15 are at the correct setting.

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Modern Classic SLRs Series :
Nikon SB-15/SB-17 - Operational Manual - Part IV

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