Flash Q&A

Send Thom a question by clicking here: QandA
last update: August 1, 2003

Question: If I set slow sync as you suggest in answers on the many online forums you visit, won't I be opening myself up to blurred shots when the shutter speed gets significantly below 1/60?

Answer: Yes and no. When you shoot with flash, there are two exposures going on: the flash exposure on the subject and the background exposure. If flash is the main source of light, a stationary subject lit by it should always be sharp, as the slowest Nikon flash duration is about 1/830 of a second. The background, however, very well may go soft or get blurred by poor handholding technique or subject movement. Many photographers have learned to use this to their advantage--there's one style of flash that uses very long shutter speeds and panning/zooming/tilting to purposefully blur the background yet still use the flash to "freeze" the subject.

Question: I have been told that in macro I can set the camera on MANUAL, set the aperture for desired DOF, and set the shutter inside the flash sync range, set the flash unit on TTL, and fire away. And that I will get a correct exposure. In fact I've done this and I DID get a correct exposure for the foreground subject (background went black). How is this possible? I thought that TTL worked because the camera knew to shut off the flash unit when the correct exposure had been achieved (when the flash unit had delivered enough light for a correct exposure). But if the camera is in manual, I thought all metering was disengaged and to my way of thinking I ought to get an overexposure every time, with the flash gun delivering its full charge. I'd use this technique more if I knew what was going on.

Answer: It's not quite that simple, as there is an aperture adjustment you should do at close distances (see page 74 of the Nikon Flash Guide). However, the answer to your question of how this is possible is simple: Nikon bodies have separate exposure and flash meters. In Balanced Fill-Flash modes, both meters are used to determine flash output; in Standard TTL (which is what you set when you switched to Manual exposure mode on your body), only the flash meter is active in determining flash amount.

Question: I seem to be making fill flash harder than it is! What's a good simple rule of thumb to use, during a wedding situation. I'm a little confused about the two seperate settings (camera, flash) working together to ensure good exposure.

Answer: Here's what I teach students as a base in my workshops (you can get more elaborate, but this addresses the main issues you face with fill flash on Nikon bodies):

  1. Camera set to Aperture-preferred exposure mode. Gets rid of aperture limitations in Program mode.
  2. Camera set to Slow Sync or Rear Sync. Gets rid of the bottom end shutter speed limitation at 1/60.
  3. Flash set to Standard TTL (press Mode button on flash until only TTL shows on flash LCD). Gets rid of camera-induced flash compensation level, which is unknown.
  4. Flash set to the fill level you want via flash exposure compensation, typically -1.0 stop for people, or Galen Rowell's "magic" -1.7 value for outdoor scenic fill. Allows you to control the fill level rather than the camera.

Question: I have a Ninon F801 (N8008). If I use AI extension tubes (with no electric contact inside) or an AI reversing ring, will the camera retain the TTL flash exposure?

Answer: It should be in your camera manual, but the answer is that when you put on a lens (or an extension) without a CPU, the N8008 can only perform either center-weighted fill flash or spot fill flash (both TTL, but note that the method used to calculate exposures changes), based upon what the metering method is. The camera also has to be in Aperture or Manual exposure mode.

Question: I shoot underwater with a TTL strobe that doesn't allow you to set flash exposure compensation. How do I set fill flash with this set up?

Answer: Let's assume that you have an N80 body in an underwater case and are using underwater TTL strobes. Here you could set flash exposure compensation from the N80 body (assuming the case let you access that control). I'd tend to set the N80 to Standard TTL if I wanted to fiddle with flash levels, though, as in balanced fill-flash modes you don't know what compensation the camera is already adding (i.e., you'll only get repeatable results with Standard TTL).

With an F100 in an underwater case, you can't set flash exposure compensation from the body, and you've indicated that your flash doesn't support it, either. The normal method of "fooling" the camera in that case is:

  1. Camera is put in MANUAL exposure mode.
  2. Set your exposure, as usual. (Your ambient exposure is now locked in)
  3. Change the ISO value to vary the flash level. If the film's ISO is 100 and you wanted -1 stop fill flash, you'd set an ISO of 200 (ISO 200 is one stop beyond 100). If you decrease the ISO, you increase the flash (+ compensation), if you increase the ISO you decrease the flash (- compensation). The F100 sets ISO values in 1/3 stop increments, so you have plenty of fine tuning available.
  4. For each new shot, reset the ISO back to the original value and go back to Step 2.

The reason why the camera has to be in manual exposure mode is that you don't want the ambient exposure you set in Step 2 to change when you manipulate ISO values in Step 3 (in any of the other exposure modes, the camera would just adjust everything to the new ISO, and the ambient/flash balance would be preserved). Again, I'd use Standard TTL mode instead of balanced fill-flash TTL, as that way you'll get repeatable results.

You'll find that once you adapt to this method, it really isn't that complicated and only takes a extra moment to perform (well, it might be difficult and slow to do if you're in nitrogen rapture on a deep dive--even simple operations seem to get difficult at great depths ;~). Personally, I'd make me a little laminated step-by-step list to attach to the back of the camera case or strobe and just follow the instructions each time I want to take a shot, something like:

1. ISO to normal value. (100)
2. Set exposure manually.
3. Vary ISO for fill. (Table below)
100 -> 64 = +.7 stop flash
100 -> 80 = +.3 stop flash
100 -> 125 = -.3 stop fill
100 -> 160 = -.7 stop fill
100 -> 200 = -1 stop fill
100 -> 250 = -1.3 stop fill
100 -> 320 = -1.7 stop fill

That's probably the only values that are useful, by the way. Adjust accordingly for whatever ISO value film you shoot regularly.

Question: I have a Nikon N6006 that is about 8 to 9 years old. All of the sudden the built-in flash stopped working. The shutter works and the in-camera flash signal functions. But the shutter acts as if the flash is not functioning, and adjusts for a long exposure. I attached a flash attachment. The fire-flash message makes it to the flash shoe, but the shutter is not in sync. So--is the flash bulb burned out or is something screwy with the electronics that syncronize the shutter and the flash?

Answer: Sounds like a serious problem, and it could be shutter related (bad). You need to have the camera looked at by an authorized repair shop. The Nikon Flash Guide has a brief troubleshooting section, but I think the key elements here are that the external flash fires but does not sync, and the camera doesn't recognize that the internal flash exists. I'd tend to guess that the issue is either a short or a break in a circuit, but it could be a component that's died. In any case, it's not user-fixable, unfortunately.

For those of you trying to figure out what's wrong with your flash, you need to be very disciplined in approach, as was the person who asked this original question. First, cancel out of any special settings--try taking a flash shot on full automatic with all default settings in place. If you suspect a problem with an internal flash, try mounting an external one (and vice versa). Carefully check settings: you need to verify that the camera is set at a syncable shutter speed, that you're in Single servo autofocus mode on autofocus cameras, that the camera and flash settings match (e.g., setting Rear on a flash and mounting it on an F4 is an "oops"). Consult the troubleshooting section of my book. If the flash doesn't fire at all, clean contacts, check batteries, verify settings. If the flash fires but the resulting picture has an underexposed "bar" in it, the shutter and flash did not sync. If the flash fires but the shot is overexposed, the problem is likely user error, not equipment error. In short, be methodical, look for clues (is the ISO value being transferred to the flash, does the distance scale update as you change apertures, etc.), and learn what the common problems look like in exposures.

top | home

Question: It seems that most recommendations for using fill flash talk about using -1.3 to -1.7 stops of flash compensation. This seems like very little flash (compared to the ambient exposure). Wouldn't -.5 or -1 stop be better?

Answer: Most nature and scenic professionals use -1.3 to -1.7 stops for their fill flash setting because they are trying to do one thing only: increase shadow detail (an alternate way of saying this: decrease overall scene contrast). Why? Because exposures for slide film need to be biased to the brightest object in the scene (i.e., overexposure of slide film is VERY bad). Since film has a limited dynamic range it can record with reasonable detail, if you set your exposure to put the highlight at the white point, you often lose shadow detail. The purpose of the fill flash, therefore, is to raise the film's response curve at the shadow point without further blowing out the detail. The -1.3 to -1.7 values are often just enough to pull another "stop" of useful shadow detail into an exposure without adding unduly to the highlight exposure. Films like Velvia are especially troublesome, as they have a steeper drop-off to black, and lose shadow detail faster (and this leads some to say Velvia is a high contrast film, which it's not). If you're using print film, you probably should opt the other direction: use as much flash you want, and don't worry about overexposure. That's because overexposure of a negative increases useful print densities (up to a point).

If you shoot people (weddings, events, etc.), you very well might want to use higher levels of flash, because here the primary thing you're trying to do is to get shadows off the face. My usual suggestion is to start with -1 stop and then work your way upward from there if that's not enough flash. I almost never go beyond -0.5 stops, by the way. Anything beyond that point is making the flash the primary source of light and the ambient lighting the "fill," which can look unnatural.

top | home

Question: I've got a studio set-up where my remote monolights are triggered by on-camera flash, but when I test fire, my flash meter indicates a setting that seems to significantly underexpose the resulting picture. What am I doing wrong?

Answer: Nikon's flash technology fires pre-flashes in TTL modes. And the D1's manual is incorrect, these pre-flashes are not canceled if you use an SB-28DX in bounce mode (as is often the case when you're using the camera flash to trigger remote slaves). So, you need to get the camera out of D-TTL mode. Here's the real trick, though: if you're only using the on-camera flash as a trigger, set it to manual flash mode at 1/64 power. Why? Because that's enough to trigger your slaves and it doesn't force the SB-28DX to recycle between flashes (i.e., the flash can fire again immediately). You can comfortably shoot at 1/64 power at the highest continuous frame rate the D1 is capable of (or an F5, for that matter).And typically 1/64 power isn't enough to make any real change to your subject lighting. Just one thing to watch for: Nikon recommends that you give the flash a rest every 30 flashes or so, lest you overheat the flash tube. Of course, on a D1, you'll fill the buffer with images before you get to that limit, while on an F5 you'll be changing film at 36 images, giving the flash a needed breather; but on a D1H you can exceed the recommendation enough that you should probably stop before the buffer fills.

top | home

Question: what is your recommendation as to the setting (3D matrix or straight TTL only) to use with an F100 and an SB-28 at night (i.e., not fill flash)?

Answer: When flash is to provide the main exposure for the subject, I tend to use Standard TTL or Automatic flash mode. All of the balanced fill flash modes, including 3D multi-sensor balanced fill flash, have a tendency to bias the flash output towards underexposure (they are, after all, labeled as "fill flash" modes). If I'm bouncing the flash, I'll usually switch to Automatic flash mode, as I've been burned one too many times by bounced TTL not providing the correct exposure.

top | home

Question: I understand from the SB-25 manual that the built-in, retractable bounce card is meant for use with the flash head in a vertical position. Should I also keep it extended when setting the flash at an angle for bounce off a ceiling?

Answer: I do (this is true of the SB-24, SB-25, SB-26, SB-28/28DX, SB-80DX). That's because it helps keep a little light from being lost, but more importantly, it provides just a bit of catchlight in the subject's eyes (the bounce directly off the card).

top | home

Question: I've taken quite a few photos with my Coolpix 990 using a single Sunpak433D. These turned out predictably. I added a second flash using a wein slave, again with predictable results. I then added a 500w quartz halogen work flood deflected from a large white polysterene surface above and behind the camera. Many of these photos turned out incredibly blue. I tried setting the white balance using an identical piece of polystyrene board in the subject position. This worsened the problem. What gives?

Answer: According to The Manual of Photography, most tungsten-halogen lamps have a color temperature of between 2700 and 3400K. Many also have a tendency to change color temperature with time. So, if you set your white balance to that needed by the halogen lamp, when you add flash, whatever they light will be remarkably blue, more than 149 MIREDs different (MIREDs are the measurement to assess color temperature differences and the difference between two MIRED numbers is used to decide filtration). Generally, if you're working with lights that have two different color temperatures, you have to filter one of the light sources to get acceptable color. You could, I suppose, bounce the halogen off a slightly blue card and set the white balance to that, but you'd be operating by trial and error until you found the correct color blue.

top | home

Question: The F601/N6006 had a special control to set the fill-flash option on the body; Is there a similar way to set fill levels on the F90x/N90s and SB-28 combo?

Answer: If you're using an SB-24 or later and a modern Nikon body that doesn't have a built-in flash, you set fill levels on the flash. With your combo, you can set fill by pressing the Minus button on the SB-28 three to five times (-1.0 to -1.7 stops). However, there's a caveat. If you have the camera set to Program (P) exposure mode and the flash to TTL, you're in what is known as a "balanced" mode. In balanced modes, the camera tries to equalize the flash and ambient light levels. But, when everything is on automatic, the camera can only set shutter speeds of 1/60 to 1/250, which might not let the camera set the proper ambient exposure. In dim light, for example, the camera would underexpose the background (though the subject would be lit by the flash). Thus, if you dial in fill flash in this situation, both the ambient light and the flash would be underexposed, ruining your shot. So, the caveat is this: don't set fill flash levels on your SB-28 unless you know that the ambient exposure is going to be correct. For dim light, that may mean you need to set Slow or Rear flash sync; in bright light, that may mean you need to set High Speed (FP) flash sync.

top | home

Question: Using an F80/N80, I dialed in flash compensation on the camera body. Then I dialed in flash compensation on my Speedlight SB-28. How are these compensations balanced? Are they cumulative, or is one ignored?

Answer: If you camera body supports flash exposure compensation (N6006, F70/N70, F80/N80, and some camera backs, for example), then you should be careful to set flash exposure compensation in only one place, as it is cumulative. Mount an SB-28 on an F80/N80 and dial in -1.3 stops of flash compensation on each, and you'll end up with -2.6 stops of compensation. This can be useful, at times, as it allows you to go beyond the +1.0 to -3.0 stop range of most Nikon equipment (i.e., your theoretical range is now +2.0 to -6.0 stops).

top | home

Question: You've written that using the built-in flash on an F80/N80 is just like having an attached Speedlight. So how do I set Standard TTL mode?

Answer: With the F80/N80, flash mode setting is automatically done based upon how the camera is set. With a D-type lens on the camera, you get 3D Multi-Sensor Balanced Fill-Flash in Aperture-priority (A), Shutter-priority (S), and Program (P) exposure modes and matrix or center-weighted metering. If you set either Manual (M) exposure mode or spot metering, the camera switches to Standard TTL. With non-D lenses, it works the same way, only you get Multi-Sensor Balanced Fill-Flash instead of the 3D variety.

top | home

Question: I'm trying to use wireless flash with a Coolpix 5400. I read somewhere that you can put a small piece of exposed film (the one near the end of a strip where it's totally black) on the built in speedlight and this acts like an IR filter on the SB-50DX, it blocks the pre-flash and only emits the IR rays from the actual flash duration thus triggering the slave of the SB-50DX. SO far i've only had a 25% success rate. I'm not sure why this is so. Shouldn't I get it right or wrong 100% of the time? I've set-up the SB-50DX both at manual and auto slave mode but both didn't give me consistent results.

Answer: Sorry, but the pre-flash can't be cancelled on most Coolpix models and the pre-flash is still emitting IR energy. Perhaps that's now filtered just enough so that it doesn't trigger the remote flash some of the time (if your success varied with distance, that would be my guess), but I can think of several other reasons why you might not get consistent results. If you want to trigger wireless from the Coolpix, put a small flash in the hot shoe, set it to its lowest power manual mode, filter out the visible light with your film strip, and cancel the internal flash. Unfortunately, the SB-50DX isn't the flash I'd use as a wireless flash in this instance, as it can only fire in automatic wireless (in which case it follows the main flash, which we just set to low manual power) or at full manual power. The best Nikon flash to use in this situation would be the SB-26, which can run its own automatic flash in wireless mode. Put the SB-50DX on the Coolpix in manual mode, filter it, turn off the internal flash, and set the SB-26 for Automatic wireless firing.

top | home

To get your question answered, send email to: QandA

bythom.com | Nikon | Gadgets | Writing | imho | Travel | Privacy statement | 2003 Thom Hogan. All rights reserved.