There are several Flash modes offered on your Nikon D5300 if you choose to add a flash to better illuminate your picture. Your Nikon D5300 offers the following flash modes:
Auto: The camera decides whether the flash fires. This mode isn't available in the P, S, A, M modes or the Food Scene mode.
Flash Off: In Auto exposure mode or the Scene and Effects modes that permit flash, choose this Flash mode to prevent the flash from firing. (In the P, S, A, and M modes and the Food Scene mode, simply close the flash unit if you don't want to use flash.)
Fill Flash: You can think of this mode, available in P, S, A, M and Food Scene modes, as normal flash. You may also hear this mode called force flash because the flash fires no matter the amount of available light.
Although most people think of flash as an indoor lighting option, adding flash can improve outdoor photos, too. After all, your main light source — the sun — is overhead, so although the top of the subject may be adequately lit, the front typically needs additional illumination.
Shooting with flash in bright light involves a couple of complications.
Red-Eye Reduction: Red-eye is caused when flash light bounces off a subject’s retinas and is reflected back to the camera lens, making the subjects appear possessed by a demon. This flash mode is designed to reduce the chances of red-eye.
When you use Red-Eye Reduction mode, the AF-assist lamp on the front of the camera lights briefly before the flash fires. The subject's pupils constrict in response to the light, allowing less flash light to enter the eye and cause that glowing red reflection. Be sure to warn your subjects to wait for the flash.
In Auto exposure mode as well as in certain other Scene and Effects modes that permit flash, Red-Eye Reduction flash is just a variation of the regular Auto flash setting. That is, if the camera sees the need for flash, it fires the flash with Red-Eye Reduction engaged. In this case, you see the word Auto next to the red-eye symbol.
Additionally, a few Scene modes use a variation of red-eye reduction, combining that feature with a slow shutter speed. This flash mode displays the little eye icon plus the words Auto Slow. It's important to use a tripod and ask your subject to remain still during the exposure to avoid a blurry picture.
Slow-Sync and Rear-Sync: In the flash modes listed so far, the flash and shutter are synchronized so that the flash fires at the exact moment the shutter opens.
Technical types call this flash arrangement front-curtain sync, which refers to how the flash is synchronized with the opening of the shutter. Here's the deal: The camera uses a type of shutter involving two curtains that move across the frame.
When you press the shutter button, the first curtain opens, allowing light to strike the image sensor. At the end of the exposure, the second curtain draws across the frame to once again shield the sensor from light. With front-curtain sync, the flash fires when the front curtain opens.
Your camera also offers these four special sync modes:
Slow-Sync: This mode, available only in the P and A exposure modes, uses front-curtain sync but allows a shutter speed slower than the 1/60 second minimum that’s in force when you use Fill Flash and Red-Eye Reduction flash. The camera has time to absorb more ambient light, which has two benefits: Background areas that are beyond the reach of the flash appear brighter; and less flash power is needed.
The downside of the slow shutter speed is, well, the slow shutter speed. Any movement of your camera or subject during the exposure can blur the picture, and the slower the shutter speed, the greater the chances of camera or subject motion. A tripod is essential to a good outcome, as are subjects that can hold very, very still.
If you're shooting a nighttime portrait and you have a subject that can maintain a motionless pose, slow-sync flash can produce softer, more flattering light.
Note that even though the official Slow-Sync mode appears only in the P and A exposure modes, you can get the same result in the M and S modes by simply using a slow shutter speed and the normal, Fill Flash mode. You can use a shutter speed as slow as 30 seconds when using flash in those modes.
Rear-Curtain Sync: In this mode, available only in shutter-priority (S) and manual (M) exposure modes, the flash fires at the end of the exposure, just before the shutter closes. The classic use of this mode is to combine the flash with a slow shutter speed to create trailing-light effects.
With Rear-Curtain Sync, the light trails extend behind the moving object, which makes visual sense. If instead you use slow-sync flash, the light trails appear in front of the moving object.
You can set the shutter speed as low as 30 seconds and as high as 1/200 second in this Flash mode.
Slow-Rear: Hey, not confusing enough for you yet? This mode enables you to produce the same motion trail effects as with Rear-Curtain Sync, but in the P and A exposure modes. The camera automatically chooses a slower shutter speed than normal after you set the f-stop, just as with regular Slow-Sync mode.
Slow-Sync with Red-Eye Reduction: In P and A exposure modes, you can also combine a slow-sync flash with the red-eye reduction feature. The symbol that represents this mode is the normal red-eye eyeball combined with the word Slow.