It seems that the Nikon D5300 does not have a commander mode to trigger flashes remotely. I want to buy an SB-700 Speedlight but don't want to purchase a remote trigger. Is there any way to use the Flash remotely with the built-in flash? If answer is Yes, how?
I couldn't find this information anywhere on this site, I would appreciate if you could shed some light on subject.
All you need to fire an off-camera flash with the built-in flash of any camera (even a P&S) is for the flash to have a "dumb" optical slave mode. Unlike the "smart" optical slaving that requires a Commander/Master mode in the pop-up flash, "dumb" slaving simply requires an optical sensor that can fire the flash when it senses another flash burst. With the SB-700, this is known as SU-4 mode. With most 3rd-party flashes, it would be known as the S1/S2 modes (or, in the case of Nissin, the SF/SD modes).
The difference between the "smart" and "dumb" modes is how much information can be communicated between the camera and the flash. In the "smart" modes, the pop-up flash basically can communicate most of the hotshoe commands via light flashes, sort of like using Morse code in light blips. The "dumb" modes can only communicate the sync (fire) signal. So, no TTL, HSS, or power control over the remote flash is possible. So, the remote flash also needs to have a physical control for M mode, so you can set the desired power level directly on the flash.
The only way to have automated power, if you're using a "dumb" optical slave is if the flash also has an autothyristor mode. In this case, you will also have to input the ISO and aperture settings used on the camera into the flash. The SB-700 and most 3rd-party flashes do not have this feature, it's mostly on vintage flashes, such as the SB-24 or SB-26, or on top-of-the line digital OEM speedlights. Nikon calls it "non-TTL Auto" mode, and you can find it on the SB-800/-900/-910.
The drawbacks of using an optical slaving mode, however, are that bright ambient light (such as sunlight outdoors) can overpower the signal, and can reduce reliability and range, and make line-of-sight requirements more stringent. Like using a TV remote, the sensor has to 'see' the commanding signal, so you have to make sure the sensor (in the case of Nikon speedlights, a red dot on the side of the speedlight; with 3rd-parties typically the red panel on the front of the flash body) is facing the camera's pop-up flash, so placing a flash behind you (since the pop-up won't turn around) or behind a solid object probably won't work.
This is why radio triggering is more typically preferred for off-camera shooting. If you plan primarily on using a flash off-camera, it might be worthwhile to look into 3rd-party flashes that have built-in radio triggering (such as those made by Godox, Phottix, Nissin, or Yongnuo) for convenience. It might also cost a lot less than an SB-700. And while it might not be as nice for on-camera use as an SB-700, it might be more powerful and still can provide TTL and (when you upgrade from a D5x00 body) HSS/FP flash.
See also: What features should one look for when selecting a flash?
