I have read in a couple of places that the standard maximum flash sync speed of the D7100 is 1/250 second, with 1/320 available at reduced flash range. Does anyone know what the implications of this are? Does it apply only to the built-in flash or can one get 1/320 with a speedlite? Since the standard 1/250 is presumably determined by when the second shutter curtain needs to start moving in order to provide a complete exposure of the frame, how can it be increased to 1/320? Thanks.
#2. "RE: D7100 flash sync speed 1/250 or 1/320" In response to Reply # 0 Wed 27-Feb-13 11:48 PM by Chris Platt
This topic should be moved to the speedlight forum, since it is applicable to a number of cameras that have more than one sync speed.
To answer the rest of your question, think of 1/320 as "just barely synced." At shorter flash distances, you will get a shorter flash pulse for proper exposure, so the flash can just make it in before the 1/320 door starts to slam shut. At greater distances, you will get a longer flash duration for proper exposure and it might not all make it in before the door starts to slam shut. It's just Nikon's way of letting you get a little higher shutter speed before FP kicks in and dramatically reduces your flash power. If you're close and you know you can get away with it, use it. In most cases, you probably won't notice any difference.
I used a Vivitar 285 flash on manual, full power, to take the following images of my basement wall. Full power ensured I had the longest flash pulse possible. Note the darker area along the bottom of the 1/320 image. The shutter was starting to close before the full pulse made it to the sensor. The 1/400 is there for a reference to make it clear what is happening. (The vertical dark streaks on the right side are from a leaking copper heater pipe that I had to repair a few weeks ago - new paint will happen - sometime)
#5. "RE: D7100 flash sync speed 1/250 or 1/320" In response to Reply # 4 Thu 28-Feb-13 04:28 PM by Chris Platt
I think he understood the point you we're making. It was helpful, so I only had to address the question about two different sync speeds. I think both replies together painted a pretty complete picture.
#6. "RE: D7100 flash sync speed 1/250 or 1/320" In response to Reply # 4
El Sobrante, US
Thanks for the comments about auto FP. I have used that in the past, but in this post I was querying the 1/320th that showed up in a few comments about the D7100's flash sync speed. Chris' explanation and samples cleared this up for me.