Sunday, November 23, 2014

HSS with the Cheetahlight CL-360 and Yongnuo YN622Ns

Several people have asked about High Speed Sync (also known as FP for Nikons).  High Speed Sync allows you to set a sync speed (and shutter speed) above your camera's regular maximum sync speed (which usually ranges somewhere between 1/60th sec to 1/250th sec depending on camera model).

The reasons for wanting to set a high sync speed aren't as intuitive as you would think.  Some people think they need a high speed sync to freeze action.  That usually isn't the case.  That is because the short duration of the flash (ranging from 1/1000 to1/10,000 sec) is usually sufficient to freeze action, at least where the flash is the main source of light.

So why would you need a high sync speed?  There are several 'use cases', but probably the most common is the desire to open up your aperture for shallow depth of field when using your flash outdoors during the day.  In those cases, in order to get to f4 or to say an f2.8, you usually have to set your shutter speed well above 1/250th of a second.

You have two choices in that case, use HSS to allow your sync and shutter speed to go above 1/250th sec, OR you could instead use a neutral density filter to bring down the ambient light so your shutter speed will be at your sync speed limit or less.  The issues with using neutral density filters are that it decreases the light your camera gets for focusing, and if using a really powerful neutral density filter, you can introduce a color cast into the image (as most are not 100% neutral).  So instead of carrying around neutral density filters, you can also use HSS to get your shutter speed up so you can use the aperture that you want.

One other use case, is if you are freezing action AND want to mix flash with ambient light.  When doing that, even though the flash freezes the action for the part of the exposure done by the flash, a long shutter speed with the ambient light could introduce some ghosting.  In those cases, you might want to use HSS to get your shutter speed up for freezing the ambient light action.

In this video, I show how to set up HSS on the Cheetahlight CL-360, the Cheetahstand CL-TX Trigger (used for remote power control of the CL-360) and my Yongnuo YN622Ns:

There are several possible set ups, some that work better than the others, and I walk through those in this video.  The CL-TX Trigger (also known as the ft16) does not directly support HSS (most of the image gets darkened by the shutter creeping into the exposure as seen in the image below),

so although you can still use that trigger to remotely control power, a different triggering system needs to be used to support HSS.  That is where the Yongnuo YN622N system (including the YN622N-TX) comes into play.

The YN-622N can recognize when your camera is set to FP mode, and automatically controls the HSS communication to the Flashes it controls.  In this case, the CL-360 has to manually be placed in HSS mode, but once that is done, it understands the communiction coming from the camera and the YN622N to properly control the flash so that you don't see the shutter mechanism in the image.

The CL-360 can also simulate HSS support in its normal mode at full power (1:1).  In this mode, the flash duration is long enough that it stays illuminated for the entire travel of the shutter so you get a properly exposed frame.  The interesting thing is, this method gives just a little more power for your exposure than using the HSS mode in full power.  I show that in the video, but also in the images below:

All three of the images below are shot at 1/8000 of a second and the CL-360 set at full power (1:1).  The first one is shot at f5.6 with the CL-360 set to 'on' on the flash.  The second one has HSS turned 'off' and is still at f5.6.  The third is with HSS  turned 'off with the aperture set to f6.3.

1) Shutter Speed 1/8000; Aperture f5.6; HSS set to 'on'

2) Shutter Speed 1/8000; Aperture f5.6; HSS set to 'off'

3) Shutter Speed 1/8000; Aperture f6.3; HSS set to 'off'

If you have any questions or comments, please post those in the comments section and I will try to respond.  Try HSS with your system and let me know how it works out.  In the meantime, Happy Shooting!