Here are some helpful tips on camera settings that you should use to capture crisp movement in the studio. I made a detailed video, but here is a breakdown of the settings you need to understand to keep your images sharp.
1. Choosing the Right Shutter Speed: Understanding Sync Speed
The sync speed is the fastest shutter speed that your camera can use and still sync with a flash. In most modern cameras, it is 1/200 s or 1/250 s. There are also flashes that have something called high-speed sync. High-speed sync allows a camera to go up to its maximum shutter speed, but with a significant loss of power.
Look at the following images. The one on the left was shot at f/8, 1/250 s, ISO 100. The one on the right was shot at f/8, 1/320 s, ISO 100.
The difference between the two images is a fraction of a stop of light on the shutter speed settings, but the result is about three stops under the exposure of the one on left. That is because with the image on the right, the camera went above the max sync speed of the camera and it forced the flash into high-speed sync. The flash still fired, but at significantly less power, even though the flash settings remained the same. The bottom line is that high-speed sync causes a huge drop in power in your lights.
When shooting crisp movement in the studio, there should not be any reason to force your strobe into high-speed sync. Keep your shutter speed at or just below the max sync speed for your camera.
2. Choosing the Right Aperture: Understanding Depth of Field
The next thing you need to look at is how much of the image you need in focus. When you shoot a subject and his or her eye is in focus, but the focus gets softer as you move back towards the ears, that is because you have a very shallow depth of field. Depth of field is the plane of focus that is controlled primarily by your aperture and your distance to the subject. Things that are within the depth of field will be in focus, while things in front of or behind that plane will be out of focus. The wider the aperture and the closer you are to a subject, the narrower the depth of field becomes. If the eye is in focus and the ears begin to soften, then you can raise your aperture or move farther away from your subject, and you'll see that the depth of field increases.
When you are capturing movement, you might need a wider depth of field. Imagine capturing a dancer in motion with an arm or leg outstretched or a model in a dress with flowy fabric. Always err on the side of a wider depth of field when capturing crisp movement.
3. Eliminating the Ambient Light
When you are shooting in the studio and capturing crisp movement, the first thing you want to do is eliminate all ambient light with your camera settings. You want to make sure that the light hitting your subject is intentional light that you are controlling, not flat light from the overheads. You don't need to turn off the overheads or modeling lights. You just need to set your camera so that they are irrelevant. Start with a shutter speed of 1/250 or whatever your max sync speed is. Set your aperture to f/8 and your ISO to 100. Take a picture with those settings with the flash turned off. Your frame should be completely black. If it is not completely black, you can adjust your aperture until it is completely black, but do not change your shutter speed above your sync speed.
4. The Most Important Factor - Understanding Flash Duration
The goal is for your camera's sensor to be exposed to light for as little time as possible. That is what captures crisp movement. With camera settings that eliminate ambient light and a shutter speed at or below the max sync speed, the flash duration is the key number that will determine the crispness of your image.
Imagine you are in a completely dark room. It's so dark that it makes no difference whether your eyes are open or not; either way, you are in total darkness. Now, imagine a light comes on in the room for 1/100th of a second while your eyes are open. Your eyes could be open for 10 seconds or they could be open for a half a second. It doesn't affect the amount of time your retinas are illuminated, as long as they are open when that burst of light hits. That is how flash duration works: the amount of time your eyes are open is your shutter speed and the time that the light is turned on and off is the flash duration. The flash duration makes your shutter speed irrelevant as long as it is below the sync speed and you have eliminated all ambient light with your other settings.
Look at the two images below. The image with the paint was shot with a strobe and the shutter speed was set to the max sync speed of the camera, 1/250 s. In the image on the right, the camera was set to 1/2,000 s, and even though the shutter speed is eight times as fast, the rain is still not anywhere as crisp as the paint. The reason is that with the strobe, the motion is stopped by the flash duration instead of the shutter speed. In the paint picture, the flash duration was about 1/4,000 s. So, even with a lower shutter speed, the sensor was illuminated for a much shorter period, resulting in a crisper image.
Studio flashes put out an intense amount of light very quickly. It might seem instantaneous, but what actually happens is the flash tube ramps up from 0 to 100% brightness and then back down to 0%. That flash duration is measured in either t.5 or t.1 numbers. Here is a chart that Lee Morris put together when comparing Godox and Profoto lights:
The t.5 measures the length of time that the flash goes from 0% up to 100% and then back down to 50%. The t.1 number measures how fast the light goes from 0 then up to 100% and then down to 10% light. The t.1 number is a much more accurate reading for measuring the amount of time your camera's sensor is illuminated by the light from the flash.
The flash duration changes with the power setting of your light. If you are shooting a Godox AD600Pro at full power, the t.1 flash duration is 1/220 s. On its lowest setting, the flash duration is much quicker at 1/10,100 s. A Profoto B1 (a less powerful and three times more expensive light) is 1/377 s at full power and 1/6,010 s at its lowest setting. This is why it is important to have a powerful flash. Shooting a 600-watt-second strobe at half power and shooting a 300-watt-second strobe at full power will give you the same light output, but the closer the light is to operating at its full power, the slower the flash duration.
If you can understand these principles, it will take the guesswork out of choosing the correct camera settings for capturing crisp movement. Let me know if you have any questions in the comments.
Good article 🙂
Great article, Jeff. I'm also working on a video about flash duration and everything in this was spot on.
Thank you my friend.
It was a good article, but you intentionally threw rocks at a competitor. That diminished the credibility of the article a bit. If you have a bias against Profoto, that's fine, but minimize it in your articles.
- You compared a discontinued Profoto strobe that is 9-years old against a newer technology currently in production. You should have compared against the current B10 family or the BiX, which is newer.
- The cost comparison was an unnecessary jab at a competitor. The section was about flash duration, not about cost savings.
If you wanted to provide additional valuable information about flash duration, why didn't you mention the Profoto D2, which has very short flash durations (1/2,600 to 1/63,000 t5) or PCB Einsteins at 1/2 the cost of the Godox AD600Pro?
Finally, because the name of the article involves capturing movement, it might have been good to include a section on not just absolutely freeze everything, but how slight blurring of a dancer's leg or arm can help convey movement. If you ever saw a photo of a prop plane flying with the propeller absolutely frozen, it would look weird. Our brains know it should be spinning. The same with rain drops. A little blur indicating motion is more realistic than absolutely frozen. Those are also important considerations when capturing movement.
Just some things to consider for your future articles.
Friend, Thank you for reading and thank you for your suggestion of including a section in my article for capturing blurry movement in an article called how to capture crisp movement. Also, thank you for your suggestion of trying to use more accurate comparisons like using a 1000ws strobe against a 600ws strobe. One of the reasons I didn't is because Profoto only uses t5 numbers in their marketing which is misleading for the reasons I outlined above. Also, the flash duration on the b10 and the b1 are almost identical (1/367 at full power and 1/6350 at its lowest power). The reason I didn't use Einsteins is 1) because that company is the betamax of lighting, and 2) because it's not an article comparing which lights have the best flash duration. I don't need to compare every t1 flash duration in order to explain what it is and why it's important. Lastly, I agree with you about movement. I have a YouTube video about capturing rain to get motion blur and to get it crisp and conclude that motion bur looks better in my opinion. Car wheels, propellers, rain, those are all things I think look good with some motion blur, but this specific article is about how to freeze motion to not get any blur. Thanks again for your comment!
Jeff, thanks for the response and I'm only trying to provide correct facts and valid comparisons to make your article stronger. For future reference here are the flash durations of the D2 - 500Ws (not the 1000Ws model) strobe from the Profoto page -
Normal or Freeze
Flash duration t0.1
Normal mode: 1/1,000 s (500 Ws) - 1/7,700 s (1 Ws)
Freeze mode: 1/1,000 s (500 Ws) - 1/13,500 s (1 Ws)
Flash duration t0.5
Normal mode: 1/2,600 s (500 Ws) - 1/17,000 s (1 Ws)
Freeze mode: 1/2,600 s (500 Ws) - 1/63,000 s (1 Ws)
The normal t1 times of the B10X Plus and BiX are fairly close to the original B1. You didn't mention the Freeze mode, which significantly shorten's the durations. I would assume because not many are aware of this feature.
Here are the B10X Plus (500Ws) times -
Flash duration t0.1
Normal mode: 1/390 s (500 Ws) - 1/4,100 s (1 Ws)
Freeze mode: 1/390 s (500 Ws) - 1/14,000 s (1 Ws)
Flash duration t0.5
Normal mode: 1/1,200 s (500 Ws) - 1/6,000 s (1 Ws)
Freeze mode: 1/1,200 s (250 Ws) - 1/35,000 s (1 Ws)
Good article and sorry if I ruffled your feathers a bit!