The Secret to Shooting a Timelapse with Changing Light (a7sIII)

[LensMeAHand]

You first have to set the camera to Interval Shooting mode (Menu>Shooting>Drive Mode>Interval Shoot Func.>On)

And you might think that's all there is to it. But it's a little trickier than that.

Let's say you're doing a sunset. If you go outside at golden hour, set your exposure in Manual mode and let the camera do its thing, your timelapse will start off looking great and then slowly fade to black. Not what we want.

If you set the camera mode to AUTO, A (Aperture Priority), or S (Shutter Priority), the camera will keep your exposure as consistent as possible, but it will change your aperture and/or shutter speed, neither of which I want to change during a timelapse.

So the trick is to use manual mode, but set the ISO to Auto. That way your exposure will remain constant, as well as your depth of field and motion blur. Just keep in mind the minimum ISO in ISO Auto is 640, meaning that you may need an ND filter if you were planning to shoot at ISO 40 during the daytime portion of the timelapse.

Although this is the best solution I've found, you can still run into the issue of your night footage being really noisy. For example if you've exposed for daytime with a 1.2 ND, the camera has to boost the noise to crazy high levels to compensate at night. I'm thinking you could avoid this by removing the ND when it starts to get dark, maybe staging two NDs in your mattebox and removing them one by one, or slowly adjusting a variable ND until it's not doing anything. I haven't had the time to test this, but please let me know your results if you try it!

P.S. A helpful tip for timelapses: Because the camera will be powered on for hours and you can't swap batteries mid-timelapse, use the USB-C port to charge the camera from wall power (or car power with a cigarette lighter to USB adapter).

[alisterchapman]

If you have an FX6 or FX9 you can use the built in intervalometer to shoot great time-lapse. This can be combined with the slow shutter to get long exposures if you want motion blur. You can also use the FX6 or FX9's programmable AE settings to add limits to the amount of auto gain that will be applied, or the range of auto iris that will be used and where the crossover between each auto function occurs. In addition you can use the variable ND on auto to further extend the range of light that you can get an acceptable exposure over. What you don't get is raw still frames, but S-Log3 is highly gradable.