Why does my time-lapse photography flash as soon as it is connected? My settings are all manual.

This scene with a great change in light ratio will flicker when it is synthesized. Because now the exposure of digital SLR is in the step of 1/3, only if the shutter or aperture changes one step, the later synthesis will flicker. There is no better solution to this. Personally, I don't know if my friends will accept:

1. It is very important to add a medium gray filter of ND4 or ND8 in front of the camera to shorten the shooting interval between two photos when shooting! Then, if you want to increase or decrease the exposure of photos, you must do it in one step, and you must add and subtract one level at a time. It is not advisable to add or subtract too much at a time, just one file. This is an early stage. 2. At the later stage, there are many methods. The more accurate method is: play it once when synthesizing, take down that frame and fine-tune the exposure (needless to say). This method is very troublesome, because the first frame moves, and everything behind it has to follow, but it is accurate. 3. Install a plug-in Adobe After Effect under 3.PS. The "color stabilizer effect" in this plug-in is said to have the function of controlling flicker and average exposure, but mine is a MAC computer, which is a plug-in for WIN. I didn't test it myself, so I don't comment. This is the method I am using. Under the MAC system, there is a software called Final Cut Pro, which is also a bit troublesome and needs to be charged (several hundred dollars). The exposure of each frame can be averaged automatically or manually, which can play a certain role, but it is also time-consuming.

I hope my answer is useful to my friends (I hope it will be adopted)