The camera doesn't come with a feature to lock exposure or manually set the exposure. Each time when you re-focus at the next frame, the exposure reading will be that of the current area. Even if you go back to the 1st frame, and press the shutter button halfway to take the reading, then shift to the next frame, the image in the next frame would be out-of-focus.

Like that how to take several shots to stitch together when the exposure for each shot differs? Much appreciate help pls.