Hello Bruno976,
Thank you for reaching out to Apple Support Communities.
You may be seeing the transition between lenses. We were able to find this:
You might see the Camera app transition to the Ultra Wide camera as you move your iPhone close to or away from a subject. You can control automatic macro switching by going to Settings > Camera, then turning on Macro Control. With Macro Control on, your Camera app displays a macro button when your iPhone is within macro distance of a subject. Tap the macro button to turn off automatic macro switching, and tap it again to turn automatic macro switching back on.
More details can be found here: About the Camera features on your iPhone
If you are experiencing an issue, can you provide a few more details? Do you experience problems when taking photographs or videos? Is anything noticeable after taking the photo? Also, what is your exact iOS version?
Cheers!