Two lens system question

[David513]

Quick and possibly stupid question: when you have two lenses, does the second lens act as the "observer" for the first lens's image, and then you are the "observer" for the second lens's image? I ask so I can know how to assign the + and - signs to the objects/images/focal points, since, if I'm not mistaken, the sign is dependent on where the object/image/focal point is in relation to the "observer."

Thank you in advance!

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[aldol16]

I guess you can think of it like that. The first lens creates an image, which is then the "object" for the second lens to create the second image.