If a rainbow was a mind created phenomenon, then a camera, which has no mind or consciousness, would not be able to photograph it.
Hold on. If rainbow was mind created phenomena, wouldn't the camera also be mind created, wouldn't the eye be mind-made and if these are likewise mind-made then why wouldn't the camera be able to photograph it? Seems like photographing would be the only thing a camera should do, it is not going to cognize the shape & color of a tree or see it, the instrument is essentially an extention to the nervous system and is not supposed to do what mind does.
Similarly, a meditator might
perceive a dissolution of the self into its constituent elements and
thus conclude that the self does not truly exist,
There is something that can be spoken of as 'a sign' in your analogy, the sign is complete with form & color, which is perceived as it is grasped & interpreted by the nervous system to be 'a rainbow' or 'sign of a rainbow'.
That which is thought about & called 'sign' can be said to be an abstract expression of what is thought to be the sign's causes & conditions coming into play. If the causes & conditions prompting the expression are understood then there is no confusion in regards to the expression and it's meaning is rightly seen with intellect.
Interpreting & grasping the signs correctly is the directed development, grasping correctly one acts correctly, acting correctly one begets the correct sign which is associated with the consummation of the 5 faculties.
When a person grasps with underdeveloped intellect he reacts badly, in example a person grasps the sign of a bodypart and assumes that it is personal or that it is a self and makes an evaluation. Based on this evaluation he may become glad or aversive. Experiencing this excitement the intellect is clouded, one is not thinking straight and is carried away on the currents of bad intention, due to bad intention there is a wrong directing of attention and a weakening of the faculties due to frequent giving of attention to unwholesome themes which become the inclination of the mind due to a frequent giving of attention.
In this way a person might grasp something as self and be stuck thinking along those lines due to obliviousness to that which is his best knowledge.
Then having calmed down one might realize that he has been stuck interpreting the signs according to the false doctrine of 'self' and having become aware he is no longer entertaining those lines of reasoning based on delusion and is at that time interpreting the signs correctly.
There is this kind of dissolution of self. I don't know another.
As a comparison, if one is asleep and dreaming, one
loses awareness of the body and the external world, yet both still
exist for others,
Well yeas but the others, like the dream, don't exist for you until you start perceiving them, so the others are here semantically just as real as the dream because both elements come into play only when they are perceived by the observer and you have absolutely no way to establish these as a truth or reality beyond a particular person's seeing, hearing, smelling, tasting, feeling with the body and grasping with intellect.
To say that external world persists beyond it's conception & perception on a base primary frame of reference is akin to saying that dreams are a place you go to and that it persists while you are awake without your participation.
Thus, only awareness would have ceased, not the objects of awareness.
It is kind of amusing how people first establish something as a truth based on it essentially being an "objects of awareness" and then attempt to remove the 'of awareness' part.
It is not defined as an object which is sometimes of awareness and sometimes not of awareness. You don't get to take something defined & understood exclusively to be an object of awareness and talk about it as an not an object of perception.
That is a mistake of mixing two mutually negating contexts and you get a contradiction where you basically say 'this object of awareness is not an object of awareness because it's an object' and on this basis you create a doctrine about an object disconnected from everything meaningful as if a term's meaning is changed by using a shorter expression, in particular 'object of awareness' to 'object [not of awareness]', that doesn't work.
The problem arises when you talk about an object of awareness as an object and then insist on overriding normal usage in making the assumption that it's affirmation of a truth & reality isn't presumed to be dependent on contact and awareness.
"Monks, I will teach you the All. Listen & pay close attention. I will
"As you say, lord," the monks responded.
The Blessed One said, "What is the All? Simply the eye & forms, ear &
sounds, nose & aromas, tongue & flavors, body & tactile sensations,
intellect & ideas. This, monks, is called the All.  Anyone who
would say, 'Repudiating this All, I will describe another,' if
questioned on what exactly might be the grounds for his statement,
would be unable to explain, and furthermore, would be put to grief.
Why? Because it lies beyond range."
To say that the perceived world & it's objects exist independently of a single observer's frame of reference is not to be done because without an observer the world can't even be talked about in terms of the electromagnetic process because there [that frame of reference] is then not a process, not without an observer to collapse the wave function.
In non physics terms;
There being no observation there is no contact, there being no contact there is no expression of causes & conditions, there being no expression there are no signs, there being no signs there is no awareness of signs, there being no awareness of signs there is no awareness and that exactly because awareness is also always associated with a sign or an object of the 6 sense doors as it's existence is postulated on it being demonstrably implicated in contact which is a requisite for expression of a sign. There being no awareness there is then no awareness of a before & after and hence it is not a process.
Think about this.
If you and i both look at a rainbow, we are actually conceiving & perceiving two different worlds altogether because you can calculate the distance light travels to hit your eye and compare it to the distance light has to travel to hit my eye and take note of the fact that it's not even technically the same light that does the travelling.
Let alone the fact that we are technically only seeing the light that was emitted before contact occured and our seeing depends on it but we are not seeing things change simultaneously. Given the variance in the distances the sign of the rainbow will even dissolve at different time assuming our clocks were calibrated correctly and we could even prove it by making timestamped video.
Of course the distance between us would have to be enormous for light to be measurably delayed but as a thought experiment..
Suppose you are looking at a rainbow from a helicopter and i teleported instantly 1 light year away, i wouldn't even see the rainbow for a year no matter what optical zoom i have because the light from the rainbow won't make contact for a year whilst my watch would still be aligned with yours if i were to teleport right back.
Furthermore were i to immediately look back at earth with superzoom, i wouldn't see the rainbow at all and would be looking at events from 1 year ago.
Furthermore with this kind of teleportation powers i could teleport and watch myself teleport to my current location appearing as a second me beside because apparently i got faster than light travel...
"When the four bases of spiritual power have been developed and cultivated in this way, a bhikkhu (monk) wields the various kinds of spiritual power: having been one, he becomes many; having been many, he becomes one; he appears and vanishes;
note: here by light speed i talk about just the speed of the smallest discernable change in the electromagnetic process. It is entirely dependent on the instrument of measure.