victoria australia
CRIMES ACT 1958 - SECT 53R Producing intimate image
CRIMES ACT 1958 - SECT 53R
Producing intimate image
(1)     A person (A) commits an offence if-
   (a)     A intentionally produces an image depicting another person (B); and
(b)     the image is an intimate image; and
(c)     A knows that the image is, or probably is, an intimate image; and
(d)     the production of the intimate image is contrary to community standards of acceptable conduct.
(Non-relevant examples omitted)
(2)     A person who commits an offence against subsection (1) is liable to 3 years imprisonment.
(3)     A does not commit an offence against subsection (1) if—
   (a)     B is not a child; and
(b)     at the time of the production of the intimate image, B consented to—
     (i)     A producing the intimate image; and
     (ii)     how the intimate image was produced.
Note
A mistaken but honest belief that the production of the intimate image is not contrary to community standards of acceptable conduct is not a defence to this offence—see section 53V.
where:
"intimate image" means an image depicting—
   (a)     a person engaged in a sexual activity; or
(b)     a person in a manner or context that is sexual; or
(c)     the genital or anal region of a person (whether bare or covered by underwear); or
(d)     if a person is female, or a transgender or intersex person identifying as female, the breasts of the person;
And:
"produce", in relation to an image, means—
   (a)     filming, recording, taking or otherwise capturing the image; or
(b)     digitally creating the image;
And:
CRIMES ACT 1958 - SECT 53U Community standards of acceptable conduct
CRIMES ACT 1958 - SECT 53U
Community standards of acceptable conduct
(1)     Whether the production or distribution of an intimate image is contrary to community standards of acceptable conduct depends on the circumstances.
(2)     For the purposes of subsection (1), the circumstances include—
   (a)     the nature and content of the intimate image;
(b)     the circumstances in which the intimate image is produced or distributed;
(c)     the age, intellectual capacity, vulnerability or other relevant circumstances of a person depicted in the intimate image;
(d)     the degree to which the production or distribution of the intimate image affects the privacy of a person depicted in the intimate image.
And:
CRIMES ACT 1958 - SECT 53V No defence of honest and reasonable mistake
CRIMES ACT 1958 - SECT 53V
No defence of honest and reasonable mistake
It is not a defence to a charge that, at the time of the conduct constituting the offence, A was under a mistaken but honest and reasonable belief that—
   (a)     for an offence against section 53R(1)—production of the intimate image was not contrary to community standards of acceptable conduct; or
(b)     for an offence against section 53S(1)—distribution of the intimate image was not contrary to community standards of acceptable conduct; or
(c)     for an offence against section 53T(1)—distribution of the intimate image would not be contrary to community standards of acceptable conduct.
Note
The reference to A in this section is a reference to the same A referred to in sections 53R, 53S and 53T.
Unless the couple who were 'making out' (i.e. engaging in a sexual activity) were first asked and consented to the taking of the photograph, then the photographer may have committed an offence.
It may be that a couple making out in a movie theatre (a public place) have committed an offence such as sexual exposure (https://classic.austlii.edu.au/au/legis/vic/consol_act/soa1966189/s19.html) if they are displaying their genitals, or another offence (such as under the SUMMARY OFFENCES ACT 1966 - SECT 17 Obscene, indecent, threatening language and behaviour etc. in public) in which case taking a photograph without consent for purposes of submitting it to the police to enable prosecution would be legal.
However, if the couple are not committing an offence when the photograph is taken and have not given consent, then the photographer has committed an offence.
While a movie theatre is a public place, a couple 'making out' at the back of a theatre so that there are no observers behind them and are hiding behind the row of seats in front of them could argue that in the circumstances, since other members of the public would be expected to be looking away, and wouldn't normally be able to see their genitals or other 'indecent' parts of their bodies, that their actions were not disruptive (the prevention of which is the purpose of the SUMMARY OFFENCES ACT 1966 - SECT 17), and therefore the taking of an intimate image without their consent was not appropriate.
So, unless genitals (or other parts of the body such as breasts or anus) are clearly visible in this public place and other patrons are obviously aware and offended by the couple's actions, taking a photo of their sexual activity (even if fully clothed) without their consent is an offence, even if you don't necessarily think that it is an offence.  In theory, you could be charged for taking such a photo even if it was given to the police if the police declined to lay charges against the couple for their actions.