NAME

    Photography::DX - Encode/decode DX film codes

VERSION

    version 0.02

SYNOPSIS

     use Photography::DX;
     
     my $film = Photography::DX->new(
       speed     => 100,
       length    => 36,
       tolerance => 2,
     );
     
     # print out the layout of contacts
     # on the roll of film as a series
     # of 1s and 0s:
     print $film->contacts_row_1, "\n";
     print $film->contacts_row_2, "\n";

DESCRIPTION

    This class represents a roll of 35mm film, and allows you to compute
    the DX encoding contacts used by film cameras that automatically detect
    film speed, the number of exposures and the exposure tolerance of the
    film (most cameras actually use only the film speed for the DX
    encoding).

CONSTRUCTOR

     my $film = Photography::DX->new;

    In addition the attributes documented below you may pass into the
    constructor:

    contacts_row_1

      The first row of contacts on the roll of film. The speed will be
      computed from this value.

    contacts_row_2

      The second row of contacts on the roll of film. The length and
      tolerance will be computed from this value.

ATTRIBUTES

 speed

    The film speed. Must be a legal ISO arithmetic value between 25 and
    5000. Defaults to ISO 100.

    Special values 1-8 denote "custom" values.

 length

    The length of the film in 32x24mm exposures. Must be one of undef
    (denotes "other"), 12, 20, 24, 36, 48, 60, 72.

 tolerance

    The exposure latitude of the film. Must be one of:

    0.5 for ±0.5 stop

    1 for ±1 stop

    2 for +2 to -1 stops

    3 for +3 to -1 stops

METHODS

 contacts

     my($row1, $row2) = $film->contacts;

    Returns both rows of contacts.

 contacts_row_1

    Returns the contact layout as a string of 1s and 0s for the first row
    of electrical contacts. 1 represents a metal contact, 0 represents the
    lack of metal.

 contacts_row_2

    Returns the contact layout as a string of 1s and 0s for the second row
    of electrical contacts. 1 represents a metal contact, 0 represents the
    lack of metal.

 is_custom_speed

    Returns true if the film speed is a custom film speed.

 logarithmic_speed

    Returns the ISO logarithmic scale speed of the film (also known as
    DIN).

CAVEATS

    In digital photography, DX also refers to Nikon's crop sensor format
    DSLRs.

    DX encoding was introduced in 1980, well after the development of 35mm
    film and so many types of film do not include DX codes.

    This module uses features in and requires Perl 5.22.

SEE ALSO

    Photography::EV

    http://en.wikipedia.org/wiki/DX_encoding

AUTHOR

    Graham Ollis <plicease@cpan.org>

COPYRIGHT AND LICENSE

    This software is copyright (c) 2015 by Graham Ollis.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

