You need to initialize the camera, and for some reason (possibly interlacing) you need to grab 2. This is a Tk gui to take a picture, notice you must initialize properly, and it's complicated by the use of the term "Channel", it's not what you think. See the grab script mentioned above for grabinfo for your setup.

#!/usr/bin/perl
use warnings;
use strict;
use Video::Capture::V4l;
use Imager;
use Tk;
use Tk::JPEG;
use MIME::Base64;

my $timestamp;
my $temp = '';

sub grab_one {
    $temp      = '';
    $timestamp = scalar(localtime);
    $timestamp =~ tr/ /_/;
    $| = 1;

    my $grab = new Video::Capture::V4l
      or die "Unable to open Videodevice: $!";

    # the following initializes the camera for NTSC
    my $channel = $grab->channel(1); #1 is composite 0 is for tuner
    my $tuner   = $grab->tuner(0);
    $tuner->mode(1);
    $channel->norm(1);
    $tuner->set;
    $channel->set;

    my $frame = 0;
    my $fr    = $grab->capture( $frame, 320, 240 );
    my $count = 0;

    for ( 0 .. 1 ) {
        my $nfr = $grab->capture( 1 - $frame, 320, 240 );
        $grab->sync($frame) or die "unable to sync";

        unless ( $count == 0 ) {

            # save $fr now, as it contains the raw BGR data
            $temp = '';
            open( JP, '>', \$temp ) or die $!;
            print JP "P6\n320 240\n255\n";    #header
            $nfr = reverse $nfr;
            print JP $nfr;
            close JP;

            my $img = Imager->new();
            $img->read( data => $temp, type => 'pnm' )
              or warn $img->errstr();
            $img->flip( dir => "hv" );
            $img->write( data => \$temp, type => 'jpeg' )
              or warn $img->errstr;
        }
        $count++;
        $frame = 1 - $frame;
        $fr    = $nfr;
    }
}

grab_one();

my $mw = MainWindow->new();
my $image = $mw->Photo( -data => encode_base64($temp) );
$mw->Label( -image => $image )->pack( -expand => 1, -fill => 'both' );

my $label =
  $mw->Label( -text => $timestamp )->pack( -side => 'top', -padx => 3 
+);

my $center = $mw->Frame->pack( -anchor => 'center' );
$center->Button( -text => 'Quit', -command => [ destroy => $mw ] )
  ->pack( -side => 'left', -padx => 3 );
$center->Button( -text => 'Update', -command => \&update )
  ->pack( -side => 'left', -padx => 3 );
$center->Button( -text => 'Save', -command => \&save_it )
  ->pack( -side => 'left', -padx => 3 );

MainLoop;

sub save_it {
    open( JP, "> $timestamp.jpg" ) or die $!;
    print JP $temp;
    close JP;
    $label->configure( -text => "$timestamp.jpg  SAVED" );
    $label->update;
}

sub update {
    grab_one();
    $label->configure( -text => "$timestamp" );
    $label->update;
    $image->configure( -data => encode_base64($temp) );
    $image->update;
    $mw->update;
}
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