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                                IMAX CORPORATION
                                  Exhibit 4.10

                          THIRD SUPPLEMENTAL INDENTURE

            Third Supplemental Indenture (this "Third Supplemental Indenture"),
dated as of February 2, 2005 among IMAX Corporation, a corporation incorporated
under the federal laws of Canada (the "Company"), the Guarantors named in the
Indenture referred to below (the "Existing Guarantors"), the First Supplemental
Guarantors named in the Supplemental Indenture referred to below, the Second
Supplemental Guarantor named in the Second Supplemental Indenture referred to
below, Automation Productions Ltd. (the "Guaranteeing Subsidiary") and U.S. Bank
National Association, as trustee under the Indenture referred to below (the
"Trustee").

                               W I T N E S S E T H

            WHEREAS, the Company and the Existing Guarantors have heretofore
executed and delivered to the Trustee an indenture (the "Indenture"), dated as
of December 4, 2003, as amended by the First Supplemental Indenture dated as of
April 1, 2004 among the Company, the Existing Guarantors, 3D Sea II Ltd. and
Taurus-Littrow Productions Inc. (the "First Supplemental Guarantors") and the
Trustee (the "First Supplemental Indenture"), and as further amended by the
Second Supplemental Indenture dated as of July 14, 2004 among the Company, the
Existing Guarantors, the First Supplemental Guarantors and Big Engine Films Inc.
(the "Second Supplemental Guarantor") and the Trustee (the "Second Supplemental
Indenture"), providing for the issuance of 9-5/8% Senior Notes due 2010 (the
"Securities");

            WHEREAS, the Indenture provides that under certain circumstances the
Guaranteeing Subsidiary shall execute and deliver to the Trustee a supplemental
indenture pursuant to which any newly-acquired or created Guarantor shall
unconditionally guarantee all of the Company's obligations under the Securities
and the Indenture on the terms and conditions set forth herein (the "Subsidiary
Guarantee"); and

            WHEREAS, pursuant to Section 901 of the Indenture, the Trustee is
authorized to execute and deliver this Third Supplemental Indenture.

            NOW THEREFORE, in consideration of the foregoing and for other good
and valuable consideration, the receipt of which is hereby acknowledged, the
Guaranteeing Subsidiary and the Trustee mutually covenant and agree for the
equal and ratable benefit of the Holders of the Securities as follows:

            1. Capitalized Terms. Capitalized terms used herein without
definition shall have the meanings assigned to them in the Indenture.

            2. Agreement to Guarantee. The Guaranteeing Subsidiary irrevocably
and unconditionally guarantees the Guarantee Obligations, which include (i) the
due and punctual payment of the principal of, premium, if any, and interest and
Special Interest, if any, on the Securities, whether at maturity, by
acceleration, redemption, upon a Change of Control Offer, upon an Asset Sale
Offer or otherwise, the due and punctual payment of interest on the overdue
principal and premium, if any, and (to

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the extent permitted by law) interest on any interest on the Securities, and
payment of expenses, and the due and punctual performance of all other
obligations of the Company, to the Holders or the Trustee all in accordance with
the terms set forth in Article XIII of the Indenture, and (ii) in case of any
extension of time of payment or renewal of any Securities or any such other
obligations, that the same will be promptly paid in full when due or performed
in accordance with the terms of the extension or renewal, whether at stated
maturity, by acceleration, redemption, upon a Change of Control Offer, upon an
Asset Sale Offer or otherwise.

            The obligations of the Guaranteeing Subsidiary to the Holders and to
the Trustee pursuant to this Subsidiary Guarantee and the Indenture are
expressly set forth in Article XIII of the Indenture and reference is hereby
made to such Indenture for the precise terms of this Subsidiary Guarantee.

            No past, present or future director, officer, partner, manager,
employee, incorporator or stockholder (direct or indirect) of the Guaranteeing
Subsidiary (or any such successor entity), as such, shall have any liability for
any obligations of the Guaranteeing Subsidiary under this Subsidiary Guarantee
or the Indenture or for any claim based on, in respect of, or by reason of, such
obligations or their creation, except in their capacity as an obligor or
Guarantor of the Securities in accordance with the Indenture.

            This is a continuing Guarantee and shall remain in full force and
effect and shall be binding upon the Guaranteeing Subsidiary and its successors
and assigns until full and final payment of all of the Company's obligations
under the Securities and Indenture or until released in accordance with the
Indenture and shall inure to the benefit of the successors and assigns of the
Trustee and the Holders, and, in the event of any transfer or assignment of
rights by any Holder or the Trustee, the rights and privileges herein conferred
upon that party shall automatically extend to and be vested in such transferee
or assignee, all subject to the terms and conditions hereof. This is a Guarantee
of payment and not of collectibility.

            The obligations of the Guaranteeing Subsidiary under its Subsidiary
Guarantee shall be limited to the extent necessary to insure that it does not
constitute a fraudulent conveyance under applicable law.

            THE TERMS OF ARTICLE XIII OF THE INDENTURE ARE INCORPORATED HEREIN
BY REFERENCE.

            3. NEW YORK LAW TO GOVERN. THE LAWS OF THE STATE OF NEW YORK SHALL
GOVERN AND BE USED TO CONSTRUE THIS THIRD SUPPLEMENTAL INDENTURE.

            4. Counterparts. The parties may sign any number of copies of this
Third Supplemental Indenture. Each signed copy shall be an original, but all of
them together represent the same agreement.

            5. Effect of Headings. The Section headings herein are for
convenience only and shall not affect the construction hereof.

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            IN WITNESS WHEREOF, the parties hereto have caused this Third
Supplemental Indenture to be duly executed and attested, all as of the date
first above written.

                        IMAX Corporation

                        By /s/ "G. Mary Ruby"
                           -----------------------------------
                        Name: G. Mary Ruby
                        Title: Sr. Vice President, Legal Affairs

                        By /s/ "Edward MacNeil"
                           -----------------------------------
                        Name: Edward MacNeil
                        Title: Vice President Finance, Special Projects

                        EXISTING GUARANTORS:

                        David Keighley Productions 70MM Inc.
                        IMAX II U.S.A. Inc.
                        IMAX Chicago Theatre LLC
                              By its Managing Member
                              IMAX Theatre Holding (California I) Co.
                        IMAX Minnesota Holding Co.
                        IMAX Rhode Island Limited Partnership
                              By its General Partner
                              IMAX Providence General Partner Co.
                        IMAX Sandde Animation Inc.
                        IMAX Scribe Inc.
                        IMAX Space Ltd.
                        IMAX Theatre Holding Co.
                        IMAX Theatre Holdings (OEI) Inc.
                        IMAX Theatre Management Company
                        IMAX Theatre Services Ltd.
                        IMAX U.S.A. Inc.
                        Miami Theatre LLC
                              By its Managing Member
                              IMAX Theatre Holding (California I) Co.
                        Nyack Theatre LLC
                              By its Managing Member
                              IMAX Theatre Holding (Nyack I) Co.
                        Parker Pictures Ltd.
                        Ridefilm Corporation
                        Sacramento Theatre LLC
                              By its Managing Member
                              IMAX Theatre Holding (California I) Co.

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                        Sonics Associates, Inc.
                        Starboard Theatres Ltd.
                        Tantus Films Ltd.
                        1329507 Ontario Inc.
                        924689 Ontario Inc.
                        IMAX (Titanica) Ltd.
                        IMAX (Titanic) Inc.
                        IMAX Music Ltd.
                        IMAX Film Holding Co.
                        IMAX Indianapolis LLC
                        IMAX Providence General Partner Co.
                        IMAX Providence Limited Partner Co.
                        IMAX Theatre Holding (California I) Co.
                        IMAX Theatre Holding (California II) Co.
                        IMAX Theatre Holding (Nyack I) Co.
                        IMAX Theatre Holding (Nyack II) Co.
                        IMAX Theatre Management (Scottsdale), Inc.
                        Strategic Sponsorship Corporation
                        Tantus II Films Ltd.
                        RPM Pictures Ltd.

                        By /s/ "G. Mary Ruby"
                           -----------------------------------
                        Name: G. Mary Ruby
                        Title: Secretary

                        By /s/ "Edward MacNeil"
                           -----------------------------------
                        Name: Edward MacNeil
                        Title: Vice President

                        FIRST SUPPLEMENTAL GUARANTORS:

                        Taurus-Littrow Productions Inc.
                        3D Sea II Ltd.

                        By /s/ "G. Mary Ruby"
                           -----------------------------------
                        Name: G. Mary Ruby
                        Title: Secretary

                        By /s/ "Edward MacNeil"
                           -----------------------------------
                        Name: Edward MacNeil
                        Title: Vice President

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                        SECOND SUPPLEMENTAL GUARANTOR:

                        Big Engine Films Inc.

                        By /s/ "G. Mary Ruby"
                           -----------------------------------
                        Name: G. Mary Ruby
                        Title: Secretary

                        By /s/ "Edward MacNeil"
                           -----------------------------------
                        Name: Edward MacNeil
                        Title: Vice President

                        GUARANTEEING SUBSIDIARY:

                        Automation Productions Ltd.

                        By /s/ "G. Mary Ruby"
                           -----------------------------------
                        Name: G. Mary Ruby
                        Title: Secretary

                        By /s/ "Edward MacNeil"
                           -----------------------------------
                        Name: Edward MacNeil
                        Title: Vice President

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                              TRUSTEE:

                              U.S. Bank National Association, As Trustee

                              By: /s/ "Frank P. Leslie III"
                                  -----------------------------------
                              Name: Frank P. Leslie III
                              Title: Vice President