<PAGE>

                                IMAX CORPORATION
                                   Exhibit 4.8

                             SUPPLEMENTAL INDENTURE

            Supplemental Indenture (this "Supplemental Indenture"), dated as of
April 1, 2004 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"), Taurus-Littrow Productions Inc.
and 3D Sea II Ltd. (each, a "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, providing for the issuance of 9-5/8% Senior Notes due 2010
(the "Securities");

            WHEREAS, the Indenture provides that under certain circumstances
each 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 Supplemental Indenture.

            NOW THEREFORE, in consideration of the foregoing and for other good
and valuable consideration, the receipt of which is hereby acknowledged, each
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. Each 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 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,

<PAGE>

whether at stated maturity, by acceleration, redemption, upon a Change of
Control Offer, upon an Asset Sale Offer or otherwise.

            The obligations of each 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 either of the
Guaranteeing Subsidiaries (or any such successor entity), as such, shall have
any liability for any obligations of such 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 each 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 each 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 SUPPLEMENTAL INDENTURE.

            4. Counterparts. The parties may sign any number of copies of this
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.

<PAGE>

            IN WITNESS WHEREOF, the parties hereto have caused this 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.

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

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

                               IMAX II U.S.A. Inc.

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

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

                                        3
<PAGE>

                               IMAX Chicago Theatre LLC
                               By its Managing Member
                               IMAX Theatre Holding (California I) Co.

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

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

                               IMAX Forum Ride, Inc.

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

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

                               IMAX Minnesota Holding Co.

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

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

                               IMAX Rhode Island Limited Partnership
                               By its General Partner
                               IMAX Providence General Partner Co.

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

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

                                        4
<PAGE>

                               IMAX Sandde Animation Inc.

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

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

                               IMAX Scribe Inc.

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

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

                               IMAX Space Ltd.

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

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

                               IMAX Theatre Holding Co.

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

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

                                        5
<PAGE>

                               IMAX Theatre Holdings (OEI) Inc.

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

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

                               IMAX Theatre Management Company

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

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

                               IMAX Theatre Services Ltd.

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

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

                               IMAX U.S.A. Inc.

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

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

                                        6
<PAGE>

                               Miami Theatre LLC
                               By its Managing Member
                               IMAX Theatre Holding (California I) Co.

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

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

                               Mitey Cinema Inc.

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

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

                               Mountainview Theatre Management Ltd.

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

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

                               Nyack Theatre LLC
                               By its Managing Member
                               IMAX Theatre Holding (Nyack I) Co.

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

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

                                        7
<PAGE>

                               Ridefilm Corporation

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

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

                               Sacramento Theatre LLC
                               By its Managing Member
                               IMAX Theatre Holding (California I) Co.

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

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

                               Sonics Associates, Inc.

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

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

                               Starboard Theatres Ltd.

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

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

                                        8
<PAGE>

                               Tantus Films Ltd.

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

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

                               Wire Frame Films Ltd.

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

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

                               1329507 Ontario Inc.

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

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

                               924689 Ontario Inc.

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

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

                                        9
<PAGE>

                               IMAX (Titanica) Ltd.

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

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

                               IMAX (Titanic) Inc.

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

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

                               IMAX Music Ltd.

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

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

                               IMAX Theatre Holding (Brossard) Inc.

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

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

                                       10
<PAGE>

                               IMAX Film Holding Co.

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

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

                               IMAX Indianapolis LLC

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

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

                               IMAX Pictures Corporation

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

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

                               Immersive Entertainment Inc.

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

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

                                       11
<PAGE>

                               IMAX Providence General Partner Co.

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

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

                               IMAX Providence Limited Partner Co.

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

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

                               IMAX Theatre Holding (California I) Co.

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

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

                               IMAX Theatre Holding (California II) Co.

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

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

                                       12
<PAGE>

                               IMAX Theatre Holding (Nyack I) Co.

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

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

                               IMAX Theatre Holding (Nyack II) Co.

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

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

                               IMAX Theatre Management (Scottsdale), Inc.

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

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

                               Panda Productions Inc.

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

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

                                       13
<PAGE>

                               Strategic Sponsorship Corporation

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

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

                               Tantus II Films Ltd.

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

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

                               RPM Pictures Ltd.

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

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

                               GUARANTEEING SUBSIDIARIES:

                               Taurus-Littrow Productions Inc.

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

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

                                       14
<PAGE>

                               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

                                       15
<PAGE>

                               TRUSTEE:

                               U.S. Bank National Association, As Trustee

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

                                       16