Privacy Policy

Version 1.0 · Effective date October 8, 2026

This Privacy Policy describes how Longlight (慢光) and longlight.gacing.com handle information: the data processed, its storage, access to it, and your choices. It applies to people who download, install, or use the App or visit the Site. The English version is the controlling version.

1. Introduction and Scope

1.1 What This Policy Covers. This Privacy Policy (this "Policy") describes information handled in connection with the App and the Site. It distinguishes processing on your device from information you choose to send to the Developer, information supplied by Apple, and technical processing needed to deliver website pages. It also describes retention, the purposes and legal bases for the Developer's processing, and your rights and choices.

1.2 Definitions. In this Policy:

• "App" means Longlight (Chinese name 慢光), Bundle ID com.gacing.Longlight, distributed through the Apple App Store for iPhone and iPad running iOS or iPadOS 18 or later.
• "Site" means longlight.gacing.com, a subdomain of gacing.com.
• "Developer" means the developer of the App, using GACING as the public signature.
• "You" and "your" mean a person using the App or the Site and, where that person acts for an organization, that organization.
• "Apple" means Apple Inc.
• "Terms" means the Terms of Use for the App and the Site, published on the Site.
• "Works" means finished photographs, optionally retained source frames, growth videos, and reports stored by the App.
• "Diagnostic Data" means the diagnostic log and capability report described in Section 5.2.

1.3 The App in Brief. The App stacks multiple short exposures on your device to create long-exposure photographs. It includes presets and "Manual" capture, "Test frame" assessment, offline astronomical time and moon-phase calculations, minute-by-minute checkpoints and recovery, optional source-frame retention, and exports. The App is free of charge, with no in-app purchases or subscriptions. It is advertising-free and works without an account.

1.4 Relationship to the Terms. The Terms refer to this Policy, and the two documents should be read together. This Policy is an informational notice about data handling. It is not incorporated into the Terms as a contractual term and does not form part of the contract between you and the Developer.

1.5 Data Handling in Summary. The App establishes no network connections. Camera processing, stacking, calculations, and storage take place on your device, and the Developer receives no data from within the App. Diagnostic materials leave the device only when you choose "Share diagnostics log" or "Share capability report" under "Settings" › "Diagnostics" and select a destination; the Developer receives only a copy you send to the Developer. Separately, the Developer receives your emails, may receive aggregate crash and usage statistics through Apple's system analytics-sharing mechanism, and operates the Site, whose server processes connections to deliver pages.

1.6 Roles. For data protection purposes, the Developer is the controller of correspondence and Diagnostic Data you send to the Developer, and of connection data processed by the Developer's website server. Apple independently determines how its App Store, account, backup, and analytics services process information. The Site is hosted by DMIT in Los Angeles, California, United States. Email is stored by a mail service operated by the Developer.

2. Data Overview

2.1 Overview Table. The table summarizes data associated with the App and the Site. "Developer Access" distinguishes local data from a copy you choose to send and from information handled through the Site or Apple.

2.2 Reading the Table. Sections 3 through 7 explain these categories. Section 8 describes the purposes and legal bases of the Developer's processing. Section 11 brings together the retention rules, and Section 12 explains your controls. A file retained by a backup or sharing destination is a separate copy; deleting the App's copy does not delete that separate copy.

3. Data Processed and Stored on Your Device

3.1 Camera and Image Processing. The App uses the camera to capture multiple short-exposure frames and stacks them on the device. Camera permission enables capture. Frames and finished photographs are processed locally, including the operations used to create a long-exposure result. The App's image processing does not send images to a server or give the Developer access to them.

3.2 Works and Optional Source Frames. Works are saved in the App’s Documents directory and can be seen in the Files app. Works include finished photographs, previews, 16-bit TIFF files, optional source frames, growth videos, work reports, and work information. "Keep every frame" is optional. With retained frames, you can exclude selected minutes using "Re-stack"; you can also use "Undo last minute". These operations take place on your device. Finished photographs (HEIF), previews, 16-bit TIFF files, work reports, and work information are included in system iCloud or computer backups according to your backup settings. The App marks retained source frames, growth videos, and recovery checkpoints as excluded from system backups.

3.3 Recovery Checkpoints. The App saves a checkpoint every minute for recovery after an interruption. Checkpoints are held in the App's Application Support directory and are excluded from backups. Recovery uses the saved state on your device when you reopen the App. Checkpoints are separate from works stored in Documents and from system backup copies.

3.4 Photos Access. "Save finished photos to Photos" is enabled by default and can be turned off in the App’s "Settings". For this purpose, the App requests only permission to add photographs. It does not read photographs already in your library. The setting for saving to Photos and the operating system's permission control are separate: saving requires the relevant permission. Images saved to Photos are separate from works in the App's Documents directory.

3.5 Location for Calculations. Location is optional. The App uses it to calculate twilight periods and moon phase offline in "Tonight"; you may enter latitude and longitude manually instead. This calculation takes place on your device and does not require sending coordinates to an online service. The App does not store location as a route or movement history. Choosing to use location for calculations does not by itself turn on the separate photograph-location setting in Section 3.6.

3.6 Location in Photograph Metadata. "Write location into photos" is off by default. When you turn it on, the App writes location into photograph metadata. Location is not transmitted by the App. If you export or share a photograph containing location metadata, that metadata accompanies the copy containing it and can be available to its recipient. Turning off the setting controls whether location is written into photographs; it does not remove metadata from photographs already saved or from copies already shared.

3.7 Motion Sensors. The App uses motion sensor readings only to display the level. The readings are not recorded.

3.8 Local Diagnostics. The App keeps a rolling diagnostic log and a capability report on the device. The capability report describes the device model, operating system version, and camera capability parameters. The diagnostic materials contain no photographs, location, or personally identifying information. Their presence on the device does not send them to the Developer. Sharing them is a separate action described in Section 5.

3.9 Exports and Sharing. Output options include HEIF, 16-bit TIFF, single-frame DNG on supported devices, and growth videos. You control the copies you export or share. When you choose a destination outside the App, that destination handles the supplied copy according to its own controls and policies. The Developer gains access to an exported work only if you choose to send that copy to the Developer, for example as an email attachment.

3.10 Deletion and Separate Copies. Deleting a work deletes it from the App's storage. Deleting the App deletes its data on the device, including local works, checkpoints, and diagnostics. The Developer cannot recover deleted local data. Photos-library copies, exported or shared files, and system backup copies are managed separately. Remove those copies at their respective destinations if you also wish to delete them.

4. Apple Services and System Backups

4.1 App Store and Accounts. Apple handles downloading the App through the App Store and the Apple account used for that distribution. Those activities are governed by Apple's privacy policy. The App does not have a user-account system, and the Developer does not receive an App account profile from your use of Longlight.

4.2 System Permissions. Apple's operating system manages camera access, add-only Photos permission, and optional location access. You can review and change the App's permissions in device settings. These controls determine which device resources the App may use; granting permission is not a direction to send the resulting images or coordinates to the Developer. Section 12.2 explains how these choices relate to capture and saving.

4.3 iCloud and Computer Backups. Finished photographs (HEIF), previews, 16-bit TIFF files, work reports, and work information are included in system iCloud or computer backups according to your backup settings. The App marks retained source frames, growth videos, and recovery checkpoints as excluded from system backups. The Developer does not operate those backups or receive their contents. Apple's handling of iCloud backups is governed by Apple's terms and privacy policy; computer backups are under your control. Inclusion of works in a system backup does not mean the App itself establishes a network connection.

4.4 Analytics Shared Through Apple. If you choose in system settings to share analytics with app developers, Apple can provide the Developer with aggregate crash and usage statistics through Apple's mechanism. The Developer does not add an analytics collection mechanism to the App. This Apple-supplied information is separate from the local diagnostic log and capability report that you may choose to share from the App’s "Settings".

4.5 Apple's Privacy Policy. Apple's processing for its services is governed by the Apple Privacy Policy. Apple independently determines the purposes and means of its processing, including for App Store distribution, accounts, iCloud backups, and the analytics it makes available. Controls for those services are provided through Apple's systems.

5. Diagnostic Data You Choose to Send

5.1 User-Initiated Sharing. The App keeps Diagnostic Data locally. To share it, open "Settings" › "Diagnostics" and select "Share diagnostics log", or select "Write capability report" followed by "Share capability report", then choose a destination, such as an email addressed to the Developer. The selected service handles delivery. The Developer receives only the copy you send to the Developer. Opening or using the App does not initiate a diagnostic transmission, and sharing a file does not grant continuing access to diagnostics on the device.

5.2 Contents. Diagnostic Data consists of the rolling diagnostic log and the capability report. The capability report contains the device model, operating system version, and camera capability parameters. These diagnostic materials exclude photographs, location, and personally identifying information. Your email address, message, and any other files you attach are correspondence under Section 7 and are distinct from the contents of the diagnostic materials themselves.

5.3 Destination and Transmission. You decide where a shared diagnostic copy goes. If you select email or another service, that service handles the transmission under its own policies. Choosing a destination other than the Developer does not send the Developer a copy. To send materials for support, use longlight@gacing.com. Review the selected destination and the material you are sending before completing the share action.

5.4 Use by the Developer. The Developer uses diagnostic materials you send to investigate and resolve the technical issue for which you requested support. They are handled with the associated correspondence described in Section 7.

5.5 Requests About Sent Copies. You may request access to or deletion of the diagnostic copy you sent by emailing longlight@gacing.com. Include the sending address and approximate sending time so the Developer can identify the relevant correspondence. Requests concern copies held by the Developer. A request to the Developer does not delete local files or copies you sent to other recipients.

5.6 Retention. Diagnostic materials you send to the Developer are retained under the correspondence rule in Section 7.3. The local rolling log remains distinct from that sent copy: changes to local diagnostics do not update an attachment already received by the Developer. Likewise, deleting the App does not withdraw a message already delivered. Section 12 describes your rights regarding information the Developer holds.

6. The Site

6.1 Operation and Hosting. The Site is a static website at longlight.gacing.com, a subdomain of gacing.com. It is hosted by DMIT in Los Angeles, California, United States. It presents information about the App, legal documents, and support information. Visiting the Site uses your browser's network connection and is separate from the App's on-device operation.

6.2 Connection Data. To respond to your browser's request for a page, the website server processes your IP address and related connection data as needed to deliver that page. Access logs are not enabled on the server. The hosting provider and network operators may process technical connection data under their own policies to deliver traffic.

6.3 Page Resources and Tracking. The Site uses no cookies, analytics, or tracking. Its pages do not load third-party fonts or scripts. The App likewise contains no analytics collection, advertising identifiers, or third-party SDKs. Apple's optional sharing of aggregate statistics, described in Section 4.4, is an operating-system mechanism and is separate from the App and Site practices described here.

6.4 Installation Page. The Site includes a beta installation page for registered devices only.

7. Correspondence

7.1 Information Received. When you email the Developer, the Developer receives your sending address, the content of your message, and the information and files you choose to include. This can include diagnostic materials or a photograph you decide to attach.

7.2 Purpose. Correspondence is used to reply to you and handle your support question or other request, including privacy requests. The Developer may also retain it as necessary to comply with legal obligations, resolve disputes, and establish, exercise, or defend legal rights. Suggestions, ideas, and feedback are addressed in the Terms. Include information relevant to your request when deciding what to send.

7.3 Storage and Retention. Email sent to longlight@gacing.com is stored by a mail service operated by the Developer. Correspondence, including diagnostic attachments, is retained for the period necessary to handle your request and thereafter for any period necessary to comply with legal obligations, resolve disputes, and establish, exercise, or defend legal rights. The same rule applies to copies of works you choose to attach. This retention concerns received correspondence, not works that remain only on your device.

8. Purposes and Legal Bases

8.1 On-Device Activities. Capture, stacking, astronomical calculations, level display, checkpoints, local diagnostics, and the creation of exports occur on your device. The Developer does not receive those data through the App. This Policy therefore does not describe those local activities as collection by the Developer. If you later send a resulting file, the Developer's handling of that copy falls under the relevant purpose below.

8.2 Diagnostic Support. Purpose: investigating and resolving technical problems in response to materials you choose to send for support. Where the General Data Protection Regulation applies, the legal basis for the Developer's processing is the legitimate interest in diagnosing technical problems and responding to requests under Article 6(1)(f). Your choice to share determines whether the Developer receives a diagnostic copy; the basis stated here concerns handling that received copy.

8.3 Correspondence. Purposes: responding to and handling requests, and retaining correspondence as needed for legal obligations, disputes, and legal rights. Where applicable, the Developer relies on legitimate interests in responding to requests and establishing, exercising, and defending legal rights under Article 6(1)(f) of the General Data Protection Regulation. Where retention is required by a legal obligation, the applicable basis is compliance with that obligation under Article 6(1)(c).

8.4 Website Delivery. Purpose: delivering the web pages your browser requests. Where applicable, the legal basis is the Developer's legitimate interest in operating and delivering the Site. The connection processing described in Section 6.2 is for delivering pages, and access logs are disabled. It is separate from image processing in the App.

8.5 Apple-Supplied Statistics. Purpose: maintaining the stability and functionality of the App. Apple collects and supplies the aggregate crash and usage statistics through its own optional sharing mechanism under its privacy policy. Where a legal basis for the Developer's review is required, it is the legitimate interest in maintaining the App.

9. Sharing and Disclosure

9.1 Commercial Data Practices. The Developer does not sell personal information or share it for cross-context behavioral advertising as those terms are defined by the California Consumer Privacy Act. Information received for support is used for the purposes described in this Policy. The Developer does not use it for targeted advertising or profiling.

9.2 Limited Disclosures. Information held by the Developer may be disclosed where required by law or legal process, where necessary to establish, exercise, or defend legal rights, or in connection with a transfer of the App or a related business to a successor. These circumstances concern information the Developer holds. They do not give the Developer access to works or other data that remain on your device.

9.3 Infrastructure and Selected Services. The Site uses DMIT hosting in Los Angeles, California. The Developer operates the mail service that stores correspondence. Hosting and network providers may process technical data as needed to supply their infrastructure under their own policies. Services you choose for sharing, and Apple services you use for backups or distribution, have the separate roles described in Sections 4 through 7. Their handling of a supplied copy is subject to their policies.

10. Cross-Border Processing

10.1 Processing Context. The Site is hosted by DMIT in Los Angeles, California, United States, and website connection data is processed there to deliver pages. Correspondence and diagnostic materials you send are handled by the Developer's mail service. Information involved in website access or correspondence may be processed outside your jurisdiction. Apple determines the locations of its own processing under its policies. This section does not describe a transfer of local photographs or coordinates by the App.

10.2 European Economic Area and United Kingdom. If you are in the European Economic Area or United Kingdom, access to the Site involves processing outside that region, including in the United States where the Site is hosted. Where applicable data protection law requires a transfer mechanism or derogation, the relevant requirements apply to that processing. Any reliance on a derogation for a specific situation, including under Article 49 of the General Data Protection Regulation, is subject to its conditions. Sending an email does not by itself waive rights under applicable data protection law. You may contact the Developer about the handling of a particular request or transmission.

11. Data Retention

11.1 Sent Diagnostics. Diagnostic copies sent to the Developer follow Section 7.3. Retention is tied to handling the support request and any necessary legal retention. The App's rolling local log and the received attachment are separate copies. A deletion request about the received copy can be made as described in Section 5.5.

11.2 Correspondence and Website Connections. Correspondence follows the rule in Section 7.3. The website server has no enabled access logs and does not retain requests in such logs. Technical processing by the hosting provider or network operators is governed by their own policies.

11.3 Local Data and Backups. Works remain in the App's storage until you delete them or delete the App. The diagnostic log rolls over, and motion readings are not recorded. Location is not stored as a track; location written into a photograph remains part of that file. Deleting the App removes its local data, including checkpoints and diagnostics. Copies in Photos, exports, recipients' storage, and backups follow their respective controls. Finished photographs (HEIF), previews, 16-bit TIFF files, work reports, and work information are included in system iCloud or computer backups according to your backup settings. The App marks retained source frames, growth videos, and recovery checkpoints as excluded from system backups. Apple-held backup copies follow Apple's policies, and you manage computer backup copies.

11.4 Apple-Supplied Information. Availability and retention of aggregate crash and usage statistics supplied through Apple are determined by Apple's platform and policies. Changing the system analytics-sharing choice is separate from deleting local App files or requesting deletion of correspondence held by the Developer.

12. Your Rights and Choices

12.1 Local Works. You can manage works in "Captures" and access the App's Documents directory through Files. You can export your works, delete a work, or delete the App and its local data. These actions take place on your device and do not require a request to the Developer. Finished photographs (HEIF), previews, 16-bit TIFF files, work reports, and work information are included in system iCloud or computer backups according to your backup settings. The App marks retained source frames, growth videos, and recovery checkpoints as excluded from system backups. Manage Photos copies and backup copies separately if you want to remove those as well.

12.2 Permissions and Photo Saving. Use device settings to control camera, add-only Photos, and optional location permissions. Camera access is needed for capture. "Save finished photos to Photos" is on by default and can be turned off in the App’s "Settings"; it also requires add-only permission. These controls do not authorize reading existing photographs in the library. Withdrawing a permission does not delete previously saved works or previously exported copies.

12.3 Location Choices. You can use optional location for "Tonight" calculations or enter coordinates manually. The separate "Write location into photos" option is off by default. Consider the metadata already included in a saved photograph when sharing it, because changing the setting does not remove previously written location from existing files. The App does not keep a route history.

12.4 Diagnostic Sharing and Apple Analytics. You decide whether to share the diagnostic log or capability report and select the destination yourself. For a copy sent to the Developer, requests may be made under Section 5.5. Apple's system option to share analytics with developers is controlled separately in system settings. Selecting that option does not send the App's local diagnostic file through the App.

12.5 California Residents. To the extent the California Consumer Privacy Act, as amended by the California Privacy Rights Act, applies to the Developer and grants you these rights, California residents have rights to know what personal information is collected; access, correct, and delete it; opt out of its sale or sharing; and receive equal treatment when exercising those rights. Sale or sharing for cross-context behavioral advertising does not occur as described in Section 9.1. To exercise applicable rights, email longlight@gacing.com, identifying the correspondence concerned, such as its sending address and approximate date.

12.6 European Economic Area and United Kingdom. To the extent the General Data Protection Regulation or UK GDPR grants you these rights, you have rights of access, rectification, erasure, restriction of processing, data portability, and objection. Contact longlight@gacing.com to exercise them for information held by the Developer. You also have the right to complain to the data protection supervisory authority in your place of residence or work. These rights are subject to applicable legal conditions; they do not create Developer access to files that remain solely on your device.

13. Children

13.1 Age Direction. The App and the Site are not directed to children under 13, or under a higher minimum age required by the law of your jurisdiction. The Developer does not knowingly collect personal information from such children. The App's on-device operation does not send children's information to the Developer. If you believe a child has sent correspondence or diagnostic materials to the Developer, contact longlight@gacing.com.

14. Security

14.1 Device and Delivery Controls. Local data is held on your device within the operating system's storage environment. You control device access, backups, and the destinations to which you share copies. The service you select to send diagnostics or correspondence handles that transmission. Before sending a work for support, review the image and any included location metadata as well as the destination.

14.2 Limits of Security. No method of electronic storage or internet transmission is completely secure. The Developer cannot guarantee absolute security.

15. Changes to This Policy

15.1 Revisions. The Developer may revise this Policy. Revisions will be published on this page, and the date displayed by the page will be updated. Material revisions will be identified on the Site. Continued use of the App or the Site after publication constitutes acknowledgment of the revised notice. This acknowledgment does not turn the Policy into a contractual term or replace consent where applicable law requires it.

15.2 Language. This Policy is written in English. Translations are provided for reference. If a translation differs from the English text, the English version controls.

16. Contact

16.1 Contact. For questions about this Policy or to exercise a right described in it, contact GACING at longlight@gacing.com. Requests under this Policy are accepted in any language. For a request concerning information you sent, include enough context to locate the relevant correspondence, such as the sending address and approximate sending time.