Version v3 — Effective date: April 30, 2026
The short version: Zeus Focus Stacking processes all your images entirely on your device. We do not upload your photos unless you explicitly opt in — either by submitting an image to Picture of the Week (a free, voluntary photographic showcase) or by sharing a project to the Engine Improvement Program (a research dataset to help us improve the alignment and stacking algorithms). On our Website you may also optionally subscribe to receive the weekly Picture of the Week (and, if you choose, occasional product updates) via email; this is a separate, fully voluntary email subscription with one-click unsubscribe. We collect anonymous usage analytics and crash reports to improve the app — no advertising IDs, no tracking for marketing purposes.
The data controller for all personal data processed in connection with Zeus Focus Stacking is:
Zeus Focus Stacking
Independent app project based in Switzerland
Email: privacy@zeusfocusstacking.com
All image capture, alignment, and focus stacking is performed entirely on your device by the Zeus Focus Stacking native engine. Your photos are never uploaded to any server as a byproduct of normal app use. Captured frames and stacked results are kept inside the App's private storage; results are written to your device's photo library only when you tap "Save to Photos" — at that moment, the App requests add-only photo library permission, which means the App can write images but cannot read your existing library.
There are exactly two flows in which content leaves your device, both of which require an explicit action and a consent step inside the App:
Zeus Focus Stacking uses Firebase Analytics and Firebase Crashlytics (operated by Google LLC) to collect anonymous usage and stability data. This helps us understand how the App is used and fix crashes quickly. The data collected includes:
This data is not linked to your identity. The App is configured so that no Apple advertising identifier (IDFA) is accessible to Firebase: the GoogleAppMeasurementIdentitySupport dependency is not linked into the build. We do not collect:
Firebase Analytics and Crashlytics data is stored on Google's servers and is subject to Google's Privacy Policy.
Picture of the Week is an opt-in, free photographic showcase. You can choose to submit an image from your gallery using the "Submit to Picture of the Week" button, which shows a disclaimer and a consent form before anything leaves your device. See the Terms of Service — Picture of the Week for the full operational rules.
When you submit to Picture of the Week, the following data is transmitted to our backend (operated by Google LLC via Firebase):
We process Picture of the Week submission data for the following purposes:
The legal basis for all of the above is your explicit consent, given through the disclaimer and consent checkboxes in the submission flow. You may withdraw this consent at any time (see Section 10).
Picture of the Week submission data is accessible only to:
We do not sell or share Picture of the Week data with any other third party. If your image is selected and published, it becomes publicly visible together with the author name you provided; no other personal data is ever made public.
On our Website you may optionally subscribe to receive the Picture of the Week by email. This subscription is independent of the App and of any Picture of the Week submission you may have made: subscribing does not create an App account, and submitting an image does not subscribe you to anything.
When you submit the subscribe form on the Website (Picture of the Week page), we store the following on our backend (operated by Google LLC via Firebase):
en, it) and your user-agent string;After you submit the form, your address is stored as pending and we send you a confirmation email. Your subscription is only activated when you click the confirmation link. If you do not click within 7 days, the confirmation token expires and the pending record is no longer usable. This double opt-in step is mandatory and protects you from being subscribed against your will.
We process your subscription data for the following purposes:
bounced and stops receiving messages);The legal basis is your explicit consent under the GDPR (Art. 6(1)(a)) and the Swiss FADP, given through the Website form and confirmed via the double opt-in click. You may withdraw consent at any time without justification.
Subscription data is accessible only to:
We do not sell, rent, or share your subscriber data with any other third party. The list is never used to enrich a profile elsewhere.
Zeus Focus Stacking includes an opt-in feature called "Contribute to Engine Improvement", available from the actions menu of any saved project. The Program lets you donate a complete capture (the original individual frames plus the stacked result) so we can use it to test and improve the alignment and stacking algorithms.
Participation is entirely voluntary, free, and has no impact on App functionality, Pro entitlement, or anything else. Nothing is sent until you tap the button, fill in the consent sheet, and confirm.
When you submit a project to the Engine Improvement Program, the following is uploaded to our backend (operated by Google LLC via Firebase):
We do not upload location coordinates, your name, your email address, your subscription tier, your gallery contents, or any data beyond the specific project you chose to submit and its consent flag.
The data is processed for the sole purpose of improving the alignment and stacking algorithms: we run new engine versions over your contributed bracket, compare results, and tune parameters. The legal basis is your explicit consent, given through the consent sheet inside the App. You may withdraw consent at any time (see Section 10).
Engine Improvement Program data is accessible only to Zeus Focus Stacking and to Google LLC as the operator of Firebase, acting as a data processor under Google's standard terms. Contributed images and frames are never published, never shown publicly, never used in marketing, and never shared with any other third party. They are used internally as test inputs against the algorithms and discarded once they are no longer useful for that purpose.
Contributed projects are retained for as long as the corresponding engine generation is being developed or maintained, then deleted. You may request earlier deletion at any time via the contact in Section 10.
If you grant location permission, Zeus Focus Stacking saves the GPS coordinates and a reverse-geocoded place name for your capture sessions locally on your device using SwiftData. This allows you to browse your stacking projects on a map within the App. Location data is never transmitted to any external server or third party — neither in Picture of the Week submissions, nor in Engine Improvement Program submissions, nor in analytics events.
Location access is optional. The App functions fully without it. The pre-permission prompt and the iOS system prompt are only shown when you actively choose to enable the feature.
Zeus Focus Stacking may download lens calibration profiles from Firebase Cloud Storage (operated by Google LLC) to improve alignment accuracy. This is a read-only download:
Zeus Focus Stacking uses the following third-party services, all operated by Google LLC via Firebase:
No advertising SDKs or marketing tracking services are integrated.
Under the Swiss Federal Act on Data Protection (FADP) and, where applicable, the EU General Data Protection Regulation (GDPR), you have rights of access, rectification, erasure, restriction, portability, and withdrawal of consent concerning the personal data we process about you, plus the right to lodge a complaint with the Swiss Federal Data Protection and Information Commissioner (FDPIC) or, if you are an EU resident, with your local supervisory authority.
The personal data we may hold about you, depending on which optional features you used, is limited to:
We do not ask for your email when you submit Picture of the Week, we do not assign you an account, and we do not track you across devices.
To request a copy, correction, or deletion of any of the above, use Settings → Privacy & Data → Submit a privacy request in the App. The request includes your Contribution ID automatically, which is what lets us locate your data. You can also write to privacy@zeusfocusstacking.com. We respond within 30 days.
Zeus Focus Stacking requests access to:
These permissions are used solely for in-App functionality. No data from these sources is transmitted externally, except for the Picture of the Week and Engine Improvement Program flows described in Section 4 and Section 6.
Zeus Focus Stacking does not require or support user accounts for normal App use. There is no sign-up, login, or authentication of any kind in the App. The first time you submit to Picture of the Week or to the Engine Improvement Program the App generates an anonymous Firebase identifier on your device and stores it locally so that subsequent submissions are scoped to the same device, but no human-readable identifier is involved.
A separate, invitation-only account system exists on the Website for members of the Picture of the Week jury. Jury accounts are not related to any App user and are never created from within the App.
Subscription and purchase transactions are handled entirely by Apple through the App Store using StoreKit 2. Zeus Focus Stacking does not process, store, or have access to any payment information. Apple shares the entitlement state with us through StoreKit; we use it only to determine whether to unlock Pro features locally and we cache the resulting tier in the App's local storage.
Zeus Focus Stacking does not knowingly collect personal data from children under 16. Picture of the Week submissions require the submitter to confirm they are at least 18 years old. The Engine Improvement Program is intended for adult photographers; we do not solicit it from minors. If we become aware that we have received personal data from a child, we will delete it promptly.
All your images and project data remain on your device by default, protected by iOS's built-in security features including device encryption and App sandboxing.
iCloud Sync (optional, Pro feature): if you enable iCloud Sync in Settings, copies of your projects (and optionally the original captured frames) are stored in your private iCloud Drive container. iCloud is operated by Apple Inc.; we do not have access to your iCloud data. Disabling iCloud Sync stops new uploads; previously synced files remain in your iCloud Drive until you remove them.
Anonymous analytics data, Picture of the Week submissions, and Engine Improvement Program submissions are transmitted to Firebase servers over HTTPS. Picture of the Week submissions and Engine Improvement Program contributions are stored on Google Cloud Storage with access restricted by Firebase Security Rules to the data controller and, in the case of Picture of the Week, to the privately-invited jury.
Google Firebase infrastructure may store data in data centers located outside Switzerland, including in the European Union and the United States. Google LLC has adopted standard contractual clauses and additional safeguards for international transfers. See Firebase Privacy and Security for details.
If we make material changes to this privacy policy, we will update the effective date and version number at the top of this page, and we will communicate material changes through an App update or in-App notice. Continued use of the App after the effective date constitutes acceptance of the updated policy.
If you have questions about this privacy policy or wish to exercise any of the rights described above, contact us at: