Version v8 — Effective date: October 17, 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, and no tracking across other companies' apps or websites. The App sends you notifications only in the categories you choose in its Settings: your Picture of the Week results, and — only if you turn them on — news about the App (at most once a week, sent only in the daytime) and reminders to take a stack, which are created on your device. When you buy or renew a subscription, the store you bought it from — Apple's App Store on iPhone and iPad, Google Play or Samsung Galaxy Store on Android — sends us a notice of the transaction, which we keep; it never includes your name, email address, store account (such as your Apple ID or Google account) or payment details. This policy covers the App on iPhone and iPad and on Android; where the two differ, it says so.
The data controller for all personal data processed in connection with Zeus Focus Stacking is its developer, who runs the App and the Website as an individual:
Roberto Sartori
Zugerstrasse 29
8816 Hirzel
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" (on Android, "Save to Gallery") — at that moment, on iPhone and iPad, the App requests add-only photo library permission, which means the App can write images but cannot read your existing library. On Android, saving a picture to your photo library needs no permission, and the App cannot read your library either: when you import photos, you choose them in the system photo picker, which gives the App only the photos you select.
Some processing steps also run entirely on your device: an on-device machine-learning ("neural network") model estimates a depth map for each stack, and — for Pro subscribers — an AI object removal neural-network model fills the areas you paint over in the built-in editor and a Super Resolution neural-network model upscales the stacked result. These are bundled inside the App and run locally on your device (on iPhone and iPad, on its Neural Engine, GPU, or CPU); your photos are not uploaded, and no cloud service is used, for any of this processing.
There are exactly two flows in which content leaves your device for our servers, both of which require an explicit action and a consent step inside the App:
Two optional features also move your content off the device, but never to us: iCloud Sync (iPhone and iPad) and Google Drive Sync (Android) keep copies of your projects in your own cloud storage (see Section 16), and Remote Control sends the live view and your results directly from your phone to the browser you connect on the same Wi-Fi network or hotspot — nothing of it passes through our servers.
Zeus Focus Stacking uses Firebase Analytics and Firebase Crashlytics (operated by Google LLC) to collect usage and stability data. This helps us understand how the App is used, which features lead people to subscribe, and fix crashes quickly. The data collected includes:
This data is pseudonymous: it is keyed to device-scoped identifiers — on iPhone and iPad, a Firebase app-instance ID and Apple's identifier-for-vendor (IDFV); on Android, a Firebase app-instance ID and the installation identifiers of Firebase and Crashlytics — which allow events from the same installation to be grouped together, but are not connected to your name, email address, or any account (the App has none; see Section 12). We use this data for product analytics only, never for advertising: no advertising identifier is accessible to Firebase — on iPhone and iPad, the GoogleAppMeasurementIdentitySupport dependency is not linked into the build, so Apple's advertising identifier (IDFA) is not read; on Android, the App removes the advertising-ID permission and turns advertising-ID collection off in its configuration, so the Android advertising ID is not read — ad-personalization signals are disabled in the App's configuration, Google Signals is disabled on our analytics property, and advertising identifiers are excluded from our analytics exports. We do not collect:
Firebase Analytics and Crashlytics data is stored on Google's servers and is subject to Google's Privacy Policy. Crash reports, and the identifiers attached to them, are kept by Crashlytics for 90 days and then deleted. Analytics data is kept for the data-retention period set on our Google Analytics property, and the copy we export for our own analysis, without any advertising identifier, for as long as we use it to compare versions of the App and to understand how it is used. Deleting the App, or on Android clearing its storage, replaces the Firebase and Crashlytics identifiers with new ones, so that later data can no longer be grouped with earlier data under them; on iPhone and iPad, Apple's IDFV changes only once no app of ours is left on the device.
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 and, for notifications, through your device's notification permission. 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, in the App's project data. This allows you to browse your stacking projects on a map within the App. Location data is never transmitted to our servers — neither in Picture of the Week submissions, nor in Engine Improvement Program submissions (location metadata is removed from the uploaded pictures), nor in analytics events — and we never share it with anyone.
It leaves your device only through the platform's own services and your own cloud storage. To turn the coordinates into a place name, the App asks your device's system geocoding service (Apple's on iPhone and iPad; on Android, the one your device provides, usually Google's), which receives the coordinates for that lookup. The map itself is drawn by Apple's MapKit on iPhone and iPad and by the Google Maps SDK on Android, which load map tiles for the area shown. And if you turn on iCloud Sync or Google Drive Sync, the location saved with a project travels with it into your own cloud storage (see Section 16).
Location access is optional. The App functions fully without it. The pre-permission prompt and the system prompt (iOS or Android) 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, operated by Google LLC via Firebase:
On Android, the App also uses these services of the platform and of the stores:
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:
Copies kept by iCloud Sync or Google Drive Sync are in your own cloud storage, not with us; Section 16 explains how to delete them.
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, the location cases described in Section 7, and the notification registration described in Section 14.
You never need to create an account, sign up or log in to use Zeus Focus Stacking. The first time you submit to Picture of the Week or to the Engine Improvement Program, open Settings → Privacy & Data (which shows the identifier as your Contribution ID), or turn on News and releases (see Section 14), the App obtains an anonymous identifier from Firebase Authentication and keeps it on your device, so that later submissions and notification registrations are linked to the same device. No name, email address or other human-readable information is involved, and the identifier itself says nothing about you. We keep it until you ask us to delete it (see Section 10).
On Android, Google Drive Sync asks you to choose a Google account and to allow the App to use its own hidden folder in that account's Google Drive (see Section 16). This does not create an account with us: the App keeps the account's email address on your device only, to remember which account you chose, and we never receive it (see Google user data).
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 the store you installed the App from: on iPhone and iPad by Apple through the App Store (StoreKit 2); on Android by Google through Google Play (Google Play Billing) or by Samsung through Galaxy Store (Samsung In-App Purchase). Zeus Focus Stacking does not process, store, or have access to any payment information — no card number, billing address, or details of your Apple ID, Google account or Samsung account ever reach the App or us. The store tells the App whether your subscription is active; we use it to determine whether to unlock Pro features locally and we cache the resulting tier in the App's local storage.
When a purchase or free trial completes, the App additionally reports a purchase confirmation event to Firebase Analytics as described in Section 3: product identifier, plan, the price and currency the store recorded for the transaction, the store's transaction or order identifier, and the App feature that led to the purchase screen. We use this to measure which features convert and to reconcile our analytics against the stores' reporting. This event is keyed to the same pseudonymous, device-scoped identifiers as all other analytics — it is not connected to your store account or to any payment instrument.
Store purchase notices. Whenever a purchase or subscription changes — a purchase, a free trial, a renewal, a change of plan, a failed renewal, a cancellation, an expiry or a refund — the store informs our servers: Apple sends a signed notice (App Store Server Notifications); Google Play sends a real-time developer notification, after which our servers read the purchase from Google Play's developer interface; Samsung sends a signed Instant Server Notification, after which our servers read the subscription and its receipt from Samsung's servers. We verify that each notice comes from the store and store it on our servers (Firebase Cloud Firestore, operated by Google; see Section 9). A notice contains, as far as the store provides it: the type of event; the product and plan; the purchase, renewal and expiry dates; the price and currency; the store country; whether the subscription will renew; the store's identifiers for the transaction (or order) and for the subscription it belongs to; for Google Play, the reason for a cancellation if you gave one in Google Play's cancellation survey; and a random token the App generates for each purchase attempt so that it can recognise its own purchase. It does not contain your name, email address, store account (Apple ID, Google account or Samsung account), or any payment details.
We use these notices to understand how subscriptions start, renew, end and are refunded, to reconcile our figures with the stores' reporting, and to keep the history of each subscription. If we introduce an optional account in the future, this history will let you restore a purchase to that account — only if you choose to link it. Our legal basis is our legitimate interest in understanding our business and keeping accurate purchase records. The notices are identified by the store's transaction identifiers; the same identifier is part of the purchase confirmation event described in Section 3, so the two can be matched, but neither is connected to your identity. We keep each notice while the subscription it belongs to exists and for up to three years after its last notice. Because the notices are not linked to your name or email, write to privacy@zeusfocusstacking.com if you want yours deleted and we will help you identify them.
To manage or cancel a subscription, use the store you bought it from (on Android, also Settings → Manage Subscription in the App); see the Terms of Service. The stores' own processing of your purchase is governed by their privacy policies: Apple's, Google's and Samsung's.
The App can send you three kinds of notifications. Each has its own switch in the App, under Settings → Notifications, and none is shown unless you allowed the App to send notifications in your device's settings.
When you turn on News and releases, the App registers your device with our servers (Firebase, operated by Google LLC). If the anonymous identifier described in Section 12 does not exist yet, the App first creates it. We keep:
We use these records to send each piece of news at most once and at most one a week, to address news only to the devices it concerns (for example, a new version only to the devices that do not have it yet), and to count to how many devices each piece of news was sent and how many of those sends the push service accepted (we do not know whether it was shown). We do not use them to build a profile of you, we do not combine them with other information about you, and we do not share them with anyone except the processors named below.
News and releases and Reminders are sent only with your consent (GDPR Art. 6(1)(a) and the Swiss FADP), which you give by turning them on in the App. You can withdraw it at any time by turning the switch off in Settings → Notifications, or by turning off notifications for the App in your device's settings. The withdrawal reaches our servers at the App's next successful sync with them (the App must be opened with an internet connection); if no category we send from our servers is still on, your device's registration is deleted. When you withdraw your consent we stop sending you news, but we keep the records of the news already sent for the rest of their retention period (see below), on the basis of our legitimate interest in never sending you the same news twice or more than one a week should you turn it on again, and in counting to how many devices each piece of news was sent. You can object to this at any time (see Section 10).
Whether you open a notification, and the choices you make in Settings → Notifications, are measured with the pseudonymous analytics described in Section 3.
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 your device's built-in security features, including device encryption and App sandboxing, on iOS and on Android alike.
iCloud Sync (optional, Pro feature, iPhone and iPad): if you enable iCloud Sync in Settings, copies of your projects, with their 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.
Google Drive Sync (optional, Pro feature, Android): if you enable Google Drive Sync in Settings and sign in with a Google account, copies of your projects — the results, their versions and edits, the location saved with them (see Section 7) and the original captured frames — are stored in a hidden app folder in that account's Google Drive. The App asks only for access to its own app folder (the drive.appdata permission): it cannot see your other Drive files, and the folder does not appear in your Drive's file list. The files count against your Google storage and are shared by your Android devices signed in to the same account. Google Drive is operated by Google LLC under your agreement with Google; the App reads and writes the folder directly from your device, our servers never receive these files, and we do not have access to them. Deleting a project in the App removes it from Google Drive on every device. Turning Google Drive Sync off brings your projects back to the device and leaves the copies in Google Drive; signing out in Settings removes the App's access to your Drive. To delete everything the App stored there, open Google Drive on the web, go to Settings → Manage apps, find Zeus Focus Stacking and choose Delete hidden app data.
Google user data (Android). When you sign in for Google Drive Sync, the App asks Google only for access to its own app folder. Through it, the App receives from Google the email address of the account you chose, which it keeps on your device to remember and show which account it is, and the files in that folder, which are your projects; Drive returns the account's storage figures together with the email address, and the App neither uses nor keeps them. The App uses these data only to keep your projects in sync between your devices and to show them to you. They are exchanged directly between your device and Google and never reach our servers: a picture or a project you yourself choose to submit to Picture of the Week or to the Engine Improvement Program is covered by Section 4 and Section 6 instead. We do not sell these data, use them for advertising, let any person read them, or use them to develop, improve or train artificial-intelligence or machine-learning models. Zeus Focus Stacking's use and transfer to any other app of information received from Google APIs will adhere to the Google API Services User Data Policy, including the Limited Use requirements. You can withdraw the App's access at any time by signing out in Settings, or in your Google Account under Third-party apps & services.
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: