For photographers who deliver large sets of images, the final step before client delivery is often the most tedious: straightening every frame. Even with a tripod, each photo can have a slightly different tilt—a handheld shot, uneven ground, or a quick change of position. Copying one correction across the entire batch leaves many images still crooked, so the work is done one by one. Suihei, a macOS app from Marginal Gains Inc., tackles this problem with an AI that estimates each photo’s tilt independently and levels the whole set at once, cropping each result cleanly so no blank corners remain.
Suihei is built for professionals who demand precision and speed. It runs entirely on the photographer’s own Mac—no cloud uploads, no data sharing, and no modification of original files. The app is free to download and offers a generous trial that includes 100 exports (with 10 more added each day), making it easy to test on real projects. For those who need unlimited exports, a single in-app purchase removes the limit for good at a fair one-time price. The following review explores what Suihei offers and why it deserves a place in any serious photographer’s toolkit.
What Is Suihei?
Suihei is a macOS utility that straightens batches of photos automatically. Its built-in AI analyzes each image individually to determine how far it leans from horizontal, then applies the correction to the entire set in one step. The app also crops each rotated frame to the largest rectangle that fits inside the image, eliminating the empty wedges that normally appear after rotation. The result is a clean, level photo without any further trimming.
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Developed by Marginal Gains Inc., an Osaka-based software company founded in 2024, Suihei was shaped by real client workflows from a working professional photographer. The interface is available in 33 languages, including right-to-left layouts for Arabic and Hebrew. The app requires Apple Silicon and macOS 26.4 or later and supports JPEG, HEIC, and PNG files. All processing, including the AI estimation, happens locally and also works offline, ensuring that sensitive client photos never leave the Mac.
What Stands Out
Individual Per-Photo Tilt Estimation
Unlike batch straightening tools that apply a single angle to every image, Suihei’s AI looks at each frame separately. This matters because tilt varies from shot to shot—a handheld camera, a slope underfoot, or a quick change of position all produce different angles. By estimating each image independently, Suihei delivers consistent leveling across the entire set without the need for manual per-photo adjustment.
Intelligent Cropping Without Blank Corners
Rotating a photo leaves empty triangles at the edges. Suihei automatically crops each rotated image to the largest rectangle that fits within the frame, so no blank corners remain and no extra trimming step is required. This saves time and ensures every exported photo is ready for presentation or delivery.
Privacy and Local Processing
All AI processing runs on the user’s Mac, not on remote servers. Photos are never uploaded, and the built-in AI does not learn from the photographer’s images during use. The App Store privacy label reads “Data Not Collected,” and the app works without an internet connection. This makes Suihei a strong choice for professionals handling confidential or client-sensitive work.
Non-Destructive Workflow
Original files are never modified. Corrected copies are saved in a separate folder with their EXIF metadata intact. Frames left uncorrected are copied byte for byte rather than being recompressed, preserving image quality. This non-destructive approach gives photographers complete peace of mind.
Generous Free Tier and One-Time Purchase
Suihei is free to download, and viewing and editing are never limited. Users get 100 free exports immediately, plus 10 more every day. When the free limit is no longer enough, a single in-app purchase of US$39.99 unlocks unlimited exports permanently. There is no subscription, and the price varies only by App Store region.
Who It’s For
Suihei is designed for photographers who regularly deliver large batches of images and need consistent leveling without spending hours on manual corrections. Wedding photographers, real estate shooters, event photographers, and product photographers will all benefit from its batch processing and per-frame accuracy. The app is also well-suited to studios that handle high volumes of client work and require a fast, reliable tool that integrates seamlessly into their existing Mac-based workflow.
Because Suihei runs locally and does not upload data, it is particularly appealing for professionals who work under strict confidentiality agreements or in environments with limited internet access. The app’s multilingual interface—33 languages including Arabic, Hebrew, Chinese, and Korean—also makes it accessible to photographers around the world. While beginners may find the AI estimates helpful, the app’s design clearly targets those who shoot for a living and demand efficiency.
Pricing and Availability
Suihei is available now as a free download from the Mac App Store. It runs on Apple Silicon Macs with macOS 26.4 or later. The free tier includes unlimited viewing and editing, plus 100 exports (10 more are added daily). To remove the export limit permanently, users can purchase the “Unlock Export” in-app purchase for US$39.99. This is a one-time payment with no subscription attached. Prices may vary by App Store region. The app supports JPEG, HEIC, and PNG files and is offered in 33 languages. More details are available at the official product website.
What Makes It Worth Considering
Suihei stands out because it solves a specific, persistent problem in professional photography: the time-consuming task of straightening each image in a batch. By estimating tilt per photo and cropping intelligently, it reduces a labor-intensive step to a quick review and approval. The local processing and non-destructive workflow address both privacy concerns and file integrity, making the app suitable for high-stakes client projects. The generous free tier allows thorough evaluation, and the one-time purchase price is reasonable for a specialized tool that saves hours of manual work.
The app’s design reflects real-world use, having been developed in collaboration with a working photographer. Small touches—like the ability to accept or reject uncertain AI estimates, keyboard-driven review, and fine manual adjustment—show an understanding of how photographers actually work. Combined with support for 33 languages and offline capability, Suihei is a thoughtfully crafted utility that earns its place in the “Video Tools” category by streamlining a key part of the image delivery process.
Verdict
Suihei delivers precise per-photo straightening with local AI, a generous free tier, and a fair one-time price—essential for serious photographers who value speed, privacy, and batch efficiency. It transforms a tedious manual task into a quick review, all without risking original files or uploading sensitive data. For anyone shooting large sets on a Mac, Suihei is a worthy addition to the toolkit.
Frequently asked questions
Suihei works with JPEG, HEIC, and PNG files.
No, it saves corrected copies in a separate folder; originals remain untouched.
No, all processing, including AI, runs locally and works offline.
Suihei requires an Apple Silicon Mac running macOS 26.4 or later.
The interface is available in 33 languages, including English, Japanese, German, French, Spanish, Chinese, and Korean.
No, the app is free to download and use for viewing and editing. Unlimited exports require a one-time in-app purchase.
Yes, you can review each estimate, accept or reject it, and fine-tune the angle manually in small steps.
