Flattr vs Celvion Stack

Merge multiple exposures into one perfectly balanced photo — real GPU exposure fusion. Free, no subscription required. Flattr is built for photographers who use exposure bracketing and want clean, natural results. Stack shots, overlay frames, combine exposures — export TIFF or JPEG. No account, no hidden fees. — WHY FLATTR — Most photo apps fake results with tone-curve filters. Flattr does real exposure fusion: it computes weight maps per pixel across contrast, saturation, and edge detail, then blends your exposures through a Laplacian pyramid. The result looks like your eyes saw the scene — not like a preset applied in batch. • Real exposure merge — not a filter • Supports RAW (.DNG) and JPEG inputs • TIFF export • GPU-accelerated — fast even on large files • Auto image alignment via Vision framework • No account, no subscription, no hidden fees — WHAT YOU CAN DO — Photo Merge & Photo Stacking: combine two or more exposures from any exposure bracketing sequence into one seamless image. Flattr aligns your shots automatically before blending, so handheld bracketing works too. Stack three, four, or five photos and get a single frame where every zone is properly exposed — highlights controlled, shadows open. Exposure Blending: weight each pixel by how well-exposed it is. The classic exposure stacking result — without Photoshop, without a desktop. Combine photos straight from your camera roll or imported DNG files. Double Exposure: overlay two photos for artistic compositions. Superimpose a portrait over a landscape, blend a city skyline into a forest, or combine photos into something entirely new. Blend modes give you full control over how the images interact. Overlay & Superimpose: layer photos on top of each other with precise control. Great for creative composites, architectural photography, and experimental work. Superimpose any two images and export at full resolution. Exposure Fusion: balanced light from bracketed shots, without an over-saturated look. Flat, natural, and true to the scene. This is what your eyes see when standing in a bright landscape — Flattr captures it the way your camera can't do alone. — HOW IT WORKS — 1. Select your bracketed exposures from your photo library or import DNG/RAW files directly 2. Reorder if needed — drag to set the blend sequence 3. Tap Merge — Flattr aligns, weights, and fuses in seconds 4. Export as TIFF (full RAW workflow) or high-quality JPEG — WHO IT'S FOR — Landscape and travel photographers who use exposure bracketing to handle tricky light. Architectural photographers dealing with bright windows and dark interiors. Night photographers blending a sharp foreground with a sky. Street photographers layering multiple frames for creative effect. Anyone who wants to combine photos, superimpose images, or fuse exposures and keep every detail. — EXPORT — RAW workflow: exports full-quality TIFF. Compatible with Lightroom, Darkroom, and any TIFF-capable raw editor. JPEG workflow: exports high-quality JPEG optimised for sharing and social. — TECHNICAL — Built on Metal GPU processing and Apple's Vision framework for image alignment. Laplacian pyramid blending preserves fine texture and edge detail that simple opacity-based layer blending destroys. Works on iPhone and iPad. Supports DNG, RAW, and JPEG inputs. Flattr. Real photo blending, made simple. Download free and merge your first bracket in under a minute.

Build a stronger image from a sequence of photos, right on your iPhone or iPad. Celvion Stack brings importing, frame review, alignment, stacking, editing, and export together in one on-device workflow. SIX WAYS TO STACK • Night scenes: combine exposures to reduce random noise while retaining natural detail. • Milky Way: align the sky separately from the foreground for sharper stars and a stable landscape. • Light trails: blend selected frames into continuous trails. • Smooth water and clouds: create a softer motion effect from a sequence. • Moving distractions: reduce the impact of people, vehicles, and other elements that appear in only some frames. • Landscapes: combine aligned frames for a cleaner result. CONTROL YOUR MILKY WAY STACK Choose a reference frame, review frame quality, adjust sky and foreground masks, and inspect which frames are included. These controls help you adapt the result to your source images. SUPPORTED RAW AND EVERYDAY PHOTOS Import supported RAW/DNG files and standard photos. RAW compatibility depends on the camera file and the available decoder. Lens correction applies geometric distortion profiles when a supported profile or embedded calibration matches; automatic vignetting and chromatic-aberration correction are not included. ON-DEVICE AI TOOLS Use optional AI denoising and up to 4× super-resolution on supported iPhone and iPad devices with iOS or iPadOS 18 or later. Results depend on the source image. Core stacking workflows require iOS or iPadOS 17 or later. FULL-RESOLUTION EXPORT Export as JPEG, PNG, 16-bit TIFF, or 10-bit HEIF. Choose available color-space and DPI options, then save locally to Files or, where supported, Photos. YOUR PHOTOS STAY ON YOUR DEVICE Photo processing runs on your device. The app does not upload your source photos for processing.