Combine a dark, a normal and a bright shot of the same scene into one photo where both the bright window and the dark room show detail. The tool aligns handheld brackets automatically and blends them with exposure fusion, so there is no tone mapping step and no RAW editor needed.
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Middle exposureMerged
Merging…
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How to use the HDR Merge
Add your bracketed photos: drop 2 to 9 exposures of the same scene (for example −2, 0 and +2 EV). A sample bracket is loaded so you can see the result first.
Check the frames: they are sorted from darkest to brightest, and the middle one is used as the alignment anchor.
Keep Align photos on for handheld shots; turn it off for tripod brackets.
Adjust the fusion weights and finish settings while watching the before / after view.
Choose an output size and format, then press Download merged photo.
How exposure fusion works
For every pixel of every frame the tool computes three quality measures, multiplies them (each raised to its slider value) and normalizes the result so the weights of all frames add up to 1 at each pixel:
Measure
Formula
Favors
Contrast C
|Laplacian of gray| (3 × 3 kernel)
Edges and texture, which are lost in clipped or murky areas
Saturation S
standard deviation of R, G and B
Rich color, which fades in over- and underexposed areas
Well-exposedness E
∏ exp(−(channel − 0.5)² / (2 × 0.2²))
Values near middle gray rather than near black or white
Weight W = Cωc × Sωs × Eωe. Blending the frames directly with these weights would create seams, so each frame is decomposed into a Laplacian pyramid (detail bands at halving resolutions) and each weight map into a Gaussian pyramid. The bands are blended level by level and collapsed back into one image, which is the method published by Mertens, Kautz and Van Reeth (2007).
Bracketing guide
Scene
Frames
Step
Example
Landscape, light clouds
2–3
1–2 EV
−1, 0, +1
Sunset, backlit subject
3
2 EV
−2, 0, +2
Room with bright windows
3–5
2 EV
−4, −2, 0, +2, +4
Night street with lights
3–5
1–2 EV
−2, −1, 0, +1, +2
Tips for clean merges
Change only shutter speed. Keep aperture, ISO, focus and white balance fixed so frames differ only in brightness (aperture priority mode with AEB does this).
Use a tripod or a fast burst. Alignment fixes small shifts, but rotation and parallax from moving the camera cannot be corrected.
Check the clipping numbers on each frame card: your darkest frame should show almost 0% white and the brightest almost 0% black.
Want a stronger HDR look? Run the merged result through the HDR Photo Effect tool for extra local contrast.
Frequently asked questions
What is HDR merge?
HDR merge combines several photos of the same scene taken at different exposures. Each frame captures part of the brightness range well: the dark frame keeps the sky and windows, the bright frame shows the shadows. Merging takes the best exposed parts of each and produces one image with detail from the darkest to the brightest areas.
What is exposure fusion and how is it different from tone mapping?
Classic HDR first builds a high dynamic range radiance map and then tone maps it back to a normal image. Exposure fusion (Mertens, Kautz and Van Reeth, 2007) skips that: it gives every pixel of every frame a weight based on contrast, saturation and how close it is to middle gray, and blends the frames with a multi-resolution Laplacian pyramid so the transitions are seamless. The result looks natural, needs no camera response curve and avoids the typical tone-mapping halos.
How many exposures do I need and how far apart?
Three frames at −2, 0 and +2 EV cover most scenes, such as interiors with windows or sunsets. For very high contrast scenes use five frames at 1 or 2 EV steps. Two frames can work for moderate contrast. Most cameras and many phone camera apps have an auto exposure bracketing (AEB) setting that shoots these automatically.
Can I merge handheld photos?
Yes. With Align photos on, the tool finds the shift between frames using median threshold bitmaps, a method that works even though the frames have different brightness. It corrects horizontal and vertical movement of up to about 60 pixels at preview size. It does not correct rotation, so hold the camera steady and use burst or bracketing mode to keep the frames close together.
Why do moving objects look ghosted?
If a person, car, tree branch or water moves between frames, it is in a different place in each exposure, and fusion blends those positions together. Shoot brackets quickly, avoid moving subjects, or use a scene where motion is small. This tool does not perform deghosting.
Should I merge RAW files or JPGs?
This tool merges JPG, PNG and WebP images. If you shot RAW, export each frame to JPG first (for example with the RAW to JPG converter) using the same white balance for all frames. JPGs straight from the camera work well because exposure fusion does not need linear sensor data.
Are my photos uploaded?
No. Alignment and fusion run in your browser with JavaScript, so the photos never leave your device.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.