What is Merge Raw?

Merge Raw allows you to combine multiple Pixel Shifted raw files into a single DNG or to do Frame Averaging with non-pixel-shifted raw files.

Pixel Shift is when your camera takes 4 or 8 photos with the sensor moved slightly so each pixel captures red, green, and blue light instead of each pixel only capturing only one color. This results in reduced noise, less moire artifacts, and more accurate color. You can even capture 16 or 32 photos at half-pixel offsets to improve resolution and further reduce moire artifacts. In order to use these photos you need to Merge the Raw files into a single file other applications can read. Merge Raw lets you do this fast and conveniently from right inside of Lightroom Classic.

Frame Averaging is when you take multiple photos and merge them together for a cleaner image with less noise that can be sharpened more and printed larger. For example, merging four ISO 64 images gives you an effective ISO 16 image, pushing your Full Frame camera well into Medium Format quality! Unlike doing Frame Averaging in Photoshop with layers and Smart Objects, Merge Raw outputs a DNG file which keeps all the editing ability of a raw file and the resulting file is up to 60% smaller than a PSD or TIFF file. Merge Raw is fast. No more making a pot of coffee while Photoshop loads all your raw files into layers and renders an image stack.


Where Can I Get It?

You may download the latest version from my website (hyperlink)

Please see the CHANGELOG (hyperlink) for more details.

Please see the INSTALL help file (hyperlink) for help installing.


Is Merge Raw an HDR App?

While Merge Raw isn't an HDR app outputting massive DNG or TIFF files, it actually does increase your dynamic range by reducing the noise in you image and giving you back more shadow detail. Merge Raw can even correctly merge frames taken with different exposure settings and will automatically "Expose To The Right" the raw data to fit as much shadow data as possible into the output file without losing any highlights. If you used a steady tripod to capture multiple images within about a 4 stop range, Merge Raw will give you all the benefits of Adobe Lightroom Photo Merge HDR in less time and with a 60% smaller output file. Maybe I should call it a "Not High, But Higher" Dynamic Range app.


How does it work?

Merge Raw does three things differently than your typical HDR app:

1. Instead of choosing a single image to get a pixel from, it does an exposure-weighted average across all the input images. That means the output image has less noise than any single input image and gives you more dynamic range into your shadows. Without bracketing, using two images with the same exposure reduces noise by about 30% and four images by 50%. If you used bracketed photos (within about a 4 stop range), your image quality improves even faster.

2. In most cameras, each pixel only records one color out of red, green or blue. "Demosaicing" is how software guesses the other two colors at each pixel, which triples the size of the TIFF/PSD file. If you're shooting with good technique and a solid tripod, Merge Raw doesn't even need to demosaic the image. Merge Raw can do its merging on the raw data (hence the name!) without ever wasting time and disk space creating this extra data. This results in *sharper* images because the demosaicing is run on the lower noise data later when you export the image or edit it in Photoshop! Merge Raw does support limited alignment if your tripod head or lens VR shifts the image slightly between frames, but it's still fast and small by using a high speed demosaicing algorithm and re-color-filtering the data before writing out the raw file.

3. For Nikon cameras with Pixel Shift, Merge Raw can combined 4 or 8 images to provide color information at every pixel. This results in extremely clean images. With 16 or 32 shot pixel shift mode Merge Raw will output the full 4x resolution DNG file. Marge Raw is faster and outputs better quality images than NX Studio Pixel Shift mode and even offers precise exposure matching and automatic moving object removal to help reduce artifacts caused by lighting/aperture shifts or subject motion.


What if something moves between frames?

Merge Raw currently offers three blend modes:

1. Exposure Weighted Average - If something moves, it will blur or "ghost." Sometimes this is exactly what you want. This can be used to take 8 1-second waterfall photos and merge them into a single 8-second exposure, with an effective ISO of 1/8th the original. That's one less ND filter you need to carry with you and you can decide how many images to combine for a pleasing blur later.

2. Average with Deghosting - Same as above, but if something moves, don't average it. This allows you to reduce the noise in only the stationary parts of the image. Any regions with movement exceeding the noise threshold will only use pixels from the active photo in Lightroom. The active photo is the is the photo with the brightest selection in the filmstrip. The algorithm here is conservative, prioritizing reducing the chance of artifacts at the expense of not reducing noise in as much of the image. I use a different algorithm to detect movement in pixel shift images. I would love feedback on which situations it works well in or not.

3. Use Brightest Pixels - This lets you combine many frames for star trails or light painting and still get a single small DNG file for output. This mode isn't quite the quality I want yet, but it's good enough for testing purposes. There's a few features on the list for future versions that will make this an even better solution (reducing noise on the stationary foreground, dark frame subtraction, and dashed line filling).


What are its limitations?

Merge Raw is beta-quality software and currently only runs on a Mac (Intel or Apple Silicon). I've been working on it in my spare time for fun and personal use but decided to try releasing it to get feedback and hopefully collect test images. If there's enough interest, I'll figure out how to get it to build for Windows.

The Lightroom plugin that makes Merge Raw extremely easy to use currently only works in Lightroom Classic. Lightroom CC doesn't support plugins. I'll work on a stand-alone UI for a future release that will make it easy to use with Lightroom CC. In a pinch, you can use the mergeraw command line interface. It has many more options than what's exposed in the UI if you want to poke at it.

So far it's been confirmed to work on a Nikon D850 and a Sony A7R IV. Pixel Shift has been tested with a Nikon Z8. It should work for most RGGB CFA cameras (Nikon, Sony, and Canon) that are supported by Adobe DNG Converter but it's never been tested. I wouldn't recommend trying it with Fuji X-Trans or a Sigma Foveon, or any non-Nikon Pixel-Shifting cameras yet. I would be very interested in examples of raw files from other recent camera models and examples of image sets that Merge Raw does a poor job on.

Image alignment is limited to small shifts and rotations. That means this tool is only useful for people shooting with good technique and a solid tripod. This is not a panorama stitching application. Alignment is disabled for pixel-shift and instead uses the know shift pattern for performance and accuracy.

Use Brightest Pixels is adequate but not excellent for star trails (yet). This is currently at "proof of concept" stage and on the roadmap for improvement in future versions. I don't recommend shooting star trails, light streaks, or light painting with pixel shift but if you do, Merge Raw tries its best to give you a usable image.


What does it cost?

Merge Raw is free.


Tips for capturing the sharpest images

1. Use a steady tripod and a solid tripod head
2. Don't re-focus between exposures
3. Turn off VR on your lens, even lenses that claim to have an automatic tripod mode
4. Use a cable release or self timer
5. Shoot in live view using silent mode, exposure delay, or mirror lock-up to eliminate shutter shock and mirror slap
6. Prefer automatic bracketing over adjusting settings by hand to avoid moving the camera