For many years, Nikon DSLRs have allowed photographers to create raw files in camera from multiple exposures. From what I've used, the higher end bodies allowed up to 10 exposures, and lower end bodies might have a lower number. This is generally something to consider as creative functionality — working with individual images as layers in an editing program allows for the most control from initial raw conversion to the finished photo. From a creative perspective, there's something fun about trying to get closer to a finished photo in the field. With the output as a raw file, lots of processing control remains afterward.
With the Z cameras, Nikon has taken away the ability to save a raw file from the multiple exposures. Only JPEG is allowed. I've read that this might be a way for Nikon to avoid dealing with lens correction profiles. If multiple exposures are shot with multiple focal lengths on the same lens, or even with entirely different lenses, which correction profile should be applied? Perhaps something in the internal processing pipeline prevents holding and saving multiple exposures as a raw file. With the D850, multiple exposures are disabled in Live View, for some unknown reason. Some Z bodies allow saving a TIFF instead of a JPEG, but the only gain is the lack of JPEG compression. Image settings such as sharpening and white balance are locked in, and the bit depth is still 8 bits. Z bodies that support HEIF do not support HEIF from multiple exposures.
As of mid-2024, Z bodies from the Z30 up to the Z9 all have this limitation. If the photographer has white balance, contrast, and sharpening dialed in, the resulting JPEG handles reasonable processing. But it's not a raw file.
I would like to see Nikon bring back the ability to save a raw file from multiple exposures, and I'm not alone, as that link shows. If it's a question of lens corrections, the solution should be obvious — disable them, or allow the photographer to choose how they are applied. The problem with locked-in lens corrections is a topic for another day.
Earlier this year, I found a reference to MergeRaw by Ryan Mack. This is a Lightroom plugin primarily designed to deal with pixel-shifted images for better output resolution, and multiple exposures for noise averaging. The plugin is flexible enough to also bring back some of the Nikon Z lost multiple exposure functionality. MergeRaw generates a DNG from multiple raw files.
With all that said, what is my use for multiple exposures? I like to play with focus shifting — the common scenario is where I want a foreground object and background object to both be in focus, but without going through a full focus stacking routine. I want to keep the out-of-focus character from both photos. This can create a photo that is simultaneously sharp and soft. Trying to achieve this without a tripod can be an exercise in frustration, but sometimes it works beautifully. Credit to Birna Rørslett, who has done similar work that inspired me to try the technique.
As an aside, the obvious question — why would I need a raw file for something that is often flawed? Why wouldn't a JPEG be enough? I want the extra precision, and that's reason enough for me.
Let's look at the merging options available with MergeRaw. I used Disabled for the Alignment Mode.
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| MergeRaw options |
First, the two input photos. I shot these on a tripod and used the camera's focus shift function to shoot nearly 100 frames. My intent was to process a full focus stack, but while working on that I liked the look of just these two frames, the result of which I'll include at the end.
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| Foreground exposure (click to view larger) |
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| Background exposure (click to view larger) |
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| Exposure Weighted Average (click to view larger) |
Exposure Weighted Average - Blurs Moving Subjects. This looks like what I would get from the in-camera multiple exposure output. Some Nikon cameras have additional blending modes, but I almost always use Average. "Blurs Moving Subjects" is just what I want, if I consider the change in focus to be a moving subject!
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| Average - Fix Color Artifacts (click to view larger) |
Average - Fix Color Artifacts from Moving Blown Highlights. There is no real change compared to Exposure Weighted Average. This scene doesn't have the issues that this setting would correct.
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| Average - Use First Frame (click to view larger) |
Average - Use First Frame Where Anything Moves. This worked exactly how it should work. The result is almost identical to the original first frame. Again, the scene is not suited to this setting.
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| Median (click to view larger) |
Median - Removes Moving Subjects Across All Images. This setting is what you'd get from loading the exposures into Photoshop as layers, converting the stack to a Smart Object, and setting its blend mode to Median. The usual example to showcase this technique is multiple photos of a city street — the median blend mode eliminates all moving cars and pedestrians, making the street look eerily empty. Again, this scene is not suited to this setting.
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| Brightest Pixels (click to view larger) |
Brightest Pixels - For Star Trails or Light Painting. The result is interesting, but not useful for this scene. I don't have a current use for this, but it is undoubtedly useful for night photographers!
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| Processed in HeliconFocus (click to view larger) |
Photos combined with HeliconFocus. I worked on this a month earlier, and it's my choice of output for this scene. Keeping the background free of an out-of-focus halo looks better, and I like the shift from soft to sharp between the flower and the background. That transition doesn't always work well, but the subject positions in this scene lended themselves to a clean transition. I did some manual masking work to make sure the background image came through cleanly.
