Would You Care for One Shot or Two?
It wasn't long after the invention of the camera that photographers started coming up with ways to combine multiple shots to produce a resulting image not otherwise be practical. But as the technology improves, the exact methods preferred and even the very need have evolved.
Back in the film era, one common method was to shoot two shots on a single frame of film, omitting the usual step of advancing to the next frame before pressing the shutter release for the second time. By recomposing for the second shot, objects not naturally adjacent could be made to appear as if together. By altering focal length or shooting position, the scale needn't be the same either, culminating in today's never-ending profusion of cityscape images with a moon so big the world must be coming to an end. But I digress.
In the digital era, even the early years when the files being edited came from scanned film rather than a true digital camera, techniques involving the blending of more than one image became popular for addressing additional challenges. As one who shoots predominately outdoors, I was once a huge fan of graduated neutral density (GND) filters as a means of toning down brightness in one section of a frame to blend more naturally with the remainder. I used to carry a dozen or more various gradations and strengths of GND filters, frequently using more than one in a shot as I labored to work around the limited exposure latitude of current camera technology and media. The move to digital enabled me to take an entirely different approach to the problem. After shooting the same scene at different exposures, I could combine the best of each to form a single composite that had the potential to look much more natural than any premade filter gradation could achieve in-camera. Producing natural looking results for digital exposure blending took a bit of skill, often trial and error, and occasional luck, but it let me get away from obsessing about tree trunks and other image elements that gave away the use of a GND filter. Bottom of the trunk light, and the top mysteriously dark, exactly the opposite of the relative brightness of sky versus foreground? That's the telltale sign of GND filter addiction. If someone you know is still suffering, please, introduce them to HDR and digital blending.
Then came the advent of blending frames shot at varying focus distance to create an image that exceeded the depth of field otherwise possible. "Focus stacking," as it's generally referred to. Thankfully, there are several good options today for programs and plug-ins that can merge the in-focus areas from a series of frames to yield very good results. Such techniques are commonly employed for high-magnification macro shots but can also work quite well for extreme depth of field landscape images. Wind gust outdoors can occasionally make merges a bit tricky, but the results can make it all worthwhile. That same gust would have been even more troublesome had I instead tried to shoot the same scene in a single shot at f/22. Small apertures require long exposures. And the breeze is rarely kind to photographers attempting long exposures.
Of course, these days, the top cameras can perform many of these blending techniques all on their own, in camera. That seems to work fairly well for focus stacking where the camera has all the proper meta data to assemble a composite based on focus distance and image sharpness. But the camera simply doesn't have what would be needed to reliably blend exposure. Cameras assume everything is supposed to be medium toned and can't judge whether something is underexposed or just in the shadows. Some things can only be done by eye and by hand.
At the same time as this technological evolution has been taking place, so too has another one that bears on our present discussion. Not only does each successive camera generation and software release introduce new and more exciting innovations, the years of dedication to image sensor design have yielded a steady steam of progressively more sensitive cameras, both in terms of basic ISO but also in the breadth of subject brightness usefully possible in a single capture. Lower noise means greater amounts of useable detail in the shadows. While it used to be considered a rule of thumb that cameras could only "see" five stops of light, newer camera sensors can go far beyond that paltry score. Better sensors mean better images.
As a consequence of having better sensors to work with than we once did, a curious situation has developed. At least some applications of digital blending are no longer needed. More than ever, cameras today can capture perfectly useable images in a single shot that used to require two or more shots digitally merged. And even more curious, not everyone has noticed.
Here's my suggestion. Next time you're out in tricky lighting, if you have your doubts as to whether your sensor is up to the task of getting everything in one shot, go ahead and shoot it as if you need multiple exposures. But when it comes time to work on that image on your computer, see what you can do with just your best frame alone. You may just surprise yourself. And if it works, you won't need to worry about that gust of wind rearranging all the wildflowers and complicating the job of merging multiple frames. And if it doesn't work out so well, you can always fall back to your tried and true blending methods since you shot to cover yourself for that.
As technology changes, don't assume the best option for pushing the limits of your camera stay the same. Makes sense, seeing as those limits are themselves beneficiaries of improving technology.