Resolved: capture better images

The three faces of resolution


Woody Sherman


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The Three Faces of Resolution

I've heard it said that the word "resolution," in digital imaging terms, tracks along with the words “clarity” and "sharpness." But that's really only the beginning. Is there only one kind of resolution? Well, when it comes to your camera or camcorder — no, not really.  Let's take a little time to talk about three basic types of resolution, which we’re choosing to call pixel resolution, optical resolution, and temporal resolution.

When we talk about resolution and cameras, we're taking apart the idea of what makes up an image. A familiarity with the different facets of the term "resolution" can help you with making creative decisions in photography and videography.

Pixel resolution

If you could blow up a digital image your camera captures by a thousand percent or so, you’d probably start to see the individual pixels that make up the picture (actually, there are individual red, green and blue elements on your camera sensor that make up these pixels, but that’s another story). Think of these as individual, rectangular color swatches. Pull back far enough, and, like a mosaic viewed from afar, the individual colors will blend to give you your overall image.

The overall number of “tiles” in your mosaic – the individual pixels – will make a difference in things like how realistic fine diagonal lines and curves look. The lower the overall number of pixels in your image, the more things like that will look jagged and stair-steppy, not smooth and continuous. We refer to the overall level of detail as granularity. Take a look at the comparison between a DSLR and a typical phone camera, below:

a pixel resolution comparison of a typical DSLR and a typical phone camera

A pixel resolution comparison of a typical DSLR and a typical phone camera. Both these images have been compressed for web display but the overall concept holds: If you wish to see fine details clearly, you'll need a higher number of pixels on your sensor.

Now, this is not to say more pixels are always better. Lots of things come in to play in the overall recipe between sensor size, camera electronics, and lens size that affect your final image. More pixel detail (finer granularity) means your camera is dealing with a lot more data in a short amount of time, and that introduces new challenges for the manufacturer, like noise, reaction time, light sensitivity, and wavy-looking interference on fine detail images (moiré).

Almost every digital camera made these days has enough pixels to make an acceptable print or web picture. But if you’re shooting for larger blow-up prints, for high-quality print applications like magazines or brochures, or for any medium where fine detail can be reproduced and perceived, it’s worth it to take your starting pixel resolution into account, and choose a higher setting. Your camera probably has a menu item for the JPEGs you take to regulate starting pixel resolution – they might be referred to as “fine” or “standard.” Consult your manual and dial in accordingly.

Even though these jets were far away, the precision optics of the Nikon AF-S 55-300mm zoom lens captured them with minimal distortion and color anomalies

Even though these jets were far away, the precision optics of the Nikon AF-S 55-300mm zoom lens (on a Nikon D90) captured them with minimal distortion and color anomalies.

Optical resolution

Your lens’s overall characteristics have a fundamental impact on your image. Things like focal length, maximum aperture, and the number and quality of lens elements all contribute to your perception of overall image quality. A poorly made/poorly designed lens will do a bad job of getting the entire visible light spectrum to line up in a coordinated way, creating artifacts like color fringing (where different frequencies, or colors of light, don't align in unison). And poor craftsmanship can show in other ways, like soft/irregular focus and image distortion. While even the most highly regarded lens isn't entirely free of design limitations, manufacturers keep moving the quality bar forward. So do software designers, as many editing programs will correct for objectionable lens characteristics.

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The ability to magnify the image, or widen the field of view, obviously changes things when it comes to your image, and the efficiency and clarity with which a lens can do such things is a matter of technical design that’s as much an art as it is a science. Almost all lenses from the brand-name manufacturers are capable of getting you good results, but as you gain experience with your camera and your lens options you will probably develop preferences. The merits of one lens over another have been argued over since the first lens was ground. Part of the joy of photography and videography is the discovery of how lens choice impacts your results, and what gear best serves your artistic vision.

Temporal resolution

This is not as obvious a form of resolution until you think about it for a second.

A second.

See what just happened? I forced you to frame an action in terms of time, not space. In a sense, your camera does too, with your control over shutter speed, or, if we’re talking in terms of video capture, both shutter speed and frame rate.

The granularity of time: On top, a fast shutter speed "freezes" the action of turbulent water. Below, a slower shutter speed gives a more impressionistic feel to the water's flow.


Take a look at the pictures at right. On the top, you see the waterfall frozen in time, by use of a fast shutter speed. Obviously, nothing is truly “frozen,” the shutter still takes a set amount of time to complete its action, but the shorter that duration is, the sharper the moving subject is.

Below that, we show the same scene, taken with a longer-duration shutter speed (yes, we modified aperture/ISO to keep the overall comparison similar). Note how the moving part of the picture, the flowing water, has smeared in appearance for an overall impressionistic effect due to motion blur. The longer you leave your shutter open, the more you’ll see this effect.

Quite often, if you look at the efforts of the pioneers of film photography, you’ll see this show up, as early film formulations weren’t terribly light-sensitive and shutters needed to be open for longer periods of time. This is also why “flash” solutions came to be. It was a way to give the camera sufficient light for a good exposure in a short amount of time, and thereby creating a different way of enforcing finer temporal resolution.

Temporal resolution in video

In motion video, another form of temporal resolution shows up: frame rate. As you know, motion video is essentially a series of still images, taken in succession. The rate at which you take those images is called a frame rate, and it can have an effect on our overall perception of the scene. The most common broadcast and film rates here in North America are 60, 30 and 24 frames per second (fps). We won’t get into the subject of interlaced versus progressive display strategies for now.  In extremely general terms, 24 fps rates feel a bit more stylized and movie-like, and 30 and 60 fps rates feel a bit more present and realistic (think broadcast news footage), but there’s a whole spectrum of camera techniques that can modify those starting points.

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More interesting effects happen when you acquire motion video at one rate (say, 60 fps) and play it back at another (let’s choose 24 fps). Because you now have 60 pictures that you took in one second playing back with only 24 pictures shown in a second, bingo! You have a video that’s playing in slow motion, 40% normal speed (also referred to as 2.5X slow-motion, because things are taking 2.5 times longer to happen than they did in actuality). The faster frame rate a camera can shoot, the more exaggerated the slow-motion effect.

In a similar fashion, you can explore fast-motion and time-lapse photography. For those effects, shoot at a slow frame rate and play it back faster.

Resolved: Take better pictures

Now that you’ve got a bit better of a grip on what resolution is, get out and take/edit some pictures with these concepts in mind. Play around and experiment so that you can see what works and what doesn’t in any given situation. Try some time-lapse photography, or take pictures at your "fine" settings and see what kind of pictures you can crop from the bigger image. If you've got an interchangeable-lens camera, join a camera club where you can meet others who might own compatible lenses you can try out. Don’t wait until the day you have to have good results from a once in a lifetime event – practice! Just like with a musical instrument or a video game, the hours spent will pay off – in this case, with better images.

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