Image Quality is More Than Megapixels

A camera’s megapixel count is often seen by consumers as the benchmark number to tell whether that camera is “good” or not. If that were true, why don’t photographers just buy a 108-megapixel smartphone to use as their main gear? The answer: because image quality goes far beyond megapixels.

Because I have a fairly high resolution camera, I tend to get a lot of “Oh, your photos are so good because your camera is 50 megapixels”. But I remember when, earlier in my career, I was trying to land a gig by taking a series of landscape photos for a hotel company. I ended up not getting hired because the manager was a photography enthusiast and said anything below 100 megapixels is no good.

While the megapixels are an image quality factor, they are actually just a very small part of what constitutes a good high quality image. Other factors that contribute to your image quality are sensor size and type, file type, lens choice, and you, the photographer.

Sensor size and type

The medium size is in general always better than full frame, full frame is usually always better than crop. I don’t care what year your crop camera is, a 2005 Phase One is even better as far as image quality goes. In fact, a 4-megapixel Canon 1D from 2001 is likely to provide much better basic image quality than a 103-megapixel phone.

The problem lies in the size of the photosites, tiny luminous cavities on a sensor that detect light. In short, a photosite is equivalent to a pixel. The more you have, the higher the resolution. Each photosite is like a scoop. The bigger the scoop, the more ice it can hold. Therefore, a small, high-resolution sensor will perform much worse because it won’t pick up as much light and therefore will have a reduced dynamic range.

This is why even if it is possible to make a extremely High-resolution APS-C or full-frame sensor, no company really wanted to do that.

Some manufacturers, like Sony with the Sony a7S range, have gone the other way, opting to use larger photo sites for lower resolution but higher image quality and low-light performance. This is why if a camera is high resolution, it will generally have poorer performance in low light.

Check out my comparison between a Canon 5DS and a Canon 5D Mark IV.

Canon 5DS (left) vs Canon 5D Mark IV (right) at ISO 12800. Click to enlarge.

The Canon 5DS is a 50.6 megapixel camera but its quality is lower at high ISO and in low light than the 30.1 megapixel Canon 5D Mark IV due to the smaller photosites (4.14 microns versus 5 .36 microns, respectively).

File type

The age-old discussion (and sometimes debate) between JPEG and RAW is settled if what you’re looking for is maximum image quality. Shoot RAW. Although your camera captures the same pixel resolution, the raw file will contain more information which will give you greater flexibility when post-processing your images.

For example, if your scene requires high dynamic range, you’d be better off shooting in RAW because much of the information in highlights and shadows won’t be removed by the camera processing the data into a JPEG file on its own. -same.

Naturally, shooting in RAW will result in larger file sizes, but it’s well worth the benefit of having all the original light data to work with.

When the exposure was reduced by two stops in post, a RAW photo (left) managed to retain more color detail while colors look distinctly different in the adjusted JPEG photo (right).

Choice of objective

Take a look at these corner crops of two images I shot with very different lenses. They were both taken on my Canon 5DS.

A more expensive lens (left) draws clearer letters

You can clearly see how one image is worse than the other. This is because the lenses have different levels of quality and of course will not be able to resolve the same amount of detail or maintain optical quality towards the edges of the frame. In fact, the lenses I currently own are frankly not enough to get the full potential of the 5DS body. Nevertheless, they are sufficient for what I do. If the job requires it, there is always the nearest equipment rental company.

One of the biggest problems with lenses is that they have chromatic aberration. This happens when the color changes along high contrast edges.

Very slight, almost barely noticeable chromatic aberration – look at the slight color changes around the edges of the white logo and checkerboard edge.

When light rays pass through a lens, they scatter. Because light is made up of different wavelengths, they will scatter at a slightly different angle separating the light rays. Simply put, once the lens fails to focus all parts of the colored light onto a single point or plane, chromatic aberration occurs.

An illustration showing axial chromatic aberration, when a lens fails to focus all wavelengths onto the same plane. Image by Bob Mellish and licensed under CC BY-SA 3.0.
This photo taken with an AF-S Nikkor 50mm f/1.8G lens shows strong axial chromatic aberration. Notice how the blurred areas in the foreground have purple fringes and the blurred areas in the background have green fringes. Photo by Slavica Panova and licensed under CC BY-SA 3.0.

Another thing to consider is reflection and diffraction inside the lens. If the light rays reflect off the glass multiple times, they will blur the whole scene. That’s why many high-end lenses have an anti-reflective coating.

Diffraction occurs when light passes through a narrow opening such as the aperture. This is why very few photographers use the f/32. Generally, anywhere between f/11 and f/13 is sharp, but anything narrower will make the image worse.

f/11 (left) is sharper than f/22 (right)

The photograph

You, the photographer, can do a lot to make the image quality perfect. One of the simplest things you can do is focus on the nails. If you can’t bring the image into focus, it will be of poor quality. Having a high resolution camera will only underline this.

Another skill you should have is good exposure. You should aim to have enough shadow and highlight detail without underexposing or overexposing your photo and losing detail. Having to correct bad exposures during post-processing will result in lower quality images.

Is image quality even important?

After reading this, you might be wondering if the image quality is even relevant. After all, isn’t photography about capturing fleeting moments in time? You may be right, and there are instances where image quality is the last thing that matters. Robert Capa’s photos of the D-Day landings, while anything but technically high quality, have gone down in history.

However, this is not always the case, there are instances when you need to capture details and do it well. For example, I (probably) couldn’t get away with filming a campaign or editorial on my phone. But I could get away with doing this on a night where the timing is more important.

For filmmakers, image quality may also be irrelevant, but that all changes when you take high-quality film and use it. The difference is huge and you’ll quickly see that film grain, while cold and sometimes desirable, can be less than ideal when clear image quality is what you need.

So overall, image quality is important in many professional applications, but you can get away with subpar images on social shoots. That said, don’t go crazy for your paid work and think you always have to rent or buy the highest-end, most expensive equipment. It probably doesn’t matter as much as camera makers would like it to – I shot on an old Canon 5D Mark II and no one batted an eyelid.


Picture credits: Photos from Depositphotos

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