What Are Megapixels and How Many Do You Need?

If you read anything at all about cameras, you will inevitably come across the phrases “pixels” and “megapixels.” It’s difficult to avoid them. These days, the majority of cameras have twenty or more megapixels (MP), and there are even certain monstrosities that have one hundred MP.

When I was a youngster, I remember going into camera shops and seeing that the top-end models had 2 megapixels, and it’s likely that in the next fifty years, everyone will have 600MP. This is something that will always stick with me. The question now is, what exactly is a pixel, and how many do you require?

What are Pixels (and Megapixels)?

Said the smallest visible unit that constitutes a digital image is referred to as a pixel. To put it another way, a digital image is composed of millions of tiny squares of varying colors, and each of those tiny squares is referred to as a pixel.

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It’s also possible to talk about the pixels on a camera sensor. In this discussion, the number of photosites that are included on a sensor is referred to as a pixel. Photosites are the individual sensor regions that catch light, which is subsequently transformed into pixels by software. Pixels are the basic unit of measurement for digital images.

Additionally, pixels are the units that are used to indicate the resolution of a camera. For instance, the Fuji X-T4 creates images with a resolution of 6240 x 4160, which indicates that the picture is 6240 pixels long and 4160 pixels wide. This results in a sum of 25,958,400 pixels in total. It is preferable to work with the megapixels unit when dealing with such a cumbersome figure as this one. One megapixel is just a million pixels. Therefore, the resolution of the X-T4 is around 26 megapixels.

Total vs. Effective Pixels

Let’s assume that your buddies have decided not to attend your birthday celebration at the last minute. What is the treatment for this? Obviously, reading the camera specifications on B&H! It is almost certain that learning that the Canon R5’s DCI 8K records at up to 1300Mb/s would give you the impression that you do not require a birthday at all.

However, if you look too carefully, there is something that might perhaps disrupt the tranquility of the evening. Almost every camera has two distinct values in its megapixel count: absolute (or total) megapixels and effective megapixels. Where do these two numbers stand in relation to one another?

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The amount of megapixels that are really usable is the metric that photographers care most about. When you open your Raw developer or export a JPEG at its maximum size, this is the number of megapixels that will be contained in the full-size version of the image that you have captured.

For instance, the Panasonic G9 is advertised as having a total effective resolution of 20.3 megapixels. But what about the “actual megapixel” value of the G9, which is 21.8? Is it possible, for the inexpensive cost of 329.95 dollars, to unlock these secret pixels and therefore obtain an even more valuable resolution? I’m afraid not. Instead, they are pixels that are located outside of the imaging region on the border of the sensor. Why does the sensor include additional pixels around its perimeter? There are two primary explanations for this.

1. First Reason: The Way Color Sensors Work

The first explanation has to do with the characteristics of color sensors. Take, as an illustration, the Bayer sensor, which is found in virtually all color digital cameras today. It employs distinct photosites to absorb red, green, and blue light, respectively:

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When you open a Raw file, what you see is the result of a process called demosaicing, which is performed by your Raw editor. If you shoot in Raw, which you absolutely should, then this process is performed. If you shoot in JPEG format, the camera will automatically conduct the demosaicing for you.

On the other hand, if there were only as many photosites as the total number of pixels that were wanted, then the edges would not have sufficient photosites to provide accurate color information. For instance, the following is what occurs when you attempt to compute color values based just on the pixels that make up the edge:

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The illustration on the right shows four by four, which equals sixteen color photosites. In most cases, the value of each pixel is determined by utilizing the four photosites that are present. When you reach the end of the row, however, you will notice that there are only two photosites available for the fourth pixel of that row.

Therefore, in order to obtain a 4×4 grid of pixels in the final image, you will want a 5×5 grid of photosites. This is necessary to ensure that each of the 4×4 pixels contains complete color information. (I attempted to make this procedure a little bit easier. In practice, the demosaicing stage almost always makes use of a more advanced method than the one I just discussed.)

2. Second Reason: Black Level and Unwanted Dark Signal

On the other hand, these additional edge pixels are not sufficient to account for all of the additional pixels. In point of fact, the vast majority of cameras feature pixels that are totally shielded from light. One way to conceptualize them is as pixels that have been painted black. These are the pixels that are defined as being optically black. Why should the sensor include pixels that are unable even to detect light?

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Unfortuitously, a sensor will continue to produce a signal (referred to as the dark signal) even when there is no light present, and this signal will be interpreted as anything other than pure black. This is not desired because it seems intuitive that you would want black to be read as black.

Using these pixels that are optically dark is one way that this might be somewhat compensated for. The camera is able to make a correction to the complete image by reading the signal that is provided by these individual pixels.

Typically, this adjustment is created using a model that is dependent on temperature, which is then calculated based on the pixels that are optically black. In practical terms, the hotter your sensor, the more undesired signal (noise) gets through, and the camera estimates this by using these additional pixels to adjust for it. In other words, the more heat your sensor generates, the more noise it generates.

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When reducing noise from long exposures, a similar approach is utilized, in which a dark frame is captured either manually or automatically by the camera. This can be done in order to minimize noise. As a result of the unfortunate fact that not all noise can be anticipated from optically black pixels (nor can hot pixels), dark frame removal is nevertheless beneficial for long exposures.

How Many Megapixels Do You Need?

Now that I’ve gone over the finer points of pixels, it’s time for the fun question: how many megapixels do you require for your camera? The answer is at least 100 megapascals, and anything less than that might lead to the disintegration of the universe.

Now that we’ve gotten that out of the way, how many megapixels is genuinely adequate? Should you acquire a camera with 45 megapixels rather than 24 megapixels? The answers to these questions may be found by examining two different factors: first, what media will be used for the final product, and second, how much will need to be cropped. Let’s delve a bit more into these two topics, shall we?

1. What is Your Final Output?

If you want to exhibit the majority of your photographs on the internet, you do not require nearly as many megapixels as you would think. A 4K display, for instance, has the capability of covering 8.3 megapixels. (On the other hand, an 8K monitor requires a resolution of 33.2 megapixels. If you want to make 8K desktop backdrops, you should keep the 33 MP threshold in mind because very few people have displays with such a high resolution, despite the fact that such monitors are becoming at least a bit more every day.

Printing your art is yet another fantastic method to show it off, but in order to achieve the quality you want, you’ll likely need a higher megapixel count, at least for larger prints. Printing with a resolution of 300 pixels per inch is generally recommended for seeing at close distances.

What exactly does that entail? This implies that for every inch that appears on your print, you’ll want there to be 300 pixels across that inch. It’s not a strict rule, but if your print has 270 pixels per inch, it should appear quite well. If you don’t have that many pixels per inch, your print could not look as good. What is the minimum number of megapixels required for printing? Just for your convenience, I’ve included a chart below with some popular large print sizes:

Print size (inches)Resolution for 300ppiMegapixels for 300ppiResolution for 250ppiMegapixels for 250ppi
8 x 102400 x 30007.2 MP2000 x 25005.0 MP
12 x 183600 x 540019.4 MP3000 x 450013.5 MP
16 x 244800 x 720034.6 MP4000 x 600024.0 MP
24 x 367200 x 10,80077.8 MP6000 x 900054 MP
32 x 489600 x 14,400138.2 MP8000 x 1200096 MP

As can be seen, the required number of megapixels balloons to an absurdly high level as the print size is increased. It seems reasonable to assume that everyone who is interested in producing huge prints should immediately run out and get a Fuji GFX 100S. No, not quite like that. The average viewing distance is another factor that affects the amount of pixels that should be used.

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Because of the way people’s eyes work, even a low-resolution print can appear clear and distinct when seen from a greater distance. To be more explicit, if you need around 300 PPI at a given distance, increasing that distance by 50 percent will bring your demand down to 150 PPI. In addition, increasing the distance by a factor of two will cut the number of needed megapixels in half.

I have devised the following more practical table for determining the required number of pixels, taking into account the fact that larger prints are less likely to be examined in great detail:

Print size (inches)PPIResolutionMegapixels
8 x 103002400 x 30007.2 MP
12 x 182603120 x 468014.6 MP
16 x 242203520 x 528018.6 MP
24 x 362004800 x 720034.6 MP
32 x 481805760 x 864050 MP

This is based on my own personal tastes as well as considerations of the locations within my home where I would display the artwork of varying sizes. In other words, it is highly scientific and cannot be questioned in any way. (If nothing else, it’s a solid foundation on which to build.)

The print media and the subject matter both have an influence on the required level of resolution. When compared to a photo of a person’s face taken at the exact resolution, a photograph that contains a lot of minute details, such as feathers, would appear to be of lower quality if those elements are removed.

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In light of the aforementioned, I propose that you do the following: If you are content to limit the size of your prints to no more than 16 by 24 inches, virtually any current sensor will suffice (given that the base model of recent cameras often has at least 20 megapixels). Therefore, this indicates that any modern camera with an APS-C sensor, a micro four-thirds sensor, or a full-frame sensor with a low resolution will do.

You may employ software solutions that are capable of doing extensive upscaling, and this will allow you to print at the appropriate PPI, even if you do not have quite enough resolution. Additionally, specific cameras, like the Panasonic GH6, feature what are known as pixel-shift or high-resolution settings. These modes are better ideal for specific situations and offer a higher resolution overall.

On the other hand, if you want to print images that are 24 by 36 inches or larger, you will have more creative leeway if you choose a high-resolution full-frame sensor such as the one found in the Nikon Z7, Canon R5 or Sony A1. People who need to produce enormous prints would benefit significantly from investing in a full-frame camera with a resolution that is even greater, such as the Sony a7R IVA, which has 61 megapixels.

And if none of these options work for you, the Fuji GFX 100S is a beautiful camera to consider purchasing.

2. How Much Do You Need to Crop?

The second thing to think about is cropping, which is something that can’t always be avoided. When I’m photographing animals, for example, I have to crop a lot of my shots since it’s challenging to get near all of the different species. Because the most excellent magnification of the macro lens frequently prevents the subject from taking up the whole frame of the shot, cropping is another technique that is frequently used in macro photography.

Because of this, I would advise photographers who frequently crop heavily to pick a camera with a greater megapixel count, such as the Canon R5, rather than a camera with a lower megapixel count, such as the Canon R6.

If you look at the print chart above, you’ll notice that the Canon R5’s 45MP resolution will provide you with a lot more printing alternatives. Even after cropping by a factor of 1.5, the Canon R5’s 45 megapixels will still leave you with 20 megapixels, whilst the Canon R6’s 20 megapixels will be reduced to 8.9 megapixels.

You also have the option of utilizing a camera with a crop sensor, such as a micro four-thirds or an aps-c, in conjunction with a long enough lens to “crop” the image. Because of the crop factor, even though the majority of these cameras have a maximum of 16 or 24 megapixels, it is possible to fit more total pixels on a distant subject than a standard full-frame camera would be able to capture.

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There is no doubt that pixel peeping is a highly calming sport; thus, purchasing a camera with a higher megapixel count should be your final consideration. The addition of more pixels presents a potential improvement in their curative effects.

Conclusion

A pixel is the most fundamental component that makes up a picture, and in general, the more pixels an image has, the better it will seem. However, photographers are in a fortunate position thanks to the development of current cameras; the majority of these devices have more pixels than are required for virtually every scenario.

It is very desirable to have more pixels, and as a result, cameras with a resolution in the region of 40-60 megapixels may be pretty helpful for very large printing and cropping. However, even a 20-megapixel camera may produce perfect huge prints, so the number of pixels in your image should not be a limiting factor. In the following remarks, I want to learn why 100 megapixels represents the highest possible degree of photography.

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