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You’ve probably heard of the word “pixel” one time or another, but what does it really mean? And what does it have to do with resolution, image size, and formats?
Have you ever wondered why an image can look exceptional on the screen yet turns out to be low in quality when printed? Do you know how the number of megapixels of the camera you’re buying affect its performance? Do you experience some difficulty sharing your images online? A great deal of confusion between size and resolution, pixels and bytes, and size and resolution seem to be apparent to the consumers.
So as to fill the void in knowledge, here’s a quick review of some of the Photoshop basics to help you understand better.
Are resolution and size the same?
It is not a rare occurrence for people to be confused with the concept behind resolution and this is mainly because resolution can mean many things. Two of these concepts about resolution are associated with the conflict at hand but before I proceed to the discussion, there’s one important thing to ponder on first: both of these concepts have something to do with pixels. If you’ve ever bought a camera, you’ve most probably heard a lot about pixels since this is one of the most important specs in the market today.
Pixel: what is it?
A digital photo is a divisible object. Zoom in far enough and you’ll see a formation of small tiles, just like a mosaic, and these are called pixels. The number of these pixels and the manner in which it distributes them are the factors needed to consider to fully comprehend what resolution is.
Pixel count
Pixel count is the first concept of resolution which involves the number of pixels that form the image. To compute this resolution, simply utilize the formula you would use to calculate for the area of any rectangle: length multiplied by the height. For an instance, if an image contains 3,000 pixels vertically and 4,500 pixels horizontally, you will get a total of 13,500,000 pixel counts. However, for an easier utilization of this number, the pixel count is usually divided by a million to convert it into megapixels. In other words, 13,500,00 divided by 1,000,000 is equal to a total of 13.5 megapixels.
Pixel density
The second concept of resolution is the way the pixels are distributed, which is termed as the pixel density. The resolution is expressed in either dpi or ppi, which is the abbreviation for dots or pixels per inch, respectively. In simpler means, an image with 72 dpi is an image with 72 pixels per inch.
Your chosen resolution largely dictates the final size of your image. An image with 4500 x 3000 pixels will be printed at 15 x 10 inches if the resolution is set at 300 dpi. However, this will change to 62.5 x 41.6 inches if the resolution is adjusted to 72 dpi. As you may have observed in the example given, although the size of the print changes, the photo size remains the same, and this is because you are simply restructuring the existing pixels.
To put it simply, visualize a rubber band. You may be shrinking it or stretching it, but you are not necessarily changing the components of the band nor are you removing or adding any of the rubber. This is how pixel density works.
To summarize, size is not the same as resolution, but both are highly correlated.
Does quantity equal to quality?
Due to the relationship between size and resolution, it is easy to think that megapixels equal quality. At one point, it does, since the more stretched out the pixels are, the greater the pixel density will become. But on the other end, the depth of the pixels should also be taken into consideration aside from the quantity. The tonal values of your photo are dependent on the depth of the pixels, which is also known as the colors per pixel. To exemplify, a 2-bit depth has the storage capacity for black, white, and two shades of grey only. Take note that the values exponentially grow. For example, an 8-bit photo (2 to the power of 8 is 256), which is the more common pixel depth, has 256 tones of blue, 256 tones of green, 256 tones of red, arriving at about 16 million colors in total.
The previous example is already way more than the eye can differentiate so a 16-bit or a 32-bit photo will most likely look identical in human eyes. The only difference a higher depth value entails is that although your photo may look identical, it will be heavier since more information is stored in each pixel. So, to answer the question: quality and quantity are not the same.
Accordingly, on top of the quantity, the size and depth of each pixel will all determine the overall quality of the photo. This brings us as to why you should not solely consider just the number of megapixels when purchasing a camera since it is not the only factor that affects the quality.
How do I correctly choose the image size and file size?
The first thing you need to take into consideration is the purpose of your photo. Are you going to print it? Where will you post it? If the image you have is to be posted online, 72 dpi is sufficient. However, for photo printing, a higher pixel density of 300 to 350 dpi is required for a great print quality.
Another thing to put into consideration is that slight differences in resolution among monitors and printers are expected. To print an 8×10-inch photo, the image should have a 300dpi x 8” = 2,400 pixels by 300dpi x 10” = 3,000 pixels. Thus, 2400×3000 is required to print an 8×10 inches image at 300dpi, and anything greater than the requirement will only be an unnecessary addition to the storage of your hard drive.
How do I resize in Photoshop?
To resize a photo,
- Open the image size menu.
- Tick the “resample image” box. If this step is skipped, the pixels will only be redistributed.
- You may also tick the “constrain proportions” option if you want the measurements of the whole image to adjust accordingly. For example, if you adjust the height, the width will automatically follow.
- On the upper portion of the window, check for the file size. This is the size of your image without compression. Here, fewer pixels equal to fewer information.
- Should you want to change the file size without resizing, you can choose the format you want before saving your image. To maximize the quality of your photo, save it in an uncompressed format so as to not lose any information. The most common uncompressed format for sharing is TIFF. On the other end, if losing a little information does not stir a problem in exchange for a lighter file, choose the JPEG format and go for the size you want. Consequently, the smaller the size you choose, the more information you lose.
- Before finalizing, you may utilize the preview button to see the end result of the compression.
Conclusion
To conclude, size, resolution, quality, and quantity are all different elements, but all are correlated with pixels. Thus, all these elements, when put together, determine the quality of your image.
You are now more equipped to choose the best options when it comes to sharing, printing, and saving your photos! Enjoy!