There are many things that you have to think about when you plan on changing the size of an image. You don’t want to make arbitrary decisions, because selecting the correct size is very important.
Here are some things that you have to take into consideration.
Dimension and size constraints of the intended purpose of your image
This may seem like it should go without saying, but many people don’t do their due diligence when changing the size of an image. They might end up coming up with an image size that doesn’t fit the dimensions they need. They might be creating a mockup for a listing on an ecommerce site they are selling on, but don’t realize that they need an image with a specific width to height ratio or one that can’t be more than 1000 px wide. They also might not know the file size constraints of the program they will be uploading it to.
Do your research before resizing an image. You have to take these factors into account.
Relationship between image size and image quality
As we have seen, resizing an image in Photoshop is quite simple. However, when resizing an image we must take into account a very important factor: preserving the quality of the image we are dealing with.
As a general rule, resizing an image to a smaller size than the original one does not cause major problems related to quality, because there is a degradation of the image when we resize it to a larger size, which can sometimes leave the image unusable.
Here is an example of an image. On the right the original image and on the left the same image but enlarged to 200%.
In the image we can see at a glance that the enlarged image has lost a large amount of detail in the image and is blurred. If we were to enlarge it further, the disaster could be even worse.
Basically this happens because Photoshop, when reducing the size of an image, removes pixels from it, and thanks to its algorithms, it does it accurately and without sacrificing quality.
Now when increasing the size of an image, there is a problem, and that is that Photoshop has to “invent” pixels that are not there, that is to say that they do not exist in the original image.
Despite all the technology behind Photoshop, increasing the size of an image is basically letting the program guess which pixels would go in a certain place, and of course this can never have a good result, it can be approximated, and the result can be useful in certain occasions, but it is impossible to use in professional projects or where a sharp and clear image is required, that is to say, well defined.
The general rule when resizing an image in Photoshop
When resizing an image in Photoshop, there is a general rule that determines that the more we have to enlarge an image, the worse it will look. Instead of having a sharp and well-detailed image, we will get a dull and blurry image. That is why if we need to enlarge an image using Photoshop, it is best to do it in a small scale, a few pixels.
In the case of needing to reduce an image, most likely we will not have any kind of problem, as long as the result of the transformation is exported in the correct image format for what we are doing, but that is the subject of another article.