Understanding Image Sizing and Resolution
Each camera manufacturer determines an ideal image size for printing that is referred to as a 1:1 ratio. This means that the image taken at the manufacturer’s predetermined size based on the camera sensor will create an image that will print to the optimal resolution and quality at that size. For example, one of my camera’s is a Nikon Z7, it has a 45.7 MP sensor with the option to take a variety of image sizes. If I set my camera to the largest FX format size, which is 8,256 pixels by 5,504 pixels and I plan to print at 300 ppi (pixels per inch (NOT dpi, dots per inch)) then I will get a print at a 1:1 ratio of about 24” by 16”. The actual image size needed for a specific print can vary greatly based on many variables and the 1:1 ratio is the optimal starting point. You can look up the manufacturer sizing for your camera online or in the camera manual. Attempting to use images at their native 1:1 resolution is the best approach for an optimal quality print.
Images are made up of pixels, each pixel is basically a square box and the image holds millions of little square boxes that “band” together to create what we, the viewer, see as a whole uninterrupted image, not just a lot of pixel boxes. The reason we see the image as a whole is because there are so many pixels pushed together that the image is seamless when viewed by the human eye, so the pixels are dense. When we crop or resize an image the pixels either squish together or spread out or pixels are created or dropped out, depending on the science of the particular camera and process. This is called resampling or interpolation. This process can affect how the viewer sees the image as it affects pixel density. Resizing and cropping can cause an image to have artifacts (that rounded band across the sky that a JPEG image can get) if the pixel interaction is pushed too far technically. These artifacts might be seen in a print if there are not enough pixels to create a smooth transition. There is much less of a problem with electronic viewing as screen resolutions are fairly low, much lower than required print resolutions, although it can also happen with electronic viewing if an image is not carefully cropped or resized.
All of these pixels create images with tones of color. Tones in an image are extremely important for viewing. An adequate amount of tones in an image are needed in order to print an optimal quality print. Resizing incorrectly can result in a loss of tones and an image that does not print optimally as it does not have smooth tones.
One variable in determining what file size is needed to ensure a quality print is viewing distance, which, to me, really only applies if the intended image size is very large. A billboard is an example that people often use to illustrate this, although most of us would not have to consider sizing for a billboard at any point in our lives. Most commercial printers want an image file sized to print at 300 ppi so using that number is a good starting point, with the understanding that larger images can be printed at a lower printing resolution, normally not below 240 ppi (the Adobe standard) for the majority of the work that most photographers create: there are always exceptions to this. Other variables include the sharpness of the image, as any image that is “upsized” for printing will only get less sharp when enlarged. Any flaws in a print will be enhanced by upsizing an image for printing. If an image is very dark or it has a lot of grain or camera noise that will be enhanced when printed. Starting with a good quality sharp image is the best bet to getting a good quality final print once sized correctly for printing at the required ppi.
To figure out what image size is needed to print at a specific size using the 1:1 ratio is fairly easy but does take a little math (and I am not good at math so I still have to resort to pencil and paper plus calculator to do this!). Using the example that I started with, my image file size of 8,256 pixels by 5,504 pixels I can determine what size I can actually print at and still maintain the optimal quality of the image. In that example at that file size, at 300 ppi, the image would print optimally at 24” by 16”. There is always “wiggle room” in this calculation so the image could probably print somewhat larger and still retain optimal quality, depending on the image variables and even the paper being used. If I wanted to print this image in a larger size, for example at 32” x 24” then I would divide the image size, using the longest side pixel dimension, by the longest size I wanted to print at, in this example it would be 32”. Thus, 8,256 pixels divided by 32” would require printing at 258 ppi for optimal quality. If I wanted to go even larger, say 40” x 32”, then I would divide 8,256 pixels by 40” and I would need to print at 206 ppi. Printing at 206 ppi would probably not provide me with the outcome I had hoped for unless the print was always being viewed very far away so I would most likely print at somewhere in the range of 32” by 24” using a ppi of between 245 ppi and 258 ppi in order to obtain the optimal quality print at a reasonable viewing distance.
One of the things I’ve done is to figure out how various pixel sizes equate to various print sizes using 300 ppi, which is what I’ve chosen to print at for the most part. I only need to know the longest size for any given image to know how the size equates. This way, I can glance at an image’s size if cropped and know if I can print it at my chosen size and ppi. My chart looks like this:
PIXELS = SIZE
2000 pixels = 7”
2500 pixels = 8”
3000 pixels = 10”
3500 pixels = 11.7”
3800 pixels = 12”
4000 pixels = 13”
4200 pixels = 14”
4500 pixels = 15”
5000 pixels = 17”
6000 pixels = 20”
7000 pixels = 24”
I generally print using the native digital sizing of my 3:2 camera so I most often print at 10” by 15” inches using 300 ppi. This means I need an image that is around 3000 pixels by 4500 pixels and my camera easily provides me with that resolution requirement. Since my camera provides a large file size I also have the option of printing much larger or of cropping a bit more if needed and I can do this without affecting the optimal print quality.
The difference between ppi and dpi is that ppi is a measure of resolution for electronic images and dpi is a measure of ink to paper ratio resolution for printing purposes. ppi = pixels per inch and dpi = dots per inch. ppi is about how many pixels in an image and dpi is about how many dots of ink are being laid down on paper.
Each camera manufacturer determines an ideal image size for printing that is referred to as a 1:1 ratio. This means that the image taken at the manufacturer’s predetermined size based on the camera sensor will create an image that will print to the optimal resolution and quality at that size. For example, one of my camera’s is a Nikon Z7, it has a 45.7 MP sensor with the option to take a variety of image sizes. If I set my camera to the largest FX format size, which is 8,256 pixels by 5,504 pixels and I plan to print at 300 ppi (pixels per inch (NOT dpi, dots per inch)) then I will get a print at a 1:1 ratio of about 24” by 16”. The actual image size needed for a specific print can vary greatly based on many variables and the 1:1 ratio is the optimal starting point. You can look up the manufacturer sizing for your camera online or in the camera manual. Attempting to use images at their native 1:1 resolution is the best approach for an optimal quality print.
Images are made up of pixels, each pixel is basically a square box and the image holds millions of little square boxes that “band” together to create what we, the viewer, see as a whole uninterrupted image, not just a lot of pixel boxes. The reason we see the image as a whole is because there are so many pixels pushed together that the image is seamless when viewed by the human eye, so the pixels are dense. When we crop or resize an image the pixels either squish together or spread out or pixels are created or dropped out, depending on the science of the particular camera and process. This is called resampling or interpolation. This process can affect how the viewer sees the image as it affects pixel density. Resizing and cropping can cause an image to have artifacts (that rounded band across the sky that a JPEG image can get) if the pixel interaction is pushed too far technically. These artifacts might be seen in a print if there are not enough pixels to create a smooth transition. There is much less of a problem with electronic viewing as screen resolutions are fairly low, much lower than required print resolutions, although it can also happen with electronic viewing if an image is not carefully cropped or resized.
All of these pixels create images with tones of color. Tones in an image are extremely important for viewing. An adequate amount of tones in an image are needed in order to print an optimal quality print. Resizing incorrectly can result in a loss of tones and an image that does not print optimally as it does not have smooth tones.
One variable in determining what file size is needed to ensure a quality print is viewing distance, which, to me, really only applies if the intended image size is very large. A billboard is an example that people often use to illustrate this, although most of us would not have to consider sizing for a billboard at any point in our lives. Most commercial printers want an image file sized to print at 300 ppi so using that number is a good starting point, with the understanding that larger images can be printed at a lower printing resolution, normally not below 240 ppi (the Adobe standard) for the majority of the work that most photographers create: there are always exceptions to this. Other variables include the sharpness of the image, as any image that is “upsized” for printing will only get less sharp when enlarged. Any flaws in a print will be enhanced by upsizing an image for printing. If an image is very dark or it has a lot of grain or camera noise that will be enhanced when printed. Starting with a good quality sharp image is the best bet to getting a good quality final print once sized correctly for printing at the required ppi.
To figure out what image size is needed to print at a specific size using the 1:1 ratio is fairly easy but does take a little math (and I am not good at math so I still have to resort to pencil and paper plus calculator to do this!). Using the example that I started with, my image file size of 8,256 pixels by 5,504 pixels I can determine what size I can actually print at and still maintain the optimal quality of the image. In that example at that file size, at 300 ppi, the image would print optimally at 24” by 16”. There is always “wiggle room” in this calculation so the image could probably print somewhat larger and still retain optimal quality, depending on the image variables and even the paper being used. If I wanted to print this image in a larger size, for example at 32” x 24” then I would divide the image size, using the longest side pixel dimension, by the longest size I wanted to print at, in this example it would be 32”. Thus, 8,256 pixels divided by 32” would require printing at 258 ppi for optimal quality. If I wanted to go even larger, say 40” x 32”, then I would divide 8,256 pixels by 40” and I would need to print at 206 ppi. Printing at 206 ppi would probably not provide me with the outcome I had hoped for unless the print was always being viewed very far away so I would most likely print at somewhere in the range of 32” by 24” using a ppi of between 245 ppi and 258 ppi in order to obtain the optimal quality print at a reasonable viewing distance.
One of the things I’ve done is to figure out how various pixel sizes equate to various print sizes using 300 ppi, which is what I’ve chosen to print at for the most part. I only need to know the longest size for any given image to know how the size equates. This way, I can glance at an image’s size if cropped and know if I can print it at my chosen size and ppi. My chart looks like this:
PIXELS = SIZE
2000 pixels = 7”
2500 pixels = 8”
3000 pixels = 10”
3500 pixels = 11.7”
3800 pixels = 12”
4000 pixels = 13”
4200 pixels = 14”
4500 pixels = 15”
5000 pixels = 17”
6000 pixels = 20”
7000 pixels = 24”
I generally print using the native digital sizing of my 3:2 camera so I most often print at 10” by 15” inches using 300 ppi. This means I need an image that is around 3000 pixels by 4500 pixels and my camera easily provides me with that resolution requirement. Since my camera provides a large file size I also have the option of printing much larger or of cropping a bit more if needed and I can do this without affecting the optimal print quality.
The difference between ppi and dpi is that ppi is a measure of resolution for electronic images and dpi is a measure of ink to paper ratio resolution for printing purposes. ppi = pixels per inch and dpi = dots per inch. ppi is about how many pixels in an image and dpi is about how many dots of ink are being laid down on paper.