Best Dpi Resolution For Printing Photos

By | 13/09/2022

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©

2022 Montclair Photo. All rights reserved.

Copyright
©
2020 Montclair Photo.

All rights reserved.

Resolution Explained

Resolution Explained



People use the term “resolution” loosely. When asking what resolution something is the answer can exist given in many ways, such every bit in pixels, dpi, or megapixels. It’s fifty-fifty used when describing sharpness and image detail.
Pixels vs DPI vs PPI vs Resolution vs Prototype Size vs Megapixles vs File Size vs Scan Resolution



What’due south the divergence betwixt pixels and resolution?  It’s kind of the aforementioned thing – they are all related to each other. Having just a couple numbers of any of the higher up you tin can calculate or judge all the other information. I’ll show yous some unproblematic math, but I must explain some details. Everything depends on pixels, pixels, and pixels.
What is resolution?



Here is a list of terms and what part of an image they refer to.

Pixel:
A tiny solid color spec. An image is created with millions of these tiny squares. See the header graphic above.

DPI:
Dots per inch unremarkably referred to how many dots a printer plots in a inch. The standard is 300 dpi for well-nigh ink jet printers. Virtually printers optimum quality is 300 dpi fifty-fifty if they don’t utilize dots. Out of all printer types ink jet printers are more than forgiving and tin can print a swell epitome at 240 dpi. More than on this later.

PPI:
Pixels per inch is used for calculator monitors and other devices with screens. Most screens display images at 72 ppi.

Resolution:
Usually refers to pixels, but mainly describes how much detail an epitome has and how big it can exist printed or magnified before it starts to pixelate. High resolution can mean more than pixels crammed into less space – for example 72 dots per inch vs 300 dots per inch. In the cease the higher resolution image will just have more pixels.

Image Size:
This is the dimension of an image – usually measured in inches. This is important to know mainly when printing. Dividing the pixels by dpi gets you how big an image can print.

Megapixel:
This is how cameras are described. Camera producers brand it seem similar the more than megapixels a camera has that information technology’s better quality – that is imitation. Information technology’s all virtually capturing light – some cameras don’t practice and then well in depression light situations. You can accept a 5MP camera take better photos than a 12MP camera. Anyway megapixels describes how large an image is past multiplying the top and width of it’southward pixels.
ie: 2000px x 3000px = six,000,000 pixels = 6MP camera sensor chip.

File Size:
This is how much infinite (bytes) an epitome takes upwardly on the hard bulldoze. A low res image can be 50kb and a large image tin be a 15mb file. You lot can get an idea of how large you can print an image past looking at the file size.  Usually A 5mb JPG should get you an 8×10 print considering I expect it to have 2400px x 3000px. But time the file size could be misleading is if the epitome was compressed into a 2mb file. A 1mb JPG file should get you a decent 4×6 photo.

Scan Resolution:
This is basically the dpi setting on a scanner when scanning a impress or negative to make a digital image. To reproduce a 4×6 picture you must scan it at 300 dpi to print it out at the aforementioned size. If you desire to double the size and print it at 8×12, you must double the dpi to 600 dpi. In the end your 8×12 image volition be printed at 300 dpi.

*Notation on scanners:  Some high end scanners will non export the image at the dpi a photo was scanned, simply consign the paradigm at 72 ppi.  What matters, and the number that doesn’t change, is the pixel count.
ie: You lot scanned a 4×6 impress at 300dpi which gives you 300dpi x vi” wide = 1800 pixels. When the scanner exports the prototype information technology may convert it to 72dpi – doing and so did not dethrone it because at present the image size is greater. Instead of having a 6″ epitome at 300dpi you lot might have (1800 px / 72dpi) = 25 inches on your screen. Run across… the width of the prototype nonetheless has 1800 pixels.


Calculating Pixels



Ok – finally the mathematical explanation on how all the terms chronicle to each other.

Lets stick with the same samples numbers I used to a higher place. 1200 x 1800 pixels.

What print size is the optimum resolution. Well, just carve up the pixels you take by 300 dpi. 1200/300 = 4″ and 1800/300 = 6″ gives you a 4×6 inch print.

If printing this image on an ink jet yous tin can hands get away with 240 dpi which will print your prototype at 1200/240 and 1800/240 = 5″ x 7.5″

Inches x DPI = Pixels.  You tin can alter the inches and dpi and keep same resolution in pixels.
ie: six” x 300dpi = 1800 pixels and ii” ten 900dpi = 1800 pixels. See a different prototype size can nonetheless be the same photo size in pixels and in file size. Some programs allow you lot change image detail like size, dpi, and pixels.

When you do modify the inches or dpi, the numbers ordinarily accommodate to keep the same pixel value, but you can force the paradigm and overwrite the other two values – doing then can damage your quality. Y’all can trick a printer by forcing or adding more than pixels (called upwards scaling), simply the paradigm volition still print as if it was a depression resolution image. You can’t change a 480 10 640 pixel epitome to 2000×3000 and expect a great 8×10 impress.

How large is the image displayed on my screen. Well split the pixels by the screen resolution. 1800/72 = 25″ and practise the aforementioned for the other dimension.

What resolution would I get if I scanned a 4×6 impress at 300 dpi vs 600 dpi.

Well 4″x300dpi = 1200px and half dozen”x300dpi= 1800px. So you lot would get a 1200×1800 image.

At 600 dpi you would get double. 4×600 and 6×600 = 2400 pixels x 3600 pixels. This give you lot a printed photograph double the size. 3600 pixels divided past 300 = 12″. And so you would get an 8×12 photo. Since your doubling the browse dpi it’southward easier to just double the pixels to go the aforementioned results.

Now if you were to scan a negative to make a 4×6 print your browse resolution will need to exist calculated by pixels needed divided by the actual size of negative. (a negative frame size is ane”x1.5″) 1800px/1.five”= 1200 dpi. (output pixels needed for press divided past the bodily print or negative size = dpi required).

A camera setting for making a 4×6 print is 1200×1800 = two,160,000 = 2.2MP Camera. For printing an 8×12 photo you lot will need an 8.6MP camera (multiply 2400 x 3600).


Quality depends on Pixels



Everyone thinks having more pixels is meliorate – wrong!  Well, upwardly to a certain signal. Oversizing is a waste material of time and space. Y’all only end up working with a super large file size which takes longer to open and uses upward more hard drive space. You will never get more detail when printing because in that location is a maximum limit for quality. If you lot are printing an 8×10, all y’all need is 3000 pixels which gives you about a 6mb file size. The printer ignores anything over 3000 pixels since it prints at 300 dpi. Why create an image where y’all accept 12,000 pixels, a 90mb file, when all you need is an 8×10 print.
Zooming in or Cropping in



When enlarging part of a photograph by zooming in or cropping in – you lot will demand more pixels to commencement with. You can’t crop into a 4×6 photo (1200×1800 pixels) and zoom in half way to enlarge part of an image into to a 4×6 print.  In this example you lot should of started with 2400×3600 pixels and cropped out the rest of the photo to still keep your 4×6 print quality. This is the only time more than resolution is needed. Zooming in is more than for computer screens – the more pixels you have the more you tin can zoom in before the image starts to pixelate.
Screen PPI vs Print DPI



Images are much larger on monitors than when printed. Most screens display images at 72ppi and printers print at 300dpi. A 1200 x 1800 pixel image is 25″ broad on the screen and only 6″ when printed. Just carve up the ppi or dpi by the pixels to the prototype size in inches. Images on screens and devices ever look adept, merely for printing them out you will need about 4 times more the resolution to make a bully print.
JPEG Compression



When saving an image to a JPG, nearly programs will take a compression settings. Saving a 1200×1800 paradigm in photoshop at the least compression (#12) will give you a 1.5mb file size. Saving it at level x compression will cut the file size in half giving yous a compressed file of 750kb. Compressing the file more volition really first to degrade the quality. Y’all will not notice it in the detailed parts of the paradigm, but in the solid color parts – like in the blue heaven. This is where the pinch first starts to break downward and it will look pixelated. Compressing the image too much will not change the resolution (pixel count). This  could be misleading to the printer because amount of pixels your image has is great, only the print quality looks pixelated.

Compression vs Downsizing



Both of these will damage your image in dissimilar ways.

Image compression takes away details past removing colour data. It’s kind of hard to explain ,but hither it goes. Each pixel has a number value (0-256) in either the Red, Light-green, and Bluish channel. Lets say yous have a photo with a overnice bluish sky. Compressing the image will take an average bluish value and reduce every fourth pixel to hold less colour. So 1 out of every four pixels will not exist a vibrant blue, but grayed out slightly. That’s why the first place you lot encounter impairment in the sky or solid colors.

Downsizing is when you reduce the pixel count lets say from 3000px to 480px. If y’all downsized to make a smaller file size you will not exist able to impress large photos anymore. This reduced the impress size from 10″ to 1.5″.

Information technology’southward important to not relieve over or overwrite the original prototype later on you make changes. It’southward good practice to relieve it every bit a new file name then your original tin can be a backup.


Does transferring an image dethrone information technology?



Copying an paradigm from one device to another doesn’t degrade the quality. Even emailing is a transfer, but with Apple tree products like a Mac or iPhone you have to select to ship the original or bodily size – or else it will downsize your prototype. Opening the epitome and resaving it does recompress it, only you can minimize the amount of degradation by selecting to non compress the epitome (save as all-time quality if you take that choice).

How large can I print?



Optimum quality is pretty much going to be 300 dpi, but there are lots of other factors too. Ink jet printers don’t demand 300.  How far will people exist when they view the photo. Most people are fine with images printing equivalent to 200 dpi. That’s near when, up close, yous will see the image starting to go soft or slightly pixelated. If you lot stand back a couple feet it volition look good. Now for an extreme horrible print example lets take a await at a billboard sign you see on the freeway. Those are huge prints and commonly printed at 72dpi. Looking at it upward shut you volition see tons of blocky, jagged pixels, but stand up back 50ft and it looks excellent.  Here is a chart for a quick guide on quality.

Impress Size Chart

A digital epitome is made up of many pocket-sized squares of colour chosen pixels. The more pixels your image has, the college the resolution and larger the file size. Hither I explicate all aspects of resolution.

Resolution Print Chart

What resolution should I scan at?

First you lot have to know your print size. Lets say you lot want an 8×10 print and your image is a 2×3 wallet size. To print an 8×10 y’all need 8×300 and 10×300 = 2400×3000 pixels. Printers always expect at the pixel number (not the dpi or inches). So 3000 pixels divided by 3″ (original photo size) = 1000dpi.  You lot volition need to scan the photo at least thousand dpi. So the adjacent scanner setting is 1200 dpi which is good because you may need to crop into the photo a niggling because the proportions of an 8×10 is more square.

Scan DPI Chart

Scan Chart

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Source: https://www.montclairphoto.com/resolution.html