Here’s a common situation: I’m sitting in my studio editing business headshots when a recent client contacts me...
Client: “I opened up a digital file I want to print and I noticed it has a DPI of 72. Is this good enough to print photographs? How do I print from a 72 DPI image? How big can I print from this 72 DPI image?
Me: “Well, at this stage it’s not the DPI you should be concerned with. It’s the number of pixels your image contains which determines how large you can print. We need to differentiate between the resolution of your digital file, and the resolution of your printer. Let me explain…”
Clients often have questions and concerns about resolution and image size. In this article, I’ll try to put those worries to rest without overcomplicating things.
Please leave a comment below if you still have questions and I will be happy to reply.
What are Pixels?
Every digital image is made up of pixels. Individual tiny square dots, each one it’s own specific color, and when combined can make an image. The more pixels you have, the better an image will look. And it’s not just the quantity of pixels, but the quantity of pixels you have per square inch.
When people start talking about pixel quantity, what they are really talking about is resolution, and this is where things can get confusing, because unfortunately the term “resolution” is not specific when talking about either screen or print resolution.
A digital camera or scanner is capable of capturing an image at a certain resolution. The monitor you view your image with has it’s own resolution. And should you decide to print a digital file, the printer has it’s own resolution.
When we use the term resolution while discussing how an image will look on a screen, we are normally talking about how many pixels an image contains, which can be determined by multiplying width by height.
When we use the term resolution when discussing printing an image, we are normally talking about how many dots per inch a printer can print. DPI.
But either way, resolution is basically describing some sort of dots per inch, either pixels or sprayed dots of ink.
What is Print Resolution?
When thinking about printing your image, I want you to think in dots per inch (DPI). Why? Because printers today spray ink onto paper, and the more dots per inch sprayed, the higher the quality of the final print. Most printers will print at a maximum of 300 DPI.
So here is the big question which brought us to the point…
How many pixels does your image need to contain if you want to print a 4×6 photograph at 300 DPI?
Doing the Math. How many pixels do I need to print a photograph?
To figure out how large a print I can make from a particular digital file, I have to do a little math.
To print a 4×6 photo at 300 pixels/inch, I would need a minimum of 4×300 (1200) pixels on the short edge and 6×300 (1800) pixels on the long edge. 1200 pixels X 1800 pixels = 2,160.00 pixels.
Your digital file will need a total of two million, one hundred and sixty thousand pixels in order to print the highest quality 4×6 photograph your 300dpi printer can print.
This same formula applies to any size of print. An 8×10 photograph at a resolution of 300 DPI would need to be 8×300 (2400 pixels) on the short edge and 10×300 (3000 pixels) on the long edge.
Client: “But wait Aric. My image editing software says my digital file is 7360 x 4,921 pixels at 72 DPI? You said my image needs to be 300 DPI to print.
Me: “Remember, first and foremost it’s all about the amount of pixels your image contains. Let me explain…”
Remember earlier we said a 4×6 printed at 300 DPI will need 2,160,000 pixels. Well lets do the math again with the image you have at 72DPI. How many pixels does it contain?
7,360 X 4921 = 36,218,560 36 million pixels! That’s a ton of information, and more than enough to print a 4×6 photograph which only requires 2 million pixels. (I used this particular pixel dimension as an example as this is the resolution of one of my own cameras.)
And this brings me to a small side note. This is where we get the term “megapixels” from. Camera companies sell their cameras based on many different features, one of the most important being megapixels. If your camera produces files that are 7,360 pixels X 4921 pixels at 72 DPI, then each image contains 36,218,560 pixels, but with numbers this large the camera companies just round to the nearest million, so in this instance you would have a 36 mega pixel camera.
Back to my client….
Me: “If your digital file is at least 1200×1800 pixels, then yes, you have enough pixels to print a 4×6 at 300DPI.”
How Do You Convert A 72 DPI file into a file that is 4×6 inches at 300 DPI For Printing?
First, using the method above, determine if your digital file has enough pixels capable of printing the size print you want at 300 dpi.
Client: “Aric, I have more pixels than I need to print a 4×6.
Me: “Perfect. We’ll need to convert your image into a 4×6 at 300 DPI so your printer will print correctly. I’ll teach you the two most basic methods; resampling and cropping. Both methods will require you have some sort of image editing software. ”
As a professional photographer I use Adobe products to edit and manipulate my images, so for the purposes of this article I will describe these two different methods of converting the size of an image using Adobe Photoshop.
The First Image Sizing Method: Resampling
In your image editing software you should find a window which shows your Image Size information. In Photoshop this window is called…. wait for it… Image Size. It looks something like this.
Next, deselect the resample box and you will notice your width and height are now displayed in terms of inches as opposed to pixels. And also notice how you can no longer manipulate the resolution of the image without effecting the width and height of your image.
Next, remember the term resolution is interchangeable between your digital file and printed image. Pixels vs Dots. With that in mind, change the resolution from 72 to 300 and see what happens.
The image size window has done all the math for you.
You see, the Image Size Window really acts as an invaluable calculator. It has first converted pixels into inches, and it has now shown you that your 7,360 x 4.921 pixel image at 72 PPI is equal to and capable of printing roughly a 24.5″ X 16.4″ photograph at 300 DPI. That’s a very nice size wall portrait!
Next, recheck the Resample box and make sure to keep your width and height in inches.
Now change your longest dimension to 6 inches. In this example our longest edge is the width, so this is a horizontal 4×6.
Notice now your Image Size went from 103.6 megs to only 6.2 megs.
And there’s something else. It turns out the digital file coming out of this particular camera is already proportional to a 4×6 photograph! Why do you suppose this is?
It’s because professional photo labs are in the business of selling paper. A 35mm negative (film) was exactly proportional to a 4×6 photograph, so labs sold 4×6 pieces of paper. And now, with the invention of the digital camera, the material used to capture the image inside most professional grade digital cameras is also exactly proportional to a 4×6 dimension, so labs can continue to sell you 4×6 pieces of paper.
At this point, go ahead and click OK and your image will be resampled, or “sized down”, to a 4×6 at 300 DPI.
The Second Image Sizing Method: Cropping
An additional way to create a specific image size at 300 DPI for printing is to use the cropping tool in your image editing software.
First make sure your image has enough pixels to print your desired image size, then simply select the cropping tool, enter in your desired width and height and set a resolution of 300 DPI.
Crop your image and the resulting file will be to your specifications.
IMPORTANT NOTE: It is possible to actually increase the size of an image with your cropping tool. For example if you crop a 4×6 300DPI image to an 8×12 300DPI image you will actually be creating new pixels, or sizing up your image and your resulting printed image quality will be rather poor.
IMPORTANT NOTE: Make sure to save your file as a new file so you do not overwrite the original larger file.
IMPORTANT NOTE: Your image is not yet ready to print.
At this point what you have actually done is told your computer to throw away information. You have actually removed pixels from your image resulting in the smaller desired image size. However this will also cause your image to appear a bit “fuzzy” or “soft”.
Sharpen Your Image Before Printing
In Photoshop, go to Filter – Sharpen -Unsharp Mask.
There are many methods to sharpening an image, but Unsharp Mask is my personal go to method after sizing down an image.
Start with the settings I’ve set here.
As a general rule, the more you sized down an image, in our case a 24″ wide image to a 6″ wide image, the more sharpening your image will need.
Simply move the Amount slider to the right, and then click in the image are where the white box is to see a before and after of the effect.
To much sharpening and you will see a halo around objects in your image. Go ahead and slide the slider all the way over to see what I mean.
Once you have found your desired level of sharpness, click OK and you are ready to send your image to your printer.
Your own personal printer or desired photo lab will have an optimal resolution for print sizes. Online printing services like Mpix will warn you if the resolution is not high enough for the size of image you would like to print. Services and printers can differ slightly, so it’s best to check and make sure. Nobody wants to hang a pixelated image on their wall.
The Myth of printing 300 DPI Images
Also relevant to the resolution discussion: I often hear people say that you need a resolution of 300 (300 pixels/inch) to create photographic quality prints. This is not always the case. An image printed on your printer at a resolution of 200DPI may look just as good as an image printed at 300 DPI. Give it a try.
The primary benefit of printing files at a resolution of 200 is the ability to create larger prints.
We know our original example above using a camera which creates a file at 7360 X 4921 is capable of printing a 24×16 at 300 DPI. Print that same file at 200 DPI and you can now print an amazing 36 X 24!
Ultimately, Don’t Get Hung Up on DPI
Remember, DPI means “dots per inch,” and it’s used to describe the sharpness and detail of a printed image but it doesn’t mean anything in the digital file itself. DPI is not an indicator of a files screen resolution, but it does tie into print quality.
Additional Resources/Tools
Here are some more in-depth discussions of image resolution, if you’re still confused or would like to learn more on the topic:
http://www.howtogeek.com/107163/htg-explains-everything-you-know-about-resolution-is-probably-wrong/
Thanks so much for sharing such a superclass tips. I really appreciate your wonderful explanation. It’s really great learning for me. I will certainly dig it and personally suggest to my friends. I’m sure they’ll be benefited from this website.
Thank you for the interesting article Aric. Just one question about down-sampling an image for printing. How necessary is it? e.g I have 15673 x 11499 image at 72 dpi and I want to produce 22″ x 16″ print. Without down – sampling these dimensions give me 712 dpi. my printer only supports max. 600dpi (canon pro-1000). what if I just print at this resolution? Won’t my print be much sharper? what are the advantages of down-sampling?
Hi Giorgi,
A 15673×11499 image at 72 converts roughly to a 26×19 in print at 600 dpi. There is no downsizing in my equation.
You want to produce 22×16 print at 600dpi.
Next use image size to downsize your image so the longest edge is 22″, which brings the other edge close to the desired 16″.
Lets take this example to the extreme. Lets imagine you want to use this image for a LinkedIn Profile Image which are normally 500×500 pixels.
When you size an image down this much, you are essentially telling the computer to throw away pixels, and the resulting image ends up looking very soft. At this point you need to resharpen your image using Unsharp Mask, or Smart Sharpen. I prefer Unsharp Mask myself.
In your situation, you really aren’t sizing down to far, but you are correct in that you may need to slightly resharpen your image.
Does this answer your question for you Giorgi?
Thanks for writing.
Very good and helpful information – Thank you.
What about larger prints in feet? I want to print a digital file onto a 4x6ft paper to make a picture to hang on the wall. For this type of image what DPI do I need. Is 300DPI too much and is 150DPI enough to get a good sharp image. I am looking at digital files in places like shutterstock and I am not sure what resolution I need – for ex. an image may be available as 3600 x 4600px. Will that be enough for a good 4x6ft print.
4×6 feet is a good size print Wanda. Here’s a link to a billboard which was printed from one of my images.
https://solarisstudios.com/headshots/realtor-headshots/houston-realtor-headshot-billboard/
That particular image was delivered on a transparent background as a png file. The resolution was 4912×7360 at a resolution of 300.
4915 X 7360 = 36,174,400 pixels
You had asked if 3600 X 4600 at 300dpi is large enough to create a 4’ x 6’ print.
Lets find out…
Open Photoshop and create a new file, 3600dpi X 4600dpi at a resolution of 300. It makes no difference the color you chose to fill the background with.
Now, under the Image Menu, pull down to Image Size.
1. Make sure Resample is checked.
2. Change Pixels to inches on either the Width or Height.
You should now see that a 3600 X 4600 at 300 DPI will produce a 12” x 15.333” print.
Now, uncheck the Resample box, and change the resolution from 300 to 200.
The same file at 200 dpi will give you an 18” x 23” print.
Do the same from 200 to 150 and you get a 24” X 30” print. Not your desired size.
BUT, don’t be discouraged just yet Wanda!
Run a test! An inexpensive test.
Lets’ size the image to 4’ X 6’ at 150dpi and send a small 8”x10” portion to the lab for printing. From there you can make up your mind about the quality.
1. Find and open an image you already have in your possession which is 3600 x 4600.
2. Image Menu -> Image Size
3. Make sure Resample is checked
4. Make the long edge 72 inches. (6 feet)
5. Change the resolution from 300 to 150
6. Click OK
You have now sized the image to the size you need. 4’ X 6’ at 150 DPI.
With the image still open in Photoshop…
1. Select the Crop Tool
2. From the Crop Tool options at the top of the window select 4 : 5 (8 : 10) ratio
3. Scale the crop tool on your image until you see the crop will equal 1200 x 1500 pixels. (1200 x 1500 = 8” x 10”)
4. Crop the image.
NOTE: It’s ok if your crop is over by a few pixels, but not under by a few pixels. If you are over by a few pixels after the crop then do the following.
1. Image Menu -> Canvas Size
2. Change the Width and Height to exactly 1200 x 1500.
3. Click OK.
Use Save As to save your image WITH A DIFFERENT TITLE. Don’t write over your original image.
Lets summarize up to this point Wanda.
1. We changed/upsized a 3600 x4600 300dpi image into a 8452 X 10800 150dpi image. (4’ X 6′)
2. We cropped a perfect 8”X10” (1200 x 1500 pixels at 150dpi) piece out of your newly sized 4′ x 6′ image.
3. You saved the cropped image using save as.
Next, send your 8×10 (1200 x1500 at 150dpi) sample to the same lab where you plan on having your 4’ X 6′ print made and have them print the 8×10 section. When the 8×10 section comes back, tape it to a wall and step about ten feet away from it.
How does it look? This should answer your question… Can you print a 3600 X 4600 at 300 dpi, resized to 10800 x 8452 at 150dpi (4’ X 6’).
Can you print it? Yes. Does it look good? This is up to the eye of the beholder, and it’s best to run a small inexpensive test/sample in order to make this determination.
When viewing your 8×10 sample, ask yourself a few important questions.
1. How far will people be standing away from the final print?
2. Will people be standing there looking at it, or just glancing at it as they walk by.
3. Will you be saving this print after your event is done, or possibly throwing it away?
A billboard, as mentioned above, is viewed from inside a car passing by at 60mph, and when the advertising contract expires the image will be covered up with a new image.
I hope this helps and saves you some money and heartache Wanda.
I know this article is a couple of years old but is it possible to ask a question (and maybe send a couple of photos to show you what I mean)? Really struggling and printing companies I’ve contacted don’t seem to understand.
Not a problem. How can I help?
Thanks so much. I can’t see an option to attach photos. Basically I wanted to have large prints of some of my photos, but when I told the company the information shown when I view properties (I’m in Windows, in the My Pictures folder; have also checked ‘image size’ in Photofiltre) they said they would be terrible quality. I have two cameras I use. The first is Fujifilm – the image shows as 4000×3000 pixels but in the properties it says 72dpi. The second is Canon – the image shows as 4320×3240 pixels, but in the properties it says 180dpi. I’m really confused as I thought with the high number of pixels I could get a good size of print with high quality. I struggle with anything relating to numbers – I’ve spent hours trying to understand photo resolution and a couple of people have explained it to me, but it’s just not making sense :/ I’m hoping to start selling my prints but wondering if all the photos I’ve taken are now too low quality. Any advice you could give me would be very much appreciated.
Hi Arlene. I tried to post a movie here in my reply which didn’t seem to work so well. So I created a new blog entry and placed the movie into the entry for you.
https://solarisstudios.com/behind-the-scenes/reply-to-arlene/
Hello Aric,
I love your post about resizing the photos and I have read all your replies.I have one question. I used to take pictures on my Samsung Galaxy S8 phone, which had 12 MPX camera. I went through some of the photos and it has 4032×3024 dimensions at 240 PPI. This was few years ago. Now, having the iPhone 11, the dimensions of its photos are the same but with 72 PPI only. How is that possible? Does it mean that if I wanted to print the images from Samsung phone, it could be printed bigger (240 ppi) than with the pictures taken by an iPhone? That just doesn´t make sense to me since it is much better and newer camera phone. I want to make sure, that my iPhone photos have the best quality possible if printed as big as possible. If I understand it correctly, I could print out an image from Samsung bigger then from the iPhone. How is that possible?
Thank you
So sorry it has taken me so long to reply. What is the resolution of your iPone 11?
Don’t worry about the 72 and 240ppi. It’s the volume of pixels that gives you the power to print larger. 12MPX is 12 million pixels.
Hi there! Thank you very much for talking about how better it is to leave our Photoshop or JPEG documents uncompressed before printing them. I’ve been assigned to print out some promotional brochures for our company’s open day next week. I’ll keep this tip in mind so the end result will be satisfactory later.
Hip-hip-hooray!
I’ve tried, unsuccessfully, for over 15 years to explain all of this to others and/or find accurate information somewhere (anywhere) on the Internet and here you have done a most perfect job of it and so concise without getting too technical for non-technical people! Thank you for sharing this important information – BTW – I found this page via your post at Night Cafe’s Discord chat rooms.
Thank you so very much. It’s not always the easiest concept to get across.