September 22, 2010

Image Size and Resolution

Image Size
Image Size is the size of your original digital photo file, measured in pixels and DPI (Dots Per Inch). What is a pixel? A pixel is a small square dot. DPI refers to the number of dots (pixels) per inch. Why is this important? Well, if an image is too small, you might not be able to order a large size print or other photo product. A general rule of thumb for image size versus print size is: the image size should be at least the size of the print you want multiplied by 300, at 300 DPI. For example, if you want to order a 4x6 print, the image size should be 1200 pixels (4 x 300) by 1800 pixels (6 x 300) at 300 DPI. If the image size was half of that (600 by 900), then the 4x6 print would likely come out distorted or pixilated if you were to order a print.

Camera Settings
Decide in advance what is more important: image quality or room on your memory card. You can set your camera to take photos that are larger or smaller in size. If you know you will only be printing 4x6 photos, then you can reduce the image quality, which allows you to store more photos on your memory card. If you will be printing enlargements or other photo products like photo books, then keep the setting on "high" for higher quality images. The image sizes will be larger and you will not be able to store as many on your memory card at one time. Also, set the file type as "jpeg" if your camera allows you to control that detail. You might have a "tiff" option, but it is not necessary to save the photos as "tiff" files, and it will only take up more room on your memory card.

If you have a point and shoot camera, open your main menu, and find the setting for "image quality" (or something similar). Usually, the options are "low," "medium," and "high." Choose "high" for higher quality (larger) photos. If you have an SLR camera, you probably have additional options. Just stick to high quality jpeg images, unless you know you will be doing extensive image editing and post-production. In that case, you might want to shoot RAW files.

The resolution of your photo is directly impacted by the image size. The more pixels your photos have, the higher their resolution is.

When you upload photos to your online account, you are given three upload options: "Regular," "Fast," and "Fastest." When you choose "Fast" or "Fastest," the photos are compressed, so the resolution will be less than the original photo file. So, if you are just uploading to order 4x6 prints, "Fastest" will be fine. But, if you wish to order enlargements, photo books, calendars, and other photo products, choose the "Regular" speed, which uploads the photos at their original resolution.

Once the photos are uploaded, you will notice three bars for each photo in your account. If all three bars are green, that means that the resolution of the photo that is in the account is sufficient enough to order just about anything on the site. If the bars are all red, you have uploaded a low resolution photo. Try to find the original photo file and check the size. If the size is sufficient enough to order prints (based on the rule we mentioned above about multiplying the desired print size by 300 and comparing to the actual image size), re-upload the photo at "Regular" upload speed. Photos with two or three red bars will generate poor quality prints, especially if you are trying to order anything larger than 4x6 prints.
We also will double check the resolution on our end. If we catch a low res file when printing, we always stop and notify you. We want you to be happy with your prints.


Additional Tips
Now that you understand image size and resolution a bit more, and understand why they are important when working in your online photo account, here are a few more extra tips about image size and resolution:
  • Most computer screens display photos at 72 DPI. That means the printed photo will look different than how it appears on your computer screen
  • If you crop a photo too much (zoom in too much), it will always look pixilated and distorted, no matter how large the image size is.
  • Once you take the photo, you cannot increase the size or resolution by increasing the number of pixels in any photo editing program. If you wish to increase the resolution or file size, you must do so by adjusting your camera settings before you take any more photos.


  1. Great advice, so many people struggle with this! We tell our photography students to set their cameras on the highest settings, with the least compression. If they want to get more pictures on their card, just buy a bigger or another card. Cards have gotten cheap enough that there's no reason to settle for lower resolution images. You never know when you want that one amazing photo to fill a 12x12 layout, or will want to zoom in to that funny face in the background!!

  2. Thank you Jenn! Yes, we are all about educating this digital world when it comes to pixels!

  3. Great article… except as most do, you are mixing up DPI and PPI.
    300 PPI = 150 DPI (approximately depending on the printer and settings used).

    DPI is what a printer uses to translate. Dots per inch as you say.
    But PPI is what your programs use and your screen on your computer sees. Pixels Per Inch.

  4. Dots per inch (DPI) in this context, refers to the smallest amount of ink that a given printer can print. Put another way, the more dots that a printer (or imagesetter) can apply per inch, the higher the resolution (and therefore quality of image reproduction) an imaging device can reproduce.
    We don't use ink at Persnickety Prints.

    Pixels per inch (PPI) is often used interchangeably with DPI. PPI is, arguably, where the confusion started from in the first place. PPI a somewhat relative term. Once a photograph is opened in a program such as Adobe Photoshop and displayed on a computer screen, its relation to print paradigm concepts such as per inch are not always helpful. In many cases it is actually more helpful to talk about the total width and height of the digital image in pixels, rather than pixels per inch or dots per inch.

    For printed reproduction, the amount of dots per inch only becomes relevant when calculating the amount of digital information against the intended output size of the image. For example, if the printed requirement of an image is 300dpi, to be output via a 150 line screen, then an image that is 1500 pixels wide and 800 pixels in depth can be printed at a size of 127mm by 67.73mm. Changing the resolution to 350dpi for a 175 line screen printing job, reduces the acceptable output size to 108.86mm by 58.06mm, however the actual dimensions of the on-screen image remain the same – 1500 pixels by 800 pixels.

    Note that we are not talking about resampling the image here, which is different in that it involves actually either reducing or adding information to the image, rather than simply defining its attributes from the digital world to the print paradigm.

    For on-screen use, such as web design, the PPI of an image is largely irrelevant. It is the PPI of the computer screen which defines the display size of an image on screen. For example images on a 96dpi monitor, will display slightly smaller than those on a 72dpi monitor.

  5. For all intents and purposes dpi and ppi are the same. Dpi refers to the out put of the machine you are printing on. Our machine prints at 300 dpi. The files technically are made from pixels, so they call it pixels per inch. Ink jet machines need to print at a much higher dpi then our machine to get the same quality.

  6. I'm impressed that you print in 300dpi! Most print only in 150-200 dpi. Kudos to your company! That's rare!

    But, dpi and ppi is not the same at all. google it. dpi is an OLD term that has been applied to everything relating to resolution incorrectly and that's why it confuses people who want to print, say scrapbook pages or art for example. New technology has made us more aware. No longer do we just hand you a roll of film to print… we are creating our own pictures our way in every form of art there is! :)

    Basically if they create the size of print they want in inches (say 12x12), then they need to create their image in 300 ppi (or 3,600x3,600 ppi) in their graphics program.
    Screen resolution has nothing to do with what I was talking about sorry if you thought that.

    I create and print art and photographs all the time and get asked the question over and over because a printer will say something like "your picture needs to be such and such size dpi." Our graphics programs work in ppi NOT dpi, and this leaves the most common users not knowing what to do.

    My wish would be for a printer to convey to the customer that if they want a good quality print, then they need to have 300 ppi in their graphics programs. So a 12x12" output size needs to be 3,600 ppi square.

    But I will say that I will be trying your product if you print in that high of a dpi! Nice to know!