How often have you been asked to supply a “High Resolution File” for an art competition or a publication or web site and to send it via email?
I have artists ask me all the time to supply them with files for this and that and I find myself asking the same questions each time and getting confused responses most of the time. So this article will try to arm you with a few simple questions to ask those who ask you for files.
There are some complex things to talk about here and the technical stuff may not be your bag but bear with me, read it through and if you have questions, email me, please.
PPI and DPI – they sound the same but are they??? The short answer is NO!
PPI stands for “Pixels Per Inch” and DPI for “Dots Per Inch”. A pixel is not a dot. Pixels relate to digital images as seen on your monitor and captured in your camera – the more pixels per inch, the sharper, more detailed image you have. Dots relate to the droplets of ink your printer spits out of the print head and its ability to print those images in detail – the smaller, finer and higher number of dots per inch, the cleaner, sharper, better quality print you will get IF the image is of sufficient quality to begin with.
You can read more about this topic here – Pixels and Dots
FILE SIZE – How big is a high resolution file?
As you know, when we copy artwork with our 1200megapixel camera, we end up with files anywhere from 500megabytes to 1.2 Gigabytes! Now that’s simply the space they take up on our hard drive. Until we look more closely at the details, we really don’t know what size print these files will make. We need to know the size of the image in PIXELS, then choose our optimum PPI (typically 300 for quality).
Let’s say you just lashed out and bought the new Canon 650D, 18megapixel camera. The thing to note here for this discussion is the number of pixels making up the sensor for this camera – its 5184 x 3456. If we divide each of these numbers by 300 – we will get our printable image size at 300ppi – 17.28″ x 11.52″ (51.3megabytes) – a whisker larger than A3. This means that if you use this camera to copy a 20″ x 30″ original, the file will need to be enlarged considerably to produce the same size.
So let’s use a typical sized original artwork as an example and list all the options…
Let’s say your original painting is 20″ x 30″. When we photograph an original that size, our camera will capture it at 12,000 x 18,000 pixels. Because we always save everything at 300PPI, we can then determine that the actual print size will be 40″ x 60″ (12,000 divided by 300 = 40, 18,000 divided by 300 = 60). The space taken up on the hard drive is 618megabytes. This is not a file you could send by email – way too big!
Even if we reduce your image to it’s original size of 20″ x 30″ (6000 x 9000 pixels) – the file size is 154.5megabytes. So, do you see how the pixels relate to the image size here?
Let’s make things a little more interesting – let’s say we lock in the number of pixels at 6000 x 9000 but we change the PPI to 100 instead of 300…
6000 / 100 = 60
9000 / 100 = 90
Remember our image is still locked in at 6000 x 9000 but we’ve spread those pixels out to only 100 in every inch instead of 300. Now our image has jumped in size to 60″ x 90″. That’s great right, we’ve got a really big image! Not quite – you see, the human eye can see up to almost 200pixels per inch, that means that (if you have good eyes) you will see the pixels when you look closely at a 100PPI image – you won’t see pixels at 300PPI.
Let’s try something else – let’s lock in those pixels again and make the image 600PPI…
6000 / 600 – 10
9000 / 600 – 15
Now the huge image we had before with the pixels spread out to 100PPI is crammed up into 600 pixels every inch and now only measures 10″ x 15″. Is this a good thing? Not really – if 300PPI is enough to get the quality we need then we don’t need any more. You simply will not see any difference between a print made at 300PPI or one at 600PPI. But you will see a difference with one made at 100PPI or more typically 72PPI.
Check out this diagram showing all the sizes we’ve discussed here…
- GREEN – Original Image size – 20″ x 30″ – 6000 x 9000pixels – 300ppi
- RED – Our scan – 40″ x 60″ -12,000 x 18,000pixels – 300ppi
- GREY – 60″ x 90″ image – still 6000 x 9000pixels – 100ppi
- BLUE – 10″ x 15″ image – still 6000 x 9000pixels – 600ppi
Next Topic – FILE TYPES and how do they affect your image.
There are a few common file types that you will come across when dealing with images. I’ve posted about these before so here’s a link to that post…. Raw, Tiff or Jpeg – What is Best?
Bottom line – the ONLY time you should use JPEG is when you are saving a copy of the image for web or email use, or as the last step to sending a file to us for printing. Always save your files in the TIFF format where possible or PSD if you use Photoshop to preserve the quality of your original file.
I will add one more explanation here comparing JPEG to TIFF or PSD. We save all your files as either TIFF or PSD – this gives us the ultimate quality. If you purchase the full file from us, we will supply you with a full file in Tiff Format, usually a smaller file, around A3 in Tiff format and a much smaller, JPEG file for web use. We only ever use JPEG when supplying images for web use. Why? Because you only need small files for them, they need to load fast on the screen otherwise people get bored and won’t look at them.
When we email you a JPEG file around 1megabyte – it will actually open in Photoshop at around 3-5megabytes depending on the range of colours in the image. Remember JPEG compresses the image and throws data away to make it smaller, then tries to regenerate what it thinks is right when you open the file again.
Often people ask us for a 300ppi image but what they don’t tell us is the size of the image. Ideally we need to know either the physical dimensions of the finished print OR the required Pixel dimensions if the image is for web use only.
So now we finally get to the point of this post -
What questions should you ask when a third party has asked you to send them a file for competition, publication etc.? If you can get the answers to these three questions, then you will know exactly what size and type of file to provide.
Question 1 – What file type do you want – JPEG, TIFF or other?
Question 2 – What PPI do you want?
Question 3 – What physical size do you want to print the image or what pixel dimensions do you want?
Question 4 – What Colourspace do you want – sRGB, AdobeRGB or CMYK?
OK, I lied, there are four questions there – the wrong colourspace will change the colour of your image in print mainly. Colourspace issues are something for another post so I won’t go into it this time. Suffice to say, if you ask these questions, and they can actually give you intelligent answers, you’ll be on the right track to supplying the perfect file for the job.
