What makes a File the Right Size for the Job

The Information on this page is designed to help both artists and Art Competition Organizers
determine the ideal image specifications for print or on-screen viewing.

The first thing I want you to remember is that there is no such thing as a "High Resolution File" - this is a misnomer.

The correct term is APPROPRIATE RESOLUTION!

If someone simply asks for a high resolution file they really have no idea what they are talking about and you need to ask more questions! 

The Right Questions to Ask When You Need to Supply Files –

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 questions, then you will know exactly what size and type of file to provide.

The Question you ask is – "What is the image being used for – print or viewing on a screen?"

Got it??  Great  – then the next piece of light reading to stock your Artist’s inbuilt knowledge bank is this…

Here’s why asking for a ‘2mb file” or “3mb file” is asking for trouble!

This photo of my cat was taken on a Sony 36megapixel camera. The list below are all for the same image, saved in different ways. In each case, except the web version,

• Full File – TIFF format – No Compression – 103.4megabytes – the printable size, at 300ppi is 41.6 x 62.3cm (roughly A2).
• Same File – JPEG format – Highest setting 12 – 18.8 megabytes
• Same File – JPEG format – Medium setting 6 – 1.82 megabytes
• Same File – JPEG format – Lowest setting 1 – 582 kilobytes (0.6mb)

Can you spot the difference? Probably not, and that is the problem! In a picture this small it is hard to see the difference but when enlarged back to full size, it is noticeable.

If you need to send a file to someone to print an A5, or perhaps as an online submission to an art competition, but send the JPEG Quality 1 from the above example, you have just sent them a file capable of printing something 8 times larger, albeit, not brilliant quality... but acceptable to many!

The scary thing about this is that if you are making these changes yourself and don’t quite understand what is happening, you could be sending a full version, meaning very saleable copy, of your image out into the world where it could be printed and sold without permission and mean a lost of income for you.

High Resolution? NO – it should be APPROPRIATE RESOLUTION!

The most common request you will get is to send them a ‘high resolution file”. The first thing to note is that “High Resolution” is an incorrect term – it should be “Appropriate Resolution”. For example, here’s a list of the “appropriate resolution” files for…

• 60 x 90cm high quality reproduction
  – 215.5megabytes – 7087px x 10630px @ 300PPI – 8bit colour – TIFF format
• A4 full page brochure – 21 x 29.7cm
  – 24.9megabytes – 2480px x 3508px @ 300ppi – 8bit colour – TIFF Format
• Posting an image on Facebook
  – ideal size seems to be 2048px or 960px on the longest edge. PPI and Megabytes are irrelevant here. Files should be saved in JPEG format which are compressed, faster loading files. For any web image the sRGB colourspace is best.

None of these, even the 215megabyte file for a high quality reproduction can be truly be called a “high resolution file” because the file we capture of you artwork is often much larger than this – they are the ‘appropriate resolution’ for the purpose. There are camera setups out there called Gigapan that can create images that are 10's of thousands of megabytes!!!!!

What makes up the measurements or File Size of your image?

The sensor in every digital camera is made up of a group of pixels – let’s use my Sony A7R 36megapixel camera as an example.

• Sensor size is  4912 x 7360 pixels
• Divide each of those numbers by 300 (as in 300ppi) and this will give you a print size in inches – 16.37″ x 24.52″ (41.6 x 62.3cm).
• Save this image as an uncompressed TIFF file and it will be 103.4 megabytes
• This is as big a file as the camera can create – anything larger needs to be enlarged/created/interpolated in Photoshop. This means that if your artwork is bigger than 41.6 x 62.3cm, then the file captured is SMALLER than your art.

As you know, when we copy artwork, we end up with files anywhere from 300 megabytes to 1000 megabytes! 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).

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 (a common size).

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 the size of your file.

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 – JPEG is great 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. Our master files are always saved in the TIFF or PSD format to preserve the quality of your original file and allow us to make changes without affecting the quality.