A guide to image quality

A guide to image quality

You have probably seen poor quality printed images and wondered why they appear that way?… well, usually it’s due to the quality of the original image that was supplied for printing.

This guide is to enable you to obtain the best quality image when printing from the supplied images. So you do not need to worry about vector files, like ai or eps vector files!

So how do you know if the supplied image is OK to use?

There are a few steps you can go through to enable you to identify any problems with an image.

Open your web browser (the easiest way to view images or graphics), then open your jpeg/gif/png in your web browser. To do this click File, then click Open and locate your file. Click the Open button.

Now here comes the really easy part, just press “Control & +” on PC, or “Command & +” on Mac, to zoom in.

Normal image on the left, and enlarged image on the right

If it looks ‘Normal’ (above) then you will see the nice sharp edges and details.

BUT if it looks ‘Enlarged’ (above) the details and edges of the image have been altered – for now, keep reading.

If it looks like the ‘Enlarged’, it has already been resized and you probably will not want it any larger than it is already. Press “Control & 0” on a PC, or “Command & 0” on a Mac to return the image back to normal size.

OK, so you have inspected the image – now for the next part… how large can it be printed without quality loss?

You’re probably thinking that you can just send your image to print and that’s all… wrong! First, you need to consider what the images or graphics are going to be used for, then would it be used in an A5 leaflet,  A4/A3 poster, A1/A0 poster, or even exhibition size images that can go up to 3 meters tall – all of which can be noticeably pixelated or blurry when viewed, the larger the finished product, the more obvious the pixelation or fuzziness.

So now we take a look at the image file more closely, so on a PC, right-click the image and select Properties, then click on the Details tab. There you will see the dimensions and the resolution of the image. On a Mac, just right-click the image and click on Get Info, there you will see similar information.

But what you need to concentrate on is the number of pixels used. By using this chart below you can see how large your image or graphics can possibly be blown up to.

Pixel Size Chart
A6 1,240 pixels wide x 1,748 pixels tall
A5 1,748 pixels wide x 2,480 pixels tall
A4 2,480 pixels wide x 3,508 pixels tall
A3 3,508 pixels wide x 4,961 pixels tall
A2 4,961 pixels wide x 7,016 pixels tall
A1 7,016 pixels wide x 9,933 pixels tall
A0 9,933 pixels wide x 14,043 pixels tall
1 Metre 11,811 pixels

All of the sizes above are at 300dpi and you could enlarge the image by up to 150% on all of these image sizes, which would then reduce the DPI (dots per inch) to 170dpi, so the good news is that they will still print ok. If the image is to be viewed from a distance, say from 3 to 6 meters plus, like a billboard for instance, then you could enlarge it to almost 200-300% and the result would still be acceptable.

Have you been given an image that has been taken on a mobile phone?

So you have been supplied with an image that is too small and blurry, with no way of using it at the size you want!

Well, this is when technology lets us down a tiny bit. The photo has possibly been shot at a high resolution, but sent to you at a reduced resolution, this is what mobile phones tend to do, to send an image easily.

In this case, you would need to contact the originator of the photo and get them to send you the original image… wait… they said they did! 9 times out of 10, they have sent it incorrectly.

So how should they send it?

iPhone:

I can tell you from experience that they didn’t! To fix this, all they need to do is to email you the images again and select ‘Actual size’ from the menu… now they are sending you the original file.

Android:

From an Android phone, they need to send you the file from the ‘Camera gallery’ or ‘Camera Roll’, and not from the files in ‘Google Photos’ (which reduces the image quality to make it ‘free unlimited storage’*). If you are using ‘Original’ then go ahead use that file.

What camera should I use if I’m taking the pictures myself and at what Mega Pixel?

Now, this is a question we get asked all the time, and the answer is quite simple. It has to be the best camera you can afford and the highest megapixel setting on the camera. Unless you’re using a professional photographer of course!

What size file do you need?

This is also another question we get asked, but this time it’s slightly more technical – I will try and explain this as simply as possible.

Ignore your camera setting (for the time being) and just take a photo of the sky, then take a photo of a car. Now have a look at the file size… you would think they would be the same… but both files have different file sizes right? Why?

It all comes down to compression! The sky image has clouds, blue sky, maybe the odd bird or two. The car image, on the other hand, has the car body, reflections, the ground, and other objects around it! So you see that the car photo is a much higher file size than the sky since there is more detail in the picture.

So just ignore the file size, and use the table above to get the best quality image at the size you need for the end product, be it leaflets, posters or exhibitions.

Images source: pexels.com

*Starting from 1 June 2021, new photos and videos that you back up in high quality will count towards your 15 GB of Free Google Account storage. So you can either upgrade to 100GB or backup your photo’s somewhere else.

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