Wednesday, January 22, 2014

Resolution and Image Quality: What is it, what does it mean and why does it matter?


Happy New Year everyone! I know I am really late, I can't believe it's almost the end of  January, but I'm back for a new blog post. Hopefully, I can write more blogs now that the holiday rush is over.

I felt like this topic needed some attention because it pretty much determines if a print will work or not. I'm talking about image resolution. Now that most people have access to a camera, people are able to print their own photos instead of finding a photo. It allows them to personalize their space or a gift.

In December, I met a photographer and he wanted to know what my most frequently asked question was from customers. I said every and anything related to image resolution. Most people have heard the terms related to resolution but don't really understand why it matters and what it means.

I think the most common understanding of resolution is that it determines the image's quality. People see it as: high resolution = excellent image quality. This is true to an extent, because there many factors that affect the image quality that are related and not related to the resolution. I've had a few people ask me if I can "add more pixels" into their photo or make their photo a higher resolution (increase the DPI). I think the confusion comes from not knowing exactly what these words mean and why I want to write this post to clear up any misunderstandings.

 The photographer I met told me that I could simply explain it like inflating a balloon:

 As it expands, the text  becomes blurry, distorted and pixelated. The deflated balloon represents a high resolution image. The inflated balloon represents the image once it has gone past it's maximum threshold. The more you expand it the lower the resolution is. Why does this happen if my original image is considered high resolution?

This is where DPI (dots per inch) and PPI (pixels per inch) are introduced and is probably the most confusing part. PPI is actually the term that affects the image's resolution on the screen and quality in a printed format. The word DPI is most commonly used for both terms, but, keep in mind; I will be talking about pixels so when I say DPI I really mean PPI.

So what are pixels? The word pixel stands for picture element, it is what makes up a photo on a screen. Most people would say something is pixelated when they can see the tiny squares that make up the photo. This happens when the photo is magnified so much that you can see each pixel.




So when a person says their image is 300 DPI, they are saying there are 300 pixels for every inch of the image. So if the image is 4x6", then the pixel dimension will be 1200x1800. The more pixels there are, the more sharp the image will be. The larger the image is the more pixels it should have in order to get an excellent print.

So in the case of the balloon, when we inflate it, the text becomes pixelated, blurry and distorted, because pixels cannot be added, they only expand to fit the new space. This is why a 300 DPI image that is 4x6" can only be printed within a certain range before it starts losing image quality. If you wanted to enlarge it to 36x54", with the larger size the pixels will expand and it will be 33 pixels per inch - making the image pixelated.

Resolution is basically all the data from the image which includes: DPI, image dimension, file size and desired print size, to tell us if an image is going to be fine for print. Of course there are software available to "fix" some of these problems. However, it will not be the same as an original high resolution, good quality image.

Many people have access to decent quality consumer cameras or smart phones with good quality cameras, but they still run into problems with the image quality, why?

There can be many factors that can affect the final outcome that has nothing to do with the resolution.  This is why I mentioned that a high resolution image does not always amount to an exceptional print. Here are some reasons why:

The lighting. If you have bad lighting, even with the latest 15 megapixel camera, it is not guaranteed that your photo will be good quality.  There are photo editing software available to fix this but you can't always rely on it. It is better to set the exposure on your camera and use light to your advantage to get a good photo.

For dark photos, if your camera is not powerful enough it will turn out grainy if you try to edit it. This is more common with cell phone cameras because they are not equip for low light settings. Once you lighten the photo you will then need to get rid of the grain but this will just over-process the image and make it low quality.
Overexposed Photo (too much light)



Shaky hand. This has happened to me a number of times. My hands were too shaky when I took a photo and it came out blurry. This usually happens when the  flash is turned off or there is no image stabilizer. It could also be that the screen on cameras and cell phones are very small so the blur isn't noticeable until you view it on the computer.

Digital Zoom. There are two types of zoom: optical and digital. The optical zoom is considered a true zoom and found on cameras and some cell phones. The optical zoom acts like binoculars by drawing in the image to capture a crisp image but it has it's limitations.

 Although most cell phones use digital zoom there are optical zoom attachments that can be purchased for your cell phones. Digital zoom doesn't actually zoom into a photo it crops out the part you want this is why many zoomed in cell phone photos are low quality.

Front Camera. This only applies to cell phones, and it is related to the resolution.  I have had a few customers try to print out photos that they have taken with the front camera. Most front cameras are only 2 megapixels but I am not sure if everyone knows this. The resolution of these photos are only good for screens. Since these photos are usually viewed on the phone, it is not the best way of judging if the photo is high resolution.

Post processing. With photo editing software available for download on phones and computers, most people choose to edit their own photos. This allows them to see exactly how it will look and they get to choose what they like.

For cell phone photos, the combination of a low resolution image and overprocessing will only result in a terrible print (depending on the size). Instagram has many filters that people can use to make their photos more fun and unique but it usually reduces the size of your photo so that it can be uploaded to the server. This is we have a limit to what size your Instagram photos can be printed.

For camera photos, most computers come with free photo editing software like iPhoto for Mac or Windows Photo Gallery for Windows. You need to make sure the output settings will save the image as high resolution.

Well I hope this post was useful in some ways. I tried to explain it as best as I could.

If you have any questions please comment or send an email to us. Please visit us at VancouverOnCanvas.com to start printing!

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