Every once in a while photographic printers have to print low resolution images - the trouble is, low resolution images don't enlarge very well and the more you enlarge them the worse they look. So what can you do to help enlarge low resolution images without them breaking up? Well, there are a lot of things you can try.
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| Low Resolution Image |
Firstly, ask the customer for a higher resolution image. You'll be surprised at the number of people that have lifted a Facebook image and sent that for printing, not realising that the original image has been downsized for Facebook. In a lot of cases they will be able to supply the higher resolution image taken by the camera which will print far better. Hint: Crop into the image, increase the resolution and send this to them so that they can see what will happen on their device. This will usually “inspire” them to retrieve the original! If you choose nearest neighbour when enlarging this will give a poorer result which helps to encourage them to find the higher resolution image. Yes, this takes extra time but it's worth it and they will appreciate that you have taken the time to get the best printing result possible.
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| Cropped Enlarged Nearest Neighbour |
Of course, if they've just lifted it from someone else's website then there are legal implications to consider with copyright breach. You can check for this by using Google's image search https://images.google.com/. Simply upload their image and hit search to see what comes back. If it's from another website then the simple answer is it can't be printed without the owner of that website's permission. For more information on preventing copyright breaches click the link below:
http://canvasprintmaker.blogspot.co.uk/2013/10/preventing-copyright-breach.html
Okay, if you have tried to obtain a larger resolution image and there isn't one available, what else can you do? If you have tried every enlarging algorithm (such as bicubic smoother) and it still isn't good enough quality then one option is to try and disguise it. Try opening the image and applying a canvas texture to the image before printing it. This has the effect of artificially adding texture detail to the image which will look like the actual texture of the canvas that it will be printed onto. When the canvas texture filter is applied to the image it will break up harsh JPEG artefacts, blurriness will have (artificial) definition added to it, blockiness becomes less obvious, and although it is far from perfect it will print much better on canvas. There is a certain amount of judgment call with this - don't enlarge too much and if the texture is too harsh then it can look very artificial. You want it to look less like a low resolution image blown up beyond what it should have been printed to without the canvas texture becoming too distracting. So there is a certain amount of trial and error before finding the best compromise. Compromise being the word as it's never perfect.
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| Canvas Texture Effect |
Perception of photos is another consideration that you should be aware of. Most people when presented with a choice between gloss and matt photographs tend to see the shinier gloss photo as being sharper than than its matt equivalent. In reality there is no difference other than the shinier gloss photograph appears brighter and more vivid which in turn they interpret as being sharper. Do bear in mind that gloss can be difficult to see when room lighting is shining on it and you need to take that into account when displaying gloss photographs. (No I'm not going to get involved in the difference between matt, satin, silk, pearl etc. Effectively it all boils down to how shiny a print is, and don't even think of mentioning super gloss! And yes, Cibachrome's were great).
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| Gloss Print Light Reflection |
Of course unsharp mask can help with images that are just a little soft and could do with that little extra punchiness. It works best with contrasting colours providing you don't overdo it. Usually a low threshold and a pixel radius of around one to three is sufficient, however, if you are having to ramp it up to a pixel radius of ten then you are never going to get a good result and the final print is going to look bad. In which case you are going to have to get creative…
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| Before Unsharp Mask |
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| After Unsharp Mask |
Depending on your customer and how much flexibility you have with the design you may have more control over the printing process. Photographic filters are a great way to deliberately alter the image to the point that anyone looking at the finished print will know that it has been intentionally altered. In which case they will assume that this was your intention all along rather than a quick bodge trying to prevent a low resolution image from looking bad when being enlarged.
Gaussian blur does what it pretty much says. Begone low resolution blockiness, JPEG artefacts and other noise in the original image. Also say goodbye to any definition whatsoever! However as a background effect to an image much like the depth of field when taking a photograph it can be deliberately introduced in order to make the foreground the centre of attention. So you could use this technique with some text before printing it and it will look really good as people will assume that this was your intent all along. The background image will look blurry but the text appears sharp.
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| Blurred Background Text Foreground |
It is also sometimes possible to apply Gaussian blur to remove the majority of undesirable low resolution artefacts, then apply Unsharp mask to enhance edge detail. It's best to do this after interpolating it using bicubic smoother. Again it's a bit trial and error and you should always compare your finished result with the original to see whether it is better or not.
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| Guassian Blur Before Unsharp Mask |
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| After Unsharp Mask |
Anyone who is used to using high ISO settings will be aware of graininess with a photograph and how this can be used to achieve an artistic effect, particularly with black and white photos. Well this same effect can be added to a picture by applying monochromatic noise to it and then blurring it slightly with Gaussian blur. It can help to take away the obvious JPEG compression artefacts from a low resolution image much like adding a canvas texture does too. As to how much noise to add vs how much to blur, it really depends on the original photo and you will have to do some testing for best results.
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| Noise Added Gaussian Blur |
Poster Edges is another useful filter, which again will obliterate low res JPEG issues and give an aesthetically pleasing appeal. It's not to everyone's taste and will work better on some images than others but it will disguise low resolution images really well. It's more of an artistic interpretation of the original and as long as your customer is happy with that then you are onto a winner. Likewise increasing an images contrast or tracing the edges and applying duotones or gradients over the image are great ways to make subtle background graphics that can be combined with other designs to give very appealing results.
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| Poster Edges |
Adding vector graphics over the top of photographs is also effective as your eye is focused on the foreground rather than the background and thus the poor resolution image becomes less noticeable. Likewise creating an image mask so that the image only shows through text works well, although, now we really are straying into graphic design rather than photographic printing. It can still be useful to do particularly if the print is a gift for someone with a personalised message.
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| Vector Graphics |
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| Text Image Mask |
Another option is to make the image even lower resolution. Yes, I know this sounds crazy, but if it is printed large enough and you stand far enough back then you will be able to see what it looks like, and as you approach the print closer it will just resemble an abstract jumble of blocks which will take on an artistic appeal. If you are trying this method then make sure there is no anti-aliasing and use nearest neighbour to downsize the image so that the individual blocks are sharp at the edges and are very distinct.
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| Really Low Resolution Image |
So, there are many ways to work around the problem and if you would like to see any of your photographic masterpieces enlarged on canvas please get in touch - we're more than happy to help. Just click the link below for more information:
http://www.canvasprintmaker.co.uk
