Printed posters are a great form of communication. Through the combination of striking visual elements, text elements and compelling design you can grab the attention of your audience and carry your message across. Chilliprinting bulk posters are a high quality print product that offers you one of the most cost-effective ways of corporate branding, event promotion or advertising for business, products and services.
To produce visually attractive posters, your image material and photos should be crystal clear and razor sharp. In the following, we are going to outline steps you can take when preparing your images for print to ensure your posters come out looking great.
Before we jump right into the specifics of poster image manipulation, keep one thing in mind: the finished print product and your computer screen are two entirely different mediums. It is only natural that there will always be a difference between how both represent your printing data. As we’ve outlined before, our highly optimized poster printing process is able to deliver high-quality posters which accurately represent your printing data. To avoid disappointment because of discrepancy between what you see on your monitor and what comes out in print, we’ll also talk about how you can accurately visualize your posters on your screen before you send off your files.
Calibration and color correction
The fundamental difference between your poster images on screen and in print is the color space. Display devices use RGB, whereas offset printing uses the CMYK color space. In addition, flat screens are generally backlit, causing a further discrepancy. To achieve a color accuracy as close as possible, the device you work with needs to be correctly calibrated and profiled. Without a properly calibrated display, color management is mere guesswork and you won’t be able to achieve any consistency. Settings depend on your monitor, and reliable calibration requires a spectrometer. Find out more about monitor calibration and download our color profiles.
We print posters with the four standard process inks cyan, magenta, yellow and black. For your print data, you should therefore use process colors, which are a combination of these four. To get a sense of what your process colors will look like in print, you can use a CMYK color fan or color chart for reference.
Resolving resolution problems
Grainy, blurry or pixelated images can be the result of resolution problems. Referring to images, resolution is a measurement of tiny visual blocks per unit of length. In print, it is stated in dots per inch (dpi), whereas on-screen, resolution is expressed as pixels per inch (ppi). The resolution shows how closely images blocks are packed together. A high resolution results in a high density, a low value loosens the blocks and spreads them out – until you can eventually discern individual ones. Therefore without changing the total number of pixels or dots, lowering the resolution will result in a larger size, increasing the resolution will shrink the size.
Optimal resolution for your poster images
Chilliprinting posters are printed at an exact resolution of 354 dpi. Your images don’t need a higher resolution than that, and the optimal value is between 300 and 354 dpi. Web images and on-screen files generally have a resolution of 72 or 96 ppi, which is unsuited for print. However, the value of 72 ppi can be confusing for some users. You need to see resolution in relation to the pixel dimensions – the size – of an image.
When you open a high quality stock photo or a picture of your DSLR camera in image processing software such as Photoshop, you might notice a resolution of 72 ppi. That doesn’t mean it’s a low-quality image – as long as the size is adequate. Looking at the pixel dimensions, you should see values for height and width in the thousands in pixels or points, for example 5760 x 3840. At 72 dpi, this would result in a size of 80 by 53 inches. Printed at 300 dpi, the same image would only be 19.2 by 12.8 inches. Note that the pixel data, the number of total pixels would be identical; at 300 dpi, the individual dots would just be closer together.
Downsampling and upsampling
Resampling is when pixels of an image are discarded (downsampling) or added (upsampling). In the image size dialog, Photoshop has a Resampling checkbox. By unchecking it and selecting a resolution of 300 dpi, you can see the maximum size of your image for printing.
If you have a low-resolution image and change the resolution with resampling activated, Photoshop will increase the size. However, this is done mathematically through a process called interpolation. However, this will introduce quality issues as well, such as blurring. For best results, you should avoid upsampling images and work with photos which are large enough to print.
Adjusting sharpness: make your poster images crystal clear
The sharpness of digital images is one of the most important quality aspects. Sharpening in image manipulation can bring out details and lend presence to the picture. However, each file requires individual treatment. Three different types of sharpening can be discerned:
- Capture sharpening: This can be done to sharpen a digital image as it is captured by a camera or scanner. Blur or color filters, different sensors, lenses and their quality, noise reduction as well as ISO and quality settings can all affect capture sharpness.
- Creative sharpening: Images can have different characteristics with areas that require more sharpening than others. This is called creative sharpening and depend on your perception as well as what is going on in the picture. Are there many edges, alternating patterns, contrasts of dark and light?
- Output sharpening: This refers to sharpening where the poster image is optimized for the desired output method, in our case offset printing.
How to sharpen your poster images
The two different ways to sharpen your images are pixel sharpening and edge sharpening. The first is easier to achieve through plugins or filters such as Unsharp Mask. The second offers the advantage that it avoids emphasizing image noise or artifacts. Edge sharpening also retains better effects even if the image is slightly resized afterwards. The way it works is by boosting contrast along edges. In addition, you can increase the sharpness by affecting overall contrast, and well as in specific areas or tonal ranges.
Tonal range sharpening
If you set the darkest and lightest tones in a poster image, you can affect how much it “pops.” You can use the black and white sliders in the Levels or Curves dialog box in Photoshop, for example. To further adjust contrast, you can boost contrast in specific ranges of tones. Say you want to bring out certain poster image details, you would try and isolate that part of the image by tone, then steep the tone curve to differentiate details in those areas.
Local contrast is different from a tonal curve: it affects areas of tones within an image, such as adjacent light and dark areas. You can use the Unsharp Mask filter to achieve this. By setting a high radius value and a low amount value, you can give a subtle boost in areas extending from the edges of image features. These changes are most effective in the midtones.
By now, the details in your image should appear much clearer, even before you’ve applied any traditional sharpening settings.
Apply sharpening tools
If you adjust tonal range and local contrast, your digital image will respond very well to sharpening tools available in your image processing software. Photoshop will present you with Sharpen, Sharpen More, Unsharp Mask and Smart Sharpen. The first two options are rather blunt, since they won’t allow you to make any adjustments. For edge sharpening with the latter two, you start with a high amount and a low radius. Smart Sharpen adds the possibility to overcome motion blur. It also offers more complexity for shadows and highlights. You can keep Smart Sharpen on default settings for everything except radius and amount and use it like a second Unsharpen Mask, using one for local contrast, the other for output sharpening.
Results are subjective
Whether you stick to small corrections and simple filter adjustments or go through a full workflow of processing your poster images, keep in mind that results are also subjective. To judge the outcome, don’t view your picture at 100% but at 50% or even 25%, if it is very large. What seems appropriate in close-up might be a different matter at a distance. Unless you frame your posters and hang them at art galleries, your audience will most likely not study them in great detail at short range. The best effect should be visible from a distance of at least a couple of feet.
With our outlined techniques, you should be able to process and improve your poster images for razor sharp results. Take note of your results with different images and remember that each image needs to be treated differently to make it crystal clear and overcome the differences between your screen and a printed product.
If you are looking for general advice on preparing your print data for poster printing, check out our post on the 10 Mistakes You Must Avoid When Printing Posters In Bulk. To get some inspiration and design ideas, we recommend reading How To Stand Out With Great Poster Design.