ImagesMagUK-Sep18

www.images-magazine.com SEPTEMBER 2018 images 55 TIPS & TECHNIQUES from web graphics and these are usually small in physical size. The first thing to do is go to Image/Image Size and upsample the image to 200-300 dpi and make it the correct physical size [see Figure 3]. Improving low quality JPG images Once the image is the correct size and resolution, zoom in on the image to see exactly what is happening up close. If the image was a low quality JPG file then you might see ‘artefacts‘ and ‘blocks‘. Unlike screen printing where these imperfections might show up in the final print, these problem areas may not actually show up as badly on a DTG image. To improve low quality JPG images you can use off-the-shelf, inexpensive JPG enhancement programs that will remove the artefacts and square boxes. Photoshop also has a filter called Reduce Noise that works well here: simply go to Filter/Noise/Reduce Noise [see Figure 4]. Improving colour saturation The conversion of RGB to CMYK will often reduce the colour saturation of an image. Also, when bringing images from a vector program such as Corel or Adobe Illustrator into Photoshop there can be a colour shift and dulling of the colours. Go to Image/Adjustments/Hue Saturation and move the Saturation slider up about 10 to 20 points. Don’t overdo it. Just get the colours to pop a little [see Figure 5]. You can also improve an image by using the Tone Curve to improve the overall contrast. I like to use what I call an ‘S‘ Curve. It darkens the shadows and lightens the highlights and can make a huge difference to a flat image. Go to Image/Adjustments/ Curves [see Figure 6]. Fixing black and white areas Areas that appear to be solid black or solid white on the monitor often aren’t. Open the Info Panel (Window/Info) and position it somewhere where you will never close it. I use this panel all the time. It reads levels of density or colour. Select the eyedropper tool (this panel works with most tools) and place the tool over areas that you think are totally black. Total black is 0 levels of RGB: any reading other than 0 means you won’t have total black in that area; you will end up with a dark grey [see Figure 7]. You can adjust these areas using either Levels or Tone Curve. I happen to like using the Tone Curve. If you move the lower left of the curve in just a little to the right that will darken the total black areas; you can read the change in the Info Panel because it is still active even when the Curve is open. It now reads ‘before and after‘ so you can see the changes [see Figure 8]. Do the same for the white areas of the image. Total white is 255 levels of RGB: any other reading means your RIP will try to put a small amount of colour there [see Figure 9]. The Curves control can also be used to adjust the total white areas: move the curve at top right to the left just a little and then read the before and after [see Figure 10]. Sharpening the image Photoshop has a great sharpening filter that when used correctly can enhance and improve the edges of the image. Go to Filter/Sharpen/ Unsharp Mask (don’t let the name fool you) and start off with a setting of Radius 1.0, Threshold 6.0 and Amount 250. Move the Amount slider up or down. Make sure Preview is checked to see the effect, but always go back and forth between Preview being checked so you can see the change to the image. You will see a huge improvement to the edges [see Figure 11]. Understanding underbases Creating an underbase sounds very simple – you could be forgiven for thinking all that’s required is to print white under all the colours. While that sounds right, in T-shirt printing the ideal underbase puts white under only non-black colours – there is no underbase under black areas as the colour Figure 5: Adjusting the saturation levels in Photoshop Figure 6: Contrast can be improved by using Tone Curve Figure 7: Dead black is 0 levels of RGB Figure 9:Total white is 255 levels of RGB Figure 10: Tone Curves can also be used to lighten the white areas Figure 8: Tone Curves can be used to darken the black areas