Never use JPEG in your workflow
Compress JPEGs save space, allow faster loading, processing and ripping, they also give good colour reproduction, so why should you never use JPEGS in print?
JPEGS are possibly one of the biggest pains in reprographics. Next to LZW Tiff files they cock up more ‘quality’ jobs than any other file format. Many of today’s brochures and magazine use JPEGS quite successfully. They have numerous advantages over other file types, which is why they are so common. But in the wrong hands they will ruin any job.
Compared to a PSD or Tiff file, JPEGS are lower quality. You can more or less always tell that a particular image was saved as a JPEG because in areas with strong contrast you can see compression artefacts. The stronger the compression the more JPEG noise or artefacts. Most other file formats (say TIF or PNG) use lossless compression. These files are larger than JPG because they use a fully recoverable (lossless) compression that preserves all of the original image data. These file formats remain full quality at all times, no matter how many times they are save them to a file.
JPEG compression algorithm changes image data while converting it. Amount of change can be controlled, but not its location which is noticeable around sharp colour changes and across gradient areas. JPEG FILES WORK BY THROWING AWAY DATA. THIS DATA CANNOT BE REPLACED – EVER.
- JPEG is primarily an RGB format
- If you save, then save again the image several times, you’d end up with an unusable image, because every time you save you throw away even more data. Photographers always make the mistake of saving their JPEG file again, thus giving the end user an inferior file to their own original.
- The name “JPEG” stands for Joint Photographic Experts Group, the name of the committee that created the JPEG standard and other still picture coding standards.
TIFF general info
- TIFF is best file format for printing
- It’s perfectly natural for a TIFF file to save image data in CMYK colour space which is used in press.
- TIFF can also compress image data but uses such an algorithm that doesn’t change source data (lossless compression).
- TIFF format also supports alpha channel (transparency).
- If you’d be opening and saving the same TIFF file, you’ll end up with exactly the same image as source. Nothing would change in terms of image data.
There is nothing inherently wrong with a JPEG file if you know what you are doing. But when it comes to your print workflow RAW and PSD files are far superior, unlike 20 years ago when disk space was at a premium today, there is no excuse in compressing files. Terrabyte storing and large format transfer means that 300mb files are common place.
Digiprint recommend that your master file should be 400dpi at 100% RGB minimum. Covert to CMYK if you need. If your understand ICC profiling then add this, if not, switch all colour profiling off.
If you want your images to stay as true to original as possible save with PSD or CR3 file format. This PSD file format can be used in InDesign CC, and Quark with no problems. If you prefer a Tiff file format that also is fine and our preference. However DO NOT SAVE WITH LZW COMPRESSION these files will often give unexpected print results – you have been warned.
Images for print
- Save as PSD or Tiff with no compression
- CMYK as colour mode.
- A minimum of 350dpi at 100%
- If you wish too use colour settings these should be with set to nothing or FOGRA 39.
Images for web
- Images Jpeg
- Recommended 72dpi
- Switch colour settings off
- Logos and other graphics we recommend the PNG file format
Images for large format
- RGB or CMYK*
- Images PSD or Tiff or EPS
- Recommended 300dpi at 25% minimum
- Switch colour settings off
- Ensure that your photograph is taken at the highest resolution possible and save at 400dpi. Why this high?, Rule of thumb is twice thy dpi to the lpi. 300dpi is suitable for presses that run screen of 150lpi. These days most good printers use 200 line screen which need a higher resolution – hence 4oodpi.
- All photography should be taken and supplied as RAW files. Note Photoshop will open these as 8bit files only, you have to tell it to open at 16bit.
- The advantages of 16 bit files are clear to see. Better gradients, better shadow areas, more control and a dam sight quicker to put a clipping path around an image.
- Insist that your Photographer supplies RAW files only.
* Note printing RGB images on large format printers offer a far larger colour range than CMYK – for instance our Epson run 11 colours, it can Pantone match and print RGB images.