101: Large Format Graphics Using Your Image Files

To optimize large format graphics using your image files, you must begin with the basic building blocks. Starting with the proper files at the onset, will bring you down the right path to excellent large format graphics. By following these basic recommendations for each file type, will aid in getting quality results.

To begin with, there are two types of digital files associated with large format graphics:

(1) bitmapped image files –  continuous tone image files, made up by pixels with RGB or CYMK values.

(2) vector-based image files – line art files which describe logos, text, and special backgrounds; and is not made up of pixels.

Bitmapped Image Files

Whether scanned images or shot in camera, you want to begin with the highest resolution possible. This means if you are purchasing stock image files,  you should purchase them at a higher resolution with the knowledge of the final output size or use. The original or “native resolution”is the original amount of data available for the final output print. You cannot pull an image off a website and simply “res it up” to squeeze out a sharp-looking image; it will be too soft regardless. The standard data provided from a scanner or digital camera for a large format graphic, is a resolution of  72 – 125 PPI at final output size. And its best if the original can begin at 300 PPI. It is rare to have a native image which can meet that PPI standard at 100% full output size or 1:1. When requesting large format graphics, it is important to recognize that large prints are viewed at large viewing distances, such that a mural is not intended to be viewed three inches away. Its not like examining a Monet painting or whatever, with large format graphics the final output is intended to be viewed across the room or across the highway.

PPI= pixels per inch at the final enlargement size.

To compensate or  for a small shortfall of pixels, commonly technicians will “res up” your file in Photoshop, Perfect Resize, or Genuine Fractals, is software designed to res up your files. This tool can help significantly. Resing up is not magic. After it is “res’d up” it may be in order to apply some ‘unsharp masking’ or use ‘gaussin blur’ to get acceptable results.  A baseline standard is to never start below a bare minimum of 32 PPI at the final output.

*To check the final output size of your image file:
Open your file in Photoshop. Go to the header titled Image and pull down to Image Size. With your Re-sample box clicked “OFF” and your Constrain Proportions box clicked “ON” – set your height and width dimension in size dimensions of your final graphic. Now look at the resolution read, and this will tell you what your PPI is from your original or native file will be at its final output size. If it falls below 32 PPI it is likely you do not have enough resolution for acceptable results.
The larger your final output size, the further your viewing distance, equates to a lower resolution requirement.
The smaller your final output size, the closer your viewing distance, equates to a higher resolution requirement.
The nature of the image itself can affect requirements, meaning the difference between a fine detail image and a dream-like image.

Images slated to become 8 to 10 feet at final output size, such as for trade show exhibits, can have satisfactory results at 32 PPI. This lets you know what you can get away with your native image file.

Vector Images  

Logos or text or special backgrounds can all be vector files. Use vector files whenever possible. This type of file is resolution independent. Vector is a mathematical equation which describes a line, line weight, color, and gradient.

A RIP (Raster Image Processor), the front end machine of the output printer, will render the vector file into a bitmapped file at the appropriate resolution for the given output device. Whether an Epson 1440 DPI or Lightjet 300 DPI, the RIP will prepare a bitmapped from your vector file. Anything that can start as a vector file, should be a vector file; to assure the sharpest graphic.

Assembling Bitmapped and Vector Files

Assembling the two parts of the final graphic together is accomplished in a page layout program such as InDesign. But it is more efficiently accomplished in Photoshop or Illustrator. All layered Photoshop files will be saved as PSD files or a layered TIFF file. This is necessary in order to allow your large format graphics provider the access to manipulate color and other corrections to your file.The assembled file from a page layout program is what you can submit to your PSP (print service provider) of large format graphics. The assembled file is fed into the RIP of the final output device being used, such as for an inkjet or Lightjet printer. This rasterized image file is a now a bitmap image file, which is saved out as a TIFF (an uncompressed bitmap image).

For additional questions pertaining to file resolution of your file for large format graphics, give us a call @ 1800-829-4562 or go to www.photoworksgroup.com

 

 

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