Image Proofing: a Guide to File Types

Category: Design | By Abby Nash | September 13, 2019

When it comes to image proofing, it’s all about the image, obviously. You want to put your best foot forward when sending work out to clients. You also want to make sure the file sizes are not too big or contain too much information (allowing your client to make off with the work without paying). 

Different file types affect how the image looks, but it can be hard to keep straight what file type does what. And how exactly does compression work, lossy versus lossless? During the image proofing process, not all file types are created equal, and some file types need to stay behind the scenes. 

JPEG

What it is:

JPEG is a compressed graphic format for images. It can support up to 24-bit color. JPEGs are compressed using lossy compression, which means that image quality may be noticeably reduced if a high amount of compression is used. Because of its compression you can store a large number of JPEG files in less space. 

When to use it:

  • Digital photos where there are smooth variations in color and tone
  • Web images, because the amount of data an image uses is important, and JPEG’s compression works well to lower data sizes

When not to use it:

  • Line drawings, text and graphics where the sharp contrasts will suffer pixelation after compression

PNG

What it is:

PNG is a raster-graphics file format that supports lossless data compression. This means the original data can still be recreated from the compressed data. PNG was originally created as an alternative to the GIF file type, so they share a lot of common traits. PNG supports a wide range of color palettes, such as 24-bit and 48-bit truecolor – you’ll also get more transparency options with PNG than with a GIF or other file type. 

When to use it:

  • Web images, where the compression will save you on size
  • Anything with text, because you’ll get crisp lines and legibility you won’t find with a JPEG
  • Also useful when image proofing an in-progress work, with its crisp lines and smaller file sizes

When not to use it:

  • Images for professional printing, as PNG doesn’t support non-RGB color spaces such as CMYK
  • Animated images, which PNG doesn’t naturally support

GIF

What it is:

GIF is a bitmap image format that supports lossless compression. It’s older than its counterpart, PNG, and so more widely supported in older browsers. Images have a 256 color palette pulled from 24-bit RGB space, and with animations, each frame has its own 256 color palette. 

When to use it:

  • Graphics and logos, images with solid colors and few gradients
  • Small animations for the web or video games, or 
  • Low-resolution videos

When not to use it:

  • Photographs, as the limited color palette isn’t suited for color gradients

PDF

What it is:

Originally created by Adobe to display fixed-layout flat documents with text, fonts, vector graphics and raster images, the PDF’s purpose is right there in the name: Portable Document Format. As PDF has evolved as a file type, specifications have also been added to enable encryptions and digital signatures, amongst other features. 

When to use it:

  • Documents! PDF format will preserve the fonts and formats of your documents 

When not to use it:

  • Not generally used for images

TIFF

What it is:

TIFF files are large files, often used after RAW files are converted. Their large size, support for layers and ability to be saved in various color formats and compression types makes them popular in the design and photography industries. A TIFF file will retain the most information possible for later editing.

When to use it:

  • High resolution images for printing, which is what TIFFs were originally created for
  • Keeping a high-quality large-sized original file 

When not to use it:

  • When you need a small file
  • Sending out files for image proofing, because it does contain all the necessary data to create high-quality copies

PSD

What it is:

PSD is the default file type when working in Adobe Photoshop, and functions as a master copy much like a TIFF can. PSDs are easy to export into any other Adobe programs for use, so if you start in Photoshop and need to switch to Illustrator you’re covered. Being a proprietary file type, it obviously won’t be compatible with non-Adobe software, so good luck opening your PSD file in Microsoft Paint.

When to use it:

  • Master file copies in Photoshop
  • Transferring between Adobe Suite programs

When not to use it:

  • Image proofing, because then you’re giving your approvers all the raw data and images for easy copying

Image Proofing in Ashore

Now, after reading through all of this info, you’ll know when you need a lossy compressed file (JPEG) versus a lossless compressed one (PNG or GIF), what you need when image proofing a document (PDF) or maintaining a master-copy (TIFF or PSD). The good news is, you can send all the appropriate files types through Ashore for proofing – but no TIFF or PSD files. You want to offer the best quality images to your clients during the image proofing process, within reason. 

Knowing what file types your work presents best in will help you avoid comments about pixelation or fuzziness and allow your approvers to focus on the quality of the work itself. Want to check out the file differences yourself? Try proofing the same image in different file types with a free Ashore account today.

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