Understanding TIFF and JPEG Image Formats

One of the things I’m often asked is “What is the difference between a TIFF and a JPEG, and when do I use one or the other?”  Here is a fairly simple look at the differences between the two formats.

In the world of digital images there are a variety of image file formats.  Some have come and gone, some seem like they are here to stay, and occasionally a new one comes along.  Some have broad usage and compatibility, some are very specific for certain systems or uses, and some are completely obsolete.

What is a file format?  A file format is simply a designation of a particular way in which the data of the digital image is stored and arranged.  A digital image consists of a whole bunch of digital information, basically ones and zeroes.  When an image is produced in a digital camera, the image is broken into tiny bits called pixels, and each pixel is then evaluated for color and brightness.  These values are assigned numerical values, and these numerical values constitute the digital image data.

There are evidently lots of different ways this data can be arranged, thus the abundance of file types, or formats.  There are, however, only two image file formats in common usage which are broadly compatible with all kinds of systems.  These are the TIFF file format and the JPEG file format.

 

 Here is the major difference between TIFF and JPEG: Compression.  TIFF files are uncompressed (usually) and JPEGs are always compressed.

TIFF files are generally regarded as the highest quality file format.  This is because TIFFs are uncompresssed.  TIFF is the best file format for preserving all of the resolution and color detail and fidelity of the original image.  Thus a TIFF file is the choice for high-quality printing, archival storage, and sophisticated image editing. JPEG files, on the other hand, are always compressed.

But what is compression?  Compression is simply a way to make a digital file smaller by throwing out nonessential information.  Less information means a smaller file.  But how can it be a good idea to throw out information?  Won’t that affect how your image looks?

The fact is that there is a lot of redundant information in a high-resolution digital image, and a lot of other information that is very nearly redundant.  It is possible to throw a lot of it away without noticeably affecting the look of the image.  A high-quality JPEG will be virtually indistinguishable from a TIFF, but substantially smaller.

It is, however, possible to throw away too much information and substantially degrade an image.  It is always a trade-off.  More compression means a smaller file size, which can be good up to a point, but beyond that, the image starts to suffer.  Less compression means a higher quality image, but an uncompressed image file can be huge and unwieldy.

That is why there are various levels of compression.  You may have noticed when you save a JPEG image you are asked to select a level of quality.  It might be “Maximum,” or “High,” or “Medium,” or “Low,” or it may be a number between 12 and 1.  What you are selecting here is the degree of compression, or how much information is thrown away.

One very important thing to remember is that the compression is done to the image when it is saved.  So every time you save a JPEG image it is compressed.  This means that if you open and re-save a JPEG several times it will be compressed several times.  Since compression throws away information, if you open and re-save a JPEG image several times you will significantly degrade the image.  This only happens if you SAVE the image.  Simply opening an image to view it and the closing it has no effect on the image.

This is not true of TIFF images.  So long as you don’t select any compression (it is possible to compress a TIFF image but it is usually avoided) when you save the image, you can open and save a TIFF image indefinitely without degrading it.

 

So when do you use one or the other?

You should always retain an original TIFF file as your master image file.  It is the highest quality image and preserves the most detail.  If you have an opportunity to print one of your images, I recommend printing from the TIFF file if possible, especially if it is a blow-up.  Also, if a book or magazine wants to use one of your images, chances are they will want the TIFF file so they have the very best quality image possible.

That said, it is true that a JPEG file saved at high or highest quality will be effectively indistinguishable from the TIFF master file, and will be about one tenth the size.  This is where JPEGs are really useful.  If you need to send a file over the Internet, or upload one to an application service, JPEG is the preferred format because of the greatly reduced file size.  That’s why all the application services specify JPEGs.

Can you convert one file type into the other?  Yes you can.  But remember, you cannot recover lost information.  You can convert a JPEG into a TIFF and it will get substantially larger, but it will have no more resolution or detail than the JPEG it was made from.  The information that was thrown out during the JPEG compression cannot be restored simply by converting the image back to a TIFF.

On the other hand, you can always make a good JPEG from your TIFF master file.  All you do is save it as a JPEG, and voila, now you have a new JPEG version.  So if you ever have any doubt about the quality of your JPEG images, simply go to your TIFF master file and make a new JPEG version of it.

 

Takeaway

Always create back-ups and copies of your images in whatever format and work from your copies.  That way you don’t risk damaging your original files.

TIFF files are the highest quality files but are very large because they are uncompressed.

Use TIFFs for archival master images and for high quality printing.

JPEG files are smaller because they are compressed.

Use JPEGs for general printing, websites, and for sending over the Internet.

Always save JPEG files at the “High” or “Highest” quality level.

Avoid re-saving JPEG images.

 

 

 

 

 

 

 

 

 

 

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