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Creating JPEGs from your Master Archive Images

Last updated: 24 January 2005
Published in: Creating new digital media |
Tags: conversion | file formats |

I need to create a copy of our master archive for online delivery. I understand that I will have to convert the high resolution TIFFs to JPEGs, what is the advantage?

Your archived TIFF files will probably be quite large, occupying valuable storage space and taking a long time to download, JPEGs on the other hand are usually much smaller and therefore easier to download. Do not do this to the master archive! Make a copy first and then convert.

Could I store my master archive as high quality JPEGs?

I wouldn't recommend it. When an image is saved as a JPEG valuable information is lost during the compression process. The user is offered a range of quality settings when saving a JPEG image, the high quality setting compresses less and retains more detail while the lower quality setting compress the image more resulting in a smaller image which has sacrificed much of the original quality. In contrast an uncompressed TIFF may be considerably larger than its JPEG equivalent but it retains all of the original image detail.

How does the JPEG quality adjustment affect the image?

The quality scale controls the amount of compression applied to the picture, a high quality setting gives priority to the original detail, reducing the file size slightly. A low quality setting gives priority to the file size and sacrifices detail. At the lower quality JPEG settings unpleasant visual artefacts resembling oversized pixels can become obvious.

When I save my images as TIFF files I am offered the JPEG compression option, will my image be a TIFF or a JPEG file?

This can be confusing, your file will still be a TIFF but it will have used JPEG compression technology to reduce the size of the final document. Thus it compresses the image at the expense of detail while offering a format, which is less compatible with the delivery of smaller files. We would discourage applying JPEG compression to TIFF files.

When saving a file as a TIFF I am offered a choice of Byte Orders to use Macintosh or IBM PC, which one should I select?

Most programs will recognise both types of TIFF, however there can be some compatibility problems so we would recommend using the setting appropriate to the archives host platform.

My black and white TIFF images have been converted to JPEGs but are now much larger than the originals, what is going on?

This at first does seem strange, but what is happening is that your black and white images are 1bit/pixel (i.e. two colours, black and white) the TIFF format can support this depth but JPEG cannot and has to convert the image to 8bit/pixel greyscale (256 separate shades of grey) which makes the file larger.

Can I retrieve the data, which has been sacrificed in the TIFF to JPEG conversion process?

No, the damage is irreversible; you will have to return to your uncompressed master archive.

Is there anything I should do to my images before creating JPEG surrogates?

You should ensure you have high quality TIFF versions in your master archive before converting.

Some of our images were captured directly as JPEGs can we convert them back to TIFF ?

Yes, but unfortunately the data lost during the compression process can not be recovered. All future capture should be directly to TIFF or RAW if possible.

I have hundreds of images in my archive, is there a way of converting automatically?

Most image optimisation programs offer batch processing to automate this type of process. There are also widely available and inexpensive utilities that will do this for you. Duplicate the archive first to avoid the risk of overwriting.

Last updated: 24 January 2005
Published in: Creating new digital media |
Tags: conversion | file formats |

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