File compression JPEG
The effects that over compressing a JPEG file can have on your images.
Perhaps when you scan in image from a print, slide or negative your scanning software does it all for you, its simple you just hit the go button and the job is done. Have you ever looked at the settings within the software to see how the software is saving your image? or if it gives you any options to alter the way the file is saved or scanned? Saving without compression or little compression is the best way to preserve detail in your image. A JPEG file is a “lossy” format, or a format where data is discarded in order to save space when saving. The higher the compression the more data is thrown away and the less detail there will be in your image.
There is no excuse these days, when hard disks are so very cheap to save your image with any other setting other than the best. It might be worth examining the software the came with your scanner or camera and check that you do have the option to change the way it saves and what format it saves your images in. Phrases to look for in the manual or software settings are “best setting” or the “lowest compression”, “lossless format” or “large file size”. You get the idea but do look for the top setting.
To give you idea of what goes on when you save I have included an example below.
It is a photo of a group of people. now let us save it at different compression ratios.
As you can see the further we go with the compression the worse the data becomes and more the image suffers. The blocks you can see in the “0%” corner are where the JPEG algorithm splits up the photo into blocks in order to save it, the more data that is thrown away the more blocks there are visible. When this happens across a detailed section of the image the detail is lost, blocks meet and slurring of colours and details occur. This is called JPEG artefacts. It is these artefacts we do not want when our software takes over and saves our images for us.
On a further note, if you do save an image in this manner and then open it and make changes to it and re-save it with the same settings then the image will just get even worse.
In order for a restoration to be carried out to a high standard then highly compressed files must be avoided!
Image-Restore Helping repair old photos