by cday (Posted Fri Mar 11, 2016 8:07 am)
You have JPEG files that are 30-50MB and want to edit them, and then save the files without visible loss of quality: is the size of the new files created an issue for you?
You should understand that although data is indeed lost when an image is saved in a lossy format such as JPEG, there is no direct correlation between file size and the visible quality of the saved image: the JPEG format is designed to exploit the characteristics of the eye so as to reduce file size, often dramatically, with no or minimal perceptible loss of quality. That is explained in this Wikipedia link, for example.
If file size is a consideration, your best option is probably to experiment with saving the edited images at different JPEG compression levels, as explained in my first post, and assess the quality of the images obtained. Depending on the intended use of the edited images, for example viewing on a screen when screen resolutions may increase in the future, or printing possibly at a large size, you may want to be conservative and leave some margin, and you may wish to archive the original large files in case they are ever needed again.
If file size is not a consideration, then sure, you can save the edited images using a lossless format, for example PNG or TIFF (not using the lossy JPEG compression option...) but you may find that the resulting files (assuming the images are in colour or grayscale) are very large, which is why JPEG is the commonly used format for saving...
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You have JPEG files that are 30-50MB and want to edit them, and then save the files without visible loss of quality: is the size of the new files created an issue for you?
You should understand that although data is indeed lost when an image is saved in a lossy format such as JPEG, there is no direct correlation between file size and the visible quality of the saved image: the JPEG format is designed to exploit the characteristics of the eye so as to reduce file size, often dramatically, with no or minimal perceptible loss of quality. That is explained in this Wikipedia link, for example.
If file size is a consideration, your best option is probably to experiment with saving the edited images at different JPEG compression levels, as explained in my first post, and assess the quality of the images obtained. Depending on the intended use of the edited images, for example viewing on a screen when screen resolutions may increase in the future, or printing possibly at a large size, you may want to be conservative and leave some margin, and you may wish to archive the original large files in case they are ever needed again.
If file size is not a consideration, then sure, you can save the edited images using a lossless format, for example PNG or TIFF (not using the lossy JPEG compression option...) but you may find that the resulting files (assuming the images are in colour or grayscale) are very large, which is why JPEG is the commonly used format for saving...
Read Main Topic