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This document deals with downloading files using anonymous ftp and offers some comments about handling .JPG image files.
General Comments
FTP (file transfer protocol) is a long established and widely used way of moving files between computers. While e-mail attachments work well for small files, for anything bigger than a couple of Mb, ftp downloads are faster and more efficient with ftp and avoid overloading mailboxes.
The URL we give you (something like ftp://ftp.aao.gov.au/pub/..../....image/yourname) has no restrictions on access. Usernames and passwords are not required. To download the files using any standard web browser, paste the full ftp URL we provide into the browser window, and hit enter. You should see something like the Firefox screen below, showing several images and a text file for user 'ado'.
A failure to download (usually via an "Access Denied" message on your computer) is almost always the result of a firewall security setting on the client (your) network or computer.
If you are unable to change your firewall or browser settings you should
contact your network administrator or local expert for advice (or go to your nearest internet cafe...). Occasionally, some download failures are due to congestion on the internet (try again later), or to some maximum permitted file size setting on your system. The following notes have been gleaned from the very few instances where there have been problems.
All current versions of Internet Explorer work perfectly well as a download interface. Usually it is set up to do so by default. If not, go into Preferences => Network => Proxies and set 'Bypass Web Proxies for ftp' to ON. The exact location of this varies with versions of IE. With Netscape 7.x it is sometimes necessary to press 'Reload', then select 'Save as...' for .TIF files. All modern browsers on all common computer platforms work cleanly with anon ftp, usually by default.
Be sure you have room on your hard disk for the files and/or empty your browser cache files. If you have not done this recently there may not be room for the big image files.
To empty the cache in Netscape, select Edit => Preferences => Advanced => Cache, then "Clear Memory Cache" and/or "Clear Disk Cache".
In Internet Explorer, select Edit => Preferences => Advanced and "Empty Cache" or similar. Other browsers have similar cache management.
Other Internet Explorer-specific Issues
Internet Explorer Does Not Save Graphics Files in the Proper Format
File Appears to Be Downloading but Is Not
Internet Explorer 5.5 Browser Window Closes When You Click a Link to Download Files
Mac specific
If you open the ftp site in your browser so that you see the list of
files there, all you have to do is drag the file to your hard disk
(desktop) or a folder and it should download unopened. If you double click on the file it will try to open with an application that is set in your Configuration Manager.
Of course we don't know what Mac operating System you are using, but if
it's Mac OS 9x it's configuration manager that decides how the
computer handles all files. Configuration Manager is in Control Panels.
Open it and go to 'Receiving Files'. In 'Download Options' you can set a
location you always want your downloads to land in.
In Mac OS-X, simply select System Preferences > Network > Proxies and click "Use passive FTP Mode (PASV)" to ON.
Finally, and neatest of all, if you are using Mac OS-X, you can go to terminal mode and simply type 'ftp ftp.aao.gov.au' and log in using 'anonymous' and your email address (e.g. username@email.address) as password
and then 'cd pub/local/dfm/image/yourname, followed by 'mget *' to copy all the files in the selected directory (yourname, supplied by us) to your local machine. If you are not familiar with Terminal there's an annotated screenshot of this here
Caution with JPG files
JPG is a lossy format and repeated changes and saves in this format quickly degrade image quality. The .JPG files we supply are usually saved out of Adobe Photoshop at maximum image quality and are typically 10% the byte size of original .TIF files. For most applications these files are indistinguishable from the original .TIFs.
If you open the JPG files in an image editor they should be saved as .TIFs (or other lossless format) before any other editing begins, and all further editing should be done on the saved TIF files.
