Sunday, November 16, 2008

Netiquette: Large images and the Internet

In July 2008, a family member far away wrote me that she had been having trouble sending images to people. So here's an article that I initially wrote for her, but decided to re-edit and publish it in here for all to read. She sent me four very large photos.


The photos in their original photographed size are very large, which is why most Internet service providers intentionally impose technical limitations in their e-mail servers on the size of e-mail that can be transferred. The original large size of the photos is useful for when there's a need make high-quality prints (even above the 3x4" or 10x15 cm range).

When view digital photos in a new computer, then it is powerful enough to be able to temporarily resize them to the proper viewing size every time they are opened for viewing. This functionality may create an illusion that the images are not as large as they really are.

An important part of the netiquette in e-mail is to send messages that have reasonable sizes, so as not to constrain all the server computers and network traffic routers through which e-mail passes through. All servers have restrictions as to how large an outgoing message can be. A user's outgoing server may have lax restrictions, the addressee server may not.

Photos that people send to others are usually very likely to appear in a message in-line, when that message is being viewed in an e-mail folder. Some e-mail programs allow automatic resizing of images, so they equally create an appearance of a size that fits.

One solution is to send large photos on a piecemeal basis, especially if there is an actual requirement to send large images.

One way to know how much a sender can send at a time is to see the error message of a returned letter. Somewhere down there must be an error message stating the permitted space limit. Note that addressees' servers' limits on the size of incoming messages always differ. Pass-through mail servers may also have their internal space limits.

Another solution to sending images is to compress them into one .zip file, for example. In Windows XP and Vista, there is a built-in compression program with functionality to select a bunch of photos, then click on the selection with the right mouse button and select "Send To" > "Compressed (zipped) Folder".

Oftentimes (and even then) the collections of photos even in a compressed file may end up too large. Compression of files also takes time, so if there are lots of large files, compressing and uncompressing them takes some time.

Resizing/scaling images

Yet another solution is to resize all images to something the expected size of people's screen resolutions. For example, the four photos I received this February were each more than two megabytes in size and that is really huge. Even individual images are large. One way to reduce their size is to scale them down with a good image processing program.

For example, a particular group pose photo I received is 3264x2448 pixels in size (width x height). This would probably fit a large wide-screen monitor or be proper for an equally capable projector. Most people's computer screens are nowadays set to 1024x768 pixels.

When opting to send a fair number of not-so-small photos through online means, then, yes, it is a really good practice to resize them.

My favourite tool for this is The GIMP &nmdash; The GNU Image Manipulation Program (GNU is a recursive acronym for GNU's not UNIX). The latest release is 2.6.2 and it contains many improvements over the 2.4.x [development] branch, the major version that I had been thinking of mentioning when writing this instruction set long before the 2.6 version suddenly came out.

The GIMP is available from

If there are many images...
For batch processing, there is a plugin for GIMP called DBP — or David's Batch Processor. DBP is available from here. (Download link on the left side of the page.)

Extract the executable (an application) into this directory (it's better if GIMP is not running at that time):
C:\Program Files\GIMP-2.0\lib\gimp\2.0\plug-ins
Run GIMP after that and the extension is under the Filters menu as a "Batch process..." command. Note that the extension also launches a command-line window. It can be minimized.

The user interface of the Batch process plugin is more or less straight-forward.
  • When adding images, choose those that are similar in their features — for example that the width of every image should be longer and height shorter: the batch processor will otherwise make a portrait-positioned image out of landscape-shaped images ugly. The resultant image can later be turned to the suitable portrait/landscape position.

  • Under Resize tab, enable the Resize function.
    If the image size is 3264x2448, then it is important to first test through an individual scale process to see what the results are. Choose Scale from the Image menu.

    For example, scale the image to resize it to a 1024 pixel width (the height is calculated automatically). The result should be 1024x768, if the aspect ratio is 4:3 (or 3:4), if memory serves me right.

    The reason for this is that while the DBP plugin's resize function allows relative resizing whilst keeping the aspect ratio, it's impossible to tell what the resultant width in pixels would be.

    That is why I choose absolute resizing, knowing that the aspect ratio will be maintained, if I set the absolute width and height to 1024x768 pixels — if a 3264x2448-pixel image scales to 768-pixel height if the width is previously set to 1024 pixels.

  • The Rename tab's functions allow choosing a different destination directory and in the Output tab a relevant image format must be specified — JPG for photos and PNG for non-photographic material (pictures, screenshots, drawings, etc.). After setting JPG as the output format, the image quality must be set to 100 (the output will still be considerably smaller, even with a 100% image quality). Other things can be left as default.

Optical Disc authoring

One way of physically sending a large batch of photos is to buy a quality optical disc (typically one with gold as the default/main metal of use; Some products are geared/optimized toward a certain task, such as audio burning, data, photos, etc.), such as a CD-R (Recordable) or CD-RW (Rewritable) from a known brand with a history of producing writeable media (EMTEC, Verbatim, TDK, Philips, Sony, Maxell) — and burn the photos there.

For more size, a recordable DVD presents a good option. There are several recordable DVD formats, but it's best to choose the format that the optical disc writer at hand supports. Both CD's and DVD's come in various sizes, so if there's only up to 200 megabytes of photos to burn, an equally fitting pocket-sized CD is the ideal option — only that it may cost less than a vanilla 650–700 Mb CD-R. Standard-issue CD-R-s can store from 650 to 700 megabytes, depending on specification.

Rewritable optical discs (marked with XXX-RW or XXX+RW) are useful for testing. When I last burned data, I discovered a rewritable CD was very useful, because of a program setting I forgot to set in K3b, an optical disc authoring program in Linux, and so several burning sessions were lost and this allowed me to make mistakes. Rewritable optical discs have lesser storage latency, though, compared to one to which data is written to permanently.

On the other hand, rewritable discs are great for short-term projects, such as when using a backup application for the first time or trying out another program for disc authoring.

In addition to selecting a quality disc, the packaging also shows the suggested recording speed or a range of speeds. I've seen TDK's CD-s' packaging with the specification of "Up to 52x" writing speed. The great thing about it is that such language is not ambiguous.

Some writeable CD's have specified 4–16x writing speed. While 52x writing speed may be fast and may save time, it may not be useful for long-time storage of data, as error correction information is not saved because of such a speed of writing, so choosing the slowest possible speed is best for long-term storage, provided that the disc is equally suited for it.

Optical discs are also sensitive to elements, so that combining all the best practices reduces the chances of data loss. Some good disc manufacturers already produce optical media that have protection against elements, such as ultra-violet light and scratching. They are more expensive and usually geared toward heavy-duty use, but are all the more durable.

Once a burn is complete, it's important to use a marker specially labelled to be used on optical discs (CDs and the like).

More in a Wikipedia article about CD-R's, with plenty of essential advice on authoring an optical disc. The right-hand sidebar also shows links to other formats, just that CD-R is one of the cheapest ways to store data longer-term off a hard drive /my own long-term experience has shown that hard drives may eventually fail.

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