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Images For Posting, Or Exchanging Images Via E-Mail

From time to time, we all have images of fish that we want to send to other Board members. However, the simple "send it as a JPEG" option may not always be the optimum solution. So, here's a guide to different image file formats, and their utility value when E-Mailing images to fellow fish fans.

[1] JPEG. The perennial favourite. JPEG stands for Joint Photographers' Expert Group, the organisation that sponsored and devised the format. If compressing an image to the smallest possible size is the top priority criterion, then JPEG is the format to use. However, it does have some disadvantages. Principal among these is the fact that the compression algorithm is a 'lossy' algorithm: depending upon the level of compression used, various levels of fine detail can be lost. These reappear as the infamous 'JPEG artefacts' in highly compressed images, and in extreme cases completely ruin an image. If you want to trash an image, a good way of doing it is to save it as a JPEG, re-open it, and re-save it multiple times. Do this often enough (20 times should suffice for most images) and the result is horrendous. The golden rule, therefore, is, keep master copies of images in a different format, and create JPEGs for mailing if you need to save disc space or bandwidth.

[2] BMP. Windows Bitmap is almost at the opposite end of the scale size wise, and the reason is simple - it contains no compression at all. Of course, this means that every last pixel is faithfully preserved, but the file sizes are huge. A large 24-bit image (say 1024 x 768 pixels) occupies nearly 2½ megabytes, compared with around 60K for the most tightly compressed JPEG of the same image dimensions. As a file format for E-Mailing, it's probably the worst choice unless you know the recipient has full-spec broadband, an E-Mail account with huge amounts of postbag space, and won't complain if you hog 2½ megabytes at a time for each image.

[3] TIFF. Another acronym, which stands for Tagged Image File Format. The beauty of this format is that it's one of the truly cross-platform formats. It is understood by applications running on Windows PCs, Macs and Unix/Linux workstations of just about every conceivable variety. It only supports limited compression, but it supports 'alpha channels' - those colour streams so beloved of PhotoShop users - including a transparency alpha channel, so you can cut out a fish from a photo, and just send the fish minus the background if you want. Trouble is, if you use transparency, the extra alpha channel eats disc space. However, if you're just sending a photo, the compression is lossless - the LZW (or Lemple-Zif-Welch) algorithm, which is one of the smarter, more mathematically sophisticated ones. Later versions of TIFF (such as the versions supported by recent incarnations of PhotoShop) also support ZIP compression, which is also lossless and pretty sophisticated. If you have PhotoShop 6 or above, you can save TIFFs using ZIP compression and save more space.

[4] GIF. Another acronym (computers are replete with these), which this time stands for 'Graphics Interchange Format'. GIF file sizes are small, and GIF also supports a limited transparency feature (as opposed to TIFF's alpha channel) but the price paid for this is image quality. GIF only supports 256 colours. For photographs, therefore, it's next to useless. However, for logos, or cartoon type graphics, GIF is fine.

[5] PNG. Yes, you guessed it, yet another acronym, this time standing for 'Portable Network Graphics'. PNG was invented to address two of the shortcomings of JPEG, namely transparency (which JPEG does not support) and lossless compression. While PNG file sizes are larger than the equivalent JPEG, they are still compressed, and sometimes compressed to a surprisingly good extent. Furthermore, the compression is genuinely lossless (courtesy of some intricate mathematics - LZW again as for TIFF above), so the pixels you compress are resurrected faithfully when the image is opened and unpacked. A 24-bit PNG image supports a transparency alpha channel if wanted. PNG was intended, as its full name suggests, to be an alternative format for Web graphics on Web pages, but support for it in browsers is chequered to put it mildly. Internet Explorer supports it reasonably well (though sometimes chooses weird background colours to place behind the transparent layer), while older incarnations of Netscape screw up badly. Mozilla Firefox handles PNG properly, so I'd get this (free!) browser now if I were you, for a host of reasons (popup killer built in, decent security) that deserve a post all of their own. Meanwhile, back to PNG: the compression level is reasonable, if not spectacular, and in any case if you want, you could always put it in a WinZip archive to try and compress it even further! PNG, incidentally, is very well supported on Macs and under Linux.

[6] PCX. This is an antique format from the old days of IBM's first ever PC way back in the early 1980s. The format has been upgraded with the passage of time, and now supports 24-bit true colour, but since it uses the RLE (run-length encoded) compression method, which is one of the simplest algorithms, it's pot luck whether or not you get decent compression. If you have acres of one colour in an image, it'll compress nicely: in the worst case scenario, where every pixel in the image is a different colour, the file size might actually increase ... at least the compression is lossless though.

[7] PhotoShop PSD Format. If image quality is your prime concern, then this is probably the ultimate format. Not only will it preserve every last pixel in its pristine state, it will also save colour space information, print space information and more, so that the optimum results are displayed either on screen or on paper every time. The price paid for this, of course, is file size. PSD files are enormous. But then, that's because they support image layers, alpha channels, embedded vector graphic paths, and more other features than you can shake a stick at. Which is just one of the reasons why PhotoShop costs as much as it does: not only does it support all of those goodies in its file format, it lets you play with them in the application itself, and also lets you customise their settings to death. You don't have to be a rocket scientist to use it, but it probably helps, as even trained professionals keep finding parts of PhotoShop they've never used before, usually after several years' hard slog using it in the workplace.

[8] Variants of the above. If you're one of those lucky people with Adobe PhotoShop, then you can customise the above formats. You can specify, for example, whether or not your TIFF files use LZW or ZIP compression. You can also specify whether or not to save any alpha channels you don't need, which means you can cut down on unwanted data. You can even save Windows Bitmaps with RLE compression if you want, although whether other applications will understand them is a moot point. Furthermore, if you decide to stick with JPEG, PhotoShop allows you to customise the compression level.

If you have Microsoft Office on a Windows PC, and had the good sense to install Photo Editor when installing Office, then this allows you to fine-tune JPEG compression to a ridiculous extent - 100 different settings! Which means that you can probably find a setting amidst all of those that delivers the goods. This simple but elegant application (please, Microsoft, can't you make *all* of your products like this?) is a 'must have' for anyone wanting to perform quick image manipulation (e.g., converting BMP to JPEG) without going to the expense of PhotoShop. There are freeware programs that do this kind of job, but if you've already splurged out the money for Microsoft Office, then use Photo Editor because it's an embedded freebie that works!

So, what do you choose to send your fish photos to a friend?

If you desperately NEED to squeeze the image into the smallest space possible, then you're forced to use JPEG, and risk having the image spoiled by compression-loss artefacts when it arrives. If you have Adobe PhotoShop, you can balance the JPEG setting somewhat, and reduce artefacts at the cost of greater file size. The only way to find out which setting is optimum for a particular job, however, is literally to 'suck it and see'. If you have Microsoft Office, then do yourself a favour and install Photo Editor. For quick file format conversion jobs and occasional cropping/image rebalancing, it's a peach, and will make you wish that Microsoft made its operating systems as crap-free!

If you need to save some space, but also need to preserve fine detail, then PNG is probably the way to go. First, because it can be previewed in a Web browser without having to fire up something like PhotoShop. Plus, if your recipient is a Mac or Linux user, there are dozens of tools for those platforms that support PNG, including numerous freeware goodies. Failing that, you could try TIFF with ZIP compression, but big images will only compress to a limited extent. Which means that 1600x1200 digital camera images will probably be better off sent as JPEGs, not least because that's the format the camera will create them in in the first place!

As an example of the kind of results you can expect, I have an image of Calloplesiops altivelis that I scanned from a book. This is a big image (1319 x 1120 pixels), and the file sizes for this are as follows:

JPEG : 496K
PNG : 2,830K
TIFF with ZIP compression : 3,001K
TIFF with LZW compression : 3,485K

Note that the differences seen here are probably due to the fact that [1] the file is large to begin with, [2] it's a very complex image (as might be expected with a fish with the body pattern of Calloplesiops altivelis). Shots of something like a Cardinal Tetra or a Panda Cory at 800x600 will probably produce better savings with PNG and TIFF.

Additionally, if you know the person at the other end has Adobe PhotoShop, and doesn't mind receiving PSD files, then the best way to send them is to pop them on a CD and post them via snail mail. It may take longer to get there, but the results will be pernanent, and won't clog up the end-user's hard drive. To give you an example of the kind of scale, a 700MB CD can contain around 150 PSD files before it gets full. The same CD can contain over 5,000 JPEGs - nearer 10,000 if high compression is selected.

So, there you have it. The Calilasseia guide to digital images. Remember, it may sometimes pay to think of something other than JPEG ...

Panda Catfish fan and keeper/breeder since Christmas 2002

nice writeup Cali! I suggest this to be stickied in the photo booth

Last edited by Dr. Bonke at 24-Feb-2005 14:29

Fallout's already rejected that idea in the chat room Dr Bonke ...

Panda Catfish fan and keeper/breeder since Christmas 2002

It has nothingn to do with taking pictures, it's a primer on file formats.

as jason pointed out once before, it doesn't say much in the description of photo booth one way or the other what goes in there. it would probably do just as much good there, although i think more people will see it here...

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"That's the trouble with political jokes in this country... they get elected!" -- Dave Lippman

I guess it doesn't have particularly much to do with taking photos, but in my opinion it may help people reduce the size of the photos that they would like to share with others, something that people on dial-up would probably appreciate. In this forum it may be a bit more visible, as more people visit this are, but on the other hand I think it'll also drown in the torrent of other threads which are added all the time. An article such as this generally does not result in all that many replies, except ones like "great write-up" such as my own, causing it to disappear even faster. In my opinion this article deserves a better fate than that. But that's just my opinion, you moderaters will always have the final call