On top of decisions about resolution there is also the aspect ratio to consider. Digital cameras usually follow the TV format and provide 1:1.33 ratio picture as opposed to the 1:1.5 of 35mm film. Sending digital cameras images to a normal photo lab can cause some problems as they will expand the image to fill the normal paper size they print on, thus usually chopping off some of your image, either ends or tops and bottoms. You have to test your chosen lab with a few different paper size requests to see what they will do to your images. Maybe you need to deliberately crop all your files to the exact proportions of the paper size you choose to try and make the crops your choice instead of theirs. Printing at home is much easier in this regard.

We are always told the TIFF file format is the best to use as no data is lost when manipulating and transferring the file. JPEG files are compressed and the nature of the compression ensures some integrity is lost. In extreme cases of compression weird artifacts appear and make the image look noisy or grainy and can cause colour banding. In digital cameras there are usually a few choices of degree of JPEG compression available, so to me it was an interesting and surprising exercise to stick the camera on a tripod, take a mess of pictures in all the available file types, then print most of them to A4 size (a 8"x10.67" image), then compare the results to see what is the best compromise of file size and quality of image.

So what did I find?....
Using the reputed "best" TIFF image I compared the available JPEG compressed modes and also the Enlarge Mode variations. The Enlarge Mode fakes a 7.68 megapixel image from the available 3.14 megapixels that the camera has. Olympus do this to yield a file suitable for their A4 size dye-sub printer which gives an 8" x 10.67" print at 300 dpi.
The surprise finding was that the Enlarge Mode JPEG at 3200 x 2400 pixels gave a better image than the uncompressed TIFF at 2048 x 1536 pixels. It was not a matter of squinting and using magnifying glasses on the 8"x10.67" print, it was clear to the naked eye. Even more surprising was that the even more compressed type of the Enlarge Mode (HQ) file looked about the same as the less compressed Enlarge Mode SHQ, maybe even a tiny bit better! So guess what file mode I now use? - the more compressed Enlarge Mode - as it gives me best quality together with smallest file size.

My example files of the same scene came out to....
TIFF 2048 x 1536 = 9.01 megabytes = definitely the worst of these three
JPEG 3200 x 2400 SHQ = 4.90 megabytes = 2nd best quality but very close
JPEG 3200 x 2400 HQ = 1.49 megabytes = best quality by a whisker, but very close.
(SHQ = Super High Quality, HQ = High Quality in Olympus parlance)
One thing that may influence the quality of the image is that I have the Sharpness in the camera set to -5 which hopefully turns it right off. Since these photos I have also set the camera to Contrast -1 as the real scene is a bit "flatter" than this. Sharpening is done in Paint Shop Pro 8 or in Qimage when I print, contrast is altered to suit. Also of course the very low amount of JPEG compression that Olympus employs helps achieve a good result.

The TIFF was bicubic interpolated to match the other two in size, then the whole lot pixel resized up by a factor of 3 so the details of the pixels can be seen more easily. Each part is a 100 x 100 pixel crop of the 3200 x 2400 image.

The JPEG compression here in the side by side comparison is fairly low so the original pixels are much what they look like in the originals. The TIFF came out to be the worst image with a slight lack of fine detail and a lot more purple fringing around highlights (note the top horizontal line which is the roof guttering). It is hard to see differences between the two Enlarge Mode files but time and time again my wife and I preferred the more highly compressed files printed to 8"x10.67" size as the detail seemed better (or smoother)  in places. Anyway, at 1/3 the file size it is preferred.

The result of this exercise is that I now always use the camera in the HQ Enlarge Mode and get the best image quality with a reasonably small file size (about 1.5 megabytes) as a bonus. Each 128 meg card I own now will hold about 85 images, more than enough for my usual days shooting. Two cards give me 170 images which is the equivalent of about  4.7 x 36 exposure films and all on two little xD memory cards. When you think about it, a long holiday usually involves up to about 2,500 shots max, that equates to about 30 of 128 meg cards. That's a bit silly, but the recent release of 512 meg cards means that only 7 of them would have nearly the same capacity. OK the price would be high to buy those 7 x 512 meg, but if you consider a couple of long holidays and the usual cost of film and processing then it all starts to make more sense. The FAT16 file system allows up to 2 gig cards in theory, I wonder if the C-730 will work with that size when it arrives in a few years, that would reduce the cards needed to 2 for a longish holiday. The alternative is something like a Nixvue Vista but that is still a significant cost and you have to carry another chunky object and manage battery recharging etc. I'm starting to like the idea of the bunch of large capacity xD cards on their little holder that takes up no room at all. Later.... I settled on using a cheaper used lightweight laptop computer to download and store when on on a longish holiday, either overseas or in Australia. That way each evening I can review the shots on a 13 inch screen and can see what worked and what didn't. Reviewing on the smaller than 2 inch screen on the back of a camera is basically useless.

The lesson is - even if you own a different digital camera it is worthwhile to waste a bit of time, paper and ink to see what quality results you get from different file types. Don't believe the usual hype that "TIFF is best". Olympus C-740 and C-750 owners will probably get the same results. I'll see if I can borrow them from somewhere. 

Later... borrowed C-740 and C-750 cameras and found that the Enlarge feature is not worthwhile using, image was slightly worse. With my Olympus C-5060 5 megapixel camera I found that there also was no advantage in using the Enlarge Size mode, the best quality and file size compromise is SHQ 5 megapixel jpegs. Tiff and RAW take too much space and RAW is a pain due to the later post processing time required. More information on this subject has flowed from the Olympus SLR forum at DPreview where many Olympus E-1 users report that they can successfully shoot in JPEG format and then go straight to printing with excellent results. That saves enormous amounts of storage space and of post processing time. In really critical situations they do report that using RAW has improved the image a little, but in general it is wiser to stay with JPEG.

After this I now have to get back to finding which aperture is best.