I'm a recent purchaser of a Toshiba PDR-M1 digital camera. I like the camera very much but am not completely satisfied with the printed output to my Epson 700 Color Photo printer. Especially with photos that I have cropped and then enlarged to a 4x6 size, there is a noticeable loss of print detail. I suspect that a cropped picture can only be enlarged so far. How do I know what the actual size of the cropped picture is, and how large I can make it to retain good print resolution?? Thanks.

-- Tim Keenan (timkeenan@compuserve.com), December 29, 1998

Answers

I own a PDR-M1 and an Epson Stylus Color printer (the original one, not the photo model). The printer only prints at 720 DPI, but I'm pretty happy with the results of printing a "Best" quality(lowest compression, about 4:1) image at the 1 per page (about 8"x10") size option using the Image Expert software bundled with the PDR-M1.

So far, my best results have come from using a coated paper designed for higher resolution printing: Canon HR-101 High Resolution Paper. While this paper wasn't intended to be used with an Epson, it works pretty well. It seems to be pretty similar to Epson's 720 DPI paper. Since it's a light bond weight coated paper I prefer to use cold laminate film over the printed surface to preserve it and give the finished product a little weight. In your hand it's reasonably obvious it's not a photo print, but it's pretty impressive. When it's observed from 18" away behind a piece of glass in a frame it's a tougher call to say it's not an enlargement. I haven't tried this without the laminating film, it might look nicer behind the glass.

I've bought some heavier weight photo paper(HP), but haven't taken the time to play with the brightness and contrast settings yet to get a good quality print. I'm hopeful, but it'll take some tweaking. By the way, the only way I know to get a decent print on different papers is to print several test images on the paper varying the brightness and contrast settings from one to the next until I get the results I like. The Epson makes it easy to do this with a couple of sliders in the printer driver rather than having to modify the actual photos. Once you know the settings for a specific paper the rest is cake. You could make a bunch of duplicate images and do the tweaking to each one, but then you'd have to tweak every one you wanted to print that way from then on. I tweak each one I'd like to print individually based on how they look onscreen and then count on the printer settings to get them to come out properly when printed.

Anyhow, to answer your question(finally), I'd say that since a 1280 wide image can be printed up to about 10" wide with no trouble, you need to allow the printer to have about 1280/10 or 128 dots of photo to work with per inch of size you wish to print. You really have to take an image of say 320x256 and try printing it at a couple of different sizes above and below 128DPI and see what you like. Don't try to print too small an image thinking that you're going to benefit by printing at nearer the resolution of the printer. If you try to print a 1280 dot wide image at 720DPI (1.78" wide) it looks awful. The reason for this is that while the printer prints at 720DPI, it can only put one drop of one color ink in that 1/720th of an inch. It takes several drops of a number of colors of ink to anywhere near accurately reproduce one pixel of the proper color on the page in both dimensions on the paper. In fact, from my 8x10" example above you can see that it uses nearly 32 dots to form one block shaped pixel on the page. 720 DPI printer res. / 128 DPI photo res. = 5.625 dots on the paper per pixel in each dimension. 5.625 x 5.625 = 31.64 dots on the page to produce one pixel. If you're using the image expert program that came with the camera, you can right click on an image that you've opened and select "properties" to see the resolution of the image.

If you print at 720 DPI you can assume that: 128 pixels of photograph per inch of printed page is a good starting point.

3"x5" = 384x640 pixel photo 4"X6" = 512x768 pixel photo 8"X10" = 1024x1280 pixel photo

If you're printing at 1440 DPI you'll have to experiment, but something between those sizes and double them in both dimensions should work pretty well. You'll have to experiment, and it may vary depending on how bright or dark an image is.

That's my 20cents, I left 2 far behind. :)

-- Gerald M. Payne (gmp@francorp.francomm.com), December 29, 1998.