I'm a mathematically challenged individual looking to get into digital photography. My questions are, how do you calculate the scanning size of different film formats (ie. for Nikon LS=30 scanner w/2700 dpi, the scanning area of 24.4x36.5mm film is 2,592x3894)? I'm also looking at purchasing on Epson printer and a still undetermined film scanner. My last question is, how can you print @ 1440x720 dpi w/35mm format and get anything but a thumbnail size photo unless you are working with a huge file size and high cost drum scans Thank you for you reply Curt

-- Curtis Buyser (cbphoto@premierweb.net), March 21, 1999

Answers

Well Curt, what you do is not calculate the scan size of different film formats, but start from your output and work backward to determine your scanning requirements. You've done the proper math on the 35mm film, but all that gives you is your file size in pixels. Which leads to the second questions, and the answer is you are asking the wrong question. You cannot (and wouldn't want to anyway) print a photograph at 1,440x720 dpi.

Most printers will give you excellent results at 300 dpi. So now take your 2,592x3,894 pixel scan, divide by 300 and you'll see what size print you can output. Depressing isn't it? That's why service bureaus still use drum scanners and professional photographers still pay to get drum scans. Your Nikon Coolscan will give you excellent results if you just want to print 8x10s on an inkjet printer, but for anything larger you'l need a drum scan.

Don't get me wrong, I'm not knocking the Coolscan or inkjet printers. You can acheive excellence with them, you just won't be able to get huge prints out. Then again, you can't get huge prints out of 35mm anyway so the point is probably moot.

Go to your nearest bookstore and pick up a copy of "Real World Scanning and Halftones" (Peachpit Press).

-- Darron Spohn (dspohn@clicknet.com), March 22, 1999.

I have produced good B&W images using a Nikon LS-20, scanning at 2700 dpi, printed on a Photo Ex on A3.

I use Epson Photographic paper which - of the papers readily available in Australia - is by far the best.

I think that the thumbnail calculation you are making misses one point. For argument's sake, let's pretend the printer is black and white only - i.e that it only has black ink. To get grey tones, the printer uses black dots with white space between them. So the effective resolution of the printer, when you take into account that it can't print grey tones as such, is a lot lower than the 1440 etc dpi would suggest.

Contrast a scanner where each pixel has a value of (at least) 0 to 255.

So, the printer resolution of 1440 x 720 dpi is only black and white - whereas the negative scan of 2700 dpi has a range of at least 0 to 255 (in the case of an 8 bit scanner).

A print at 300 dpi will give you a good result. When I say 'good', I am used to printing high quality B&W prints on fibre based papers, using Leitz enlarger. Obviously, the print on a Photo EX using a cool scan is not in the same league. But frankly - providing you use the right paper - you can get a result which is practically the next best thing (unless you take into account archiveability). Certainly, it challenges a resin based print on an ordinary enlarger.

See http://www.scantips.com for an excellent introduction to scanning and printing.

There are rumours that the newer printers (e.g Epson Stylus 900)use a greater number of inks therefore making better use of the resolution of the printer. Further, there are companies that make a 3 tone grey ink cartridge to sit in place of your colour cartridge. However, once you have used this cartridge, you apparently can't switch back to colour.

Regards Gareth Jolly

-- Gareth Jolly (sgfj@minters.com.au), March 25, 1999.