HP-35: Clean images

[Dieter]

(08-17-2018 09:30 PM)Gerson W. Barbosa Wrote:  

(08-17-2018 06:21 PM)striegel Wrote:  Reasonably good results can be attained by laying the calculator, face-down of course, on a flatbed scanner.

Thanks for the tip, but very poor results so far on my DeskJet 3636. Perhaps the scanner is not good enough or I just don’t know how to use it.

Using a scanner for such things indeed may work very well – if (!) it's a conventional CCD scanner.

There are two common types of flatbed scanners: CCD and CIS. The former offers good depth of field which is crucial for copying three dimensional objects. Your Deskjet 3636 multifunction device includes a CIS scanner – which is the technique used in most of today's very flat scanner models. But these provide virtually no depth of field at all, which means that they work fine for flat objects but nor for anything else. You may take a look at this website to see the difference. Please also note the link to a page with slide rule pictures generated with a CCD scanner.

However, your HP35 picture can be improved. Please do not use a wide angle lens (or a cell phone) for this kind of pictures. Since you are very close to the subject the lens sees some parts of it from below and others from above (take a look at the upper and lower key rows). What you need is a larger distance – and therefore a moderate telephoto lens. If you got an old Sony P93 set it to the longest telephoto setting and carefully align the camera exactly (!) vertical to the calculator surface.

Dieter