I owe Steve K an apology. In a discussion of scanning last Saturday he said he did not think his scanner needed to upsample to obtain higher resolution. I said it did. Assuming he has a scanner purchased in the last few years he was probably right and I was probably wrong. Given this, my position that the better method of enlarging an existing print is to scan at 300 ppi and upsample in your image editor is not as certain as I stated it in the meeting.
To see my mea culpa and a further discussion of overscanning vs upsampling to pump up the pixel count to enlarge an existing print Click Here.
June 23, 2008 at 2:46 pm |
First of all, thank you for the apology, Jim. I will check out your comparison, since it’s usually something I don’t do. I try to be very careful to scan at the largest size I think I will need to start with, but we never know when we will need the upsampling info for photos from other sources. Thanks a bunch!!
June 23, 2008 at 11:29 pm |
Jim, could you be into deep doo-doo here? I don’t know…
My one, cut-to-the-chase question is – Why can modern consumer scanners go up to at least 4800 ppi (and, commercial drum scanners a lot more) if all they’re producing is an image file composed of (mostly) fake pixels? Is this mentioned in their literature or user guides? Maybe they do this in a special way.
For example, how would I scan a postage stamp or a fancy engraving or a $100.00 bill if I’m putting out fake pixels? On the other hand, fake money, fake pixels. Makes sense.
I might be missing something really important here. Did I purchase a nice, new All-In-One printer a year ago for the wrong reasons? It replaced a 15-yr old (max) 300 ppi scanner. Maybe I should have kept it ’cause that’s all I need (coupled with my Adobe Photoshop (up-sampling) software?
I wonder what Bob DuVernay at HAL-PC HQ would say to all this…?
At any rate, I appreciate those of you who know a lot about these subjects for pitching in and giving us your opinion. We’re all the better for it…
July 2, 2008 at 2:42 pm |
Carl, I wasn’t aware of your reply until just now.
I’m not entirely sure I understand your questions but if I do then . . .
Let’s assume a modern consumer grade scanner can really produce a 4800 ppi optical scan. A color print does not have enough image definition to take advantage of this resolution. Scanning color prints at more than 300 ppi is just making fuzzy images bigger and fuzzier. Scanning color prints at 600, 1000 or 4800 ppi doesn’t get any more image detail/data than scanning them at 300 ppi. It just makes a bigger file.
To illustrate this for yourself, take one of the sharpest negatives you have and print it the size of a postage stamp, and print it 11×14. Then, scan the stamp size print at 4800 dpi and print it 11×14. The enlargement of the stamp size print will be MUCH fuzzier than the original 11×14 print from the negative, even though it was made from the same negative. This is because the print cannot reproduce the image data available in the negative. The upper limit of the paper’s ability to hold image clarity/data is about 300 ppi. And these are high quality prints. Scanning drugstore prints at more than 200 ppi is probably a waste of disk space too.
My article is about scanning color prints, not real objects. A real object, such as a leaf, scanned at higher and higher resolutions continues to produce greater and greater detail, because that detail is really there.
To answer your question, ‘Did I buy a new scanner for the wrong reasons?” If it was a good quality scanner and you use for it to scan color prints, then answer is probably yes. The 300 ppi scanner produced all the useful data you will get from your color prints. If you plan to scan leaves, maybe not.