Scanning question?

[saverio]

Just did my first scans of 4x5 type 55 neg. On an Epson 3200 photo, there was an option, in professional mode, of scanning in 300dpi or, for instance, 1200dpi.
What is the difference? I noticed the larger file size, what is the advantage of more dpi? Thanks for responding to a novice scanning question.
saverio

[Kirk Gittings]

Your scan needs to generate a file size that gives you enough pixels to print at a given size.

What is the largest size you want to print at? For instance 300 ppi at 4x5" gives you the pixels you need for a 4x5" print.

[saverio]

Let's say 16x20?

[Kirk Gittings]

a 4x5 scanned 16 bit to print a 16x20 is a 164.8 Mp file or scanning a 4x5 at 1200 ppi.

Now, if you plan to crop in PS you need to scan higher,and I prefer to send a 360 MP file(Xprint size) to the printer etc. Some go as low as a 240MP (Xprint size) file for the printer. This is not cast in stone, but you want to be scanning to the largest size you want to print. You do not want to be upressing a file to print it.

[Ted Harris]

To add to what Kirk just said, for a 16x20 print (which is really pushing the capabiities of the scanner BTW), you are bettr off scanning at 2400 dpi and then donrezing in Photoshop. Properly handled, T55 scans very well, I use it a lot. Also, make sure you are careful i setting your white and black point.

Time for a small bit of blatant self promotion .... Kirk and I are now scheduling our next Scanning & Digital Workflow Workshop for late January or early February. Send me a PM for more info.

[Kirk Gittings]

Ted is right. He is sharper than I am right now as I have the inlaw flu and am all doped up, but I scan 4x5 routinely at 2400 just to keep it simple and then downrez as he states.

[saverio]

thanks guys, will try what you have recommeded.

[Gene McCluney]

Unlike film, which has its maximum resolution (more or less) built into the emulsion when it is designed and manufactured, scanners have to be "set" to the resolution and file size you need. If you are scanning only for a low resolution medium such as the internet, then you can speed your scanning along, and reduce your file size by only scanning at a low resolution. If you intend to make paper prints of your images, then you need to know what is the maximum size print you wish to make. The final image size should be in the neighborhood of 300 pixels per inch at the final print size. Some go as low as 240 pixels per inch. Others, higher.