Scanning for Enlargements

[Doug Nelson]

The pixels touch. No void. It's just a numerical statement of the value at a given coordinate.

How many coordinates are used determines the resolution. If you enlarge using the same number of coordinates, that numerical value has to be spread to cover a larger area.

Interpolation looks at these 'coordinate values' and guesses what should fall between. The varying theories as to HOW it should guess make up all the different resampling schemes.

There's very little corelation between the number of pixels per inch in a file and the dots per inch a printer is capable of laying down. To ease the concept, assume the resolution of the printer is infinite and perfect (it isn't, of course, but we're talking theory here).

Imagine a 'pixelated' image. Big squares, jaggy diagonals. That's the coordinate values being spread to cover larger areas.

[akj]

Hi All--it looks like I've got everyone thinking here. Thanks for all your input.

A question for you Tom:

Originally posted by thomasgeorge
Akj, Scanning at around 300 to 400 dpi will give you enough data to make a good 8x10 blow up from a 4x6 size. If you have around a 7 to 10 mb file size, after resampling, you should be OK.

Did you mean to say resampling? Or scaling? If you change the image size (with resample box unchecked) this will change the resolution but not the actual number of pixels (otherwise known as scaling). So shouldn't the file size stay the same before and after you've changed the dimensions? If you have the choice between resampling an image and scaling it--isn't it best to scale?

So, to touch on what Doug said--if I scan in an image at let's say 400 pixels--I scale the size up--and as long as the resolution is 150-200 dpi, I should be OK? And, like Ed said, the quality of the enlargement will depend entirely on the quality of the original. So, I guess the only way to judge whether an enlargement is satisfactory enough is to simply print it out and see? Should I not worry so much about "scan quality"?

Maybe I may be making this topic more complicated than necessary.

Amanda

[Ed_L]

Doug,

I think what you are saying is exactly what I had in mind to begin with.

Amanda,

You are not making this thread too complicated. I think it got a lot of responses because of the way posts were worded and/or interpreted. (Hope this doesn't start another one)

Ed

[thomasgeorge]

Akj, You are right. Poor choice of words on my part. I was refering to upsampling which can be either fixed or variable resolution type. Sorry! With fixed resolution type the file size increases. With variable type the the file size,actually the number of pixels, is unchanged. Tom

[thomasgeorge]

Ed, the program Genuine Fractals from Altimira is useful if you do alot of enlarging or compositing work as you can scan or otherwise import an image at a relatively small size then upsample or down sample it as your needs dictate without having to have multiple images at different sizes stored on your hard drive eating up valuable storage space. Unless you do lots of that sort of stuff where the work must undergo some pretty radical changes, it probably isnt a necessary "plug in" to aquire. I only use it a couple of times a month if even that but when you need it its nice to have. It works well, but keep in mind that VIEWING DISTANCE enters into the equation as well. An enlarged image viewed from say 2 feet is going to look better than the same one viewed from 6 inches. The bigger the finished image the more "fuzz etc " there may be, and Fractals cant compensate for a borderline original image.If its fuzzy or otherwise less than perfect, so it will be after fractals finishes its work. Tom

[Ed_L]

Thanks Tom. It's probably not something that I'll get, but like I said before, I've heard about it, and it sounded like it might be something interesting. I don't remember where I heard about it, but it sounded kind of "magic like".

Ed

[thomasgeorge]

Ed , Alot of the programs out there especially the ones dealing with improving image quality when importing or manupilating size sound real good, and to be fair most do have some value. Trouble is none of them will do much without the user paying attention to detail and using common sense when implementing a course of action and most of the programs with the exception of some of the scanner programs, like the one you use, are pretty narrow in what they do. Its easy to drop a bundle and discover too late that what you thought you were getting isnt exactly the absolutely necessary must have or perish thing you initially thought it was. I know from sad experience, of course a hundred years or so ago I'd probably have been the first yokel to crowd up to the Patent medicine sellers wagon with a buck in my fist. Tom