Scaling up tiffs

[athlene.catherine]

Wondering if anyone could shed some light with rescaling and resaving as tiff's/jpegs.
I have an old photo from a book scanned at 300 dpi 60cm x 30cm as a tiff.
I need to print this 600cm x 300cm (we have a large format textile printer) Anyway need to know how to execute with the best outcome ( I realise it's going to be pretty shoddy anyway) should I rescale to 600cm and print it as a jpeg? With resizing if I get the right image can I compress it to jepg to save file space?
A little stumped. Thanks!

[Leigh]

A TIFF is basically a raw image, with one or two bytes per pixel, depending on your scanner settings. It was invented to be a lossless (i.e. retaining the original information) file format, and thus was done without compression. Some compression algorithms are available to reduce the file size,

In comparison JPEG was designed to be a lossy and compressed format, so you lose some information when you convert the TIFF to JPEG format. The amount that's lost is a direct function of the compressed size, with smaller files containing less information. The value is settable when the file is generated.

You could re-size it up, but you won't gain any information. All it does is cut the existing pixels into smaller pieces, all of which are the same. It can't add any information to what's alredy in the scan.

I expect the real limitation will be the halftone mask used to print the image in the book in the first place. These are typically much coarser than 300 dpi. Any high-res scan is just going to faithfully reproduce the halftone image.

I would suggest just sending your 300 dpi TIFF file to the printer and let the print driver upscale it to the 300x600 final image size. That's one thing that print drivers are designed to do rather efficiently.

- Leigh

[athlene.catherine]

Thanks Leigh! That should do it fine.
So just to recap - When upscaling the photo, it will never get any "better" because all it can't create more information within the file. It's just creating more of the same pixels?
Thanks again.

[Leigh]

That's right. What you have in the scanner output file is all you have. You can't add any new information.

- Leigh

[SergeyT]

...When upscaling the photo, it will never get any "better" because all it can't create more information within the file. It's just creating more of the same pixels?


The answer to whether it could be "better" depends on may factors. The editing skills, software and algorithms used to interpolate, the tone curve applied to the final image, the sharpening technique, and some more.

Photoshop alone has 3 useful resampling algorithms.
Qimage has some additional.
One has to experiment ...

And I would stay away from JPEGs when it comes to any serious image processing\ printing.

SergeyT.

[Greg Lockrey]

FWIW I have made 10x12 foot displays using 8x10" 300 dpi JPEG files that were e-mailed to me using Qimage. It does all the work for you.

[Jim Michael]

Since the photo is from a book won't that be a dot pattern? If so, I think all you'll wind up with is some bigger dots. Not that there's anything wrong with that - it might look good on fabric.