Major uprez question

[percepts]

Just curious because I don't do digital processing normally but what is the current state of the art software for uprez of image files.

Say for example I scanned a 35mm neg at 4000 dpi so that I get a file something like
5670 x 3780 pixels.

If I want to print that as 30x20 print I would need to uprez to 9000 x 6000. So what is the best software for doing that today and just how good is it?

And would printing at 189ppi give better results than uprezzing using state of the software just so I can print at 300ppi ?

[Joanna Carter]

Just curious because I don't do digital processing normally but what is the current state of the art software for uprez of image files.

Say for example I scanned a 35mm neg at 4000 dpi so that I get a file something like
5670 x 3780 pixels.

If I want to print that as 30x20 print I would need to uprez to 9000 x 6000. So what is the best software for doing that today and just how good is it?

And would printing at 189ppi give better results than uprezzing using state of the software just so I can print at 300ppi ?

Do not confuse the printer's resolution in dpi (usually 360, 720, etc) with the resolution in ppi needed to retain quality in the image.

To determine how large you can print an image, simply divide the pixel count by something like 240, which will give you an acceptable quality of print.

So, in your example, 5670/240 = 23.6" x 3780/240 = 15.75" - in round numbers, 24" x 16" without upscaling.

To achieve 30" x 20", you would only need to resize the image by 25%. This is achievable using Photoshop's own resizing feature, or, better still, my personal recommendation would be Genuine Fractals if you are really fussy about quality.

Regardless of how you resize the image, always use the highest quality/resolution your printer allows; the printer driver will interpolate your 240ppi file to suit the printing resolution without any problems.

[percepts]

I'll rephrase the question so there's no confusion.

Is there better software for up sizing images than the Photoshop internal up sizing algorythms? Forget about dpi, ppi and spi, I'm just interested in which software gives the best results when up sizing more than a little and whether there is any quality falloff as a result of up sizing using that software.

I know historically up sizing lost quality but that was then. What about the here and now.

[Joanna Carter]

Is there better software for up sizing images than the Photoshop internal up sizing algorythms?

Like I said, I bought Genuine Fractals when Photoshop wasn't so good at resizing. Although I gather that Photoshop is now much better, I still like the results I get from Genuine Fractals.

I also find that it is better to sharpen your image in Photoshop before using GF.

[rdenney]

I would add that one's expectations should be controlled when printing 35mm at 20x30". Making more pixels will not make more detail, and it will not correct lens faults. The loss of detail from enlarging beyond the capabilities of the film and optics will be there no matter how you make more pixels in the file you send to the printer.

Rick "whose experience is that the Nikon's 4000-spi scan is already pushing film and lenses up to and often beyond their limits" Denney

[Mike1234]

Like I said on the other forum...

Just my personal opinion but I hate to resize images beyond the original scan resolution. You may not notice such a small change but degradation WILL occur. There's a reason they call it "pixel interpretation"... it's INTERPRETATION. Adjacent pixels are averaged/blurred... information is LOST. It may not be a whole lot in this situation but loss of information is inevitible none-the-less.

I would simply add a border arount the image and leave the resolution alone. But I'm a picky SOB. YMMV.

OTOH... as Rick states... you'll not likely see a big difference in such a large print since this came from 135 size film. Not to impugn 135 film, of course.

[Patrick Dixon]

Just my personal opinion but I hate to resize images beyond the original scan resolution. You may not notice such a small change but degradation WILL occur. There's a reason they call it "pixel interpretation"... it's INTERPRETATION. Adjacent pixels are averaged/blurred... information is LOST. It may not be a whole lot in this situation but loss of information is inevitible none-the-less.

Loss of information is only inevitable if you resize down. If you resize up, then you don't get any more information (resolution), but you shouldn't loose any either (*).

I don't know who calls it pixel interpretation, but the engineering term is interpolation and there is plenty of maths to back up the technique.

* If you're struggling to believe this, then consider the simple case when you print a 300dpi image at 150dpi - twice as large.

[Mike1234]

^^^ Not intending to argue but this is simply not the case. Resizing (or rather altering pixel count *not just cropping*) "always" results in pixel "interpretation" (averaging/blurring) and this is never a good thing.

Okay, you got me. It's "interpolation" not "interpretation". Please forgive this feeble failing brain of mine. But I'm still right about scaling resolution up or down resulting in loss of information.

[Patrick Dixon]

I ain't going to argue, but you're wrong. I spent a great many years doing this sort of stuff for TV broadcast equipment manufacturers!

[Mike1234]

Patrick, I've been working in Photoshop since version 2.0. Altering pixel count for a given print size "always" degrades image quality. Up or down... always, always, always.

Some definitions of "interpolation"...

1. the process of approximating a given function by using its values at a discrete set of points

2. change or falsify by introducing new or incorrect material

3. estimate a value of (a function or series) between two known values

4. make insertions or additions

None of these are acceptible in best processing procedures, IMHO.