post with large files

[jamesklowe]

if i could, i would've photographed it in one shot. but i didn't have enough lights to do so
nor did i want to pull a bigger generator.
i already had a 25kva on the day. and that was a mission to get out

what's currently possible in new zealand is a 60'' wide printer.
so it'd roughly be around 1.5m x 2.5m. but i'm looking overseas to print aswell- mainly australia being so close. without having to join two seperate rolls of paper i'dlike to get to maybe a 2m+ high print.
much like the work of james casabere if anyones seen his work inperson.

I'm not quite ready to work backwards from the printers just yet

here's what i've got so far: (to give you an idea. very rough of what it will look like)


it's roughly a 3gb file. except for the next row which will add 1.8gb ish on
and then there's the adjustments etc. and everything is taken out of the shot and put somewhere else

[Joanna Carter]

what's currently possible in new zealand is a 60'' wide printer.
so it'd roughly be around 1.5m x 2.5m. but i'm looking overseas to print aswell- mainly australia being so close. without having to join two seperate rolls of paper i'dlike to get to maybe a 2m+ high print.

And that answers my question and should give you a clue as to why you need not have scanned at such a high resolution. If you were to use the whole of your sheets of film, your files are big enough to give you a print of 8.5m x 10m !!! You could easily have scanned at half that size, thus reducing your file sizes to a quarter of the present sizes, thus possibly avoiding many of the problems you have encountered.

[jamesklowe]

right now, at 300dpi 8bit (from the mock i did earlier) i have a print that is 1000mm x 1700mm. so i don't see why i would scan it smaller?

[Joanna Carter]

right now, at 300dpi 8bit (from the mock i did earlier) i have a print that is 1000mm x 1700mm. so i don't see why i would scan it smaller?

Because, if you are printing at such large sizes, you don't need 300ppi; depending on the viewing distance, you could use anything between 150 and 240 ppi.

So, to work out your scanning resolution, you take the finished size as a magnification of the film size and multiply, say, 240 by that figure.

e.g.

In your image, you have 6 x 4" sheets across the image and 4 x 5" sheets in the height.

Now, let's say that you are using half of those dimensions as your merged images size; so that will give you a film area of 12" x 10".

Now, take the shorter dimension (the height) and multiply it by a scanning resolution resolution of 1200ppi - when divided by the print resolution of 240ppi, this gives you a print size of :

12" x (1200ppi/240ppi) = 60" or 1.5m

by

10" x (1200ppi/240ppi) = 50" or 1.25m.

I would agree that it seems that you are using less than half the height of the top row but would that not be counteracted by the the row yet to be added.

You will also find that such images can easily be interpolated by up to twice the size without significant degradation, but that can happen after you have done all the grunt work of stitching.

However, you stated your original scans were made, not only at 2040ppi but also at 200%. This means you not only have 66% more pixels per inch than my example, you also have double that resolution !!

So, if we take the same image area that I used of 12" x 10" and do the calculations, we get :

12" x ( (2040ppi x 200%) / 240ppi) = 204" or 5m

by

10" x ( (2040ppi x 200%) / 240ppi) = 170" or 4.25m

Now, by simply reducing the scan magnification from 200% to 100%, you will still get a finished print size of 2.5m x 2.125m

Don't forget that by reducing the magnification to half that which you used, you reduce your file sizes to a quarter of their present sizes. Rather than getting the images scanned again, you could simply resize your original files to half their present sizes and still get that 2.5m x 2.125m print.

[jamesklowe]

i must have something completely different-

just running numbers through photoshop
i get 300mmx 170mm @ 2040ppi is equivalent to 2040 x 1171 @ 300dpi

besides some printers not being able to take a 900mb file, why would i not print at 300dpi? isn't it just as important to have a large print as clear as possible compared to a small print

[J. Gilbert Plantinga]

I think you're still missing the point. You've scanned at the Imacon's max, 2040, but you've already upsampled to 200%. Now you've got a file that is actually _less_ clear due to the upsampling, and is too big to work with. What you need to do is to do everything, that includes all of your adjustments, your cropping, and your stitching with the original 2040ppi files. Then upsample the final flattened (and perhaps 8-bit per channel -- most printer drivers will ignore the extra accuracy in the 16-bit colors) image to whatever size your printer needs. You may want to do some sharpening as the final step. Trust me, I do his sort of thing all the time.

[Joanna Carter]

i must have something completely different-

just running numbers through photoshop
i get 300mmx 170mm @ 2040ppi is equivalent to 2040 x 1171 @ 300dpi

besides some printers not being able to take a 900mb file, why would i not print at 300dpi? isn't it just as important to have a large print as clear as possible compared to a small print

As Gilbert says, you have missed the point that you have not only used 2040ppi for the scan, you have also upsampled to 200% for the scan; something that you could do after stitching, if you really need to.

And, as far as printing resolution goes, 240ppi is perfectly adequate for, even, closeup inspection; most large prints will never be viewed from 300mm but from much further away, thus you can use lower image resolutions for very large prints. Many large images are made at resolutions as low as 150ppi for printing purposes.

Note that image resolution is not the same as printer resolution - just because you set the image resolution at 240 ppi doesn't preclude printing at a printer resolution of 2880dpi.