Scanning and Final Image Sizes

  • Thread starter Thread starter Jack Frillman
  • Start date Start date
J

Jack Frillman

I have been experimenting using Vuescan, GIMP and my new Minolta 5400 on
my Linux system before I begin to scan in 50 years worth of slides and
negatives. I think I have Vuescan pretty much figured out except for
controlling the final image size.
I have 3 slides that I scanned at full (5400) resolution and I want to
splice the three scans into one image
using GIMP. When I scan each slide I set the size to 8x10 inches in
Vuescan and scan at 5400. When I pull one of the three scanned
images into GIMP the image size > 200 inches. Wow! I certaintly don't
want something that's 600 inches big when I splice the 3 images together.

Why?
What am I missing?

What I am shooting for is to splice the 3 images so it will fit on
a 8x10 or 11x14 photo paper.

How do I do this?
 
I have been experimenting using Vuescan, GIMP and my new Minolta 5400 on
my Linux system before I begin to scan in 50 years worth of slides and
negatives. I think I have Vuescan pretty much figured out except for
controlling the final image size.
I have 3 slides that I scanned at full (5400) resolution and I want to
splice the three scans into one image
using GIMP. When I scan each slide I set the size to 8x10 inches in
Vuescan and scan at 5400. When I pull one of the three scanned
images into GIMP the image size > 200 inches. Wow! I certaintly don't
want something that's 600 inches big when I splice the 3 images together.

Why?
What am I missing?

What I am shooting for is to splice the 3 images so it will fit on
a 8x10 or 11x14 photo paper.

How do I do this?
Click to expand...


There are many basics involved here, way too much for one little usenet
message. But the very first thing to know is that digital images are
dimensioned in pixels, not in inches. Inches exist only on the printed
paper. And inches exist on the scanned 35 mm film. Inches exist on things
you can hold in your hand. But the digital image is dimensioned only in
pixels.

See the VueScan UserGuide (at Help menu) about the Output tab subject,
where it says:

Printed size

Use this option to select the target size of the saved images. This is used
to compute the resolution of the saved TIFF and JPEG files. The dpi of the
saved files will depend on the dpi produced by the scanner and the image
size.

Note that "Printed size" does not affect the number of pixels in the image,
so this setting does not affect the file size. "Image size" controls
logically how far apart the pixels should be displayed in order to fit in
the bounds specified. This also means that "Printed size" does not cause
VueScan to resample the image.

----------

So it doesnt matter what you specify there for printed size, you will still
get the same image size in pixels. Printed dpi only specifies some future
spacing on paper (of those pixels). When you specify 5400 dpi, it is
going to scan at 5400 dpi. From 35 mm film (full frame is roughly about
1.4x0.9 inches) then 5400 dpi will create:
(1.4 inches x 5400 dpi) x (0.9 inches x 5400 dpi) = 7560x4860 pixels.

Assuming 24 bit color, this is over 100 MB, a gigantic image. When you
print it at say 300 dpi, that meaning is that you space THESE pixels on
paper at 300 pixels per inch, so 7560x4860 pixels will print about 25x16
inches (one of them). Because 7560 pixels / 300 dpi = 25 inches. That is
how far they go when spaced at 300 per inch. This huge size seems
excessive for your goal of 1/3 of 8x10. You have too many pixels, meaning
you used excessive scan resolution, for this goal.

I cant get any 200 inch number in this case... Even the 7560 pixels spaced
over 200 inches is 7560 pixels / 200 inches = 37 dpi. I cant imagine what
might have happened to show that 37 dpi. Something else happened.

If your goal is to print 3 of these on 8x10, then one choice is that each
one should be about 8 x 3.333 inches (1/3 of 8x10). This is much smaller
than 26x16 inches, so you need much less than 5400 dpi (to create an
appropriate number of pixels, to space over 8x10 inches at 300 dpi).

If your goal is 8x10 inches at 300 dpi on paper, then THAT total overall
goal is 2400x3000 pixels (8x300 and 10x300). If that is three images, then
perhaps each one is 1/3 of that, or 2400x1000 pixels.

Scanning at 1350 dpi (1/4 of 5400) is probably not enough, because 1350 dpi
x 1.4 inches = 1890 pixels, which is not the 2400 pixels needed to fill 8
inches at 300 dpi. I am not sure of your orientation situation, but try
scanning at 5400/3 or 5400/2 dpi instead.

This 1/3 shape (the 2.4 to 1 shape) is very wide and short, not the same as
the shape of 35 mm film, which is 3:2 aspect ratio (a bit closer to
square), so some considerable croppig will be necessary. I suspect that
wont be easy, because the middle picture cant be cropped in one
direction... depends on the overlap, etc... It will surely best to work
with a little larger image (perhaps like up to 2x larger) than needed, to
be able to get it combined right, and then resample the result to smaller
desired size (the 2400x3000 pixels for 8x10 at 300 dpi).

The bottom status bar of VueScan shows all of these numbers before the
scan. You need to learn to think in terms of pixels. Scanning creates
pixels. Digital images are dimensioned in pixels. Pixels is all there is.

Then later you decide how to space those pixels on paper (by printing
spaced at 300 dpi). You can print any image at any size in inches (by
printing at any dpi on paper), but printing at around 300 dpi is most
appropriate, normally will come out best. So it is good to think ahead,
and plan how many pixels you need to create to be right for that future
printing job.

The site below may help with understanding the basics of scanning.
Hope it helps.
 
Jack Frillman said:
I have been experimenting using Vuescan, GIMP and my new Minolta 5400 on my
Linux system before I begin to scan in 50 years worth of slides and
negatives. I think I have Vuescan pretty much figured out except for
controlling the final image size.
I have 3 slides that I scanned at full (5400) resolution and I want to
splice the three scans into one image
using GIMP. When I scan each slide I set the size to 8x10 inches in
Vuescan and scan at 5400. When I pull one of the three scanned
images into GIMP the image size > 200 inches. Wow! I certaintly don't want
something that's 600 inches big when I splice the 3 images together.

Why?
What am I missing?

What I am shooting for is to splice the 3 images so it will fit on
a 8x10 or 11x14 photo paper.

How do I do this?
Click to expand...

Assume the images you want fit in 8X10 are landscape and the 8X10 is
portrait.

I am not familiar with Gimp, but I understand Gimp is similar to Photoshop.
There are several things that have to be done to fit a 5400 dpi scan of 35
mm film or slide into an 8 x 10 print, much more to fit three 5400 dpi scans
into an 8 X 10. (Two fit better.)

Do all of the following on copies of the original images. Do not use the
original image. (Unless you just want to rescan them!)

The first step is to resize the images into the size that will fit into one
third of an 8 X 10.
A little math, 10 / 3 = 3.333 inches (I assume 8x10 is portrait ). So you
want to resize the image by changing the dpi rating of the image so that the
landscape image is 3.333 inches high. In Photoshop Image>Resize. Uncheck the
check box that says resample image. Check the one that is keep proportions.

Type the 3.333 inches in the long dimension of the image so that it fits one
third of the final 8 X 10.

Note the DPI of these images, You want all of them to have the same dpi.
You may not be able to get all images the same size at the same dpi. DPI is
the important number.
Resize all of the images this way.

In Photoshop (Gimp) create a New image that is 8 X 10 inches (White
background) and the same DPI as the resized images. (Must do). From below
calculation dpi=957.

Open each of the resized images. Select All. Copy the selected image. Paste
the Copied image into the new 8x10 image . Resize or move as needed (you may
use the Move command). Put the first image in the top third of the 8X10.
Repeat for each of the other images. Paste below the first and second.

You may have to crop the images to fit three into 8 x 10, two images will
fit better.
You may have to Flatten the 8X10 after pasting in all three images.

If the scanned image (35mm film scanned at 5400 dpi) is 7653 X 5102 then,
the dpi needed to fit into 8 x 3.333 inches is 957 dpi. That will fit the
long size (7653 pixels to the 8 inch of the 8 x10). The short size will
become 5.33 inches, you will have to crop the top and bottom of each image
to fit the 3.33 inches .

Two images will fit the 8 X 10 much better.
 
Wayne said:
There are many basics involved here, way too much for one little usenet
message. But the very first thing to know is that digital images are
dimensioned in pixels, not in inches. Inches exist only on the printed
paper. And inches exist on the scanned 35 mm film. Inches exist on things
you can hold in your hand. But the digital image is dimensioned only in
pixels.

See the VueScan UserGuide (at Help menu) about the Output tab subject,
where it says:

Printed size

Use this option to select the target size of the saved images. This is used
to compute the resolution of the saved TIFF and JPEG files. The dpi of the
saved files will depend on the dpi produced by the scanner and the image
size.

Note that "Printed size" does not affect the number of pixels in the image,
so this setting does not affect the file size. "Image size" controls
logically how far apart the pixels should be displayed in order to fit in
the bounds specified. This also means that "Printed size" does not cause
VueScan to resample the image.

----------

So it doesnt matter what you specify there for printed size, you will still
get the same image size in pixels. Printed dpi only specifies some future
spacing on paper (of those pixels). When you specify 5400 dpi, it is
going to scan at 5400 dpi. From 35 mm film (full frame is roughly about
1.4x0.9 inches) then 5400 dpi will create:
(1.4 inches x 5400 dpi) x (0.9 inches x 5400 dpi) = 7560x4860 pixels.

Assuming 24 bit color, this is over 100 MB, a gigantic image. When you
print it at say 300 dpi, that meaning is that you space THESE pixels on
paper at 300 pixels per inch, so 7560x4860 pixels will print about 25x16
inches (one of them). Because 7560 pixels / 300 dpi = 25 inches. That is
how far they go when spaced at 300 per inch. This huge size seems
excessive for your goal of 1/3 of 8x10. You have too many pixels, meaning
you used excessive scan resolution, for this goal.

I cant get any 200 inch number in this case... Even the 7560 pixels spaced
over 200 inches is 7560 pixels / 200 inches = 37 dpi. I cant imagine what
might have happened to show that 37 dpi. Something else happened.

If your goal is to print 3 of these on 8x10, then one choice is that each
one should be about 8 x 3.333 inches (1/3 of 8x10). This is much smaller
than 26x16 inches, so you need much less than 5400 dpi (to create an
appropriate number of pixels, to space over 8x10 inches at 300 dpi).

If your goal is 8x10 inches at 300 dpi on paper, then THAT total overall
goal is 2400x3000 pixels (8x300 and 10x300). If that is three images, then
perhaps each one is 1/3 of that, or 2400x1000 pixels.

Scanning at 1350 dpi (1/4 of 5400) is probably not enough, because 1350 dpi
x 1.4 inches = 1890 pixels, which is not the 2400 pixels needed to fill 8
inches at 300 dpi. I am not sure of your orientation situation, but try
scanning at 5400/3 or 5400/2 dpi instead.

This 1/3 shape (the 2.4 to 1 shape) is very wide and short, not the same as
the shape of 35 mm film, which is 3:2 aspect ratio (a bit closer to
square), so some considerable croppig will be necessary. I suspect that
wont be easy, because the middle picture cant be cropped in one
direction... depends on the overlap, etc... It will surely best to work
with a little larger image (perhaps like up to 2x larger) than needed, to
be able to get it combined right, and then resample the result to smaller
desired size (the 2400x3000 pixels for 8x10 at 300 dpi).

The bottom status bar of VueScan shows all of these numbers before the
scan. You need to learn to think in terms of pixels. Scanning creates
pixels. Digital images are dimensioned in pixels. Pixels is all there is.

Then later you decide how to space those pixels on paper (by printing
spaced at 300 dpi). You can print any image at any size in inches (by
printing at any dpi on paper), but printing at around 300 dpi is most
appropriate, normally will come out best. So it is good to think ahead,
and plan how many pixels you need to create to be right for that future
printing job.

The site below may help with understanding the basics of scanning.
Hope it helps.
Click to expand...

Thanks for the good kick in the but to change my thinking to pixels
instead of inches.
Based on that I will start the process from the begining after I have
saved the raw scans.

My ultimate goal is to take a scanned image to a photo outfit and have
photo quality prints made.

How many DPI do you need to get a photo quality print?

This DPI number will suffice if I want a 8x10 or a 11x14 print but will
result ia a different file size.
Is this correct?
 
Jack said:
I have been experimenting using Vuescan, GIMP and my new Minolta 5400 on
my Linux system before I begin to scan in 50 years worth of slides and
negatives. I think I have Vuescan pretty much figured out except for
controlling the final image size.
I have 3 slides that I scanned at full (5400) resolution and I want to
splice the three scans into one image
using GIMP. When I scan each slide I set the size to 8x10 inches in
Vuescan and scan at 5400. When I pull one of the three scanned
images into GIMP the image size > 200 inches. Wow! I certaintly don't
want something that's 600 inches big when I splice the 3 images together.

Why?
What am I missing?

What I am shooting for is to splice the 3 images so it will fit on
a 8x10 or 11x14 photo paper.

How do I do this?
Click to expand...


In the resize, make sure the print resolution is 300 dpi. For a 10 inch
dimension printed, the image should be 3000 pixels in that dimension.
 
My ultimate goal is to take a scanned image to a photo outfit and have
photo quality prints made.

How many DPI do you need to get a photo quality print?
Click to expand...

300 dpi will be about right for a fine image on such commerical machines, at
least for 8x10 inches or less. It doesnt have to be exact, but in the
ballpark. However if it is much larger than 8x10 inches, then it might be
much less dpi, due to the capability of these printer machines.

300 dpi means that 8x10 inches should be printed from 2400x3000 pixels, which
is how it gets to be 300 dpi. They will print whatever pixels you bring them,
however large you say to print it, so you need to be aware of this arithmetic
beforehand if you want 300 dpi results.
This DPI number will suffice if I want a 8x10 or a 11x14 print but will
result ia a different file size.
Is this correct?
Click to expand...

Yes, 8x10 at 300 dpi is 2400x3000 pixels, which is 2400x3000=720,000 pixels,
and at 3 bytes per pixel for 24 bit RGB is 21.6 million bytes.

11x14 at 300 dpi is 3300x4200 pixels, or x3 = 45.6 million bytes. (MB is
about 5% less than millions). A high quality JPG file is compressed to
much smaller, but still pretty large, MBs.

If larger than 8x10, you might inquire first at the place that will print
them, as some machines have much less capability at larger sizes. Assuming
you can find a clerk that actually knows, just tell them what you expect to
bring in, and your size goal, and ask if it is optimum for their machine. If
they go larger than 8x10, some machines may have to jump to 16x20, often at
much lower resolution, maybe even near 100 dpi for the large ones. Someone
there will know, but it may not be the first clerk you find. The people
running the machine should know about pixels.

Otherwise these shops dont say much about this need, and are much more likely
to tell you about an absolute minimum size instead about of optimum size, but
minimum wont match optimum for quality. Their business needs to be able to
print whatever people bring them, without making it complex, but 300 dpi is
the way to go, at least up to 8x10 inches.
 
How many DPI do you need to get a photo quality print?

This DPI number will suffice if I want a 8x10 or a 11x14 print but will
result ia a different file size.
Is this correct?
Click to expand...

At the size you mention, 300 ppi. DPI is a printing value.

And yes, the size of the image will be different - a 300 ppi image
will be 2400x3000 pixels in size for 8x10 and 3300x4200 pixels in size
for an 11x14 print.
 
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