Saving slides as jpg's

[pef105]

Version: 2008 Operating System: Mac OS X 10.6 (Snow Leopard) Processor: Intel I would like to save slides as jpg's at 300 dpi, but even though I set the options at 300 dpi (or any other dpi for that matter), the slides are always saved at 72 dpi. I've tried every combination of options in the dialogue box, but the jpg's are always 72 dpi. What am I doing wrong?

 

[Steve Rindsberg]

Version: 2008 Operating System: Mac OS X 10.6 (Snow Leopard)
Processor: Intel I would like to save slides as jpg's at 300 dpi,
but even though I set the options at 300 dpi (or any other dpi for
that matter), the slides are always saved at 72 dpi. I've tried
every combination of options in the dialogue box, but the jpg's are
always 72 dpi. What am I doing wrong?

Nothing, other than trusting whatever's telling you that the JPGs are
at 72dpi.

DPI is a ratio between two measurements (pixels or dots and inches),
not a measurement itself. Unless you know both, it tells you nothing.

You can quite easily create an image that's 100 pixels across and
another that's 10,000 pixels across, both 72dpi. It's the pixel count
that matters.

So ... what do you need to do with the images? How many PIXELS do you
need?

 

[pef105]

Thanks for replying! I need images 11.08" x 8.58" and 3324 pixels x 2574 pixels. I created the slides at the above size. Powerpoint gives two options for exporting slides as pictures: The first is dpi, the second is pixel count. One would think that, since the above numbers work out to 300 dpi, choosing 300 dpi would give me an image the same size as the slide and the correct number of pixels. Instead, Powerpoint simply increases the size of the image so that the number of pixels come out right but the image is still 72 dpi. So one can export jpg's at the correct pixel count, but then one has to take them all into photoshop to adjust the size. All the dpi option seems to mean is that, if one subsequently reduces the images to their original (slide) size in another program then they will be at the chosen dpi. This is totally counterintuitive. Why have any dpi option if all Powerpoint is doing is changing the pixel count AND size while maintaining the dpi at 72?

 

[Jim Gordon Mac MVP]

Thanks for replying! I need images 11.08" x 8.58" and 3324 pixels x 2574
pixels. I created the slides at the above size. Powerpoint gives two
options for exporting slides as pictures: The first is dpi, the second
is pixel count. One would think that, since the above numbers work out
to 300 dpi, choosing 300 dpi would give me an image the same size as the
slide and the correct number of pixels. Instead, Powerpoint simply
increases the size of the image so that the number of pixels come out
right but the image is still 72 dpi. So one can export jpg's at the
correct pixel count, but then one has to take them all into photoshop to
adjust the size. All the dpi option seems to mean is that, if one
subsequently reduces the images to their original (slide) size in
another program then they will be at the chosen dpi. This is totally
counterintuitive. Why have any dpi option if all Powerpoint is doing is
changing the pixel count AND size while maintaining the dpi at 72?

Well, there's a story behind this feature that can't be told due to
non-disclosure agreements. It goes something like this: The ability to
save as pictures by using a user specified dpi or pixel depth is a Mac
first feature. It worked really well in previous PowerPoint for TIFF
files, but not for other file formats. When it came to Office 2004,
somethings happened. ... was done on ... and things .... during the ...
but then they found ... and so .... at the last minute ... didn't happen
as planned. Then the 2008 version... and they tried, but ... and
then...not only that...new graphics engine...Snow Leopard...Office 2010.

As it turns out, right now would be an excellent time to head to
PowerPoint's Help menu and choose the send feedback to Microsoft
feature. Explain exactly how you would like this feature to work, and
let Microsoft know why this particular feature is useful to you. I know
the Mac Business Unit at Microsoft wants to make this feature right.
Whether or not they can depends a lot on how much people tell Microsoft
how much the feature means to them.

-Jim

 

[Steve Rindsberg]

Thanks for replying! I need images 11.08" x 8.58" and 3324 pixels x
2574 pixels. I created the slides at the above size. Powerpoint
gives two options for exporting slides as pictures: The first is
dpi, the second is pixel count. One would think that, since the
above numbers work out to 300 dpi, choosing 300 dpi would give me an
image the same size as the slide and the correct number of pixels.
Instead, Powerpoint simply increases the size of the image so that
the number of pixels come out right but the image is still 72 dpi.

But y'see, DPI and Inches are little lies. They're handy at times ...
if you know you want an image to import into your DTP or other app at
10" it's nice to be able to set that in advance. So some graphics file
formats allow for storing size and dpi as bits of data. If the
importing app respects that data, great.

Other formats don't allow for this. If I undertand it correctly, JPG
allows for, but doesn't REQUIRE any dpi number to be recorded
internally, so there may be no DPI stored in the file, or (as seems
more likely) an arbitrary value might be stored.

But Photoshop and some other image editing apps INSIST on assigning a
DPI value to every image they open; if there's none in the file itself,
they have to assign a default value. I don't have current versions of
Photoshop, but every version I ever worked with used a default of 72.
A totally made-up number to make itself happy and confuse unsuspecting
users who believe it to be gospel truth. Or as Click 'n Clack would
have it: BOOOWWWWWWWWGUSSSS!

So one can export jpg's at the correct pixel count, but then one has
to take them all into photoshop to adjust the size.

Why should you have to do this?

All the dpi
option seems to mean is that, if one subsequently reduces the images
to their original (slide) size in another program then they will be
at the chosen dpi. This is totally counterintuitive. Why have any
dpi option if all Powerpoint is doing is changing the pixel count
AND size while maintaining the dpi at 72?

Because pixel count is the only bit that's meaningful.
The rest is BS.

 

[pef105]

Again, thanks to both of you for replying.

I understand Steve's point that only pixel count matters fundamentally in the computer, but then why is dpi (or size/resolution) nearly always specified -- as in "scan at 1200 dpi"?

In answer to "Why should you have to change the image size?", the book publishing software that I'm using stipulates pixel count AND size.

To Jim - if Steve is right, why are the two options needed in Powerpoint since only pixel count matters?

 

[Steve Rindsberg]

Again, thanks to both of you for replying.

I understand Steve's point that only pixel count matters
fundamentally in the computer, but then why is dpi (or
size/resolution) nearly always specified -- as in "scan at 1200
dpi"?

When you're scanning, DPI *is* meaningful.

There you don't know the number of pixels you have because you haven't
scanned the file yet. You've got inches (the size of the thing you're
about to scan) and if you specify DPI, that tells the scanner how many
samples (ie, pixels) to take per inch of original.

And by the way, scanning instructions in DPI usually leave out an
important piece of information: Scan at xxxx DPI *IF you'll be
reproducing the image at the same size as the original*. If you're
scanning a 10" original to be reproduced at 5", you'd cut the dpi in
half.

In answer to "Why should you have to change the image size?", the
book publishing software that I'm using stipulates pixel count AND
size.

OK, it's a convenience thing. If the images are saved in a format that
allows the DPI/Inches lie to be embedded in the file and the inches are
set correctly, then the images will likely import into their publishing
app at the correct size.

Somewhere way back when it became "accepted wisdom" that resizing
images in a dtp program was evil incarnate. It's not.

But you can't convince some people of that, and when the image isn't
set up for them ahead of time (inches/dpi), they'd sooner play rugby
with a rolled up rattlesnake than simply resize the images as needed.

All that matters is that there are enough pixels to carry the image
detail through the reproduction process.

But if you don't give them inches/dpi, they'll do The FootStop Dance of
the Petulant Fool, whine, cavil and generally make your life as
miserable as their own.

So export the images at the correct pixel size out of PPT then use
something like Photoshop's batch processing to resize them to however
many inches/dpi is appropriate (but don't let it resample). That'll
set the size properly w/o altering the image.

And fwiw, if they're really asking for JPGs, they're operating right on
the edge of their clue zone, if not well outside it.

 

[pef105]

Interesting!

Thanks, Steve.