O/T: Nibbling on an Apple

On 8/13/2013 5:49 PM, Sandman wrote:
In article ,
PeterN wrote:

lets forget all the technoblab.
The first image is 651 x 400 @ 96 ppi
The If you make the same image 651 x 400 @ 24 ppi

Which image will be larger in inches.

The lower number produces the largest physical representation. 24 dots
per inch is fewer than 96, so more inches are needed for all the dots to
be displayed.

A 651 x 400 image printed ad 24 DPI would be 27 x 17 inch. Each pixel
would be


Again, the term "PPI" refers to your monitor, not to the image. "DPI"
refers to printed size of the image, which is what you set in Photoshop.

At times, these are used interchangeably by software, but that's not
strictly correct.



Tell that to nospam

What I found interesting is that the original jpeg image was 48.7 kb.

I reduced the ppi to 24 & 10, and saved the two reduced images. Both
reduced images were the same size, 42 kb. The size diffrence must have
been due to a factor that I did not consider.

--
PeterN

In article , PeterN
wrote:

What I found interesting is that the original jpeg image was 48.7 kb.

out of the camera?

I reduced the ppi to 24 & 10, and saved the two reduced images. Both
reduced images were the same size, 42 kb.

in other words, they're the same size as i said, and not just number of
pixels, but the size on disk too.

The size diffrence must have
been due to a factor that I did not consider.

different jpeg compression.

In article ,
PeterN wrote:

lets forget all the technoblab.
The first image is 651 x 400 @ 96 ppi
The If you make the same image 651 x 400 @ 24 ppi

Which image will be larger in inches.

The lower number produces the largest physical representation. 24 dots
per inch is fewer than 96, so more inches are needed for all the dots to
be displayed.

A 651 x 400 image printed ad 24 DPI would be 27 x 17 inch. Each pixel
would be


Again, the term "PPI" refers to your monitor, not to the image. "DPI"
refers to printed size of the image, which is what you set in Photoshop.

At times, these are used interchangeably by software, but that's not
strictly correct.

Tell that to nospam

Why? Nospam is quite correct.

And he corrected me on one point, and I have to rephrase.

PPI are digital pixels represented in the physical world.
DPI is the resolution of your printer.

Sorry, nospam.

What I found interesting is that the original jpeg image was 48.7 kb.

I reduced the ppi to 24 & 10, and saved the two reduced images. Both
reduced images were the same size, 42 kb. The size diffrence must have
been due to a factor that I did not consider.

You changed the image in some way. Altering the PPI of an image doesn't
change the image data in any way. I bet you saved it as another image
format, or with another JPG compression level.





--
Sandman[.net]

In article ,
nospam wrote:

lets forget all the technoblab.
The first image is 651 x 400 @ 96 ppi
The If you make the same image 651 x 400 @ 24 ppi

Which image will be larger in inches.

The lower number produces the largest physical representation. 24 dots
per inch is fewer than 96, so more inches are needed for all the dots to
be displayed.

no. they are exactly the same size on screen.

Yes, I obviously thought he was talking about printing to paper, because
that's what I was talking about in my post which he replied to.

he said to just change the ppi tag in the image editor, leaving the
pixel dimensions the same. that does nothing. they are the same size.

He didn't say that above, hence my answered talked about the wrong thing.

A 651 x 400 image printed ad 24 DPI would be 27 x 17 inch. Each pixel
would be

and if it's not printed, which it is not, they are the same size.

Of course. Everyone knows this.




--
Sandman[.net]

In article , Sandman
wrote:

lets forget all the technoblab.
The first image is 651 x 400 @ 96 ppi
The If you make the same image 651 x 400 @ 24 ppi

Which image will be larger in inches.

The lower number produces the largest physical representation. 24 dots
per inch is fewer than 96, so more inches are needed for all the dots to
be displayed.

no. they are exactly the same size on screen.

Yes, I obviously thought he was talking about printing to paper, because
that's what I was talking about in my post which he replied to.

he changes things a lot and it's often hard to keep up.

he said to just change the ppi tag in the image editor, leaving the
pixel dimensions the same. that does nothing. they are the same size.

He didn't say that above, hence my answered talked about the wrong thing.

he did in another post:

In article , PeterN
wrote:
The first image is 651 x 400 @ 96 ppi
The If you make the same image 651 x 400 @ 24 ppi

Which image will be larger in inches.

exactly the same.

You really should open the image in a photo editor, and look at the
result. But, you would never admt being wrong.


A 651 x 400 image printed ad 24 DPI would be 27 x 17 inch. Each pixel
would be

and if it's not printed, which it is not, they are the same size.

Of course. Everyone knows this.

no, not everyone.

In article ,
nospam wrote:

and if it's not printed, which it is not, they are the same size.

Of course. Everyone knows this.

no, not everyone.

No.. not everyone...


--
Sandman[.net]

On 8/13/2013 6:07 PM, nospam wrote:
In article , PeterN
wrote:

What I found interesting is that the original jpeg image was 48.7 kb.

out of the camera?

I reduced the ppi to 24 & 10, and saved the two reduced images. Both
reduced images were the same size, 42 kb.

in other words, they're the same size as i said, and not just number of
pixels, but the size on disk too.

The size diffrence must have
been due to a factor that I did not consider.

different jpeg compression.

possibly. I thought I had only one variable in each of the three images.

...

--
PeterN

On 8/13/2013 6:10 PM, Sandman wrote:
In article ,
PeterN wrote:

lets forget all the technoblab.
The first image is 651 x 400 @ 96 ppi
The If you make the same image 651 x 400 @ 24 ppi

Which image will be larger in inches.

The lower number produces the largest physical representation. 24 dots
per inch is fewer than 96, so more inches are needed for all the dots to
be displayed.

A 651 x 400 image printed ad 24 DPI would be 27 x 17 inch. Each pixel
would be


Again, the term "PPI" refers to your monitor, not to the image. "DPI"
refers to printed size of the image, which is what you set in Photoshop.

At times, these are used interchangeably by software, but that's not
strictly correct.

Tell that to nospam

Why? Nospam is quite correct.

And he corrected me on one point, and I have to rephrase.

PPI are digital pixels represented in the physical world.
DPI is the resolution of your printer.

Sorry, nospam.

What I found interesting is that the original jpeg image was 48.7 kb.

I reduced the ppi to 24 & 10, and saved the two reduced images. Both
reduced images were the same size, 42 kb. The size diffrence must have
been due to a factor that I did not consider.

You changed the image in some way. Altering the PPI of an image doesn't
change the image data in any way. I bet you saved it as another image
format, or with another JPG compression level.

I know. That is why I said there must be a factor that I didn't consider.


--
PeterN

In article ,
PeterN wrote:

in other words, they're the same size as i said, and not just number of
pixels, but the size on disk too.

The size diffrence must have
been due to a factor that I did not consider.

different jpeg compression.

possibly. I thought I had only one variable in each of the three images.

I think, but I'm not sure, that PS defaults to last used JPG
compression. So if you open the original image which was compressed at,
say, 60% and then saves it at compression level 80%, then the size will
differ. At the time of saving the copy, you may not have readily been
able to see the original files compression level (as far as I know, PS
has no way to show this).



--
Sandman[.net]

On 2013-08-13 15:33:58 -0700, PeterN said:

On 8/13/2013 6:07 PM, nospam wrote:
In article , PeterN
wrote:

What I found interesting is that the original jpeg image was 48.7 kb.

out of the camera?

I reduced the ppi to 24 & 10, and saved the two reduced images. Both
reduced images were the same size, 42 kb.

in other words, they're the same size as i said, and not just number of
pixels, but the size on disk too.

The size diffrence must have
been due to a factor that I did not consider.

different jpeg compression.

possibly. I thought I had only one variable in each of the three images.

Did you resample when you changed ppi?
If you did the physical document size should remain the same and the
pixel dimensions will change as will the file size. If you don't
resample the pixel dimensions will remain the same, as will the file
size. However, the physical document size (print) will change due to
fitting the different number of pixels into the same pixel dimensions.
This image will appear to be the same size with no pixel dimensional
change on a display.

So, here we have an image file 648x960 @ 360 ppi, 528KB & 648x960 @ 72
ppi, 518KB. Both display on screen at the same size with no discernible
quality difference. However, if you try to print images from those
files you will find a change from a decent looking 8'' x 12'' to a
downright awful and pixelated 41'' x 61''.
https://dl.dropbox.com/u/1295663/Fil...NC5967-E1w.jpg
https://dl.dropbox.com/u/1295663/Fil...C5967-E1pw.jpg


--
Regards,

Savageduck