This is Interesting: Free Magazines for Graphics designers and webmasters
Home > Archive > Computer Graphics with Photoshop > May 2006 > Saving for Web - Image Size
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
Saving for Web - Image Size
|
|
| C Wright 2006-05-27, 6:16 pm |
| This is a simple nit of a question. Often, when preparing images to be
uploaded to the Web, we are advised to save them at 72ppi because that is
the resolution of many older monitors. Along with that advice we are often
also told to restrict our images to a certain size, for example a long
dimension of 600 pixels. Is there any point in doing both of these resizing
operations? If I save an image as, for example, a 600x400 pixel image it
will appear at that absolute size on a monitor regardless of whether it is
saved at a resolution of 72ppi or 150ppi! If the image were to be printed
that, of course, could make a difference but if the only concern is to
properly display the image on other's monitors is there any point to
resizing to both an absolute dimension AND a certain ppi size?
Chuck
| |
| Harry Limey 2006-05-27, 6:16 pm |
|
"C Wright" <wright9_nojunk@nojunk_mac.com> wrote in message
news:C09DD224.5BFB9%wright9_nojunk@nojunk_mac.com...
> This is a simple nit of a question. Often, when preparing images to be
> uploaded to the Web, we are advised to save them at 72ppi because that is
> the resolution of many older monitors. Along with that advice we are
> often
> also told to restrict our images to a certain size, for example a long
> dimension of 600 pixels. Is there any point in doing both of these
> resizing
> operations? If I save an image as, for example, a 600x400 pixel image it
> will appear at that absolute size on a monitor regardless of whether it is
> saved at a resolution of 72ppi or 150ppi! If the image were to be printed
> that, of course, could make a difference but if the only concern is to
> properly display the image on other's monitors is there any point to
> resizing to both an absolute dimension AND a certain ppi size?
> Chuck
Just use the save for web function in Photoshop, put in your dimensions
600x400 or whatever - I don't believe you are even asked for ppi
| |
| Bill Hilton 2006-05-27, 6:16 pm |
| > C Wright asks ...
>
>if the only concern is to properly display the image on other's
>monitors is there any point to resizing to both an absolute
>dimension AND a certain ppi size?
No, as you say the ppi figure is meaningless for display purposes ...
| |
|
| C Wright wrote:
> This is a simple nit of a question. Often, when preparing images to be
> uploaded to the Web, we are advised to save them at 72ppi because that is
> the resolution of many older monitors. Along with that advice we are often
> also told to restrict our images to a certain size, for example a long
> dimension of 600 pixels. Is there any point in doing both of these resizing
> operations? If I save an image as, for example, a 600x400 pixel image it
> will appear at that absolute size on a monitor regardless of whether it is
> saved at a resolution of 72ppi or 150ppi! If the image were to be printed
> that, of course, could make a difference but if the only concern is to
> properly display the image on other's monitors is there any point to
> resizing to both an absolute dimension AND a certain ppi size?
> Chuck
>
As the others have said, no. The pixel dimensions are all you should
concern yourself with.
--
Comic book sketches and artwork:
http://www.sover.net/~hannigan/edjh.html
Comics art for sale:
http://www.sover.net/~hannigan/batsale.html
| |
|
| In article <C09DD224.5BFB9%wright9_nojunk@nojunk_mac.com>,
C Wright <wright9_nojunk@nojunk_mac.com> wrote:
> This is a simple nit of a question. Often, when preparing images to be
> uploaded to the Web, we are advised to save them at 72ppi because that is
> the resolution of many older monitors. Along with that advice we are often
> also told to restrict our images to a certain size, for example a long
> dimension of 600 pixels. Is there any point in doing both of these resizing
> operations? If I save an image as, for example, a 600x400 pixel image it
> will appear at that absolute size on a monitor regardless of whether it is
> saved at a resolution of 72ppi or 150ppi! If the image were to be printed
> that, of course, could make a difference but if the only concern is to
> properly display the image on other's monitors is there any point to
> resizing to both an absolute dimension AND a certain ppi size?
No.
The people who tell you to save at 72 ppi do not understand resolution.
When an image is displayed in a Web browser, the Web browser strips off
and disregards any ppi information. The only thing--the ONLY thing--that
matters to a browser, any browser, is the total number of pixels. All
Web browsers display an image at one pixel inthe image equals one pixel
on the screen.
A 300x200 pixel image at 72 pixels per inch is absolutely, completely
identical, in all Web browsers and on all platforms, to the same 300x200
pixel image at 96 pixels per inch, the same 300x200 pixel image at 300
pixels per inch, and the same 300x200 pixel image at 3,000,000 pixels
per inch. For Web use, resolution in terms of pixels per inch is
completely irrelevant.
--
Art, photography, shareware, polyamory, literature, kink:
all at http://www.xeromag.com/franklin.html
Nanohazard, Geek shirts, and more: http://www.villaintees.com
| |
|
|
| Eric P. 2006-05-28, 6:17 pm |
| In article <kn6j729bb9lc3gip9e67pjmm6c1hje1ie6@4ax.com>,
Owen Ransen <willy@wonker.com> wrote:
> On Sat, 27 May 2006 14:53:40 GMT, C Wright
> <wright9_nojunk@nojunk_mac.com> wrote:
>
>
> This might help explain things:
>
> http://www.ransen.com/Articles/DPI/Default.htm
>
> and
>
> http://www.ransen.com/Articles/MegaPixels/default.htm
>
>
> http://www.ransen.com/
It is my understanding that the human eye can't distinguish much
above 72 or perhaps 75 dpi, so for images that will be viewed on
a monitor, but not printed, there's no advantage to setting the
resolution above this. For printing, though--and here my understanding
isn't so clear--it appears preferable to set images much higher,
so settings of 600 or more shouldn't be unreasonable. I don't
know if what I said about the human eye extends to printed pages
or not.
On a somewhat related note, if scanning an image to bring into
an image editing program, my instinct is to scan at a very high
resolution, and then have the option to save/print edited versions
at lower resolutions.
Hoping for further clarification here...
Happy computing,
Eric
--
For e-mail replies, please send to "thustar at yahoo dot com."
| |
| John McWilliams 2006-05-28, 6:17 pm |
| Eric P. wrote:
> In article <kn6j729bb9lc3gip9e67pjmm6c1hje1ie6@4ax.com>,
> Owen Ransen <willy@wonker.com> wrote:
>
>
> It is my understanding that the human eye can't distinguish much
> above 72 or perhaps 75 dpi, so for images that will be viewed on
> a monitor, but not printed, there's no advantage to setting the
> resolution above this.
It's actually ppi, not dpi at this stage. Most monitors now are around
96 ppi, a rule of thumb when setting pixel dimensions for monitor viewing.
> For printing, though--and here my understanding
> isn't so clear--it appears preferable to set images much higher,
> so settings of 600 or more shouldn't be unreasonable. I don't
> know if what I said about the human eye extends to printed pages
> or not.
Most folks are fine with 300 or so ppi for printing, and it's not clear
that more ppi makes a discernable difference in final product, and it
prints much slower. Here's where dpi comes in: Some printers can be set
to print at 360, 720, 1440 etc. dpi, all from the same image. Other
printers may call it HQ, or fine, or medium, or draft, etc.
>
> On a somewhat related note, if scanning an image to bring into
> an image editing program, my instinct is to scan at a very high
> resolution, and then have the option to save/print edited versions
> at lower resolutions.
That instinct is right! Unless you have dozens of images to scan and
they will go only onto a web page....
--
John McWilliams
| |
|
| In article
<ericp06-385ADD.06454128052006@newsclstr02.news.prodigy.com>,
"Eric P." <ericp06@sbcglobal.net> wrote:
> It is my understanding that the human eye can't distinguish much
> above 72 or perhaps 75 dpi, so for images that will be viewed on
> a monitor, but not printed, there's no advantage to setting the
> resolution above this. For printing, though--and here my understanding
> isn't so clear--it appears preferable to set images much higher,
> so settings of 600 or more shouldn't be unreasonable. I don't
> know if what I said about the human eye extends to printed pages
> or not.
This is factually incorrect. The human eye can easily distinguish detail
above 72 pixels per inch.
However, a monitor is a fixed pixel device. It is made up of a grid of
pixels. A monitor who's resolution is set to 72 pixels per inch always
displays all images under all circumstances at 72 pixels per inch,
without exception. A monitor who's resolution is set to 96 pixels per
inch always displays all images at 96 pixels per inch.
--
Art, photography, shareware, polyamory, literature, kink:
all at http://www.xeromag.com/franklin.html
Nanohazard, Geek shirts, and more: http://www.villaintees.com
| |
|
|
"tacit" <tacitr@aol.com> wrote in message
news:tacitr-32B6C2.11333328052006@news-server2.tampabay.rr.com...
> [...] A monitor who's resolution is set to 96 pixels per
> inch always displays all images at 96 pixels per inch.
Tacit: Isn't the Apple Cinema Display 120 ppi?
| |
| Eric P. 2006-05-28, 6:17 pm |
| In article <tacitr-32B6C2.11333328052006@news-server2.tampabay.rr.com>,
tacit <tacitr@aol.com> wrote:
> In article
> <ericp06-385ADD.06454128052006@newsclstr02.news.prodigy.com>,
> "Eric P." <ericp06@sbcglobal.net> wrote:
>
>
> This is factually incorrect. The human eye can easily distinguish detail
> above 72 pixels per inch.
There is an upper limit somewhere. I just don't recall what it is.
> However, a monitor is a fixed pixel device. It is made up of a grid of
> pixels. A monitor who's resolution is set to 72 pixels per inch always
> displays all images under all circumstances at 72 pixels per inch,
> without exception. A monitor who's resolution is set to 96 pixels per
> inch always displays all images at 96 pixels per inch.
I didn't say anything to suggest that that's not the case. Again, though,
there's an upper limit to a monitor's resolution, due to physical
limitations. I don't know what that might be, either.
Thanks,
Eric
--
For e-mail replies, please send to "thustar at yahoo dot com."
| |
|
| In article <127jl6ajc9agef8@news.supernews.com>,
"2" <nhoj@droffats.ten> wrote:
> Tacit: Isn't the Apple Cinema Display 120 ppi?
The highest resolution Cinema Display has a pixel pitch of .25mm, which
roughly translates into an effective resolution of about 96 pixels per
inch in its highest resolution setting.
That seems reasonable to me, as anything higher resolution might make
fine detail on the screen hard to view.
--
Art, photography, shareware, polyamory, literature, kink:
all at http://www.xeromag.com/franklin.html
Nanohazard, Geek shirts, and more: http://www.villaintees.com
| |
| Eric P. 2006-05-28, 6:17 pm |
| In article <BPCdner5Ss0YJuTZnZ2dnUVZ_tidnZ2d@comcast.com>,
John McWilliams <jpmcw@comcast.net> wrote:
> Eric P. wrote:
>
> It's actually ppi, not dpi at this stage. Most monitors now are around
> 96 ppi, a rule of thumb when setting pixel dimensions for monitor viewing.
I forgot how to assign this. My Monitors cp allows me to select
resolutions at certain refresh rates, but I don't see where to
assign a "per inch" setting.
>
> Most folks are fine with 300 or so ppi for printing, and it's not clear
> that more ppi makes a discernable difference in final product, and it
> prints much slower. Here's where dpi comes in: Some printers can be set
> to print at 360, 720, 1440 etc. dpi, all from the same image. Other
> printers may call it HQ, or fine, or medium, or draft, etc.
>
>
> That instinct is right! Unless you have dozens of images to scan and
> they will go only onto a web page....
Oh, yes. In the case of .jpg files, I choose Save for Web in Photoshop.
For .gif files, I don't like to alter things too much, because the more
I do, the more degradation in quality I see.
Thanks,
Eric
--
For e-mail replies, please send to "thustar at yahoo dot com."
| |
|
| "tacit" <tacitr@aol.com> wrote in message
news:tacitr-A16814.14190728052006@news-server1.tampabay.rr.com...
> The highest resolution Cinema Display has a pixel pitch of .25mm, which
> roughly translates into an effective resolution of about 96 pixels per
> inch in its highest resolution setting.
Thanks for that. I thought I recalled a control-panel monitor setting of
120.
> That seems reasonable to me, as anything higher resolution might make
> fine detail on the screen hard to view.
That must have something to do with the way the image is formed, because we
don't have trouble seeing more detail on paper. FWIW, tests have shown that
while the human eye has a nominal 'resolution' of 6 lp/mm it can often tell
when an image (especially of type) is of a higher resolution; it can't count
the lp/mm, only sense the difference.
| |
|
|
"Eric P." <ericp06@sbcglobal.net> wrote in message
news:ericp06-3CBF15.11211528052006@newsclstr02.news.prodigy.com...
> In article <BPCdner5Ss0YJuTZnZ2dnUVZ_tidnZ2d@comcast.com>,
> John McWilliams <jpmcw@comcast.net> wrote:
>
>
> I forgot how to assign this. My Monitors cp allows me to select
> resolutions at certain refresh rates, but I don't see where to
> assign a "per inch" setting.
>
>
> Oh, yes. In the case of .jpg files, I choose Save for Web in Photoshop.
> For .gif files, I don't like to alter things too much, because the more
> I do, the more degradation in quality I see.
>
> Thanks,
> Eric
>
> --
> For e-mail replies, please send to "thustar at yahoo dot com."
| |
|
| "Eric P." <ericp06@sbcglobal.net> wrote in message
news:ericp06-3CBF15.11211528052006@newsclstr02.news.prodigy.com...
> I forgot how to assign this. My Monitors cp allows me to select
> resolutions at certain refresh rates, but I don't see where to
> assign a "per inch" setting.
Well, it really shouldn't ever be put in such terms, but if you are using
XP, then just right-click on the desktop, then take Properties, then the
Settings tab. Click in there on Advanced and (daminit) there's "DPI"
settings (96, 120, custom). Go crazy and take the Custom settings, like
20%, and see how silly it can get.
| |
| Bart van der Wolf 2006-05-28, 10:16 pm |
|
"2" <nhoj@droffats.ten> wrote in message
news:127jr46nobvv997@news.supernews.com...
SNIP
> FWIW, tests have shown that while the human eye has a nominal
> 'resolution' of 6 lp/mm it can often tell when an image (especially
> of type) is of a higher resolution; it can't count the lp/mm, only
> sense the difference.
It's called Vernier acuity:
<http://www.photonicshistory.com/dir...m=5559&letter=v>
as relative to visual acuity:
<http://www.photonicshistory.com/dir...m=5605&letter=v>
So according to that source, Vernier acuity is about 6x higher than
visual acuity, which is why typeface needs to be printed at much
higher resolution than continuous tone images.
Bart
| |
|
| In article <127jr46nobvv997@news.supernews.com>,
"2" <nhoj@droffats.ten> wrote:
> That must have something to do with the way the image is formed, because we
> don't have trouble seeing more detail on paper.
It has to do with the assumptions that programmers make when they design
user interface controls, more likely.
User interface objects on a computer screen are often designed to be a
certain number of pixels in size; for example, the standard size of a
button is typically 20 pixels high. If a screen has a resolution of 200
pixels per inch, that makes the size of a button one-tenth of an inch
high.
Now, it's easy to see an object one-tenth of an inch high on paper. But
we typically look at a sheet of paper from a much closer distance than
we look at a computer monitor--and a sheet of paper isn't glowing, it's
using reflected light. Looking at an object a tenth of an inch high on a
glowing screen that's much farther away is a whole 'nother story. :)
A computer screen that had a higher resolution but did not make the
objects smaller would probably look significantly better. If the size of
a button were the same on a 200 pixel per inch screen, say, and the
button were composed of more pixels, it'd probably look quite good. But
that'd involve dramatically re-thinking the way things are displayed on
a screen.
The Mac uses PDF (in OS X) or QuickDraw (in older versions) to draw
images on the screen,a nd it is possible for a programmer to write a
program that would display its user interface elements and text and so
forth on the screen at the same physical size regardless of the
resolution of the monitor if he so chose, because both PDF and QuickDraw
are resolution independent. (He wouldn't be able to use pre-built OS
controls; he'd have to draw them himself.) On Windows, which does not
have a resolution-independent system for displaying things on the
screen, it'd be much more difficult. (Windows Vista was supposed to
include this kind of functionality, but Microsoft has announced that it
has been dropped.)
--
Art, photography, shareware, polyamory, literature, kink:
all at http://www.xeromag.com/franklin.html
Nanohazard, Geek shirts, and more: http://www.villaintees.com
| |
|
| "tacit" <tacitr@aol.com> wrote in message
news:tacitr-5CE003.23170028052006@news-server2.tampabay.rr.com...
> The Mac uses PDF (in OS X) or QuickDraw (in older versions) to draw
> images on the screen,a nd it is possible for a programmer to write a
> program that would display its user interface elements and text and so
> forth on the screen at the same physical size regardless of the
> resolution of the monitor if he so chose, [...]
neXt used Postscript display. I wish I had seen it IRL.
| |
|
| In article
<ericp06-3CBF15.11211528052006@newsclstr02.news.prodigy.com>,
"Eric P." <ericp06@sbcglobal.net> wrote:
> I forgot how to assign this. My Monitors cp allows me to select
> resolutions at certain refresh rates, but I don't see where to
> assign a "per inch" setting.
When you set different resolutions, you are setting different "per inch"
settings.
Let us say that your monitor is, for example, ten inches wide. If you
set your monitor to 1024x768, it would be 102.4 pixels per inch. If you
set it to 640x480, it owuld be 64 pixels per inch. If you set it to
800x600, it would be 80 pixels per inch.
Pixels per inch is the number of pixels divided by the number of inches,
that's all.
--
Art, photography, shareware, polyamory, literature, kink:
all at http://www.xeromag.com/franklin.html
Nanohazard, Geek shirts, and more: http://www.villaintees.com
| |
| Eric P. 2006-05-30, 6:16 pm |
| In article <tacitr-59AB1C.23194728052006@news-server2.tampabay.rr.com>,
tacit <tacitr@aol.com> wrote:
> In article
> <ericp06-3CBF15.11211528052006@newsclstr02.news.prodigy.com>,
> "Eric P." <ericp06@sbcglobal.net> wrote:
>
>
> When you set different resolutions, you are setting different "per inch"
> settings.
>
> Let us say that your monitor is, for example, ten inches wide. If you
> set your monitor to 1024x768, it would be 102.4 pixels per inch. If you
> set it to 640x480, it owuld be 64 pixels per inch. If you set it to
> 800x600, it would be 80 pixels per inch.
>
> Pixels per inch is the number of pixels divided by the number of inches,
> that's all.
OK, I was confused between pixels and dots. I'm pretty sure that an
aperture grill can't be made to be nearly as high as some of those higher
resolutions.
And I used to know all this stuff...'specially when I worked at Radius!
Oh, well, I've slept since then ;)
Thanks,
Eric
--
For e-mail replies, please send to "thustar at yahoo dot com."
|
|
|
| | Copyright 2003 - 2008 forum4designers.com Software forum Computer Hardware reviews |
|