Could someone please explain why, when I rotate a picture 90° degrees in a
viewing/editing program, the picture is stretched so that long faces appear
rounder? The actual change (as measured with a ruler on the monitor screen)
is from 1:1.25 in normal view to 1:1.43 in rotated view.
This happens with pictures from Kodak, Pentax, and Ricoh digital cameras,
when opened and rotated in Irfanview, Kodak, Adobe Elements, or The Gimp .
On Sun, 12 Aug 2007 10:24:25 +0100, "Jeff Layman" <jmlayman@thetapetcp.co.uk>
wrote:
>Could someone please explain why, when I rotate a picture 90° degrees in a
>viewing/editing program, the picture is stretched so that long faces appear
>rounder? The actual change (as measured with a ruler on the monitor screen)
>is from 1:1.25 in normal view to 1:1.43 in rotated view.
>
>This happens with pictures from Kodak, Pentax, and Ricoh digital cameras,
>when opened and rotated in Irfanview, Kodak, Adobe Elements, or The Gimp .
It means that your monitor is not correctly adjusted for a 1:1 aspect ratio.
Just because you can select various desktop resolutions for display doesn't mean
that they are all supposed to be stretched to the very edges of your monitor.
To correct for this use any editing program and use the vector graphic tools to
draw a perfect circle (or square). Make sure you use a "lock aspect-ratio"
function so that you are not drawing an ellipse or rectangle when doing this.
Then measure the vertical axis and the horizontal axis of the object on your
screen. Adjust the vertical and horizontal height of your monitor display until
the horizontal and vertical distances of the circle or square are equal. Now
your images from all cameras in any software will display as they should no
matter how you rotate them.
Be prepared to see all your familiar faces in the photos as rounder than you
have been seeing them. The new and correct aspect ratio will be halfway between
what you have been seeing before and after rotating.
On Sun, 12 Aug 2007 10:24:25 +0100, "Jeff Layman"
<jmlayman@thetapetcp.co.uk> wrote:
>Could someone please explain why, when I rotate a picture 90° degrees in a
>viewing/editing program, the picture is stretched so that long faces appear
>rounder? The actual change (as measured with a ruler on the monitor screen)
>is from 1:1.25 in normal view to 1:1.43 in rotated view.
I suspect you are using an inappropriate resolution that
doesn't match the aspect ratio of your monitor. Monitors may
be 5:4, 4:3, or other formats like 16:9. My guess is that
your monitor is physically 5:4 but you're using a resolution
intended for 4:3 displays.
k. harvey wrote:
> On Sun, 12 Aug 2007 10:24:25 +0100, "Jeff Layman"
> <jmlayman@thetapetcp.co.uk> wrote:
>
>> Could someone please explain why, when I rotate a picture 90°
>> degrees in a viewing/editing program, the picture is stretched so
>> that long faces appear rounder? The actual change (as measured with
>> a ruler on the monitor screen) is from 1:1.25 in normal view to
>> 1:1.43 in rotated view.
>>
>> This happens with pictures from Kodak, Pentax, and Ricoh digital
>> cameras, when opened and rotated in Irfanview, Kodak, Adobe
>> Elements, or The Gimp .
>
> It means that your monitor is not correctly adjusted for a 1:1 aspect
> ratio. Just because you can select various desktop resolutions for
> display doesn't mean that they are all supposed to be stretched to
> the very edges of your monitor.
>
> To correct for this use any editing program and use the vector
> graphic tools to draw a perfect circle (or square). Make sure you use
> a "lock aspect-ratio" function so that you are not drawing an ellipse
> or rectangle when doing this. Then measure the vertical axis and the
> horizontal axis of the object on your screen. Adjust the vertical and
> horizontal height of your monitor display until the horizontal and
> vertical distances of the circle or square are equal. Now your images
> from all cameras in any software will display as they should no
> matter how you rotate them.
>
> Be prepared to see all your familiar faces in the photos as rounder
> than you have been seeing them. The new and correct aspect ratio will
> be halfway between what you have been seeing before and after
> rotating.
Many thanks for this explanation and simple correction! OK, I lose a little
of the screen top & bottom, but at least the images are identical when
rotated.
Out of interest, do different printers suffer from this effect, too?
Jeff Layman added these comments in the current discussion du
jour ...
> Could someone please explain why, when I rotate a picture 90°
> degrees in a viewing/editing program, the picture is stretched
> so that long faces appear rounder? The actual change (as
> measured with a ruler on the monitor screen) is from 1:1.25 in
> normal view to 1:1.43 in rotated view.
>
> This happens with pictures from Kodak, Pentax, and Ricoh
> digital cameras, when opened and rotated in Irfanview, Kodak,
> Adobe Elements, or The Gimp .
>
You're doing something wrong, Jeff. Simple rotations, whether small
degree or 90 deg. increments will neither elongate nor foreshorten
an image, they simply rotate the pixels. Please explain more of
what you're doing and the results you're getting. e.g., if you're
using some sort of deform tool to do your rotates, you may be
stretching a corner of the image and elongating it. Pure rotates
shouldn't cause a change in aspect ratio.
k. harvey added these comments in the current discussion du jour
....
>>Could someone please explain why, when I rotate a picture 90°
>>degrees in a viewing/editing program, the picture is stretched
>>so that long faces appear rounder? The actual change (as
>>measured with a ruler on the monitor screen) is from 1:1.25 in
>>normal view to 1:1.43 in rotated view.
>>
>>This happens with pictures from Kodak, Pentax, and Ricoh
>>digital cameras, when opened and rotated in Irfanview, Kodak,
>>Adobe Elements, or The Gimp .
>
> It means that your monitor is not correctly adjusted for a 1:1
> aspect ratio. Just because you can select various desktop
> resolutions for display doesn't mean that they are all
> supposed to be stretched to the very edges of your monitor.
How does this affect anything? I have my screen resolution in
Windows set to 1280 x 960 on a normal 4:3 monitor. Are you
talking about a wide-screen monitor where the graphics app or
Windows is doing the stretching to fill the screen, the way that
a normal TV show elongates when viewed incorrectly on a 16:9 HDTV
screen?
> To correct for this use any editing program and use the vector
> graphic tools to draw a perfect circle (or square). Make sure
> you use a "lock aspect-ratio" function so that you are not
> drawing an ellipse or rectangle when doing this. Then measure
> the vertical axis and the horizontal axis of the object on
> your screen. Adjust the vertical and horizontal height of your
> monitor display until the horizontal and vertical distances of
> the circle or square are equal. Now your images from all
> cameras in any software will display as they should no matter
> how you rotate them.
>
> Be prepared to see all your familiar faces in the photos as
> rounder than you have been seeing them. The new and correct
> aspect ratio will be halfway between what you have been seeing
> before and after rotating.
I simply do not understand your recommendation, unless it is
related to the aspect ratio of the monitor and how the image is
zoomed. There are some settings for my video card/monitor
combination that WILL change aspect ratio because they are
designed for other than a standard 4:3 aspect ratio.
As to "lock aspect ratio", that sounds more to me what needs to
be done generally when resizing up or down, not rotating which is
the OP's problem. There are also situations where you WANT to
change the aspect ratio, but that's a different discussion than
this one, to me at least.
John Bean added these comments in the current discussion du jour
....
>>Could someone please explain why, when I rotate a picture 90°
>>degrees in a viewing/editing program, the picture is stretched
>>so that long faces appear rounder? The actual change (as
>>measured with a ruler on the monitor screen) is from 1:1.25 in
>>normal view to 1:1.43 in rotated view.
>
> I suspect you are using an inappropriate resolution that
> doesn't match the aspect ratio of your monitor. Monitors may
> be 5:4, 4:3, or other formats like 16:9. My guess is that
> your monitor is physically 5:4 but you're using a resolution
> intended for 4:3 displays.
That sounds right to me, John. Some people are buying the new wide-
screen LCD monitors and have video adapters that support them.
Improperly used, they WILL mess up the aspect ratio of an image
that was created at 4:3 or the typical DSLR 3:2. BTW, I've never
heard of 5:4 aspect ratio. 4:3 is a throwback to TVs and became the
PC standard in the earliest days of CGA/EGA/VGA adapters. I've
therefore never seen a 5:4 monitor. I see either 4:3 "standard"
monitors or the new wide-screen kind, which may be 16:9 or
something less for Windows vs. HDTV use.
On Sun, 12 Aug 2007 12:10:50 GMT, "HEMI-Powered"
<none@none.en> wrote:
>BTW, I've never
>heard of 5:4 aspect ratio.
Ordinary LCDs (not widescreen) are typically 5:4, like the
1280x1024 display I'm using right now. A similar sized CRT
would have been set to 1280x960 (4:3) instead.
On Sun, 12 Aug 2007 11:41:17 +0100, "Jeff Layman" <jmlayman@thetapetcp.co.uk>
wrote:
>k. harvey wrote:
>> On Sun, 12 Aug 2007 10:24:25 +0100, "Jeff Layman"
>> <jmlayman@thetapetcp.co.uk> wrote:
>>
>>> Could someone please explain why, when I rotate a picture 90°
>>> degrees in a viewing/editing program, the picture is stretched so
>>> that long faces appear rounder? The actual change (as measured with
>>> a ruler on the monitor screen) is from 1:1.25 in normal view to
>>> 1:1.43 in rotated view.
>>>
>>> This happens with pictures from Kodak, Pentax, and Ricoh digital
>>> cameras, when opened and rotated in Irfanview, Kodak, Adobe
>>> Elements, or The Gimp .
>>
>> It means that your monitor is not correctly adjusted for a 1:1 aspect
>> ratio. Just because you can select various desktop resolutions for
>> display doesn't mean that they are all supposed to be stretched to
>> the very edges of your monitor.
>>
>> To correct for this use any editing program and use the vector
>> graphic tools to draw a perfect circle (or square). Make sure you use
>> a "lock aspect-ratio" function so that you are not drawing an ellipse
>> or rectangle when doing this. Then measure the vertical axis and the
>> horizontal axis of the object on your screen. Adjust the vertical and
>> horizontal height of your monitor display until the horizontal and
>> vertical distances of the circle or square are equal. Now your images
>> from all cameras in any software will display as they should no
>> matter how you rotate them.
>>
>> Be prepared to see all your familiar faces in the photos as rounder
>> than you have been seeing them. The new and correct aspect ratio will
>> be halfway between what you have been seeing before and after
>> rotating.
>
>Many thanks for this explanation and simple correction! OK, I lose a little
>of the screen top & bottom, but at least the images are identical when
>rotated.
You can also try different desktop resolutions to see if you like one more than
another so that the visible area fits your monitor's screen more accurately.
Each one produces slightly different aspect ratios. I do well with a 1280x1024
resolution desktop on my monitor with little to no distortion and being able to
use most of the space. It's a bit low for my tastes, but it helps with aspect
ratios. Just a little of the left and right sides become wasted when adjusted to
display perfect circles.
>
>Out of interest, do different printers suffer from this effect, too?
For any printers in the last decade or so, for all intents and purposes, the
answer is no.
However, depending on the thickness of paper used, how accurate the paper-feed
mechanism, how accurate the printing head can move from side to side, there are
*slight* variations in aspect ratios but none so great that you'd probably ever
notice. You would most likely have to measure accurately to notice any
difference between the vertical and horizontal axis in the vast majority of
printers today. Some printers also allow you to lock them in a uni-directional
print-head mode, so that ink is only laid down as the print-head is always going
in the same direction, always starting from the same side. As opposed to
bi-directional printing where ink is laid down in each pass back and forth. This
uni-directional mode used when aspect ratio and ink-dot alignment is of the
utmost importance, but it is much slower so it's not the default mode. In any
case you will not see any distortions in prints as great as you would find on
your monitor. In the past this was not true, with distortions as great or
greater than you saw on your monitor. Printer drivers had to be frequently
tweaked on dot-matrix printers to avoid any aspect-ratio distortions. (I know of
this from first-hand experience by editing the binary code of many of them to
try to make them the least bit accurate.) I have however found aspect-ratio
distortions in some flat-bed scanners that can be terrible at times. Sometimes
even different passes of the exact same scanned material producing two different
sizes in the same axis. Something to watch out for.
> You can also try different desktop resolutions to see if you like one more than
> another so that the visible area fits your monitor's screen more accurately.
> Each one produces slightly different aspect ratios. I do well with a 1280x1024
> resolution desktop on my monitor with little to no distortion and being able to
> use most of the space.
If you are using a typical 4:3 CRT display I recommend using a
resolution of 1280x960 instead - it's got the same aspect ratio as
your display, and you will get square pixels. If you want a higher
resolution, the next step up is 1600x1200, though some display
adapters may offer some in-between options as well - just make sure
that width/height is 1.33333.
(typical 17" LCD's are confusing in that their 1280x1024 resolution actually
does have square pixels. That's because their aspect ratio is 5:4, not 4:3.)
Rotation & aspect ratio 
Linear Mode
