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Resizing Images - How to get best quality outcome

 
 
Alan
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      11-08-2008
Hi All,

I am resizing images and I would like to understand how to get the
best outcome possible when printing (ignoring the issue of the paper
type).

I am using IrfanView v4 but my question is generic I think.

For example, I have an image that is:

4000 x 2670 pixels at 300dpi = 338.7mm x 226.1mm

I would like to rezise the image to be a native 290mm x 194mm (more or
less - the aspect ratio being unchanged).

I could do this by at least one of the following approaches (or
another that you suggest!):


1) Reducing the pixels to be 3425 x 2286 still at 300dpi

What does this actually do though? Does the computer go through and
average out the pixels (when reducing the number) hence creating
fuzziness?


2) Maintaining the pixels at 4000 x 2670 but increasing the resolution
to 350dpi

On the face of it, it seems non-sensical to increase the resolution of
an existing image, but the number of pixels remain the same, so there
is no averaging of pixels to worry about.


3) Should I be taking into account the maximum resolution of my
printer? It is an HP Laserjet with maximum resolution setting of
ImageREt 2400 - I guess that means 2400dpi?

If I aim for 2400dpi, then I would change the pixels to:

27402 x 18291 at 2400dpi = 290mm x 194mm

Perhaps that is the best approach, since adding more pixels appears
less 'lossy' than taking them out?



Is there one best way to do this?

Thanks,

--

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Your Name
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      11-08-2008

"Alan" <(E-Mail Removed)> wrote in message news:gf54ck$snl$(E-Mail Removed)...
> Hi All,
>
> I am resizing images and I would like to understand how to get the
> best outcome possible when printing (ignoring the issue of the paper
> type).
>
> I am using IrfanView v4 but my question is generic I think.
>
> For example, I have an image that is:
>
> 4000 x 2670 pixels at 300dpi = 338.7mm x 226.1mm
>
> I would like to rezise the image to be a native 290mm x 194mm (more or
> less - the aspect ratio being unchanged).
>
> I could do this by at least one of the following approaches (or
> another that you suggest!):
>
>
> 1) Reducing the pixels to be 3425 x 2286 still at 300dpi
>
> What does this actually do though? Does the computer go through and
> average out the pixels (when reducing the number) hence creating
> fuzziness?
>
>
> 2) Maintaining the pixels at 4000 x 2670 but increasing the resolution
> to 350dpi
>
> On the face of it, it seems non-sensical to increase the resolution of
> an existing image, but the number of pixels remain the same, so there
> is no averaging of pixels to worry about.
>
>
> 3) Should I be taking into account the maximum resolution of my
> printer? It is an HP Laserjet with maximum resolution setting of
> ImageREt 2400 - I guess that means 2400dpi?
>
> If I aim for 2400dpi, then I would change the pixels to:
>
> 27402 x 18291 at 2400dpi = 290mm x 194mm
>
> Perhaps that is the best approach, since adding more pixels appears
> less 'lossy' than taking them out?
>
>
>
> Is there one best way to do this?
>
> Thanks,


Printing to a laser printer or inkjet printer with a resolution of more than
150dpi is pretty pointless (assuming you are printing the image at 100% of
it's X-Y mm size). It simply wastes time sending data that the printer
doesn't print anyway.The printer may say it's resolution is 600dpi, 1200dpi,
2400dpi etc., but that's when printing in only one-bit depth pages (ie. pure
black or white). A colour / grayscale image is made of of multiple dots
printed in a pattern to fool the eye into seeing a certain colour, as can be
seen in old newspapers and comic books when the dots were bigger.

You are also wasting time when you scale a large image down after inserting
it into a Word document (or InDesign, etc.) since the application is still
sending data the printer doesn't use. Images should always be printed at
100% of their X-Y mm size. Images on websites should also be displayed at
100% of their X-Y size, and at a resolution of 72pdi - 96dpi.

Reduce the resolution of the image to 150dpi. Then scale the image to the
290mm x 194mm in Photoshop or whatever application you're using. The image
may go slightly blurry / lose small detail since the application has to
average the pixels (ie. if you were scaling by 50%, then every four pixels,
two X and two Y, has to become one pixel). In Photoshop or similar you can
carefully use a sharpen function to clean it up a bit if it's really
noticeable once printed ... to a large extent ignore what's on-screen since
a screen only has a resolution of 72dpi - 96dpi and will display the images
as blurry anyway.

And ignore what some idiots will try tell you about resolution being
irrelevant ... it's not, which is why a professional print company or
newspaper will ALWAYS say to send them images at particular resolutions for
the process they are using.


 
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Alan
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      11-09-2008


"Your Name" <(E-Mail Removed)> wrote in message
news:gf56j8$hui$(E-Mail Removed)...
>
>
> Printing to a laser printer or inkjet printer with a resolution of
> more than
> 150dpi is pretty pointless (assuming you are printing the image at
> 100% of
> it's X-Y mm size). It simply wastes time sending data that the
> printer
> doesn't print anyway.The printer may say it's resolution is 600dpi,
> 1200dpi,
> 2400dpi etc., but that's when printing in only one-bit depth pages
> (ie. pure
> black or white). A colour / grayscale image is made of of multiple
> dots
> printed in a pattern to fool the eye into seeing a certain colour,
> as can be
> seen in old newspapers and comic books when the dots were bigger.
>


Hi,

Whilst it may be a waste of time, will I get a worse outcome if I send
a 2400dpi image to a printer that actually only does 150dpi?

Is it different if I send a 2400dpi image to a 250dpi printer?

I chose those numbers to ask the generic question as to whether I will
get a better outcome by the dpi of the image being an exact integer
multiple of the dpi of the printer, as opposed to a non-integer
multiple?

>
> You are also wasting time when you scale a large image down after
> inserting
> it into a Word document (or InDesign, etc.) since the application is
> still
> sending data the printer doesn't use. Images should always be
> printed at
> 100% of their X-Y mm size. Images on websites should also be
> displayed at
> 100% of their X-Y size, and at a resolution of 72pdi - 96dpi.
>


Okay - I'm not doing any of that, but noted.

>
> Reduce the resolution of the image to 150dpi. Then scale the image
> to the
> 290mm x 194mm in Photoshop or whatever application you're using. The
> image
> may go slightly blurry / lose small detail since the application has
> to
> average the pixels (ie. if you were scaling by 50%, then every four
> pixels,
> two X and two Y, has to become one pixel). In Photoshop or similar
> you can
> carefully use a sharpen function to clean it up a bit if it's really
> noticeable once printed ... to a large extent ignore what's
> on-screen since
> a screen only has a resolution of 72dpi - 96dpi and will display the
> images
> as blurry anyway.
>
> And ignore what some idiots will try tell you about resolution being
> irrelevant ... it's not, which is why a professional print company
> or
> newspaper will ALWAYS say to send them images at particular
> resolutions for
> the process they are using.
>
>


Thanks,

--

Alan.

The views expressed are my own, and not those of my employer or anyone
else associated with me.

My current valid email address is:

(E-Mail Removed)

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Alan
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Posts: n/a
 
      11-09-2008


"ChristianKnight" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...


Try opening a picture with the standard paint program and resizing
there.
You should have a clearer picture with the smaller
Christ's love


Hi,

Thanks for that.

Which of the three options will give me the *best* printed results (in
the general case)?

Thanks,

--

Alan.

The views expressed are my own, and not those of my employer or anyone
else associated with me.

My current valid email address is:

(E-Mail Removed)

This is valid as is. It is not munged, or altered at all.

It will be valid for AT LEAST one month from the date of this post.

If you are trying to contact me after that time,
it MAY still be valid, but may also have been
deactivated due to spam. If so, and you want
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email address.

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Alan
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      11-09-2008



"OZZY Boy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Sun, 9 Nov 2008 11:36:33 +1300, "Alan" <(E-Mail Removed)> wrote:
>
>>Hi All,
>>
>>I am resizing images and I would like to understand how to get the
>>best outcome possible when printing (ignoring the issue of the paper
>>type).
>>
>>

>
>
> Go post this on the Many Photo news groups, then you should get
> facts not just guess here..
>
>


Hi,

Thanks for replying.

I may do that, but since I posted here, I'll engage the answers I get
first, then see how it goes.

Thanks,

--

Alan.

The views expressed are my own, and not those of my employer or anyone
else associated with me.

My current valid email address is:

(E-Mail Removed)

This is valid as is. It is not munged, or altered at all.

It will be valid for AT LEAST one month from the date of this post.

If you are trying to contact me after that time,
it MAY still be valid, but may also have been
deactivated due to spam. If so, and you want
to contact me by email, try searching for a
more recent post by me to find my current
email address.

The following is a (probably!) totally unique
and meaningless string of characters that you
can use to find posts by me in a search engine:

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Lawrence D'Oliveiro
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Posts: n/a
 
      11-09-2008
In message <gf6arq$8fq$(E-Mail Removed)>, Alan wrote:

> Whilst it may be a waste of time, will I get a worse outcome if I send
> a 2400dpi image to a printer that actually only does 150dpi?


Honestly, once you get up to numbers that large, I wouldn't worry about it.

> I chose those numbers to ask the generic question as to whether I will
> get a better outcome by the dpi of the image being an exact integer
> multiple of the dpi of the printer, as opposed to a non-integer
> multiple?


There are different kinds of resampling algorithm, giving various tradeoffs
between image quality versus computational simplicity. Last time I looked
at Photoshop, for example, it gave you a choice between simple bilinear
interpolation versus a more complex bicubic (slower, but better-quality)
interpolation.

With the better algorithms, and with typical photographic images, it makes
very little difference whether the scaling ratio is an integer or not. And
also, if the pixel density remains above 150dpi, it's going to be rather
hard to tell the difference anyway.
 
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Enkidu
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Posts: n/a
 
      11-09-2008
Alan wrote:
>
> Thanks for replying.
>
> I may do that, but since I posted here, I'll engage the answers I get
> first, then see how it goes.
>

Hmm, Roger's replies are, by rule of thumb, less than correct or
helpful. I'll just say that same model printers *can* produce vastly
different results. It might be best to experiment.

Cheers,

Cliff

--

Tax is not theft.
 
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Alan
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Posts: n/a
 
      11-09-2008


"Lawrence D'Oliveiro" <(E-Mail Removed)_zealand> wrote in
message news:gf6b5j$7k7$(E-Mail Removed)...
> In message <gf6arq$8fq$(E-Mail Removed)>, Alan wrote:
>
>> Whilst it may be a waste of time, will I get a worse outcome if I
>> send
>> a 2400dpi image to a printer that actually only does 150dpi?

>
> Honestly, once you get up to numbers that large, I wouldn't worry
> about it.
>
>> I chose those numbers to ask the generic question as to whether I
>> will
>> get a better outcome by the dpi of the image being an exact integer
>> multiple of the dpi of the printer, as opposed to a non-integer
>> multiple?

>
> There are different kinds of resampling algorithm, giving various
> tradeoffs
> between image quality versus computational simplicity. Last time I
> looked
> at Photoshop, for example, it gave you a choice between simple
> bilinear
> interpolation versus a more complex bicubic (slower, but
> better-quality)
> interpolation.
>
> With the better algorithms, and with typical photographic images, it
> makes
> very little difference whether the scaling ratio is an integer or
> not. And
> also, if the pixel density remains above 150dpi, it's going to be
> rather
> hard to tell the difference anyway.


Hi Lawrence,

Once the image has been created (in whatever application), if I send
it to print, there will be further processing though, with the
exception of whatever the printer driver on the PC, and then the
printer itself does (I think!)

If that is the case, then the algorithm used to get to the end image
won't come into it per se?

So, if I take the same image, and resample it to 600dpi and also
500dpi, then send each of those to print to a printer with a 150dpi
maximum resolution, from a pure image viewing / printing application,
will the 600dpi image come out better than the 500dpi image (in
general)?

Thanks,

--

Alan.

The views expressed are my own, and not those of my employer or anyone
else associated with me.

My current valid email address is:

(E-Mail Removed)

This is valid as is. It is not munged, or altered at all.

It will be valid for AT LEAST one month from the date of this post.

If you are trying to contact me after that time,
it MAY still be valid, but may also have been
deactivated due to spam. If so, and you want
to contact me by email, try searching for a
more recent post by me to find my current
email address.

The following is a (probably!) totally unique
and meaningless string of characters that you
can use to find posts by me in a search engine:

ewygchvboocno43vb674b6nq46tvb



 
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Alan
Guest
Posts: n/a
 
      11-09-2008


"Enkidu" <(E-Mail Removed)> wrote in message
news:4916b0ab$(E-Mail Removed)...
> Alan wrote:
>>
>> Thanks for replying.
>>
>> I may do that, but since I posted here, I'll engage the answers I
>> get first, then see how it goes.
>>

> Hmm, Roger's replies are, by rule of thumb, less than correct or
> helpful. I'll just say that same model printers *can* produce vastly
> different results. It might be best to experiment.
>
> Cheers,
>
> Cliff
>
> --
>
> Tax is not theft.


Hi Cliff,

Absolutely! For a single printer, and given time, I would definately
just try the various options.

However, I was looking for a more generic approach that would work
across images and printers, such that it would be *likely* (no
guarantees of course) to give the best quality outcome from a given
image / printer.

Hope that makes sense!

--

Alan.

The views expressed are my own, and not those of my employer or anyone
else associated with me.

My current valid email address is:

(E-Mail Removed)

This is valid as is. It is not munged, or altered at all.

It will be valid for AT LEAST one month from the date of this post.

If you are trying to contact me after that time,
it MAY still be valid, but may also have been
deactivated due to spam. If so, and you want
to contact me by email, try searching for a
more recent post by me to find my current
email address.

The following is a (probably!) totally unique
and meaningless string of characters that you
can use to find posts by me in a search engine:

ewygchvboocno43vb674b6nq46tvb



 
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Your Name
Guest
Posts: n/a
 
      11-09-2008

"Alan" <(E-Mail Removed)> wrote in message news:gf6arq$8fq$(E-Mail Removed)...
>
> Hi,
>
> Whilst it may be a waste of time, will I get a worse outcome if I send
> a 2400dpi image to a printer that actually only does 150dpi?
>
> Is it different if I send a 2400dpi image to a 250dpi printer?
>
> I chose those numbers to ask the generic question as to whether I will
> get a better outcome by the dpi of the image being an exact integer
> multiple of the dpi of the printer, as opposed to a non-integer
> multiple?


There's no point in going above 150dpi with a desktop printer. The printer
will simply throw away the extra dots, so you're just extending the time it
takes to send all those extra dots across the printer connection. As to
whether a higher dpi image will give a "better" printout, you are not going
to notice any real difference.

Changing the resolution of the image doesn't affect the image's data in any
way (assuming you are keeping the number of X-Y pixels the same). It's when
you scale the image that you lose pixels and it gets a little blurrier.


 
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