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best compression for saving photos in jpeg?

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December 23, 2004 4:51:56 AM

Archived from groups: rec.photo.digital (More info?)

What is the best compression (1 - 100%) to use when saving a scanned
colour photo in jpeg?
I was to be able to display the photo on the computer screen and also
be able to print the saved photo on a inkjet printer.

If I have very little compression then the saved photo file size is
too big in size. Is there a general rule I can use to decide the best
compression to use?

Regards Brian
Anonymous
December 23, 2004 4:51:57 AM

Archived from groups: rec.photo.digital (More info?)

On Thu, 23 Dec 2004 01:51:56 +1300, Brian <bclark@es.co.nz> wrote:

>What is the best compression (1 - 100%) to use when saving a scanned
>colour photo in jpeg?
>I was to be able to display the photo on the computer screen and also
>be able to print the saved photo on a inkjet printer.
>
>If I have very little compression then the saved photo file size is
>too big in size. Is there a general rule I can use to decide the best
>compression to use?

0% .. :-) jpg being a "lossy" compression every compression factor
applied will degrade picture quality ... so you will have to balance
between picture size and stored/needed/expected quality ..
(Paintshop pro 9 has a nice (save_as/optimizer) feature that will show
you picture deterioration versus compression factor applied ... )
FWIW
Anonymous
December 23, 2004 4:51:57 AM

Archived from groups: rec.photo.digital (More info?)

Brian wrote:
> What is the best compression (1 - 100%) to use when saving a scanned
> colour photo in jpeg?
> I was to be able to display the photo on the computer screen and also
> be able to print the saved photo on a inkjet printer.
>
> If I have very little compression then the saved photo file size is
> too big in size. Is there a general rule I can use to decide the best
> compression to use?

You need to determine this for yourself - what is acceptable to one person
may not be to another. Printing is likely to require a higher quality of
image than display on the computer screen (as the screen is limited to
about 1MP and your scan is likely to be more than that). You also need to
be sure that you are scanning to a sufficient number of pixels per inch.

David
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December 23, 2004 4:51:57 AM

Archived from groups: rec.photo.digital (More info?)

I tend to use:

For best quality printing or editting later 1 to 5% (assuming you need to
save space and do not want to use TIFF etc)
For viewing on PC or 'general' printing 10%
For internet 15 to 25 %

"Brian" <bclark@es.co.nz> wrote in message
news:a8ris0ddj1haksfgpgetrdkculjgck8mjn@4ax.com...
> What is the best compression (1 - 100%) to use when saving a scanned
> colour photo in jpeg?
> I was to be able to display the photo on the computer screen and also
> be able to print the saved photo on a inkjet printer.
>
> If I have very little compression then the saved photo file size is
> too big in size. Is there a general rule I can use to decide the best
> compression to use?
>
> Regards Brian
>
>
Anonymous
December 23, 2004 4:51:57 AM

Archived from groups: rec.photo.digital (More info?)

Brian <bclark@es.co.nz> writes:

> What is the best compression (1 - 100%) to use when saving a scanned
> colour photo in jpeg?

It sounds like the compression factor in the program you're using is
reversed from the -quality switch in the cjpeg program I use, so switch 0%
and 100% in the information below, from cjpeg's manual page.

I personally find quality 75 to work well even with photos that have
lots of high-contrast transitions.

The -quality switch lets you trade off compressed file size against
quality of the reconstructed image: the higher the quality setting, the
larger the JPEG file, and the closer the output image will be to the
original input. Normally you want to use the lowest quality setting
(smallest file) that decompresses into something visually indistin-
guishable from the original image. For this purpose the quality set-
ting should be between 50 and 95; the default of 75 is often about
right. If you see defects at -quality 75, then go up 5 or 10 counts at
a time until you are happy with the output image. (The optimal setting
will vary from one image to another.)

-quality 100 will generate a quantization table of all 1's, minimizing
loss in the quantization step (but there is still information loss in
subsampling, as well as roundoff error). This setting is mainly of
interest for experimental purposes. Quality values above about 95 are
not recommended for normal use; the compressed file size goes up dra-
matically for hardly any gain in output image quality.

In the other direction, quality values below 50 will produce very small
files of low image quality. Settings around 5 to 10 might be useful in
preparing an index of a large image library, for example. Try -quality
2 (or so) for some amusing Cubist effects. (Note: quality values below
about 25 generate 2-byte quantization tables, which are considered
optional in the JPEG standard. cjpeg emits a warning message when you
give such a quality value, because some other JPEG programs may be
unable to decode the resulting file. Use -baseline if you need to
ensure compatibility at low quality values.)



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December 23, 2004 4:51:57 AM

Archived from groups: rec.photo.digital (More info?)

"Brian" <bclark@es.co.nz> wrote in message
news:a8ris0ddj1haksfgpgetrdkculjgck8mjn@4ax.com...
> What is the best compression (1 - 100%) to use when saving a scanned
> colour photo in jpeg?
"Best" with respect to what?
"Best quality" = least amount of compression
"Best size" = most amount of compression.
Most people select a medium compression value, and that might be OK for you
provided that you do not edit the image very many times.
Jim
December 23, 2004 4:51:58 AM

Archived from groups: rec.photo.digital (More info?)

My figures are from PSP where 1 is highest quality and goes down to 100
which is highest compression.

"dylan" <spam@none.com> wrote in message
news:cqbs4u$3ih$1@news7.svr.pol.co.uk...
>I tend to use:
>
> For best quality printing or editting later 1 to 5% (assuming you need to
> save space and do not want to use TIFF etc)
> For viewing on PC or 'general' printing 10%
> For internet 15 to 25 %
>
> "Brian" <bclark@es.co.nz> wrote in message
> news:a8ris0ddj1haksfgpgetrdkculjgck8mjn@4ax.com...
>> What is the best compression (1 - 100%) to use when saving a scanned
>> colour photo in jpeg?
>> I was to be able to display the photo on the computer screen and also
>> be able to print the saved photo on a inkjet printer.
>>
>> If I have very little compression then the saved photo file size is
>> too big in size. Is there a general rule I can use to decide the best
>> compression to use?
>>
>> Regards Brian
>>
>>
>
>
Anonymous
December 23, 2004 6:07:46 AM

Archived from groups: rec.photo.digital (More info?)

Brian wrote:
> What is the best compression (1 - 100%) to use when saving a scanned
> colour photo in jpeg?
> I was to be able to display the photo on the computer screen and also
> be able to print the saved photo on a inkjet printer.
>
> If I have very little compression then the saved photo file size is
> too big in size. Is there a general rule I can use to decide the best
> compression to use?
>
> Regards Brian
>
>
Use the minimum compression that will give you the file size you need
for your purpose. The more you compress, the more data you lose.
Always save the original. Remember, HD space is something like $.50US a
gigabyte these days, so adding HD space is a pretty cheap alternative.


--
Ron Hunter rphunter@charter.net
Anonymous
December 23, 2004 6:07:47 AM

Archived from groups: rec.photo.digital (More info?)

"Ron Hunter" <rphunter@charter.net> schrieb
> Brian wrote:
>> What is the best compression (1 - 100%) to use when saving a scanned
>> colour photo in jpeg?

> Use the minimum compression that will give you the file size you need for
> your purpose. The more you compress, the more data you lose. Always save
> the original. Remember, HD space is something like $.50US a gigabyte
> these days, so adding HD space is a pretty cheap alternative.

I can second that.
And 95% quality level really gives you the optimal value to start with.
A 100% doesn't scale to the gain you get for quality and everything less is
covered by the 50 cent/GB (nice value BTW ;)  )

--
Regards
Jürgen
http://cpicture.de/en
Anonymous
December 23, 2004 9:49:21 AM

Archived from groups: rec.photo.digital (More info?)

Jürgen Eidt wrote:
> "Ron Hunter" <rphunter@charter.net> schrieb
>
>>Brian wrote:
>>
>>>What is the best compression (1 - 100%) to use when saving a scanned
>>>colour photo in jpeg?
>
>
>>Use the minimum compression that will give you the file size you need for
>>your purpose. The more you compress, the more data you lose. Always save
>>the original. Remember, HD space is something like $.50US a gigabyte
>>these days, so adding HD space is a pretty cheap alternative.
>
>
> I can second that.
> And 95% quality level really gives you the optimal value to start with.
> A 100% doesn't scale to the gain you get for quality and everything less is
> covered by the 50 cent/GB (nice value BTW ;)  )
>
Yes, considering that only a very few years ago, a 1GB HD cost $2200!!!!
Amazing!

--
Ron Hunter rphunter@charter.net
Anonymous
December 23, 2004 11:32:08 AM

Archived from groups: rec.photo.digital (More info?)

Ron Hunter <rphunter@charter.net> writes:

> Always save the original. Remember, HD space is something like
> $.50US a gigabyte these days, so adding HD space is a pretty cheap
> alternative.

I agree that you should always save the original. However, isn't that
50cent number ignoring the time/money required to keep things backed up?


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December 25, 2004 4:59:08 AM

Archived from groups: rec.photo.digital (More info?)

"Jim" <j.n@nospam.com> wrote:

>
>"Brian" <bclark@es.co.nz> wrote in message
>news:a8ris0ddj1haksfgpgetrdkculjgck8mjn@4ax.com...
>> What is the best compression (1 - 100%) to use when saving a scanned
>> colour photo in jpeg?
>"Best" with respect to what?
>"Best quality" = least amount of compression
>"Best size" = most amount of compression.
>Most people select a medium compression value, and that might be OK for you
>provided that you do not edit the image very many times.
>Jim
>
I just want to scan some camera photos that I borrowed.
I may not have access to the photos again as they will be sent
overseas, so I need a good scan job.

Regards Brian
!