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better to compress the jpeg or reduce resolution or reduce pixel size?



 
 
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  #1  
Old September 23rd 04, 11:29 PM
Mr.Will
external usenet poster
 
Posts: n/a
Default better to compress the jpeg or reduce resolution or reduce pixel size?

Heya guys,

If anyone can offer me some science on the matter I'd be most grateful. I am
taking shots at high jpeg setting on my Canon d60. These files come out
between 3 and 4 Mb.

The people that want the photos want the size to be no bigger than 2mb so
that their server can handle each one. Problem is, with photoshop I arent
entirely sure what is the best way of achieving this file size, or how to
calculate it without saving as a different filename and previewing using the
"properties" of the image icon.

If I reduce resolution this brings down the file size, as does reducing the
image dimensions (pixels) as does compressing. Which would you reccomend as
the best method? I notice photoshop has THREE maximum settings (10,11,12).

Also I arent entirely sure how much of each does to the filesize. For
instance I started with a 3 mb file, I reduced it in size and saved it, and
the file, despite being smaller was now 3.5 mb!!!

Any light ANYONE can shed will be most appreciated.

Mr.Will


  #2  
Old September 23rd 04, 11:37 PM
Not Dick Daley
external usenet poster
 
Posts: n/a
Default

If you decrease the resolution of the pictures via Photoshop, Paint Shop Pro
etc....you're losing picture image quality.

If you simply reduce the photo size in the camera, it will be more than
sufficient for viewing, unless you're going to blow these things up.

It's best likened to developing an 8X10 of a photo that was shot at 100 ISO,
to doing the same picture 8X10 of a photo using 800 ISO.

I use Paint Shop Pro's Photo Album sofware. It's GREAT for batch resizing
(or renaming) of photo's. I can do 50 12MB files into 50 500k files in
about 20 minutes. If you did them individually....it'd take all night!

Hope this helped you a bit.


"Mr.Will" wrote in message
...
Heya guys,

If anyone can offer me some science on the matter I'd be most grateful. I

am
taking shots at high jpeg setting on my Canon d60. These files come out
between 3 and 4 Mb.

The people that want the photos want the size to be no bigger than 2mb so
that their server can handle each one. Problem is, with photoshop I arent
entirely sure what is the best way of achieving this file size, or how to
calculate it without saving as a different filename and previewing using

the
"properties" of the image icon.

If I reduce resolution this brings down the file size, as does reducing

the
image dimensions (pixels) as does compressing. Which would you reccomend

as
the best method? I notice photoshop has THREE maximum settings (10,11,12).

Also I arent entirely sure how much of each does to the filesize. For
instance I started with a 3 mb file, I reduced it in size and saved it,

and
the file, despite being smaller was now 3.5 mb!!!

Any light ANYONE can shed will be most appreciated.

Mr.Will




  #3  
Old September 23rd 04, 11:37 PM
Not Dick Daley
external usenet poster
 
Posts: n/a
Default

If you decrease the resolution of the pictures via Photoshop, Paint Shop Pro
etc....you're losing picture image quality.

If you simply reduce the photo size in the camera, it will be more than
sufficient for viewing, unless you're going to blow these things up.

It's best likened to developing an 8X10 of a photo that was shot at 100 ISO,
to doing the same picture 8X10 of a photo using 800 ISO.

I use Paint Shop Pro's Photo Album sofware. It's GREAT for batch resizing
(or renaming) of photo's. I can do 50 12MB files into 50 500k files in
about 20 minutes. If you did them individually....it'd take all night!

Hope this helped you a bit.


"Mr.Will" wrote in message
...
Heya guys,

If anyone can offer me some science on the matter I'd be most grateful. I

am
taking shots at high jpeg setting on my Canon d60. These files come out
between 3 and 4 Mb.

The people that want the photos want the size to be no bigger than 2mb so
that their server can handle each one. Problem is, with photoshop I arent
entirely sure what is the best way of achieving this file size, or how to
calculate it without saving as a different filename and previewing using

the
"properties" of the image icon.

If I reduce resolution this brings down the file size, as does reducing

the
image dimensions (pixels) as does compressing. Which would you reccomend

as
the best method? I notice photoshop has THREE maximum settings (10,11,12).

Also I arent entirely sure how much of each does to the filesize. For
instance I started with a 3 mb file, I reduced it in size and saved it,

and
the file, despite being smaller was now 3.5 mb!!!

Any light ANYONE can shed will be most appreciated.

Mr.Will




  #4  
Old September 24th 04, 12:30 AM
Peter
external usenet poster
 
Posts: n/a
Default

On Thu, 23 Sep 2004 22:29:09 GMT, Mr.Will wrote:

If anyone can offer me some science on the matter I'd be most grateful. I am
taking shots at high jpeg setting on my Canon d60. These files come out
between 3 and 4 Mb.

The people that want the photos want the size to be no bigger than 2mb so
that their server can handle each one....


The pixel dimensions you want are primarily determined by how someone will
view your images. If they're always going to be viewed on a 800x600
computer screen, there is no point in making the image pixel size bigger
than that. On the other hand, if the images are going to be printed in high
quality, you should plan on 100-300 pixels per inch of printed size. (This
wide range reflects differing opinions on this).

Once you have determined the pixel dimensions, the file size will be
determined by the amount of detail in each image and by the JPEG
compression level (or inversely the quality setting).

[In tests I conducted on photo images with the same pixel dimensions and
the same JPEG compression level, file sizes vary over a range of more than
3-to-1, depending on the detail present in the images.]

Sounds like you could use a versatile image resizer that will automatically
figure out what JPEG compression level is needed to achieve your desired
file size. Suggest you try the link below.

Peter
--

================================================== =======
Need to resize images for email attachments or web pages?
Try Jpeg Sizer at: http://www.tangotools.com?s=ng
================================================== =======
  #5  
Old September 24th 04, 12:30 AM
Peter
external usenet poster
 
Posts: n/a
Default

On Thu, 23 Sep 2004 22:29:09 GMT, Mr.Will wrote:

If anyone can offer me some science on the matter I'd be most grateful. I am
taking shots at high jpeg setting on my Canon d60. These files come out
between 3 and 4 Mb.

The people that want the photos want the size to be no bigger than 2mb so
that their server can handle each one....


The pixel dimensions you want are primarily determined by how someone will
view your images. If they're always going to be viewed on a 800x600
computer screen, there is no point in making the image pixel size bigger
than that. On the other hand, if the images are going to be printed in high
quality, you should plan on 100-300 pixels per inch of printed size. (This
wide range reflects differing opinions on this).

Once you have determined the pixel dimensions, the file size will be
determined by the amount of detail in each image and by the JPEG
compression level (or inversely the quality setting).

[In tests I conducted on photo images with the same pixel dimensions and
the same JPEG compression level, file sizes vary over a range of more than
3-to-1, depending on the detail present in the images.]

Sounds like you could use a versatile image resizer that will automatically
figure out what JPEG compression level is needed to achieve your desired
file size. Suggest you try the link below.

Peter
--

================================================== =======
Need to resize images for email attachments or web pages?
Try Jpeg Sizer at: http://www.tangotools.com?s=ng
================================================== =======
  #6  
Old September 24th 04, 01:39 AM
Bob
external usenet poster
 
Posts: n/a
Default

On Thu, 23 Sep 2004 22:29:09 GMT, "Mr.Will" wrote:

Heya guys,

If anyone can offer me some science on the matter I'd be most grateful. I am
taking shots at high jpeg setting on my Canon d60. These files come out
between 3 and 4 Mb.

The people that want the photos want the size to be no bigger than 2mb so
that their server can handle each one.


First - you need to know what dimensions are needed, not the file size...

Once you know that, you can worry about the file size...

But generally speaking, for the Internet, you decrease file size by increasing
the compression of the image. This is because Internet images are usually just
for viewing, and not blowing up or printing, therefore you can get away with
huge compressions.

On my own web site, I re-size to 1024x680 or so, to fit the biggest screen, and
then I compress to an average 125k bytes. The originals are 3m, 3000x2000....

I use Micrografx software but Photoshop has a 'quality' option in saving as
well.

You need to manipulate both the image size and image compression to achieve the
results you want.


Problem is, with photoshop I arent
entirely sure what is the best way of achieving this file size, or how to
calculate it without saving as a different filename and previewing using the
"properties" of the image icon.

If I reduce resolution this brings down the file size, as does reducing the
image dimensions (pixels) as does compressing. Which would you reccomend as
the best method? I notice photoshop has THREE maximum settings (10,11,12).

Also I arent entirely sure how much of each does to the filesize. For
instance I started with a 3 mb file, I reduced it in size and saved it, and
the file, despite being smaller was now 3.5 mb!!!

Any light ANYONE can shed will be most appreciated.

Mr.Will


  #7  
Old September 24th 04, 01:39 AM
Bob
external usenet poster
 
Posts: n/a
Default

On Thu, 23 Sep 2004 22:29:09 GMT, "Mr.Will" wrote:

Heya guys,

If anyone can offer me some science on the matter I'd be most grateful. I am
taking shots at high jpeg setting on my Canon d60. These files come out
between 3 and 4 Mb.

The people that want the photos want the size to be no bigger than 2mb so
that their server can handle each one.


First - you need to know what dimensions are needed, not the file size...

Once you know that, you can worry about the file size...

But generally speaking, for the Internet, you decrease file size by increasing
the compression of the image. This is because Internet images are usually just
for viewing, and not blowing up or printing, therefore you can get away with
huge compressions.

On my own web site, I re-size to 1024x680 or so, to fit the biggest screen, and
then I compress to an average 125k bytes. The originals are 3m, 3000x2000....

I use Micrografx software but Photoshop has a 'quality' option in saving as
well.

You need to manipulate both the image size and image compression to achieve the
results you want.


Problem is, with photoshop I arent
entirely sure what is the best way of achieving this file size, or how to
calculate it without saving as a different filename and previewing using the
"properties" of the image icon.

If I reduce resolution this brings down the file size, as does reducing the
image dimensions (pixels) as does compressing. Which would you reccomend as
the best method? I notice photoshop has THREE maximum settings (10,11,12).

Also I arent entirely sure how much of each does to the filesize. For
instance I started with a 3 mb file, I reduced it in size and saved it, and
the file, despite being smaller was now 3.5 mb!!!

Any light ANYONE can shed will be most appreciated.

Mr.Will


  #8  
Old September 24th 04, 01:42 AM
Tony Morgan
external usenet poster
 
Posts: n/a
Default

In message , Not Dick Daley
writes
Snipped...

It's best likened to developing an 8X10 of a photo that was shot at 100
ISO, to doing the same picture 8X10 of a photo using 800 ISO.


Really? I always thought that the higher ISO introduced noise and not
artefacts, but that it did not reduce resolution.

In answer to the OP, I'd suggest that it's best to shoot at max
resolution (pixels) and minimum compression, then to resample to the
size that you require in your photo editing software.
--
Tony Morgan
http://www.camcord.info
  #9  
Old September 24th 04, 01:42 AM
Tony Morgan
external usenet poster
 
Posts: n/a
Default

In message , Not Dick Daley
writes
Snipped...

It's best likened to developing an 8X10 of a photo that was shot at 100
ISO, to doing the same picture 8X10 of a photo using 800 ISO.


Really? I always thought that the higher ISO introduced noise and not
artefacts, but that it did not reduce resolution.

In answer to the OP, I'd suggest that it's best to shoot at max
resolution (pixels) and minimum compression, then to resample to the
size that you require in your photo editing software.
--
Tony Morgan
http://www.camcord.info
  #10  
Old September 24th 04, 02:08 AM
Tony Morgan
external usenet poster
 
Posts: n/a
Default

In message , Bob
writes
But generally speaking, for the Internet, you decrease file size by
increasing the compression of the image.


Do so with great care. Increasing compression introduces artefacts. And
never resize (again it introduces artefacts), but rather resample to
size.
--
Tony Morgan
http://www.camcord.info
 




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