Resolution or Compression?

All digicams provide several resolution levels and compression levels. Using the highest resolution and the lowest compression produces maximum image file sizes. If you wanted to pack more photos into your card, you would have to reduce file sizes by either reducing resolution, by increasing compression, or both.

When is increasing compression better than reducing resolution?

And when is reducing resolution better than increasing compression?

Regards - JW

Reducing either is ill advised. If the detail is not on the chip then it can
never be in the photo. Don't think of it as a compromise from best
JPG...best JPG is a compromise. Its best to take RAW files....some cameras
can't do that so their best is TIF. Both of these take a lot of chip space
and time between shots so many of us advocate the compromise of best JPG.
Any more compromise is too much. Buy another chip.

That being said....try it and see. Take the same shot at all levels of JPG
and print using a wet process (normal photo print processing) at 8x10 to see
if you can see a difference. If you start with a 12 mp camera then maybe a
smaller number of pixels is ok....you don't say what you start with.


"John Wright" wrote in message
u...
All digicams provide several resolution levels and compression levels. Using
the highest resolution and the lowest compression produces maximum image
file sizes. If you wanted to pack more photos into your card, you would have
to reduce file sizes by either reducing resolution, by increasing
compression, or both.

When is increasing compression better than reducing resolution?

And when is reducing resolution better than increasing compression?

Regards - JW

Reducing either is ill advised. If the detail is not on the chip then it can
never be in the photo. Don't think of it as a compromise from best
JPG...best JPG is a compromise. Its best to take RAW files....some cameras
can't do that so their best is TIF. Both of these take a lot of chip space
and time between shots so many of us advocate the compromise of best JPG.
Any more compromise is too much. Buy another chip.

That being said....try it and see. Take the same shot at all levels of JPG
and print using a wet process (normal photo print processing) at 8x10 to see
if you can see a difference. If you start with a 12 mp camera then maybe a
smaller number of pixels is ok....you don't say what you start with.


"John Wright" wrote in message
u...
All digicams provide several resolution levels and compression levels. Using
the highest resolution and the lowest compression produces maximum image
file sizes. If you wanted to pack more photos into your card, you would have
to reduce file sizes by either reducing resolution, by increasing
compression, or both.

When is increasing compression better than reducing resolution?

And when is reducing resolution better than increasing compression?

Regards - JW

John Wright writes:

When is increasing compression better than reducing resolution?

They resolve to the same thing, actually. A highly compressed image of
large dimensions will be no more detailed than an uncompressed image of
small dimensions. So it's your call.

In general, I tend to increase compression when I reduce size, instead
of the opposite. The logic is that any image that is really small
doesn't have to have much detail, anyway, since file size is probably
the real issue, so why not just increase compression as well? For very
high-resolution photos, I set the compression very low--otherwise why
bother with the high-resolution?

Overall, the total amount of information is the same either way. And
you can tell how much information the image contains by the number of
bytes required for the compressed file.

--
Transpose hotmail and mxsmanic in my e-mail address to reach me directly.

"Mxsmanic" wrote:
John Wright writes:

When is increasing compression better than reducing resolution?

They resolve to the same thing, actually. A highly compressed image of
large dimensions will be no more detailed than an uncompressed image of
small dimensions. So it's your call.

That would be true if image data were random, but it's not. Most images have
enormous areas of slowly varying colors and tones. Even landscapes with
corner to corner detail often have vast expanses of sky.

As a practical matter, best quality jpeg in photoshop compresses images
files to 1/3 the size with no visible reduction in detail/quality. And best
quality jpeg from the Sony F707 was indistinguishable from the tiff for the
same image.

In general, I tend to increase compression when I reduce size, instead
of the opposite. The logic is that any image that is really small
doesn't have to have much detail, anyway, since file size is probably
the real issue, so why not just increase compression as well?

Bad logic. Small files will almost always be viewed at 100% on the screen,
so the jpeg artifacts will be blatant. Larger files are usually printed, and
unless printing very large, quite a bit less sensitive to minor jpeg
artifacts.

For very
high-resolution photos, I set the compression very low--otherwise why
bother with the high-resolution?

For files one is going to manipulate, one wants to keep the compression low
or zero.

Overall, the total amount of information is the same either way.

Again, that assumes that the information in the file is truly random. It's
not, and there's lots of room for compression. The pixel matrix is a
horrendously innefficient way to represent images.

And
you can tell how much information the image contains by the number of
bytes required for the compressed file.

While that's correct in theory, in practice (with digital cameras), the size
of a compressed file is most closely related to the noise, i.e. the ISO at
which it was shot.

David J. Littleboy
Tokyo, Japan

"Mxsmanic" wrote:
John Wright writes:

When is increasing compression better than reducing resolution?

They resolve to the same thing, actually. A highly compressed image of
large dimensions will be no more detailed than an uncompressed image of
small dimensions. So it's your call.

That would be true if image data were random, but it's not. Most images have
enormous areas of slowly varying colors and tones. Even landscapes with
corner to corner detail often have vast expanses of sky.

As a practical matter, best quality jpeg in photoshop compresses images
files to 1/3 the size with no visible reduction in detail/quality. And best
quality jpeg from the Sony F707 was indistinguishable from the tiff for the
same image.

In general, I tend to increase compression when I reduce size, instead
of the opposite. The logic is that any image that is really small
doesn't have to have much detail, anyway, since file size is probably
the real issue, so why not just increase compression as well?

Bad logic. Small files will almost always be viewed at 100% on the screen,
so the jpeg artifacts will be blatant. Larger files are usually printed, and
unless printing very large, quite a bit less sensitive to minor jpeg
artifacts.

For very
high-resolution photos, I set the compression very low--otherwise why
bother with the high-resolution?

For files one is going to manipulate, one wants to keep the compression low
or zero.

Overall, the total amount of information is the same either way.

Again, that assumes that the information in the file is truly random. It's
not, and there's lots of room for compression. The pixel matrix is a
horrendously innefficient way to represent images.

And
you can tell how much information the image contains by the number of
bytes required for the compressed file.

While that's correct in theory, in practice (with digital cameras), the size
of a compressed file is most closely related to the noise, i.e. the ISO at
which it was shot.

David J. Littleboy
Tokyo, Japan

In article ,
says...

This is a multi-part message in MIME format.

------=_NextPart_000_005B_01C49582.794C7F00
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

All digicams provide several resolution levels and compression levels. =
Using the highest resolution and the lowest compression produces maximum =
image file sizes. If you wanted to pack more photos into your card, you =
would have to reduce file sizes by either reducing resolution, by =
increasing compression, or both.

When is increasing compression better than reducing resolution?

And when is reducing resolution better than increasing compression?

Regards - JW
[HTML SNIP'ped]

It is all a matter of what you can live with. If you are only going to Web,
then 640x480 (or similar) High JPG compression will probably get you by. If
you are going to a full-page magazine ad, then none - RAW would be your best
choice, or, as said above, TIFF. You have to define the end use. Just
remember, you can't go back, once you choose low rez, or high-compression, or
any combination of the two.

Hunt

In article ,
says...

This is a multi-part message in MIME format.

------=_NextPart_000_005B_01C49582.794C7F00
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

All digicams provide several resolution levels and compression levels. =
Using the highest resolution and the lowest compression produces maximum =
image file sizes. If you wanted to pack more photos into your card, you =
would have to reduce file sizes by either reducing resolution, by =
increasing compression, or both.

When is increasing compression better than reducing resolution?

And when is reducing resolution better than increasing compression?

Regards - JW
[HTML SNIP'ped]

It is all a matter of what you can live with. If you are only going to Web,
then 640x480 (or similar) High JPG compression will probably get you by. If
you are going to a full-page magazine ad, then none - RAW would be your best
choice, or, as said above, TIFF. You have to define the end use. Just
remember, you can't go back, once you choose low rez, or high-compression, or
any combination of the two.

Hunt

"John Wright" wrote in message
u...
"David J. Littleboy" wrote
Most images have
enormous areas of slowly varying colors and tones. Even landscapes with
corner to corner detail often have vast expanses of sky.

As a practical matter, best quality jpeg in photoshop compresses images
files to 1/3 the size with no visible reduction in detail/quality. And
best
quality jpeg from the Sony F707 was indistinguishable from the tiff for
the
same image.

What you say makes sense.

Are you therefore saying that where I am forced to reduce the file size, I
am *ALWAYS* better off increasing compression rather than reducing
resolution? Are there no exceptions to this rule?


Yes, as long as you do not compress to such a degree that artifacts are
visible to the normal eye on the target media at a given size.



I shoot with a 5 megapixel camera, jpeg at 8:1, and get nice 11x14 prints,
I do this all the time. I can even get a 16x20. You couldn't get a 16x20
enlargement with a one megapixel tiff.


Patrick

"John Wright" wrote in message
u...
"David J. Littleboy" wrote
Most images have
enormous areas of slowly varying colors and tones. Even landscapes with
corner to corner detail often have vast expanses of sky.

As a practical matter, best quality jpeg in photoshop compresses images
files to 1/3 the size with no visible reduction in detail/quality. And
best
quality jpeg from the Sony F707 was indistinguishable from the tiff for
the
same image.

What you say makes sense.

Are you therefore saying that where I am forced to reduce the file size, I
am *ALWAYS* better off increasing compression rather than reducing
resolution? Are there no exceptions to this rule?


Yes, as long as you do not compress to such a degree that artifacts are
visible to the normal eye on the target media at a given size.



I shoot with a 5 megapixel camera, jpeg at 8:1, and get nice 11x14 prints,
I do this all the time. I can even get a 16x20. You couldn't get a 16x20
enlargement with a one megapixel tiff.


Patrick