How much information does jpeg lose?

On Apr 16, 8:59 am, "HEMI-Powered" <n...@none.sn> wrote:
> Today, tomm42 made these interesting comments ...
>
>
>
>
>
> >> >if a tree falls in a forest and nobody is there to see/hear
> >> >it, does it make any noise?
>
> >> It didn't fall.
>
> > You obviously aren't from the NE US trees are falling all over
> > the place, Mt Washington in New Hampshire had winds of 120mph.
> > Open a RAW file save as max quality jpeg, send, re open in PS
> > save as PSD what do you loose?
> > 16bit if you opened the file in 16bit mode.
> > You took a minor hit by saving in jpeg but in PS the max
> > setting it is very small, virtually unnoticeable. With the
> > change back to PS and then saving in PSD or another nonlosy
> > format, you retain the jpeg attributes but again you will
> > never see it. BUT if that file gets converted to jpeg and
> > resized to jpeg etc then the jpeg artifacts will start to
> > build. What you can't get back is the 16bit (well 12 bit)
> > dynamic range and editing capabilities. I have had to send
> > images to medical journal publishers recently and they all
> > asked me to send them email as max jpegs. I offered to send a
> > CD, they said email as jpeg. If publishers are trusting jpegs
> > seems like an OK practice as long as the files doesn't get
> > resaved as a jpeg.
>
> Tom, in my experience, the subject(s), lighting, exposure,
> requirement for DOF, and many other criteria affect when/if
> defects are noted in a JPEG saved even at minimum compression in
> a camera or when saving from a graphics app. But, so does the
> photographer's definition of "good", "adequate", "lousy" and
> their definition of "defects". Besides all this, there is the
> very long discussion of where and how an image will be used
> later, e.g. view on monitor, print, and if print, to what size
> (s), viewing distance from whatever, etc.
>
> I have found that for subjects with fine detail, such as my hobby
> of car pictures, artefacts can show up rather quickly as can
> posterization, thus I save a very conservative compression
> settings, certainly no more than 12, maybe 15 max on the standard
> 1-100 scale. Then, I immediately reopen the just-saved JPEG and
> look carefully for damage that disturbs me. In about 1% of the
> cases, maybe less, I do see some damage, most often artefacts
> around the details of the car such as door handles, moldings,
> badges, grilles, etc. To remedy that, I will first try lowering
> the compression and if still evident, changing to one of 4 Chroma
> sub-sampling settings I commonly use.
>
> I would comment also that this is hardly a digital camera only
> issue, it is just as important and just as prevalent for those of
> us who scan continuous tone photos and half-tone printed photos
> from books, magazines, calendards and the like. Here, besides the
> general JPEG issues, there is also the mutually exclusive
> compromise of least noise with maximum detail and sharpness.
>
> When an OP posts a general question as here, I find that it is
> impossible to give a reasonable answer if they do not provide
> some specifics as to what they are doing, what they are trying o
> accomplish, how they intend to use the resulting images, and
> their individual tolerance for defects.
>
> I am certain, though, that RAW will always be superior, given
> equal conditions. However, both the 80/20 Rule and the Law of
> Diminishing Returns enters into this quickly, meaning that it can
> take more and more and more time to extract ever smaller amounts
> of improvements in what one is trying to do, thus the post-
> processing of snapshots takes a different workflow for me than do
> pictures I take at a car show or in a museum, with its own
> difficulties.
>
> --
> HP, aka Jerry


Jerry,
I agree with you, I'm talking about max quality setting in Photoshop,
not max compression. I do get worried after a save or two with jpeg.
But my jpeg work is generally going to PowerPoint so we are not
talking about critical images.
I am surprised at publishers going for jpeg though, but the way it was
explained was that their deadlines are tight and the person working on
the layout wants the image right away and emailing TIFF files requires
waiting no matter what.
Just wanted to let the OP know that a single save with jpeg was not
going to ruin his image.

Tom

Bill Tuthill wrote:
> Al Dykes <adykes@panix.com> wrote:
>> I know that you can't replace lost info and that saving a jpeg on
>> itself is a Bad Idea.
>
> Al, if you save with minimum compression, for instance Photoshop Q12,
> very little information is lost. But the files are not very small.
>
> The most efficient space/quality tradeoff is relatively high quality,
> say around 94-96 on the IJG scale, with 4:2:2 chroma subsampling.
> Most good digicams (Canon, Fuji) produce something like this nowadays.
> You cannot write this combination with any version of Photoshop,
> unless Adobe added 4:2:2 in CS3. You can do it with GIMP.

My belief is that the most efficient storage is a DNG file with edits,
keywords, etc. in the metadata, or, second, the RAW file with a sidecar
containing same.

Mileage varies, of course.

--
John McWilliams

You can do an amazing amount of adjustments to the RAW image itself in
recent versions of ACR and the release version of Lightroom. Using one of
those, you could quickly go back to the source image and start afresh, or
use the full image already adjusted to generate a new TIFF or PSD.
>
> --
> John McWilliams

I know a saving a RAW to TIFF is lossless, is it also when going to PSD?
Which would be preferred when saving from Lightroom?
Rob

On Apr 16, 3:01 pm, "Scubabix" <Scuba...@comcast.net> wrote:
> You can do an amazing amount of adjustments to the RAW image itself in
> recent versions of ACR and the release version of Lightroom. Using one of
> those, you could quickly go back to the source image and start afresh, or
> use the full image already adjusted to generate a new TIFF or PSD.
>
>
>
> > --
> > John McWilliams
>
> I know a saving a RAW to TIFF is lossless, is it also when going to PSD?
> Which would be preferred when saving from Lightroom?
> Rob

I would not say that saving from RAW to TIFF is lossless, converting
from the Bayer pattern to RGB values will lose information. Having
said that I don't think it matters much whether you use TIFF or PSD.

Scott

Scott W wrote:
> On Apr 16, 3:01 pm, "Scubabix" <Scuba...@comcast.net> wrote:
>> You can do an amazing amount of adjustments to the RAW image itself in
>> recent versions of ACR and the release version of Lightroom. Using one of
>> those, you could quickly go back to the source image and start afresh, or
>> use the full image already adjusted to generate a new TIFF or PSD.
>>

>> I know a saving a RAW to TIFF is lossless, is it also when going to PSD?
>> Which would be preferred when saving from Lightroom?
>> Rob
>
> I would not say that saving from RAW to TIFF is lossless, converting
> from the Bayer pattern to RGB values will lose information. Having
> said that I don't think it matters much whether you use TIFF or PSD.

Agreed. Another reason for saving in RAW or DNG is that both conversion
ease and accuracy is bound to increase over the years, as well as one's
own competence in using same. Put another way, I can't believe what I
did to some RAW conversions a few years ago....

--
John McWilliams

Today, tomm42 made these interesting comments ...

> On Apr 16, 8:59 am, "HEMI-Powered" <n...@none.sn> wrote:
>> Today, tomm42 made these interesting comments ...
>>
>>
>>
>>
>>
>> >> >if a tree falls in a forest and nobody is there to
>> >> >see/hear it, does it make any noise?
>>
>> >> It didn't fall.
>>
>> > You obviously aren't from the NE US trees are falling all
>> > over the place, Mt Washington in New Hampshire had winds of
>> > 120mph. Open a RAW file save as max quality jpeg, send, re
>> > open in PS save as PSD what do you loose?
>> > 16bit if you opened the file in 16bit mode.
>> > You took a minor hit by saving in jpeg but in PS the max
>> > setting it is very small, virtually unnoticeable. With the
>> > change back to PS and then saving in PSD or another nonlosy
>> > format, you retain the jpeg attributes but again you will
>> > never see it. BUT if that file gets converted to jpeg and
>> > resized to jpeg etc then the jpeg artifacts will start to
>> > build. What you can't get back is the 16bit (well 12 bit)
>> > dynamic range and editing capabilities. I have had to send
>> > images to medical journal publishers recently and they all
>> > asked me to send them email as max jpegs. I offered to send
>> > a CD, they said email as jpeg. If publishers are trusting
>> > jpegs seems like an OK practice as long as the files
>> > doesn't get resaved as a jpeg.
>>
>> Tom, in my experience, the subject(s), lighting, exposure,
>> requirement for DOF, and many other criteria affect when/if
>> defects are noted in a JPEG saved even at minimum compression
>> in a camera or when saving from a graphics app. But, so does
>> the photographer's definition of "good", "adequate", "lousy"
>> and their definition of "defects". Besides all this, there is
>> the very long discussion of where and how an image will be
>> used later, e.g. view on monitor, print, and if print, to
>> what size (s), viewing distance from whatever, etc.
>>
>> I have found that for subjects with fine detail, such as my
>> hobby of car pictures, artefacts can show up rather quickly
>> as can posterization, thus I save a very conservative
>> compression settings, certainly no more than 12, maybe 15 max
>> on the standard 1-100 scale. Then, I immediately reopen the
>> just-saved JPEG and look carefully for damage that disturbs
>> me. In about 1% of the cases, maybe less, I do see some
>> damage, most often artefacts around the details of the car
>> such as door handles, moldings, badges, grilles, etc. To
>> remedy that, I will first try lowering the compression and if
>> still evident, changing to one of 4 Chroma sub-sampling
>> settings I commonly use.
>>
>> I would comment also that this is hardly a digital camera
>> only issue, it is just as important and just as prevalent for
>> those of us who scan continuous tone photos and half-tone
>> printed photos from books, magazines, calendards and the
>> like. Here, besides the general JPEG issues, there is also
>> the mutually exclusive compromise of least noise with maximum
>> detail and sharpness.
>>
>> When an OP posts a general question as here, I find that it
>> is impossible to give a reasonable answer if they do not
>> provide some specifics as to what they are doing, what they
>> are trying o accomplish, how they intend to use the resulting
>> images, and their individual tolerance for defects.
>>
>> I am certain, though, that RAW will always be superior, given
>> equal conditions. However, both the 80/20 Rule and the Law of
>> Diminishing Returns enters into this quickly, meaning that it
>> can take more and more and more time to extract ever smaller
>> amounts of improvements in what one is trying to do, thus the
>> post- processing of snapshots takes a different workflow for
>> me than do pictures I take at a car show or in a museum, with
>> its own difficulties.
>
> Jerry,
> I agree with you, I'm talking about max quality setting in
> Photoshop, not max compression. I do get worried after a save
> or two with jpeg. But my jpeg work is generally going to
> PowerPoint so we are not talking about critical images.
> I am surprised at publishers going for jpeg though, but the
> way it was explained was that their deadlines are tight and
> the person working on the layout wants the image right away
> and emailing TIFF files requires waiting no matter what.
> Just wanted to let the OP know that a single save with jpeg
> was not going to ruin his image.
>
> Tom
>
Tom, I didn't think you and I were in disagreement, I just
thought I'd add a few more thoughts to the discussion, some of
which had already been mentioned.

--
HP, aka Jerry

John McWilliams <jpmcw@comcast.net> wrote:
>
> My belief is that the most efficient storage is a DNG file with edits,
> keywords, etc. in the metadata, or, second, the RAW file with a sidecar
> containing same.

A lossless JPEG 2000 (JP2) file would be much smaller, wouldn't it?

I'm not sure an image must record all the steps the photographer took
going from icky to nice.

Bill Tuthill wrote:
> John McWilliams <jpmcw@comcast.net> wrote:
>> My belief is that the most efficient storage is a DNG file with edits,
>> keywords, etc. in the metadata, or, second, the RAW file with a sidecar
>> containing same.
>
> A lossless JPEG 2000 (JP2) file would be much smaller, wouldn't it?

Nobody in his right mind would use that for archival storage, and of
course it's smaller.
>
> I'm not sure an image must record all the steps the photographer took
> going from icky to nice.

Not close to the point, besides which DNGs don't necessarily capture the
history of edits.

Efficient includes ease of use, quality of the image, completeness of
information, not size alone.

--
John McWilliams