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CSS tables - more confused

 
 
dorayme
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      04-25-2005
> Whoa. Chemicals. I used to do b/w darkroom work, too. I can smell
> the stop bath, now.
>
> --
> Blinky



Yes, nice isn't it! You are right, the stop bath is the distinctive thing
that smells...

dorayme

 
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Jim Scott
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      04-25-2005
On Mon, 25 Apr 2005 10:12:48 +1100, dorayme wrote:

>> From: Jim Scott <(E-Mail Removed)>

>
>>> In addition to the comments of David: The quality of the pictures is *very*
>>> bad. You must have done something wrong in your picture editor. If you post
>>> a link to an original, someone might give you some advice.

>>
>> Can you be more specific? All the photos are mine and I have most of the
>> originals. Some I have changed, some I have scanned and not yet changed and
>> some I don't think need changing. I have a limit on webspace and there are
>> lots here.
>> --
>> Jim on Tyneside UK

>
>
> Sorry Jim, I missed your bit about scanning in my last post and just
> noticed! So maybe we need to look at your method of scanning. My remarks can
> be transposed for the scanning procedure: scan at the highest quality and go
> from there in a good photo editor.
>
> If you are not sure about what is not the best about your pics - and as I
> said, many are *very nice and acceptable* - perhaps look at Windfarm and
> look at around the props, the pole on the left; look at Anchors2 and over
> the bridge to the right of the windmill there... sort of watery aberrations,
> possibly the sign of over compression (the poor algorithm does it best!).
> Yes, I know around the props look almost ok because it might be air
> disturbance! But it is a fault I think that can be seen in a few pics where
> there is not this "excuse"
>
> dorayme


One of the problems is that photos like Wind Warm and the 1993 shipyard
series were all scans from 6.5" x 4.5" prints.
Most of them were worked on with Adobe Photoshop and "Seved for the Web"
--
Jim on Tyneside UK
Remove X to email me.
http://freespace.virgin.net/mr.jimscott/
 
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dorayme
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      04-25-2005
> From: Jim Scott <(E-Mail Removed)>

> On Mon, 25 Apr 2005 10:12:48 +1100, dorayme wrote:
>
>>> From: Jim Scott <(E-Mail Removed)>

>>
>>>> In addition to the comments of David: The quality of the pictures is *very*
>>>> bad. You must have done something wrong in your picture editor. If you post
>>>> a link to an original, someone might give you some advice.
>>>
>>> Can you be more specific? All the photos are mine and I have most of the
>>> originals. Some I have changed, some I have scanned and not yet changed and
>>> some I don't think need changing. I have a limit on webspace and there are
>>> lots here.
>>> --
>>> Jim on Tyneside UK

>>
>>
>> Sorry Jim, I missed your bit about scanning in my last post and just
>> noticed! So maybe we need to look at your method of scanning. My remarks can
>> be transposed for the scanning procedure: scan at the highest quality and go
>> from there in a good photo editor.
>>
>> If you are not sure about what is not the best about your pics - and as I
>> said, many are *very nice and acceptable* - perhaps look at Windfarm and
>> look at around the props, the pole on the left; look at Anchors2 and over
>> the bridge to the right of the windmill there... sort of watery aberrations,
>> possibly the sign of over compression (the poor algorithm does it's best!).
>> Yes, I know around the props look almost ok because it might be air
>> disturbance! But it is a fault I think that can be seen in a few pics where
>> there is not this "excuse"
>>
>> dorayme

>
> One of the problems is that photos like Wind Warm and the 1993 shipyard
> series were all scans from 6.5" x 4.5" prints.
> Most of them were worked on with Adobe Photoshop and "Seved for the Web"
> --
> Jim on Tyneside UK



This should not be a problem that results in such marks. A good quality scan
from a decent pic of that size will result in a good pic that would more
than fill most screens (because the pixels on a screen are very much less
than the equivalent dots bunched in a digital print of the same file. Plenty
enough material to work with). Try not to use such commands as "save for the
web" if you can help it - because you mostly don't know what is happening
and therefore lose control and experience. Scan at a high resolution. Open
in PS. In one or other order (I am awaiting feedback on a slight question on
this), reduce the pic to a size you roughly want and compress choosing a
number from 1 to 10 in JPG levels. Try 5 or 6 to begin. 4 might be ok. I
suspect the faults I mentioned are due too much compression (lower numbers
like 0,1,2). You can keep compressing a bit (don't go the other way though)
and you can adjust the px dimensions down (again, don't go the other way)
till you get a result you want. You will get experienced and not have to
fiddle too much after a while...

Good luck...

dorayme

 
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Oli Filth
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      04-25-2005
dorayme wrote:
>>From: Oli Filth <(E-Mail Removed)>

>
>>JPEG compression almost certainly works by uncompressing back to a
>>bitmap, resizing (decimating and interpolating), and then recompressing
>>to JPEG. Hence two lots of compression, hence more loss.
>>

> When starting with a big px size high quality file of any type, two
> operations are usually necessary:
>
> 1. Reducing the pixel size
>
> 2. Compressing the info using say jpg.
>
> Of course, both operations will result in loss of quality. I was using the
> term compression to refer to the operation in 2.
>
> What exactly are you saying more than this?
>


If you resize a JPEG, what's actually happening (AFAIK) is:

* decompression (JPEG -> bitmap)
* resize
* compression (bitmap -> JPEG)

The JPEG is decompressed to a bitmap before resizing, and then recompressed.

So in resizing *after* converting to JPEG, you've performed two lots of
JPEG compression and one resize. Whereas resizing *before* conversion
means one JPEG compression and one resize.


--
Oli
 
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Spartanicus
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      04-25-2005
dorayme <(E-Mail Removed)> wrote:

>>> If you don't want to go into everything, this is my advice: take pics at the
>>> highest res.

>>
>> Pointless if most of the information will be thrown away as is common
>> with web images.

>
>It is not pointless if you do not know what use you will make of the pic or
>if you might want to print later.


You claimed that it would enhance the quality of the web images the OP
is currently publishing (the biggest size he uses is about 560x400).

>And it is not pointless if they are to be
>given later to someone else to prepare - who would not want better orig pics
>to work with?


Anyone with common sense, handling bigger and/or non compressed images
significantly increases resource usage, it's slower, needless for most
web images. Bigger doesn't mean better.

>>> Use very good software like Photoshop to jpg

>>
>> Expensive advice, and unnecessary, Photoshop uses the same jpeg
>> algorithms as other software.

>
>I am sure there is a lot of good software besides PS. If it is really true
>that there is a lot of cheap software that does this job just as well, then
>fine.


Not just cheap, there is plenty of free software that does at least as
good a job at resizing and/or jpeg compression as the $599 Photoshop.

>Suck it and see, I would not tend to be too trusting beforehand
>though... But I don't think (not quite on your point, I realise) the same
>can be said for resizing (px size, height, width wise) algorithms in
>different software. In PS it is very good in quality (using the bicubic,
>which was slow on old computers but lightening on modern)


Bilinear and bicubic resizing is quite fast on my Pentium 2/266Mhz, but
I use sensible source images.

>>> Compress before you resize (there being more information for the jpg
>>> algorithm to work on).

>>
>> Resizing is performed on uncompressed 24 bit bitmaps, the above advice
>> would therefore result in extra information loss.

>
>Oli was saying something on this bit, I am not fully with you. Could you
>spell out this argument please.


Assuming photo type images for the web, the final images need jpeg
compression, this compression can only be applied after they've been
resized, if you compress before you resize you loose information twice.

--
Spartanicus
 
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dorayme
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      04-25-2005
> From: Spartanicus <(E-Mail Removed)>

> dorayme <(E-Mail Removed)> wrote:
>
>>>> If you don't want to go into everything, this is my advice: take pics at
>>>> the highest res.
>>>
>>> Pointless if most of the information will be thrown away as is common
>>> with web images.

>>
>> It is not pointless if you do not know what use you will make of the pic or
>> if you might want to print later.

>
> You claimed that it would enhance the quality of the web images the OP
> is currently publishing (the biggest size he uses is about 560x400).

-------------------------------------------------------------
With respect, I did not quite do this. It was general and conservative
advice to avoid the pitfalls of going too far the other way and keeping
control of the situation. How do you know what the quality of the camera
used is? How do you know how it all worked or how the scans were made or how
deft the OP is in these matters? Again, it was not pointless advice. It
might have been very conservative.
-------------------------------------------------------------
>> And it is not pointless if they are to be
>> given later to someone else to prepare - who would not want better orig pics
>> to work with?

>
> Anyone with common sense, handling bigger and/or non compressed images
> significantly increases resource usage, it's slower, needless for most
> web images. Bigger doesn't mean better.

----------------------------------------
I did not imply it was certainly better. Is no subtlety allowed? The point
is it is a safer route. Once taken, a pic cannot always be retaken. It can
be degraded but rarely upgraded. If you know the chain of responsibilities
in these matters you can be more confident in your common sense. The point
is not that bigger is necessarily better, it is that it is safer. I have
cases of this sort of thing quite regularly, if clients had only taken their
pics at higher res I would be able to actually use *a part* of the pic for
something I need, but as it is, that possibility is closed off. Beware of
too much common sense - it has a history of being wrong...
----------------------------------------
>>>> Use very good software like Photoshop to jpg
>>>
>>> Expensive advice, and unnecessary, Photoshop uses the same jpeg
>>> algorithms as other software.

>>
>> I am sure there is a lot of good software besides PS. If it is really true
>> that there is a lot of cheap software that does this job just as well, then
>> fine.

>
> Not just cheap, there is plenty of free software that does at least as
> good a job at resizing and/or jpeg compression as the $599 Photoshop.
>
>> Suck it and see, I would not tend to be too trusting beforehand
>> though... But I don't think (not quite on your point, I realise) the same
>> can be said for resizing (px size, height, width wise) algorithms in
>> different software. In PS it is very good in quality (using the bicubic,
>> which was slow on old computers but lightening on modern)

>
> Bilinear and bicubic resizing is quite fast on my Pentium 2/266Mhz, but
> I use sensible source images.

---------------------------------------------------------------
Good for you. (I don't like the implication about sensible but what can I
do? I am destined to be hurt badly by you all and I will speak to my shrink
about curbing over-sensitivity...) I sometimes have to resize huge files
designed for printing and it takes almost no time using the bicubic (forget
the other one these days) And this on an uncharacteristically unmodern Mac.
Truth is I do not always have control over what I get, but I sure as hell
prefer big to start with. And when I do have control as when scanning I
start higher than common sense might suggest and work down.
----------------------------------------------------------------
>
>>>> Compress before you resize (there being more information for the jpg
>>>> algorithm to work on).
>>>
>>> Resizing is performed on uncompressed 24 bit bitmaps, the above advice
>>> would therefore result in extra information loss.

>>
>> Oli was saying something on this bit, I am not fully with you. Could you
>> spell out this argument please.

>
> Assuming photo type images for the web, the final images need jpeg
> compression, this compression can only be applied after they've been
> resized, if you compress before you resize you loose information twice.
>

_________________________________
Well, I gave some reasoning to show that either way you lose info twice, if
there is something to clear this up, I would be interested. But you just
repeat the claim. Perhaps there is something that is obvious to you that you
can detect and explain that I am missing?
__________________________________
dorayme

 
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Spartanicus
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      04-25-2005
dorayme <(E-Mail Removed)> wrote:

>> Bilinear and bicubic resizing is quite fast on my Pentium 2/266Mhz, but
>> I use sensible source images.


>I sometimes have to resize huge files
>designed for printing and it takes almost no time using the bicubic (forget
>the other one these days)


Bicubic and bilinear are both needed, in fact bicubic is poorly suited
to scale downwards. Rule of thumb for photo realistic images: use
bicubic to scale upwards, and bilinear to scale down.

>>>>> Compress before you resize (there being more information for the jpg
>>>>> algorithm to work on).
>>>>
>>>> Resizing is performed on uncompressed 24 bit bitmaps, the above advice
>>>> would therefore result in extra information loss.
>>>
>>> Oli was saying something on this bit, I am not fully with you. Could you
>>> spell out this argument please.

>>
>> Assuming photo type images for the web, the final images need jpeg
>> compression, this compression can only be applied after they've been
>> resized, if you compress before you resize you loose information twice.


>Well, I gave some reasoning to show that either way you lose info twice


Your calculation is flawed, using your example you lose information 3
times (compress to save space, rescale downward, compress for web
publication).

--
Spartanicus
 
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dorayme
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      04-26-2005
> From: Spartanicus <(E-Mail Removed)>

>
> dorayme <(E-Mail Removed)> wrote:
>
>>> Bilinear and bicubic resizing is quite fast on my Pentium 2/266Mhz, but
>>> I use sensible source images.

>
>> I sometimes have to resize huge files
>> designed for printing and it takes almost no time using the bicubic (forget
>> the other one these days)

>
> Bicubic and bilinear are both needed, in fact bicubic is poorly suited
> to scale downwards. Rule of thumb for photo realistic images: use
> bicubic to scale upwards, and bilinear to scale down.
>


I have always thought it a bad idea to scale up in pixel based images. But
it is an interesting matter. Have you anything to back up your claims? And
your rule of thumb? Arguments from the nature of the algorithms, examples,
references and *explanations* from experts in these matters (please do not
give general links that do not go to the heart of the matter)?

My knowledge is that bicubic in PS gives smoother tonal gradations. I got my
view from official PS publications and my own experiences. In one PS manual,
an Adobe PS User Guide (and a beautifully produced book if I may add!) to
hand it describes 3 interpolation algorithms, "Nearest neighbour, Bilinear,
and Bicubic and says these are respectively slower in operation but better
in quality.

Here is a similar quote from the help files attached to many PS programs:

When an image is resampled, Adobe Photoshop uses an interpolation method to
assign color values to any new pixels based on the color values of existing
pixels in the image. The more sophisticated the method, the more quality and
detail from the original image are preserved.

The General Preferences dialog box lets you specify a default interpolation
method to use whenever images are resampled with the Image Size or
transformation commands. The Image Size command also lets you specify an
interpolation method other than the default.

To specify the default interpolation method:
1 Choose File > Preferences > General.
2 For Interpolation, choose an option:
Nearest Neighbor for the fastest, but least precise, method. This method
can result in jagged effects, which become apparent when distorting or
scaling an image or performing multiple manipulations on a selection.
Bilinear for a medium-quality method.
Bicubic for the slowest, but most precise, method, resulting in the
smoothest tonal gradations

dorayme

 
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dorayme
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      04-26-2005
> From: Spartanicus <(E-Mail Removed)>

> Your calculation is flawed, using your example you lose information 3
> times (compress to save space, rescale downward, compress for web
> publication).



You give no explanation or argument at all. Plus you add an unfair factor
(see after *). The basic issue is information loss in two possible
operations, you have a big image file and try for a reasonable file size and
width/height size. Either you compress first and then resize or the other
way round. In both cases you lose info twice. I did advise someone to do it
in one direction to which you objected. I admitted i had done it it both
ways but that my intuitions were for one. I am not so sure now, it is true.
But I am pretty sure it makes little if any difference. You (and Oli) are
saying the one direction loses info twice and I say it loses info twice
anyway.

I did some tests this morning on a new very sharp and big monitor. I made a
gradient 5000 * 400 psd, flattened and made two tests. There was no
difference that I could detect at all (and not in speed either). The file
sizes and appearances of the results were identical. (I was rather hoping to
back my initial intuition that jping first was superior... but it was not at
all true!). Given this, would probably now advise people to do what I often
do because it is very convenient (not for the unsubstantiated claims you
make): resize and then jpg. I still hanker for a test that might make any
difference more apparent. I will look at some 100+ MB pic files I have when
I have more time (Hassleblad negatives professionally scanned at - I am told
- approx $100 US each. Ouch, even tho I did not pay for them) ...

dorayme

(you are picking up an irrelevancy in a "third" to do with advice about re
jpging or sizing if not happy with previous attempts - of course you lose
even more info then, but you would if you went back to the original file and
made a more forceful 2 step to get to what you want)

 
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Spartanicus
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      04-26-2005
dorayme <(E-Mail Removed)> wrote:

>> Bicubic and bilinear are both needed, in fact bicubic is poorly suited
>> to scale downwards. Rule of thumb for photo realistic images: use
>> bicubic to scale upwards, and bilinear to scale down.

>
>I have always thought it a bad idea to scale up in pixel based images. But
>it is an interesting matter. Have you anything to back up your claims? And
>your rule of thumb? Arguments from the nature of the algorithms, examples,
>references and *explanations* from experts in these matters (please do not
>give general links that do not go to the heart of the matter)?


From the help file of my editor: (search the web for confirmation)

In the Resize Type box, select the type of resizing for Paint Shop Pro
to apply. There are four choices:

1) Smart size, where Paint Shop Pro chooses the best algorithm based on
the current image characteristics.

2) Bicubic resample, which uses a process called interpolation to
minimize the raggedness normally associated with expanding an image. As
applied here, interpolation smoothes out rough spots by estimating how
the "missing" pixels should appear, and then filling them with the
appropriate color. It produces better results than the Pixel resize
method with photo-realistic images and with images that are irregular or
complex. Use Bicubic resample when enlarging an image.

3) Bilinear resample, which reduces the size of an image by applying a
similar method as Bicubic resample. Use it when reducing photo-realistic
images and images that are irregular or complex.

4) Pixel Resize, where Paint Shop Pro duplicates or removes pixels as
necessary to achieve the selected width and height of an image. It
produces better results than the resampling methods when used with
hard-edged images.

>My knowledge is that bicubic in PS gives smoother tonal gradations. I got my
>view from official PS publications and my own experiences. In one PS manual,
>an Adobe PS User Guide (and a beautifully produced book if I may add!) to
>hand it describes 3 interpolation algorithms, "Nearest neighbour, Bilinear,
>and Bicubic and says these are respectively slower in operation but better
>in quality.


If that's all it says on the topic then bin the book.

--
Spartanicus
 
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