Photoshop How To Use: alt.graphics.photoshop - 16 new messages in 3 topics

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* discount wholesaler Air MAX 89 shoes - 1 messages, 1 author
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* JRDunn provides Full Factory Warranty on all Chopard Watches, Free Shipping -
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* Working at 8 / 16 / 32 bits per channel... - 14 messages, 8 authors
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TOPIC: discount wholesaler Air MAX 89 shoes
http://groups.google.com/group/alt.graphics.photoshop/t/d0fe4987424a84d2?hl=en
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TOPIC: JRDunn provides Full Factory Warranty on all Chopard Watches, Free
Shipping -(www.trade8.cc)
http://groups.google.com/group/alt.graphics.photoshop/t/2fba5b08079ee21c?hl=en
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== 1 of 1 ==
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TOPIC: Working at 8 / 16 / 32 bits per channel...
http://groups.google.com/group/alt.graphics.photoshop/t/e0aae034df289e03?hl=en
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== 1 of 14 ==
Date: Tues, Apr 7 2009 8:43 am
From: "Robert Barnett"

Actually John rounding errors are a much bigger problem than you think. In
fact it can be used to interesting effect. Back in the days of CS2 Russell
Brown of Adobe created a free script for Photoshop called shake, rattle and
roll. This script made use of the rounding errors in Photoshop to create
some very interesting effects. While the script unfortunately has never been
updated for CS3 or CS4 you can still do it manually.

If you would like to see just how bad and how quickly rounding errors can
affect your images load a low resolution image (high resolution will work
but will take longer) and then rotate the image by 8 degrees using the
transform tool. Now repeat this over and over again. Do it 20 or 30 times
and you will see that the image is slowly destroyed, this is because of
rounding errors in Photoshop. The script I mentioned did other things for
example it would rotate back and forth, spin it around and things like this
to give some very interesting effects. If you would like to get an idea of
the effect keep rotating the image the more you do it the more dramatic the
effect.

I have tried to get Russell to update the script but he says he doesn't have
the time.

The moral of this is don't transform any more than you have to. Each time
you do you damage the image. It may take some doing to notice it, but the
damage is happening from transformation one. This is also just one area of
Photoshop that has rounding errors. Now does this mean that in 16-bit or
32-bit that you have less rounding errors or get less damge I don't know, I
don't care. I never transform an image enough to really worry about it. And,
since just about any output is 8-bit it just isn't worth the trouble in my
opinion. If others thing it is awesome, have fun.

Robert

== 2 of 14 ==
Date: Tues, Apr 7 2009 11:58 am
From: erpy

John J:
> Johan W. Elzenga wrote:
>> 32 bits is for HDR (High Dynamic Range) photography only.
>
> Today I read a claim that editing in 16 or 32-bit reduced rounding
> errors, thus increasing quality. Rubbish?
>
> And is this just snake-oil?
> http://www.epson.com/cgi-bin/Store/jsp/ProImaging/EpsonInnovations.do?invMoreInfo=EpsonInv16BitPrinterDrivers
>

That's correct.
16bit and 32bit floating point linear editing yields much more precision
when using many layers with different effects/adjustments.
When using only a few layers it might not be that noticeable...
otherwise it makes much more difference.

As for 32bit editing in Photoshop, it depends whether Adobe is
dedicating part of the precision to HDR data or not.
Anyway, 32bit floating point editing is much more precise than 16bit
(which is integer anyway).

See: http://en.wikipedia.org/wiki/Floating_point

== 3 of 14 ==
Date: Tues, Apr 7 2009 1:21 pm
From: Mike Russell

On Tue, 07 Apr 2009 20:58:57 +0200, erpy wrote:

> As for 32bit editing in Photoshop, it depends whether Adobe is
> dedicating part of the precision to HDR data or not.
> Anyway, 32bit floating point editing is much more precise than 16bit
> (which is integer anyway).

Any examples where any of this matters? Didn't think so.

--
Mike Russell - http://www.curvemeister.com

== 4 of 14 ==
Date: Tues, Apr 7 2009 2:22 pm
From: mike

In article <49db74a3$0$95539$742ec2ed@news.sonic.net>, nospam@nospam.com
says...
> Actually John rounding errors are a much bigger problem than you think. In
> fact it can be used to interesting effect. Back in the days of CS2 Russell
> Brown of Adobe created a free script for Photoshop called shake, rattle and
> roll. This script made use of the rounding errors in Photoshop to create
> some very interesting effects. While the script unfortunately has never been
> updated for CS3 or CS4 you can still do it manually.
>
> If you would like to see just how bad and how quickly rounding errors can
> affect your images load a low resolution image (high resolution will work
> but will take longer) and then rotate the image by 8 degrees using the
> transform tool. Now repeat this over and over again. Do it 20 or 30 times
> and you will see that the image is slowly destroyed, this is because of
> rounding errors in Photoshop. The script I mentioned did other things for
> example it would rotate back and forth, spin it around and things like this
> to give some very interesting effects. If you would like to get an idea of
> the effect keep rotating the image the more you do it the more dramatic the
> effect.
>
I think this has very little to do with the bit-depth of the image and
almost everything to do with the resolution of the image. For example,
create a small 8-bit per channel image (100x100 pixels square is fine)
and draw a vertical black single pixel width line down the centre of the
white background. Now apply an arbitrary rotation like 4.56 degrees
(don't choose an angle that is a factor of 360) and apply iy just once.
Now repeat by rotating in the opposite direction by the same angle.If
you zoom into the image far enough to see the individual pixels as
monotone squares you will note that the line is now a fuzzy shape
approximately 2 pixels wide (with outliers up to 3-4 pixels wide) in
shades of grey. This is not due to any lack of bit depth as the result
is almost identical if you repeat the task with a 16-bit image. Rather
it is due to the fact that, when rotated, the pixels of the line don't
map exactly onto individual new pixels so their colour value is
'smeared' across 4 or more neighbouring pixels. So it is a resolution
issue. If you repeat the experiment with a 10 pixel wide line in a
1000x1000 image, you can see that at the same scale of magnificatiobn
there is less apparent damage to the line.

Mike

== 5 of 14 ==
Date: Tues, Apr 7 2009 6:13 pm
From: John J

In article <49db74a3$0$95539$742ec2ed@news.sonic.net>, nospam@nospam.com
> says...
> Actually John rounding errors are a much bigger problem than you think. In
> fact it can be used to interesting effect. Back in the days of CS2 Russell
> Brown of Adobe created a free script for Photoshop called shake, rattle and
> roll. This script made use of the rounding errors in Photoshop to create
> some very interesting effects. While the script unfortunately has never been
> updated for CS3 or CS4 you can still do it manually.
>
> If you would like to see just how bad and how quickly rounding errors can
> affect your images load a low resolution image (high resolution will work
> but will take longer) and then rotate the image by 8 degrees using the
> transform tool. Now repeat this over and over again. Do it 20 or 30 times
> and you will see that the image is slowly destroyed,

I use photoshop for photographs. I don't ever need to manipulate the
image in such bizarre ways.

== 6 of 14 ==
Date: Tues, Apr 7 2009 9:23 pm
From: "Robert Barnett"

Mike we are talking about round errors and if they can have a visible effect
on the image. If you try my suggestion you will see that the round errors
can really have an impact and pretty quickly, surprisingly quickly. I made
and make no statement on wheater 8-bit, 16-bit or 32-bit mode will increase
or reduce rounding errors. I don't know and I really don't care. What I was
trying to show is that round errors are there and they have affect your
images and the rounding errors are quite easy to encounter.

Robert

== 7 of 14 ==
Date: Tues, Apr 7 2009 9:28 pm
From: "Robert Barnett"

No per my example no. But, it does show that if you have to do more than one
or two transformations (rotations to straighten a horrizon), resize up or
down, correct for keystoning and the like you are definately damaging your
images as you are then encountering rounding errors. All of the
tranformation tools introduce data damage to your image (except for flip
horzontal and flip verticle. All of the others damage. So if you use any of
the tools (and who knows what other tools) you are damaging your images. As
a photographer myself you can avoid having to use these tools at some point,
it is best to keep their use to a minimum and not to keep applying them over
and over to correct a single issue. Straigtening the horizon with a single
application or rotate is fine, having to apply it several times to do it
isn't. Though honest using the ruler with the rotate command I see no reason
why you would have to apply rotate more than once.

I am sure that many of the filters have rounding errors as well.

My point for my post was that rounding errors are real, they do damage your
images and if you want to see them do it I provided a way to see it. Proof
that they are real in other words. For most they won't be a problem, but one
needs to keep them in mind.

Robert

== 8 of 14 ==
Date: Tues, Apr 7 2009 10:15 pm
From: Mike Russell

On Wed, 8 Apr 2009 09:22:12 +1200, mike wrote:

> I think this has very little to do with the bit-depth of the image and
> almost everything to do with the resolution of the image.

Good point. I did the experiment. Applying repeated rotations to an 8 bit
image, versus a 16 bit image, results in nearly the same result. Doubling
the resolution preserves image detail much better, will both 8 bit and 16
bit producing nearly identical results.

http://www.curvemeister.com/forum/index.php?topic=2569
--
Mike Russell - http://www.curvemeister.com

== 9 of 14 ==
Date: Wed, Apr 8 2009 12:21 am
From: "Henk de Jong"

> How many of you work at higher bits per channel than 8?
> Will gradients be rendered more smoothly in those situations?
> What do printers do with those files? Any problems?
> When should one work at 16 or 32 bits per channel?
> Thanks.

This question has been asked many times. Part of it is answered in this
article:
http://www.creativepro.com/article/out-of-gamut-the-high-bit-advantage

With kind regards,
Henk de Jong

http://www.hsdejong.nl
Nepal and Myanmar (Burma) - Photo Galleries

== 10 of 14 ==
Date: Wed, Apr 8 2009 3:00 am
From: Mike Russell

On Wed, 8 Apr 2009 09:21:42 +0200, Henk de Jong wrote:

> This question has been asked many times. Part of it is answered in this
> article:
> http://www.creativepro.com/article/out-of-gamut-the-high-bit-advantage
>
>
> With kind regards,
> Henk de Jong

Have you tried to duplicate what the article describes? I have.
--
Mike Russell - http://www.curvemeister.com

== 11 of 14 ==
Date: Wed, Apr 8 2009 4:34 am
From: Joel

Mike Russell <groupsRE@MOVEcurvemeister.com> wrote:

> On Wed, 8 Apr 2009 09:22:12 +1200, mike wrote:
>
> > I think this has very little to do with the bit-depth of the image and
> > almost everything to do with the resolution of the image.
>
> Good point. I did the experiment. Applying repeated rotations to an 8 bit
> image, versus a 16 bit image, results in nearly the same result. Doubling
> the resolution preserves image detail much better, will both 8 bit and 16
> bit producing nearly identical results.

In general it pretty much depends on the codition of the photo, or how
much detail and large you want to print. Example

- If you have to work on some detail of a small photo (like 200-400K) then
you may want to switch to 16-bit mode.

- If you want to work on detail of a photo taken by average P&S, then you
may want to give 16-bit a try.

- If you work on a photo taken by high-end DSLR camera with good lens, and
you just want to print 8x10 or little larger then 8-bit should be fine. If
have to work on the EDGE and need to print to something like 20x30 or larger
then you may want to try 16-bit with the combination of Photoshop's Enlarger
feature.

- If you work on a photo taken by high-end camera but with poor lens or some
damaged channel etc. then you may need to give 16-bit mode a try.

There is a HUGE difference between 8-bit and 16-bit, and depend on the
photo or condition you may have to zoom in 200-300% or so to learn the
difference. With the lousy photo you should be able to see without zooming.

== 12 of 14 ==
Date: Wed, Apr 8 2009 5:48 am
From: John J

Robert Barnett wrote:

> My point for my post was that rounding errors are real, they do damage
> your images and if you want to see them do it I provided a way to see
> it.

He who needs to do excessive iterative rotations for a photograph, or
has to make so very many non-adjustment layer manipulations to a
photograph can live with the degradation alleged to occur through
rounding errors.

Only someone with more monitor time than lifetime can care about such
unrealistic bench-racing metrics that require a damned spreadsheet to
'see' and still have nothing to do with real-world outcomes as it
regards photography.

== 13 of 14 ==
Date: Wed, Apr 8 2009 8:02 am
From: Sir F. A. Rien

John J <nohj@droffats.ten> found these unused words:

>Robert Barnett wrote:
>
>> My point for my post was that rounding errors are real, they do damage
>> your images and if you want to see them do it I provided a way to see
>> it.
>
>He who needs to do excessive iterative rotations for a photograph, or
>has to make so very many non-adjustment layer manipulations to a
>photograph can live with the degradation alleged to occur through
>rounding errors.
>
>Only someone with more monitor time than lifetime can care about such
>unrealistic bench-racing metrics that require a damned spreadsheet to
>'see' and still have nothing to do with real-world outcomes as it
>regards photography.

Another "Close is good enough"?

== 14 of 14 ==
Date: Wed, Apr 8 2009 11:57 am
From: erpy

Mike Russell:
> On Tue, 07 Apr 2009 20:58:57 +0200, erpy wrote:
>
>
>> As for 32bit editing in Photoshop, it depends whether Adobe is
>> dedicating part of the precision to HDR data or not.
>> Anyway, 32bit floating point editing is much more precise than 16bit
>> (which is integer anyway).
>>
>
> Any examples where any of this matters? Didn't think so.
>
>

Whenever you need a smooth result with many layers using different
blending modes.
You can do this easy test... sometimes you see this banding artifact on
TV adverts too...

- make a new 24bit image, let's say HD 1080 resolution, pick two close
colors, say RGB(0,100,100) and RGB(0,150,150)
- make a radial gradient from the center to one corner of the picture.
- Duplicate twice the layer and set the duplicates to Multiply.
Duplicate twice again and set these other duplicates to Overlay.
- Notice the banding.(100% zoom)
- Convert the image to 16 bit/component...
- The banding is gone.

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