Lightroom vs. Apertu Curves

In article , Floyd L. Davidson
wrote:

That is because highlight are usually clipped or near to being clipped
simply because nature has a higher dynamic range than the camera can
record.

Which of course is irrelevant to the topic being discussed.

Probably is, for you. The rest of the world is trying
to understand how to make good photographs, not how to
beat their chest on Usenet.

a good description of you, who pretends to know about apps he's never
used and then tries to tell everyone else they're wrong, including
those who use the apps quite frequently.

On Wed, 13 Aug 2014 18:11:24 -0800, (Floyd L.
Davidson) wrote:

Eric Stevens wrote:
On 13 Aug 2014 09:18:11 GMT, Sandman wrote:
It would, if the image was taken with RAW. Software works with 14 bits of
data in a 8 bit workspace (your monitor colorspace) and if the software
supports it, it can access that data and bring it up/down into 8 bit.

Providing that the colour space does not change, going fro 14 bit to 8
bit (and vice versa) does not change the depths of the dark shadows or
the brightness of the highlights which have been seen by the camera.
With 14 bit data you can chop up the full dynamic range of (say) red
into 2^14 = 16,384 divisions. If you instead convert it to 8 bit data
you can chop up the full dynamic range 2^8 = 256 divisions.

14 bit gives you much smoother colour and luminance transitions. It
does not extend the dynamic range of the camera.

Except that it does.

A 14 bit linear file can encode a maximum dynamic range
of (6.02n + 1.76) dB, where n is the number of bits per
sample. Hence the maximum dynamic range that can be
recorded by a 14 bit depth RAW file is 86 dB, or 14.3
fstops.

Compare that to an 8 bit gamma corrected data set that
can encode about 9.1 fstops. It's more than 8 because
of the gamma correction.

The significance is the reason we have 14 bit depth RAW files
today instead of the 10 bit files from the 1990's. And we
will soon enough be working with 16 bit depth RAW files,
specifically because the dynamic range of sensors is getting
larger.

At the beginning of your response you said "Except that it does" and
then you go on to say "can". When you say something 'can' it doesn't
mean that it actually 'does'.

My understanding is that few (if any) cameras encode more image detail
at 14 bits than they do at 12 or even 10. Nor did I recognise that
equation in your first paragraph: so I went hunting.

I found Cambridge Color which at
http://www.cambridgeincolour.com/tut...amic-range.htm said:

"As an example, 10-bits of tonal precision translates into a
possible brightness range of 0-1023 (since 210 = 1024 levels).
Assuming that each A/D converter number is proportional to actual
image brightness (meaning twice the pixel value represents twice
the brightness), 10-bits of precision can only encode a contrast
ratio of 1024:1.

Most digital cameras use a 10 to 14-bit A/D converter, and so their
theoretical maximum dynamic range is 10-14 stops. However, this
high bit depth only helps minimize image posterization since total
dynamic range is usually limited by noise levels. Similar to how a
high bit depth image does not necessarily mean that image contains
more colors, if a digital camera has a high precision A/D converter
it does not necessarily mean it can record a greater dynamic range.
In effect, dynamic range can be thought of as the height of a
staircase whereas bit depth can be thought of as the number of
steps. In practice, the dynamic range of a digital camera does not
even approach the A/D converter's theoretical maximum; 8-12 stops
is generally all one can expect from the camera."

Also http://theory.uchicago.edu/~ejm/pix/.../noise-p3.html

"Both Canon and Nikon have introduced a finer level quantization of
the sensor signal in digitizing and recording the raw data, passing
from 12-bit tonal gradation in older models to 14-bit tonal depth
in newer models. A priori, one might expect this transition to
bring an improvement in image quality -- after all, doesn't 14-bit
data have over four times the levels (16384) compared to 12-bit
data (4096)? It would seem obvious that 14-bit tonal depth would
allow for smoother tonal transitions, and perhaps less possibility
of posterization. Well, those expectations are unmet, and the
culprit is noise."

--- and later ---

"Quantizing the signal from the sensor in steps much finer than the
level of the noise is thus superfluous and wasteful; quantizing the
noise in steps much coarser than the level of the noise risks
posterization. As long as the noise exceeds the quantization step,
the difference between the coarser and finer quantization is
imperceptible. As long as noise continues to exceed the
quantization step in post-processing, it doesn't matter how one
edits the image after the fact, since any squeezing/stretching of
the levels also does the same to the noise, which will always be
larger than the level spacing no matter how it is squeezed or
stretched. On the other hand, quantizing the signal in steps
coarser than the noise can lead to posterization. Ideally, the
noise should slightly exceed the quantization step, in order that
roundoff errors introduced by quantization are negligible, and that
no bits are wasted in digitizing the noise.

--- and later again ---

"Curiously, most 14-bit cameras on the market (as of this writing)
do not merit 14-bit recording. The noise is more than four levels
in 14-bit units on the Nikon D3/D300, Canon 1D3/1Ds3 and 40D. The
additional two bits are randomly fluctuating, since the levels are
randomly fluctuating by +/- four levels or more. Twelve bits are
perfectly adequate to record the image data without any loss of
image quality, for any of these cameras (though the D3 comes quite
close to warranting a 13th bit). A somewhat different technology is
employed in Fuji cameras, whereby there are two sets of pixels of
differing sensitivity. Each type of pixel has less than 12 bits of
dynamic range, but the total range spanned from the top end of the
less sensitive pixel to the bottom end of the more sensitive pixel
is more than 13 stops, and so 14-bit recording is warranted.

A qualification is in order here -- the Nikon D3 and D300 are both
capable of recording in both 12-bit and 14-bit modes. The method of
recording 14-bit files on the D300 is substantively different from
that for recording 12-bit files; in particular, the frame rate
slows by a factor 3-4. Reading out the sensor more slowly allows it
to be read more accurately, and so there may indeed by a
perceptible improvement in D300 14-bit files over D300 12-bit files
(specifically, less read noise, including pattern noise). That does
not, however, mean that the data need be recorded at 14-bit tonal
depth -- the improvement in image quality comes from the slower
readout, and because the noise is still more than four 14-bit
levels, the image could still be recorded in 12-bit tonal depth and
be indistinguishable from the 14-bit data it was derived from."

Both sites are well worth reading in full. The point is that unless
Sandman's camera has exceptionally low noise levels there almost
certainly will be no useful information from the last few bits added
to bring it up to 16 bit data.

http://discover.store.sony.com/sony-...h_imaging.html
describes the BIONZ X processor used in Sandman's camera, as receiving
14 bits from the sensor, processing it in 16 bits, and sending it on
as a 14 bit raw.

Presumably the 16 bit processing is to minimise the significance of
truncation errors in the arithmetic. Basically it is 14 bit data in
and 14 bit data out. Regretably it doesn't look as though there is any
extra data to be recovered even if Sandman is somehow going to
conveert it to 16 bit.

It also looks as though what Floyd has written below is fine in theory
but isn't what happens in practice. The limit remains the overall
noise level.

Nor, if the original image was overexposed will changing exposure allow
details to be recovered from burned out highlights. All it will do is
raise or lower brightness between the two extremes of bright and dark.

There is a difference between burned out highlights in 8 bit space and 14
bit space.

In short:

|-------------- 14 bit range ------------|
|------ 8 bit range ------|

It is possible to compress that 14 bit range into a 8 bit range and thus
reveal data that was otherwise invisible to you via your monitor.

I am afraid that in your example above the 8 bit range and the 14 bit
range are identical. It's whatever is built into sensor. It's just
that the 14 bit chops it up more finely.

No, but that doesn't make Sandman right either! When compression is
not used, the comparison looks more like this:


Dark Light
|-------------- 14 bit range ------------|
|------ 8 bit range ------|
|---- Displayed ------|

|-- blocked -| |--
/ \
/ \
Recoverable

The blocked part cannot be recovered from the 8 bit range.
What can be "recovered" from the 8 bit range is the part that
is too dark to show up on a display (print or monitor).

And while what is shown has nothing in the highlights
that can be recovered, sometimes there is. But it is
usually a very slight amount of information. For example,
most prints and monitors wash out any 8 bit values
greater than about 1/2 stop down from pure white. In most
editors that means any value above about 245 is pure white
and has no detail. If the brightness is reduced to where the
brightest value is at 245, about 1/2 an fstop of detail is
"recovered".

It is also possible to compress the 14 bit dynamic range into
an 8 bit dynamic range. The low compression will not look right,
but detail from the original range will exist rather than be
just clipped.
--

Regards,

Eric Stevens

In article , Eric Stevens
wrote:


Also http://theory.uchicago.edu/~ejm/pix/.../noise-p3.html

...

"Curiously, most 14-bit cameras on the market (as of this writing)
do not merit 14-bit recording. The noise is more than four levels
in 14-bit units on the Nikon D3/D300, Canon 1D3/1Ds3 and 40D. The
additional two bits are randomly fluctuating, since the levels are
randomly fluctuating by +/- four levels or more. Twelve bits are
perfectly adequate to record the image data without any loss of
image quality, for any of these cameras (though the D3 comes quite
close to warranting a 13th bit). A somewhat different technology is
employed in Fuji cameras, whereby there are two sets of pixels of
differing sensitivity. Each type of pixel has less than 12 bits of
dynamic range, but the total range spanned from the top end of the
less sensitive pixel to the bottom end of the more sensitive pixel
is more than 13 stops, and so 14-bit recording is warranted.

A qualification is in order here -- the Nikon D3 and D300 are both
capable of recording in both 12-bit and 14-bit modes. The method of
recording 14-bit files on the D300 is substantively different from
that for recording 12-bit files; in particular, the frame rate
slows by a factor 3-4. Reading out the sensor more slowly allows it
to be read more accurately, and so there may indeed by a
perceptible improvement in D300 14-bit files over D300 12-bit files
(specifically, less read noise, including pattern noise). That does
not, however, mean that the data need be recorded at 14-bit tonal
depth -- the improvement in image quality comes from the slower
readout, and because the noise is still more than four 14-bit
levels, the image could still be recorded in 12-bit tonal depth and
be indistinguishable from the 14-bit data it was derived from."

Both sites are well worth reading in full. The point is that unless
Sandman's camera has exceptionally low noise levels there almost
certainly will be no useful information from the last few bits added
to bring it up to 16 bit data.

there is definitely a benefit from 14 bit, but it will only be realized
if the scene has dynamic range wide enough where 12 bit would be a
limiting factor. if the subject has only 9 stops, then even 12 bit is
overkill.

http://www.clarkvision.com/imagedeta...formance.summa
ry/dynamic_range_a.gif

http://discover.store.sony.com/sony-...C/tech_imaging.
html
describes the BIONZ X processor used in Sandman's camera, as receiving
14 bits from the sensor, processing it in 16 bits, and sending it on
as a 14 bit raw.

Presumably the 16 bit processing is to minimise the significance of
truncation errors in the arithmetic. Basically it is 14 bit data in
and 14 bit data out. Regretably it doesn't look as though there is any
extra data to be recovered even if Sandman is somehow going to
conveert it to 16 bit.

16 bits is because that's the way computers work.
the data is still 14 bit.

It also looks as though what Floyd has written below is fine in theory
but isn't what happens in practice. The limit remains the overall
noise level.

a lot of what he writes isn't what happens in practice since he writes
about stuff he doesn't actually use and gets a lot of things wrong.

Sandman wrote:

In article , sid wrote:

Floyd L. Davidson:
Call it increased intensity then.

Sandman:
You can call it whatever you want, you won't get it anyway. Or
better yet, why not give a detailed explanation just what the
exposure slider in Lightroom does, or Aperture.

It doesn't matter *what* the slider labelled "exposure" actually
does in your favourite software, it most definitely is not adjusting
exposure.

Which is just semantics. It does its best to simulate the effect of camera
exposure.

but not really, your data from above says

"With the base values of rgb(0, 30, 250), these are the results:

True brightness +10: rgb(10, 40, 255)
New PS brightness +10: rgb(3, 36, 255)
Exposure +10: rgb(3, 40, 253)"

which suggests 2 things.

1. the exposure slider has increased brightness just not in a linear fashion
2. the exposure slider doesn't emulate exposure


It can not create data that does not exist

No! Really?

(unless it's using
RAW data extended dynamic range, but I don't think any does).

Now that's just babble

The point is that it is NOT adjusting image brightness.

Of course it is, you said so above.


It may very well be adjusting the image in a very pleasing
way for you, giving the impression that it's adjusting exposure, but
it isn't. As is oft said around here "it does *way* more than that"

Indeed. And I don't care what they call it. It's not a brightness slider.

Sandman:
I know, I know, you can't becaus eyou know nothing about neither
application so you're just here to add white noise about stuff you
know nothing about. Oh, as usual, then.

It has already been shown in this thread that the exposure slider in
lightroom does not adjust the image in a uniform way, it treats the
highlights midtones and shadows differently.

Much like how exposure works in a camera.

Not really, it does something else that makes for a pleasing image.

That's not how exposure works is it?

It is, as close as it can anyway.

It's not as close as it can, it could do it exactly right if that was what
was wanted, but it's not.

If I increase the exposure time on my camera the image is exposed for
longer right across the frame, regardless of highlight or shadow in the
scene. Does that mean that an image would get brighter or darker
depending on the length of exposure?

Changing the shutter speed of your camera will not make the image
uniformly brighter or darker.

That does not answer the question I asked.

Your camera has a higher dynamic range than
your monitor.

What does that have to do with the effects of image brightness in relation
to exposure length?

It will differ from camera to camera.

I shouldn't think so. Opening the shutter for twice as long lets twice the
light in regardless of camera model

But if you expose longer, the
brightness will be more pronounced in ligher parts than in darker parts of
the scene.
Here's a picture to show this:

http://sandman.net/files/luminance_exposure.jpg

As you can see, the lighter parts of the scene have higher brightness than
the darker parts.

Dark: ~10 difference
Midtones: ~20 difference
Light: ~35 difference

What? you mean that if you double exposure length you get twice the light?

--
sid

nospam wrote:

In article , sid
wrote:



It has already been shown in this thread that the exposure slider in
lightroom does not adjust the image in a uniform way, it treats the
highlights midtones and shadows differently. That's not how exposure
works is it?

http://www.sprawls.org/ppmi2/FILMCON/FILMCON03.jpg

Apart from the fact that relates to film not digital, it's not right anyway
according to the data that Jonas furnished us with.

--
sid

On Thu, 14 Aug 2014 07:25:37 -0700, Savageduck
wrote:

On 2014-08-14 09:14:05 +0000, Eric Stevens said:

On Wed, 13 Aug 2014 22:38:29 -0700, Savageduck
wrote:

Don't get back to me on this subject until you have done at least that.
You say you prefer DxO, but you have yet to make the comparison. Make
it and let me know what you have discovered.

I think I prefer DxO to ACR as a raw editor for Photoshop.

That much is clear.

Now try LR5.

I intend to. I will when the time comes but right now I want to do
things that LR can't do.
--

Regards,

Eric Stevens

On Thu, 14 Aug 2014 15:45:49 -0400, nospam
wrote:

In article 2014081322382923711-savageduck1@REMOVESPAMmecom,
Savageduck wrote:

"Not in LR or in ACR, only when it is converted for use in another
application such as Photoshop."

It's converted every time you do anything with it.

You put a lot of work into that speculative essay, but no.

Now if you had put as much effort into actually using LR and ACR, you
might be able to look at this from the perspective of a user.

that's the key.

floyd and others are looking at it from the perspective of a software
developer and arguing over details that make no difference to actually
using the software.

But actually using the software is not the point. It's what software
can actually achieve which is currently what the argument is about.
The actual buttons and levers available to the user are a secondary
consideration.

Somehow I
doubt that you have even taken the time to look at any of the LR
tutorial videos.

he probably hasn't.

Don't get back to me on this subject until you have done at least that.
You say you prefer DxO, but you have yet to make the comparison. Make
it and let me know what you have discovered.
--

Regards,

Eric Stevens

On Thu, 14 Aug 2014 15:45:39 -0400, nospam
wrote:

--- vast snip ---

It's converted every time you do anything with it.

it's not converted to an interim format. everything is rendered on the
fly.

I agree with that but I still think we are talking about different
things.

A NEF file from my camera contains formatted raw data which is
different the raw data from an ARW file from Sandman's camera. While
they stay different, the raw data from the two cameras require
different rendering software.

What I am saying is that as soon as they are loaded into LR each of
the files are converted into a common LR internal format. This entails
demosaicing, setting the color profile etc and ends up with the
respective images being held in the same internal format. Because the
two files are no longer different they no longer need two different
rendering/editing engines.

All of the transformation from the raw files to the common internal
format happens in the brief period of time it takes to load the raw
image and is transparent to the user.

Yeah, I know that with raw files you have ACR first, but I expect ACR
employs the same trick, otherwise you would need individually
different software for each raw file.
--

Regards,

Eric Stevens

On 2014-08-14 23:04:10 +0000, Eric Stevens said:

On Thu, 14 Aug 2014 07:25:37 -0700, Savageduck
wrote:

On 2014-08-14 09:14:05 +0000, Eric Stevens said:

On Wed, 13 Aug 2014 22:38:29 -0700, Savageduck
wrote:

Don't get back to me on this subject until you have done at least that.
You say you prefer DxO, but you have yet to make the comparison. Make
it and let me know what you have discovered.

I think I prefer DxO to ACR as a raw editor for Photoshop.

That much is clear.

Now try LR5.

I intend to. I will when the time comes but right now I want to do
things that LR can't do.

Aah! You are going grocery shopping.
--
Regards,

Savageduck

On 14 Aug 2014 09:28:36 GMT, Sandman wrote:

In article , nospam wrote:

Eric Stevens:
I think he is right. It's not the raw file which is edited. What
is edited is a file derived from which ever one of the very my
different raw files has been presented. The raw file remains
untouched.

the raw file is never touched.

all of the adjustments are applied to the raw data on the fly.

This is a pretty interesting aspect. When you're looking at a catalog in
Lightroom that contains 20k files in the smallest thumbnail in grid mode,
it will show you on screen about 40 photos.

I have a very hard time, especially considering that scrolling is very
smooth, that all these photos are RAW files read from disk, have
adjustments applied to them and portrayed as thumbnails. In fact, I
outright claim they are not.

Hence the use of previews - cached preview versions of these files. Now,
this isn't in contradiction to your statement above, of course, you said
nothing about thumbnail view.

But that would explain why Lightroom is so slow to open the develop view
for a photo, in that it reads the RAW data, and the apply the adjustment
chain, each and every single time.

I expect that's what it does. I am surprised you find it slow. I find
raw images appear in less than a second. Mind you, that's 12 Mb images
and yours may be larger. Maybe it's something to do with the way you
have it catalogued?

Aperture has a, to me, better way to handle this, everything that is shown
on screen is the JPG preview version. And when you make edits, they are
made to the JPG but saved in relation to the RAW file. Whenever an edit
requires data from the RAW file (like the extended curves), it will read
that data, make the adjustment and update the JPG.

DxO does a similar thing. All of the edits you see on the screen are
to a stripped down preview screen while the heavy work is going on in
the background.

That's why Aperture is so fast to work in, everything is done with "smart
previews" as Lightroom seem to call it. But full-size smart previews.

When exporting images from Aperture, the RAW files are again accessed, the
adjustment chain applied and then exported to disc.

That's also why Aperture, when an image has been processed by an older
Aperture version, has the option of "reprocess original", which does the
initial RAW - JPG conversion again, but now with the updated RAW engine.

Makes sense.
--

Regards,

Eric Stevens