Histograms in the new Vuescan: Do you like them?

Personally, I have problem with reading them. They are
crowded and very jagged ( I compare 7.6.73 to my preferred
version 7.6.66 which I use for quite a while.) Since the
histograms appear so jagged now, even while dealing with
48bit/pixel data, I suspect that something is wrong.

I am also not sure how to interpret the lower histogram
and what use gives me the feedback provided by this
histogram.

Thomas.

On Mon, 26 Jan 2004 09:25:55 +0000, ThomasH wrote:

> Personally, I have problem with reading them. They are
[...]
> I suspect that something is wrong.

I think the idea of displaying as for now is good, but when I compare them
to a histogram in Gimp ... I don't have the same results !

Maybe a (minor) bug in Vuescan ?

--
Christian Tsotras - ICQ:37288308
http://www.photo.net/shared/communi...?user_id=295376

Christian Tsotras wrote:
>
> On Mon, 26 Jan 2004 09:25:55 +0000, ThomasH wrote:
>
> > Personally, I have problem with reading them. They are
> [...]
> > I suspect that something is wrong.
>
> I think the idea of displaying as for now is good, but when I compare them
> to a histogram in Gimp ... I don't have the same results !

If I compare them histograms in a recent Vuescan 7.6.66,
they also look completely different. They are now very
"jagged" what might suggest a posterization problem.

Thomas

>
> Maybe a (minor) bug in Vuescan ?
>
> --
> Christian Tsotras - ICQ:37288308
> http://www.photo.net/shared/communi...?user_id=295376

The upper histogram is prior to applying SOME of the color tab
settings, such as brightness and clipping, but does reflect changes to
film profile (and contrast index with tmax). The lower histogram is
after all settings are applied. I like it, the upper histogram gives
me a feel for whether or not a lowering of the contrast index setting
would be beneficial.

On Mon, 26 Jan 2004 18:58:06 -0800, Mendel Leisk wrote:

> The upper histogram is prior to applying SOME of the color tab
> settings, such as brightness and clipping, but does reflect changes to
> film profile (and contrast index with tmax). The lower histogram is
> after all settings are applied.

This is what is said in the documentation.

But did you compare the lower histogram with the histogram of the final
picture in a picture editor ?

I see a difference: Vuescan does not stretch correctly the lower
histogram. I use it only to "measure" the colorcast, wich is already
very useful to me.

--
Christian Tsotras - ICQ:37288308
http://www.photo.net/shared/communi...?user_id=295376

"Christian Tsotras" <3188@free.fr> wrote in message
newsan.2004.01.26.22.03.13.920007@free.fr...
SNIP
> I think the idea of displaying as for now is good, but when I compare them
> to a histogram in Gimp ... I don't have the same results !
>
> Maybe a (minor) bug in Vuescan ?

Or in Gimp ;-)

I'm not saying that that is impossible, but I presume that the difference
between the low resolution Preview and the higher resolution final Scan is
what you are seeing. Or did you compare the histograms after scanning full
res?

Bart

Christian Tsotras <3188@free.fr> wrote in message news:<pan.2004.01.27.07.26.03.984802@free.fr>...
> On Mon, 26 Jan 2004 18:58:06 -0800, Mendel Leisk wrote:
>
> > The upper histogram is prior to applying SOME of the color tab
> > settings, such as brightness and clipping, but does reflect changes to
> > film profile (and contrast index with tmax). The lower histogram is
> > after all settings are applied.
>
> This is what is said in the documentation.
>
> But did you compare the lower histogram with the histogram of the final
> picture in a picture editor ?
>
> I see a difference: Vuescan does not stretch correctly the lower
> histogram. I use it only to "measure" the colorcast, wich is already
> very useful to me.
Hi,
This thread is a bit complicated for me. Somebody used the histograms
to set the contrast. How is this done with Vuescan? You say that you
use the histograms to "measure" the colorcast. Could you tell me how
this is done and how you use the result? Also I found some triangels
(pointers) in the upper bar that could be moved and affect the picture
colours! How should these pointers be used? I do not find the manual
very informative on these points! Maybe its only because I could not
find the relevant information.
Regards
ThomasD

On Tue, 27 Jan 2004 11:08:05 +0100, Bart van der Wolf wrote:

>> Maybe a (minor) bug in Vuescan ?
> Or in Gimp ;-)
>
> I'm not saying that that is impossible, but I presume that the difference
> between the low resolution Preview and the higher resolution final Scan is
> what you are seeing. Or did you compare the histograms after scanning full
> res?

Full res.

Make a test with Photoshop ...

--
Christian Tsotras - ICQ:37288308
http://www.photo.net/shared/communi...?user_id=295376

"Christian Tsotras" <3188@free.fr> wrote in message
newsan.2004.01.27.19.58.05.455591@free.fr...
> On Tue, 27 Jan 2004 11:08:05 +0100, Bart van der Wolf wrote:
>
> >> Maybe a (minor) bug in Vuescan ?
> > Or in Gimp ;-)
> >
> > I'm not saying that that is impossible, but I presume that the
difference
> > between the low resolution Preview and the higher resolution final Scan
is
> > what you are seeing. Or did you compare the histograms after scanning
full
> > res?
>
> Full res.
>
> Make a test with Photoshop ...

They look kind of similar to me, but the VueScan histogram is much wider and
has 65536 underlying bins (493 displayed on a 1024x768 screen).
Photoshop/Gimp and other histograms display very few (256) bins, so there
can hardly be gaps/spikes with 16-bit/channel images.

Bart

On Tue, 27 Jan 2004 04:30:33 -0800, thomas wrote:

> Hi,
> This thread is a bit complicated for me. Somebody used the histograms to
> set the contrast.
> How is this done with Vuescan?

Brightness, and black and white point settings.

Your visualize clipped pixels with the "pixel colors" setting in the color
tab. If you have the contrast you want with the fewer pixels clipped, then
you're ok.

> You say that you
> use the histograms to "measure" the colorcast. Could you tell me how
> this is done and how you use the result?

This is my own recipe, it works for me, but I don't pretend teaching a
method to anybody.

It depends on the picture and its histogram. In the Vuescan histogram look
at the relative positions of the red, green and blue histograms.

Try to make them coincide on the point you think is more important in your
photo: the highlights, the shadows, the midtones. It all depends on your
feeling when looking the picture.

First, I use the global settings like "white balance", "auto levels" or
"neutral". If it doesn't work, I use one of these settings with some "try
and guess" on the "brightness red", green or blue settings.

Another method: right click on a supposed grey part of the picture.
More doc here: http://www.hamrick.com/vuescan/html/vuesc2.htm#topic1

> Also I found some triangels
> (pointers) in the upper bar that could be moved and affect the picture
> colours! How should these pointers be used?

See "Black point" and "White point" in:
http://www.hamrick.com/vuescan/html/vuesc21.htm#topic20

The black triangles are a graphical view of these settings.
The colored triangles are a graphical view of the red, green and blue
black and white points.

--
Christian Tsotras - ICQ:37288308
http://www.photo.net/shared/communi...?user_id=295376