Vuescan histogram question

[tinnews]

I'm trying out Vuescan with my Epson V700 and I'm trying to understand
its histograms.

Is the only histogram display the one with a graph (rather than a
histogram) with three separate Red, Green and Blue plots? This is a
little more difficult to interpret/use than a real histogram (for me
anyway).

I also don't seem to be able to see a way to set the end points
separately for Red, Green and Blue.

Am I missing something in the interface?

 

[Robert Feinman]

I'm trying out Vuescan with my Epson V700 and I'm trying to understand
its histograms.

Is the only histogram display the one with a graph (rather than a
histogram) with three separate Red, Green and Blue plots? This is a
little more difficult to interpret/use than a real histogram (for me
anyway).

I also don't seem to be able to see a way to set the end points
separately for Red, Green and Blue.

Am I missing something in the interface?

There are several histogram displays (Control 1-4).
One shows the raw data, one allows setting the black
and white end points, one allows changing the gamma curve
and one shows the final results.
To set each channel separately you need to do a preview,
then lock exposure, then do another preview, then lock base
color (for negatives) and lock image color. You will then
see three colored triangles on the appropriate histogram
and can set each as you wish. View the results on the last
histogram.

 

[tinnews]

There are several histogram displays (Control 1-4).
One shows the raw data, one allows setting the black
and white end points, one allows changing the gamma curve
and one shows the final results.
To set each channel separately you need to do a preview,
then lock exposure, then do another preview, then lock base
color (for negatives) and lock image color. You will then
see three colored triangles on the appropriate histogram
and can set each as you wish. View the results on the last
histogram.

Thanks for the comprehensive explanation.

It's a bit of a laborious process getting to where you can set
separate end points for the three colours isn't it! Are there other
approaches to removing colour casts from faded slides with Vuescan?

The approach on www.scantips.com looks straightforward but to do it
with Vuscan looks somewhat difficult.

 

[Roger S.]

"Are there other approaches to removing colour casts from faded slides
with Vuescan? "

Scan in Vuescan with color balance set to none and do this in
Photoshop. You can save and reuse adjustements if you find one that
works for a few slides.

 

[tinnews]

"Are there other approaches to removing colour casts from faded slides
with Vuescan? "

Scan in Vuescan with color balance set to none and do this in
Photoshop. You can save and reuse adjustements if you find one that
works for a few slides.

I may try this, I have Photoshop, I'll probably come up with lots of
questions about Photoshop instead!

 

[Roger S.]

I may try this, I have Photoshop, I'll probably come up with lots of

questions about Photoshop instead!

Photoshop gives you a lot more tools to work with (curves, hue
saturation, color balance, layer masks, channel mixer, etc) and choice
is generally a good thing for post-processing. Feel free to come back
with questions about how to get the most from your scans.

 

[Noons]

Thanks for the comprehensive explanation.

Yeah, that was a good one. Thanks!

It's a bit of a laborious process getting to where you can set
separate end points for the three colours isn't it! Are there other
approaches to removing colour casts from faded slides with Vuescan?

You can try the auto thing vuescan does in the filters tab, just after
the "crop" tab. There is a checkbox in there for "restore fading"
IIRC.
I don't use that, though.

The approach on www.scantips.com looks straightforward but to do it
with Vuscan looks somewhat difficult.

Well, the problem with any post-vuescan adjustments is that
in most cases you'll be working with 8-bit colour images
rather than 16-bit: do a lot of colour adjustments and I can
virtually guarantee you'll get banding and other problems.
this is because 8bit colour doe snot have much roon for a
lot of adjustment. It's good for minor colour casts but not for
major restoration work.

The approach I use is slightly different:
I save all output from vuescan as raw scan files at 48-bit depth,
full rez - this is only until I sort out the colour balance, after that
for disk space reasons I either back these up to cd or drop them.

Then I preview these files with vuescan, at 1200 or even 2400ppi
preview rez, neutral colour setting. This lets me zoom-in to the
preview and get a darn good idea of what I need to do in terms of
colour adjustments. The next step is to pick auto-levels and see
what it does. If that is not enough, I then use the inividual colour
controls, black and white point controls and such in the auto-levels
option to fine tune.

The output re-scan is then saved as a 24-bit (8-bit colour) base
image which is the start point for any further manipulations such
as cropping, rotating, sharpening, what have you. Most of the major
colour restoration is now done, so there is little danger of any colour
"after effects".

Works for me.

 

[tinnews]

Yeah, that was a good one. Thanks!


You can try the auto thing vuescan does in the filters tab, just after
the "crop" tab. There is a checkbox in there for "restore fading"
IIRC.
I don't use that, though.

It does a fair job on less faded slides but doesn't cope too well with
some that are badly faded and/or underexposed.

Well, the problem with any post-vuescan adjustments is that
in most cases you'll be working with 8-bit colour images
rather than 16-bit: do a lot of colour adjustments and I can
virtually guarantee you'll get banding and other problems.
this is because 8bit colour doe snot have much roon for a
lot of adjustment. It's good for minor colour casts but not for
major restoration work.

The approach I use is slightly different:
I save all output from vuescan as raw scan files at 48-bit depth,
full rez - this is only until I sort out the colour balance, after that
for disk space reasons I either back these up to cd or drop them.

Then I preview these files with vuescan, at 1200 or even 2400ppi
preview rez, neutral colour setting. This lets me zoom-in to the
preview and get a darn good idea of what I need to do in terms of
colour adjustments. The next step is to pick auto-levels and see
what it does. If that is not enough, I then use the inividual colour
controls, black and white point controls and such in the auto-levels
option to fine tune.

The output re-scan is then saved as a 24-bit (8-bit colour) base
image which is the start point for any further manipulations such
as cropping, rotating, sharpening, what have you. Most of the major
colour restoration is now done, so there is little danger of any colour
"after effects".

Thanks for the ideas.

 

[Robert Feinman]

Thanks for the comprehensive explanation.

It's a bit of a laborious process getting to where you can set
separate end points for the three colours isn't it! Are there other
approaches to removing colour casts from faded slides with Vuescan?

The approach on www.scantips.com looks straightforward but to do it
with Vuscan looks somewhat difficult.

Three items:

1. There is a new version of Vuescan out which allows you to lock
the color balance for all frames at once (using the steps I mentioned).
Then if you have a batch of images with similar color properties you
can just scan them using the locked values.
2. I have tip on my web site about restoring faded color transparencies.
You may find the steps helpful. Just follow the tips link on my home
page.
3. I scan at 16 bit per channel, with the resolution about where I
expect to need it for the final image I wish to print. Then in photoshop
I adjust contrast, brightness and color balance using a curves
adjustment layer. I may also add some masked adjustment layers to
alter specific regions. After I have all these adjustment done I
flatten the image and convert to 8 bit for printing and archiving.

 

[Bart van der Wolf]

SNIP

It's a bit of a laborious process getting to where you can set
separate end points for the three colours isn't it!

That may seem so, however most scanners (or rather their software
drivers) start with a simple preview exposure level (unable to predict
what is the optimal scan exposure level). Only after that that level
is acquired, the optimal exposure time can be calculated. VueScan does
the right thing.