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Photoshop Levels & camera Histograms

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December 27, 2004 12:28:11 PM

Archived from groups: rec.photo.digital (More info?)

It occured to me that unless you want a soft image (I like bold high
contrast pics) there is almost no loss in using the levels adjustment in
photoshop to clip off the dead space at the high & low ends in the
levels adjustment. If it's flat, there isn't anything to lose
theoretically though you may need to readjust the center point back.
However this doesn't always work: if I do so, I can see highlights
getting (nearly) blown out so aprt from the logic it doesn't seem to
work. I've read that curves are more sophisticated than levels and I
agree because you can increase the contrast of just the shadows or just
the highlights & hold the middle tones or not as desired.

Either way, increasing the contrast can overdo the saturation so I
usually desaturate a bit afterwards

I don't know how you'd correct a histogram while shooting if it's
getting dead space at the highs & or lows. Perhaps the aperture effects
this? ISO? I assume that dead space means you are missing out on
potential dynamic range. There are cases where you want a soft look &
it's OK but my preference is usually for something very rich.
Anonymous
December 27, 2004 9:47:03 PM

Archived from groups: rec.photo.digital (More info?)

You should be careful how much you draw back the sliders on the levels
control: if the midpoint marker moves you are getting a very gross
adjustment of the midtones that is better adjusted using curves. Fortunately
all these adjustments can be made non-destructively as separate layers and
regional areas of the image can be adjusted by painting/erasing the mask, or
using other techniques.

There are actually many ways to approach the issue of how to "normalize" the
histogram and what are the best ways to adjust each value.
December 27, 2004 9:47:04 PM

Archived from groups: rec.photo.digital (More info?)

bmoag wrote:

> You should be careful how much you draw back the sliders on the levels
> control: if the midpoint marker moves you are getting a very gross
> adjustment of the midtones that is better adjusted using curves. Fortunately
> all these adjustments can be made non-destructively as separate layers and
> regional areas of the image can be adjusted by painting/erasing the mask, or
> using other techniques.
>
> There are actually many ways to approach the issue of how to "normalize" the
> histogram and what are the best ways to adjust each value.



I know how to get the look I want using curves. Maybe do that & just use
the levels histogram to see how I did, or maybe forget about that whole
concept because it doesn't seem to work very well. It just looked like
it ought to work.
Related resources
Anonymous
December 28, 2004 3:00:26 AM

Archived from groups: rec.photo.digital (More info?)

paul wrote:

> bmoag wrote:
>
>> You should be careful how much you draw back the sliders on the levels
>> control: if the midpoint marker moves you are getting a very gross
>> adjustment of the midtones that is better adjusted using curves.
>> Fortunately all these adjustments can be made non-destructively as
>> separate layers and regional areas of the image can be adjusted by
>> painting/erasing the mask, or using other techniques.
>>
>> There are actually many ways to approach the issue of how to
>> "normalize" the histogram and what are the best ways to adjust each
>> value.
>
>
>
>
> I know how to get the look I want using curves. Maybe do that & just use
> the levels histogram to see how I did, or maybe forget about that whole
> concept because it doesn't seem to work very well. It just looked like
> it ought to work.

If you're conversant with Curves, why use Levels as well?

This is really a question, not a challenge, as I am wrestling with the
same thing, using layers. Sometimes I seem to use just Levels, sometimes
Curves, sometimes both. Kinda depending on the image, but I haven't
worked out a real system yet.
--
John McWilliams
December 28, 2004 3:00:27 AM

Archived from groups: rec.photo.digital (More info?)

John McWilliams wrote:
> paul wrote:
>
>> bmoag wrote:
>>
>>> You should be careful how much you draw back the sliders on the
>>> levels control: if the midpoint marker moves you are getting a very
>>> gross adjustment of the midtones that is better adjusted using
>>> curves. Fortunately all these adjustments can be made
>>> non-destructively as separate layers and regional areas of the image
>>> can be adjusted by painting/erasing the mask, or using other techniques.
>>>
>>> There are actually many ways to approach the issue of how to
>>> "normalize" the histogram and what are the best ways to adjust each
>>> value.
>>
>>
>>
>>
>>
>> I know how to get the look I want using curves. Maybe do that & just
>> use the levels histogram to see how I did, or maybe forget about that
>> whole concept because it doesn't seem to work very well. It just
>> looked like it ought to work.
>
>
> If you're conversant with Curves, why use Levels as well?
>
> This is really a question, not a challenge, as I am wrestling with the
> same thing, using layers. Sometimes I seem to use just Levels, sometimes
> Curves, sometimes both. Kinda depending on the image, but I haven't
> worked out a real system yet.


I have been using only curves but it occurred to me that the levels
diagram looks like a digicam histogram and presumably there is wasted
dynamic range if you see blank space at the right & left. Unfortunately
using levels that way sometimes makes a mess of the picure because you
can't curve the adjustment so the whole range gets whacked. Curves give
better control over what you are changing but levels seems to show what
you have in terms of dynamic range.

Ah, OK I just played around with a picture & I put a curves adjustment
layer, did my best eyeball to improve contrast, then put a levels
adjustment layer with no changes just to read the histogram & move it
above & below the curves layer to see what I changed & whether I had
pushed some of the highlights or shadows too far or not. That was a
helpful technique. Then I tried duplicating the effect with another
levels layer & it was not as smooth (as viewed throught the top levels
histogram). Curves allowed me to stretch out some more shadows without
clipping shadow detail. Levels showed what I had done clearly.
December 28, 2004 3:01:26 AM

Archived from groups: rec.photo.digital (More info?)

paul wrote:

> Curves give
> better control over what you are changing but levels seems to show what
> you have in terms of dynamic range.
>

Of the two, I've found curves to be much more useful.
--

Stacey
Anonymous
December 28, 2004 10:28:15 AM

Archived from groups: rec.photo.digital (More info?)

Stacey wrote:
> paul wrote:
>
>
>>Curves give
>>better control over what you are changing but levels seems to show what
>>you have in terms of dynamic range.
>>>
> Of the two, I've found curves to be much more useful.

Yes. My question tho was more along the lines of: Are there some times
when levels are more useful than curves? Do experienced PSers sometimes
use both?

--
John McWilliams
Anonymous
December 28, 2004 3:22:01 PM

Archived from groups: rec.photo.digital (More info?)

> Curves give
> better control over what you are changing but levels seems to show what
> you have in terms of dynamic range.

Photoshop CS has a histogram palette which updates dynamically - and that
includes as you adjust curves. I don't think I've touched levels since they
provided that.
Anonymous
December 29, 2004 12:40:41 AM

Archived from groups: rec.photo.digital (More info?)

In message <33c7l6F3rl3utU2@individual.net>,
Stacey <fotocord@yahoo.com> wrote:

>paul wrote:

>> Curves give
>> better control over what you are changing but levels seems to show what
>> you have in terms of dynamic range.

>Of the two, I've found curves to be much more useful.

It would be even more useful if the interface were bigger, and had more
resolution, and had better curve control tools. Splines are not very
useful, IMO.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
December 29, 2004 12:40:42 AM

Archived from groups: rec.photo.digital (More info?)

In article <9ek3t05e4mf092jd5523g2qsan016qi58u@4ax.com>, <JPS@no.komm>
wrote:

> It would be even more useful if the interface were bigger, and had more
> resolution, and had better curve control tools. Splines are not very
> useful, IMO.

you do realize you can click the grow box to expand the window into a
larger version, and option-click (mac) or alt-click (windows) to get 10
divisions instead of 4, right?
Anonymous
December 29, 2004 1:28:45 AM

Archived from groups: rec.photo.digital (More info?)

John McWilliams wrote:
> Stacey wrote:
>
>> paul wrote:
>>
>>
>>> Curves give
>>> better control over what you are changing but levels seems to show what
>>> you have in terms of dynamic range.
>>>
>>>>
>> Of the two, I've found curves to be much more useful.
>
>
> Yes. My question tho was more along the lines of: Are there some times
> when levels are more useful than curves? Do experienced PSers sometimes
> use both?
>

Yes, I think so John. There are times when I have adjusted levels and
found no need to use curves and there are times when I didn't need to
adjust levels yet touched-up using curves. Then there are times when I
have used both; not too often but I have used both.

When adjusting levels, the entire photo may be affected (depending upon
how the adjustment is done). When using curves, areas of a photo are
affected. As you can see, there may be times when both are applicable.

nick
Anonymous
December 29, 2004 3:16:52 AM

Archived from groups: rec.photo.digital (More info?)

In message <281220041735540872%nospam@nospam.invalid>,
nospam <nospam@nospam.invalid> wrote:

>In article <9ek3t05e4mf092jd5523g2qsan016qi58u@4ax.com>, <JPS@no.komm>
>wrote:
>
>> It would be even more useful if the interface were bigger, and had more
>> resolution, and had better curve control tools. Splines are not very
>> useful, IMO.
>
>you do realize you can click the grow box to expand the window into a
>larger version, and option-click (mac) or alt-click (windows) to get 10
>divisions instead of 4, right?

I do, and that was the context of my complaint. The endpoints need
subtle adjustment often, and the curve is too coarse. The controls are
too simplistic.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
January 4, 2005 12:27:54 AM

Archived from groups: rec.photo.digital (More info?)

paul <paul@not.net> wrote in news:6Kednftmds2y203cRVn-jw@speakeasy.net:

> I don't know how you'd correct a histogram while shooting if it's
> getting dead space at the highs & or lows. Perhaps the aperture effects
> this? ISO? I assume that dead space means you are missing out on
>

If you have dead space at the highs OR lows, then you just need to change
either the aperature or the shutter speed to let in more light or less.

If you have dead space in both highs and lows at the same time, then with
some cameras (My Coolpix 5000, for instance) I can change the contrast
setting in the shooting menu and it will expand the curve. I found this
handy when shooting a distant skyline on a hazy day.

Bob
!