iphoto/adjust/levels...???

On Oct 28, 8:04 pm, Shawn Hirn <s....DeleteThis@comcast.net> wrote:
> In article <1193476062.095758.49....DeleteThis@y27g2000pre.googlegroups.com>,
> The Translucent Amoebae <transamoe....DeleteThis@seanet.com> wrote:
>
> > So--
> > in the iphoto's application, there is an edit feature,
> > And within that:
> > Brightness, Contrast, Exposure
> > and Levels.
> > i think i have a good idea of what Brightness, Contrast & even
> > Exposure are/do...
> > But Levels completely baffles me.
> > i've looked and compared the graph to the pictures and i can not see
> > any correlation whatsoever...!!!
> > What is that representing...???
> > What does the x & y axis' represent...???
>
> > Thanx!
>
> Open up a very contrasty photo where there's a lot of light and dark
> areas, then fiddle with the settings under levels such as exposure.
> Notice that as you change the exposure and other controls, the histogram
> in the levels window changes. If you move the end points in the levels
> area to the point where the histogram begins, then adjust the middle
> point, you can bring out a lot of detail in the photo.

i think about them this way...
Brightness seems to increase/decrease the whiteness of all pixels
uniformly
Contrast seems to make dark pixels darker, and light pixels lighter
Exposure is more complicated;
When you lighten a picture, the light pixels get lighter, but the dark
pixels remain pretty much the same darkness. This occurs along a
curve, so the dark pixels are effected, but not by as much.
likewise, when you darken a picture with Exposure, the dark pixels get
darker, and the light pixels remain pretty much the same.

i do use the Levels controls, and i've noticed that when the spikes
are clumped together in the middle, and i slide the dark or light
towards the mountains, it seems to bring out detail by enhancing
surface texture with local contrast...???

But i STILL don't SEE what the mountains are supposed to be
representing...
Obviously; it's a graph of somekind, and as such, the x & y axis must
represent SOMETHING...???
But i just don't see what...???

thanx...???
 >> Stay informed about: iphoto/adjust/levels...??? 

In article <1193733169.993827.142570.DeleteThis@k35g2000prh.googlegroups.com>,
The Translucent Amoebae <transamoebae.DeleteThis@seanet.com> wrote:

> i think about them this way...
> Brightness seems to increase/decrease the whiteness of all pixels
> uniformly
> Contrast seems to make dark pixels darker, and light pixels lighter
> Exposure is more complicated;
> When you lighten a picture, the light pixels get lighter, but the dark
> pixels remain pretty much the same darkness. This occurs along a
> curve, so the dark pixels are effected, but not by as much.
> likewise, when you darken a picture with Exposure, the dark pixels get
> darker, and the light pixels remain pretty much the same.
>
> i do use the Levels controls, and i've noticed that when the spikes
> are clumped together in the middle, and i slide the dark or light
> towards the mountains, it seems to bring out detail by enhancing
> surface texture with local contrast...???
>
> But i STILL don't SEE what the mountains are supposed to be
> representing...
> Obviously; it's a graph of somekind, and as such, the x & y axis must
> represent SOMETHING...???
> But i just don't see what...???

I just googled for "digital photo histogram" and the first hit was
http://www.photoxels.com/tutorial_histogram.html which does a good job
of explaining what the histogram means.
 >> Stay informed about: iphoto/adjust/levels...??? 

On Oct 30, 6:28 pm, Shawn Hirn <s... RemoveThis @comcast.net> wrote:
> In article <1193733169.993827.142... RemoveThis @k35g2000prh.googlegroups.com>,
> The Translucent Amoebae <transamoe... RemoveThis @seanet.com> wrote:
>
>
>
> > i think about them this way...
> > Brightness seems to increase/decrease the whiteness of all pixels
> > uniformly
> > Contrast seems to make dark pixels darker, and light pixels lighter
> > Exposure is more complicated;
> > When you lighten a picture, the light pixels get lighter, but the dark
> > pixels remain pretty much the same darkness. This occurs along a
> > curve, so the dark pixels are effected, but not by as much.
> > likewise, when you darken a picture with Exposure, the dark pixels get
> > darker, and the light pixels remain pretty much the same.
>
> > i do use the Levels controls, and i've noticed that when the spikes
> > are clumped together in the middle, and i slide the dark or light
> > towards the mountains, it seems to bring out detail by enhancing
> > surface texture with local contrast...???
>
> > But i STILL don't SEE what the mountains are supposed to be
> > representing...
> > Obviously; it's a graph of somekind, and as such, the x & y axis must
> > represent SOMETHING...???
> > But i just don't see what...???
>
> I just googled for "digital photo histogram" and the first hit washttp://www.photoxels.com/tutorial_histogram.htmlwhich does a good job
> of explaining what the histogram means.

Thanx, i have never been able to figure out how to get search engines
to return anything useful either...!!!
 >> Stay informed about: iphoto/adjust/levels...???