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Hi
If I load a digital picture into Photoshop, how do I know that it's
overexposed?

Many thanks
J

"Jack" <> wrote in news:bormck$lv3$:

> If I load a digital picture into Photoshop, how do I know that it's
> overexposed?

You can either make a histogram or you can use the "adjust levels" tool.

In both cases you will see approximately the same. If it is overexposed,
the histogram will be cut at maximum value.


Roland

"Jack" <> wrote in message
news:bormck$lv3$...
> Hi
> If I load a digital picture into Photoshop, how do I know that it's
> overexposed?

Dumb answer coming... It's overexposed if the highlight details you care
about are clipped off the high end. You don't need Photoshop to tell you
this.

Thanks Roland

Dumb question coming...
How does one make a histogram ?

J

"Roland Karlsson" <> wrote in message
news:Xns9430EB6F9696Arolandkarlssonchello@130.133. 1.4...
> "Jack" <> wrote in
news:bormck$lv3$:
>
> > If I load a digital picture into Photoshop, how do I know that it's
> > overexposed?
>
> You can either make a histogram or you can use the "adjust levels" tool.
>
> In both cases you will see approximately the same. If it is overexposed,
> the histogram will be cut at maximum value.
>
>
> Roland

"Jack" <> wrote in message
news:bost7r$qsi$...
> Thanks Roland
>
> Dumb question coming...
> How does one make a histogram ?
>

The levels tool displays the histogram in PS. The y-axis is the pixel value
from 0 to 255. The x-axis is the relative number of pixels with the y value.
An overexposed image will be jammed to the right with a pile-up at 255 and
,usually, with a low x value at the 0 side of the graph. Likewise, an under
exposed image will have low x values on the right side, say from y= 200 to
255.


>
> "Roland Karlsson" <> wrote in message
> news:Xns9430EB6F9696Arolandkarlssonchello@130.133. 1.4...
> > "Jack" <> wrote in
> news:bormck$lv3$:
> >
> > > If I load a digital picture into Photoshop, how do I know that it's
> > > overexposed?
> >
> > You can either make a histogram or you can use the "adjust levels" tool.
> >
> > In both cases you will see approximately the same. If it is overexposed,
> > the histogram will be cut at maximum value.
> >
> >
> > Roland
>
>

In addition to the histogram, as others have suggested, you can use the
color picker to analyse the color and brightness of small regions. Use
the color picker to pick the darkest color you can find in the image.
Now look at the brightness or luminance value of that color. It should
be a VERY low number. If it is in the teens or less, you are probably
okay. If it is 25 or 30, or even higher, you may be a bit overexposed.

This check is in ADDITION to the histogram check, not instead of it.

Jack wrote:
>
> Hi
> If I load a digital picture into Photoshop, how do I know that it's
> overexposed?
>
> Many thanks
> J

--
Don Stauffer in Minnesota

webpage- http://www.usfamily.net/web/stauffer

The best way is to analyze it yourself, digital histogams are nice, and
often a useful tool, but they are only a fairly simplistic tool and often
miss the mark if the predominate colors or lighting in the photo are
intended to be light or dark. Color histograms can provide additional
insight into the accuracy of colors portrayed at the extremes, since they'll
show when a single channel gets clipped and that can at times be very
difficult to judge on your own. However, if the colors are still appealing
and relaistically graduated, its hard to imagine that insight mattering all
that much. There is no rule that all the colors in a photo have to avg out
or fall within a predetermined range, or have certain graphically depicted
characteristics, most photos are too complex for that, with the simpler
compositions often giving histogam analysis the biggest challenge. Have a
look at your main subject, are there areas where detail is lost that may
have been within the capabilities of the camera to capture? Are there
surrounding areas of distraction that are exposure related?

"Jack" <> wrote in message
news:bormck$lv3$...
> Hi
> If I load a digital picture into Photoshop, how do I know that it's
> overexposed?
>
> Many thanks
> J
>
>

"Jack" <> wrote in message
news:bost7r$qsi$...
> Dumb question coming...

Doh. Alright. Better answer coming.

> How does one make a histogram ?

Levels shows a histogram, and more importantly the effects your changes are
making. More on this below. (Don has the x-y axes reversed in his
description, but otherwise OK with the remainder of his description.) Ps CS
lets you dock the histogram window in a toolbox. It's a real nice addition,
and reflects its relative importance while manipulating and evaluating
pictures.

Judging usefulness of an exposure goes beyond simply noting how many pixels
sit where on the graph. In context of overexposure, you still might have the
detail you were trying to capture, even though other areas are blown out to
pure white. It depends on what you're photographing, and what your intents
were. Hence, my earlier glib answer.

Levels is a good tool for exploring the tonal range. Aside from just looking
at the histogram, Alt+drag the highlight slider to see what details clip at
each level. The same works for the shadow slider. If the important highlight
details clip immediately, you could reasonably call it overexposure. If they
don't clip unreasonably, it just means you photographed a bright scene.

Curves is the better tool for manipulating the tones, after using Levels for
the initial adjustment and to see what you have. Ctrl+click on your picture
to set a point on the curve. Use the up-down cursor keys to adjust its tone.
Ctrl+Tab to select the next curve point. It's difficult to know what you're
really doing when plunking down points directly with the mouse and then
dragging them around while hoping.