Re: Print stills question

Cathy wrote:
> "Mark²" <mjmorgan(lowest even number here)@cox..net> wrote in message
> news:R7cgf.5051$dv.2587@xxxxxxxxxxxxx
>> Cathy wrote:
>>> "ASAAR" <caught@xxxxxx> wrote in message
>>> news:1c52o1de7khig2a5frdurctjre535nlmr6@xxxxxxxxxx
>>>> On Sun, 20 Nov 2005 16:19:59 -0500, Cathy wrote:
>>>>
>>>>>> The histogram (I assume that the W5 has one) can
>>>>>> also help point out exposure problems. If you don't like what
>>>>>> you see there, make whatever adjustments are necessary and
>>>>>> reshoot. That'll save a lot of time back at the computer and
>>>>>> probably reduce the amount of wasted photo paper and ink.
>>>>>
>>>>> I am not ready to go into histograms. They seem very complicated
>>>>> to me. I wonder if most people who have histograms ever use them
>>>>> or understand them. I like things kept simple.
>>>>
>>>> You could train a chimp to understand histograms.
>>>> Just because
>>>> it's a chart doesn't mean that there's any advanced math involved.
>>>> Some, but not all, of the more advanced photographers here
>>>> denigrate histograms because they're too simple and don't provide
>>>> enough information. But for typical shots, there's nothing to
>>>> work out. At a glance you can look at the curve and tell if the
>>>> exposure was probably good or not. They're really very, *very*
>>>> simple. It's only unfamiliarity that has you thinking that
>>>> histograms are complicated. The truth is that they're the
>>>> opposite, quite simple. Basically, you'll want the curve in the
>>>> histogram to be centered most of the time. If you see that it has
>>>> shifted far to the left, the shot is probably underexposed. If
>>>> shifted too far to the right, you probably gave the shot too much
>>>> exposure. Calculations not needed. If you have the flu and
>>>> aren't thinking too clearly, it may slow you down such that it
>>>> takes much longer to understand the histogram's implication, maybe
>>>> half a second or so. Normally, when you're in good health, you'll
>>>> need much less time than that. <g>
>>>
>>> I don't have the flu so the half a second has past and my thinking
>>> is the best it is going to be, for the moment at least. Thanks for
>>> the histogram information. Now I know :) But how often do people use
>>> histograms? mainly when they are not sure if the picture will be too
>>> dark or light? I don't imagine you would need it outside.
>>
>> Actually, the presense of strong light isn't the determining factor
>> of when it is helpful. An example of this fact is snow.
>> You could be under VERY sunny skies, but your snow pictures will
>> often come out FAR too dark.
>
> Well luckily we have had no snow yet, but eventually we will get some.
> There is a snow mode setting on the W5. wouldn't do much good for
> those living in Florida or CA or southern climes.
>
>> Remember...there is PLENTY of light. That's not the issue.
>> The issue is the fact that your camera doesn't have any idea what
>> it's pointing at.
>> For all it "knows", you're pointing at a grey dress, and so it turns
>> the exposure value WAY down to compensate what the snow...which it
>> assumes is a grey color that is far too bright...and therefore in
>> need of less exposure.
>
> In the case I was talking about where my photos were a bit too dark -
> not all of them were dark. The ones which turned out ok were taken in
> areas of the living room where there was no light, so yes, it makes a
> difference.

Yes, it does make a difference once you reach the limits of what light the
lens allows in, or the length of time your camera will allow your shutter to
remain open. If you've got it in full auto mode, your camera will attempt
to compensate...until it reaches the limt of lens aperture size or shutter
speed duration. Once you pass those limits, it can't create more
light--unless you crank up the ISO, which simply means your camera will
increase the amplification of what little light signals your sensor picks up
(this is a gamma increase), which is what leads to overly noisy renditions
in images. It might manage to present a well-exposed image, but at the
expense of noise as a result of the heavy gamma amplification.

>I notice this myself, even in film cameras. If some of the
> picture composition is a bit dark area, its going to be darker than
> the rest of the picture.

I never meant to imply that the difference of lighting WITHIN a shot wasn't
a problem. That's the bane of ALL photographers! -Finding light that is
"gentle" enough to allow shadow detail...AND highlights that are overly
bright (blown)....

No camera can set differing levels of exposure for portions within the same
image in the actual exposure. They can take the sum of those values and
attempt a happy medium, but it's never going to be perfect in shots
containing more contrast than the film/sensor can handle. The camera has to
choose what portion of the image to expose for. This is why shooting
landscapes at mid-day is not the best plan--because the light areas are SO
much brighter than the shadow areas (under trees, next to boulders, etc.)
that you'll end up with super-bright light elements, and pitch-black shadow
areas. Why? -Because you only get one exposure level for the entire scene.

Some people take multiple shots, identically framed, but taken at different
exposure levels. Then in Photoshop, they combine the two images...keeping
the shadows in the image from the shot that had more exposure...and the
bright areas of the scene they keep from the less-exposed shot. This is one
of the few ways to deal with the fact that cameras only get to use one
exposure for an entire shot.

-Mark


.

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