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Tips interpreting histogram on 20D please

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Anonymous
January 7, 2005 12:22:16 PM

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

Does anyone have any advice regarding 20D histograms, like what does a
good one generally look like, and when should exposure be adjusted? I
realize it's hard to be specific but generally speaking. I don't see
anything in the manual other than the reference to the flashing
highlights, indicating overexposure. Are there any web pages covering
this subject? TIA.

Paul
Anonymous
January 7, 2005 12:22:17 PM

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

pjruiz(nospaam) wrote:
> Does anyone have any advice regarding 20D histograms, like what does
a
> good one generally look like, and when should exposure be adjusted? I

> realize it's hard to be specific but generally speaking. I don't see
> anything in the manual other than the reference to the flashing
> highlights, indicating overexposure. Are there any web pages covering

> this subject? TIA.

I am also reading on the subject a bit. For best results, just google
for "interpreting histogram digital". Read all you can and then come
back to the NG with the doubts.

http://www.sphoto.com/techinfo/histograms/histograms4.h...
http://www.acdsystems.com/English/Community/ColumnsArti...
- Siddhartha
Anonymous
January 7, 2005 1:30:17 PM

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

In general, a healthy histogram should look like a bell curve. Tall in
middle, short on sides. The far left signifies the darks, & far right
the lights. If you have the histogram extending into either side, it
means that you have 'clipped' , over-exposed or under-exposed your
image, and that is not good. Adjust your aperture, ISO, or shutter.
Related resources
Anonymous
January 7, 2005 4:25:40 PM

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

Thanks to all.

Paul
Anonymous
January 7, 2005 8:41:02 PM

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

http://www.luminous-landscape.com/tutorials/understandi...
ing-histograms.shtml

http://www.luminous-landscape.com/tutorials/expose-righ...









"pjruiz(nospaam)" <"pjruiz(nospaam)"@charter.net> wrote in message
news:wVxDd.11248$vS.324@fe03.lga...
> Does anyone have any advice regarding 20D histograms, like what does a
> good one generally look like, and when should exposure be adjusted? I
> realize it's hard to be specific but generally speaking. I don't see
> anything in the manual other than the reference to the flashing
> highlights, indicating overexposure. Are there any web pages covering
> this subject? TIA.
>
> Paul
Anonymous
January 8, 2005 12:37:39 AM

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

zimmy51@aol.com wrote:
> In general, a healthy histogram should look like a bell curve. Tall in
> middle, short on sides. The far left signifies the darks, & far right
> the lights. If you have the histogram extending into either side, it
> means that you have 'clipped' , over-exposed or under-exposed your
> image, and that is not good. Adjust your aperture, ISO, or shutter.
>
I'm sorry, but that's plain wrong. Some perfectly exposed images are way
clipped on purpose, or simply because there's no way to expose the
subject properly without over or underexposing other elements that are
part of the composition.

In such cases, no adjustments are warranted.

--
John McWilliams
January 8, 2005 11:24:38 AM

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

John McWilliams wrote:
>
> Some perfectly exposed images are way
> clipped on purpose, or simply because there's no way to expose the
> subject properly without over or underexposing other elements that are
> part of the composition.
>
> In such cases, no adjustments are warranted.


Of course you might want that effect but it seems it would be a simple
thing for digital cameras to work in some sort of 'filter' for softening
high contrast scenes so that all the histogram is filled but not
overfilled. Increasing contrast is easy post processing because you just
dump information, in fact many cameras have software contrast
enhancement. Even if you want a harsh contrast effect, it'd be better to
capture a more full range image and adjust it later with curves.
Anonymous
January 8, 2005 3:09:25 PM

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

paul wrote:
> John McWilliams wrote:
>
>>
>> Some perfectly exposed images are way clipped on purpose, or simply
>> because there's no way to expose the subject properly without over or
>> underexposing other elements that are part of the composition.
>>
>> In such cases, no adjustments are warranted.
>
>
>
> Of course you might want that effect but it seems it would be a simple
> thing for digital cameras to work in some sort of 'filter' for softening
> high contrast scenes so that all the histogram is filled but not
> overfilled. Increasing contrast is easy post processing because you just
> dump information, in fact many cameras have software contrast
> enhancement. Even if you want a harsh contrast effect, it'd be better to
> capture a more full range image and adjust it later with curves.

Well, ah, yes. This is exactly one of the benefits of capturing in RAW.
You can output several exposures from the same image file, and then
blend them as you like, effectively increasing the range of detail by a
large amount.

--

John McWilliams
Anonymous
January 8, 2005 4:17:10 PM

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

John McWilliams wrote:
> paul wrote:
>
>> John McWilliams wrote:
>>
>> Of course you might want that effect but it seems it would be a simple
>> thing for digital cameras to work in some sort of 'filter' for
>> softening high contrast scenes so that all the histogram is filled but
>> not overfilled. Increasing contrast is easy post processing because
>> you just dump information, in fact many cameras have software contrast
>> enhancement. Even if you want a harsh contrast effect, it'd be better
>> to capture a more full range image and adjust it later with curves.
>
>
> Well, ah, yes. This is exactly one of the benefits of capturing in RAW.
> You can output several exposures from the same image file, and then
> blend them as you like, effectively increasing the range of detail by a
> large amount.
>
To expand: Yes, you bring in one exposure on top of another, and so
you'd have (at least) two layers. Using layer masks is the best, but not
intuitive for many PS users. A crude but immediately effective way is to
erase parts of one layer to reveal what's below it.

Another method that I am curious about is whether tinkering with Blend
modes could achieve a good result.

--
John McWilliams

ps. I answered onto my own post because the question removed all
context. Leaving in just enough of the previous quote is helpful.
January 8, 2005 5:20:15 PM

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

How do you mean? Like layering them in Photoshop?

Paul
!