Sign in with
Sign up | Sign in
Your question

D70 - Histogram - what am I looking at?

Last response: in Digital Camera
Share
Anonymous
January 25, 2005 3:27:09 PM

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

OK, so I've rtfm'd, and have an idea of the basics, but any tips on
the histogram? I gather horizontal axis is brightness and vertical
is nr of pixels. (Not actually described in the manual). I suppose
you want the 'centroid' to be reasonably centred, and fairly well
spread but with not too much area in the left or right tails.
Any good primers?

I also gather that the blown highlight display lets me see what
parts of the pic are clipped, and I have a few options:

- knock exposure down manually and "burn"/"dodge" in an off-line prog
- reduce contrast in image optimisation (JPG)
- switch to NEF, where I'll have more bits to recover detail by
doing manual adjustments later off-line

Is that basically right? What am I missing?

--
Ken Tough

More about : d70 histogram

Anonymous
January 25, 2005 3:27:10 PM

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

"Ken Tough" <ken@objectech.co.uk> wrote in message
news:ZrdFGQD97h9BFwnp@objectech.co.uk...
>
> OK, so I've rtfm'd, and have an idea of the basics, but any tips on
> the histogram? I gather horizontal axis is brightness and vertical
> is nr of pixels. (Not actually described in the manual). I suppose
> you want the 'centroid' to be reasonably centred, and fairly well
> spread but with not too much area in the left or right tails.
> Any good primers?
>
> I also gather that the blown highlight display lets me see what
> parts of the pic are clipped, and I have a few options:
>
> - knock exposure down manually and "burn"/"dodge" in an off-line prog
> - reduce contrast in image optimisation (JPG)
> - switch to NEF, where I'll have more bits to recover detail by
> doing manual adjustments later off-line
>
> Is that basically right? What am I missing?
>
> --
> Ken Tough
-------------------
There is a good description of the histogram here:
http://luminous-landscape.com/

Use the pull down menu found on the "Understanding Series" button.

The only thing noteworthy (other than the tutorial), I found, is that
each camera may assign a preference to one of the RGB channels in the
histogram display.
You can verify this by looking at the histograms for each channel separately
in PS.
It is possible to have a "normal" looking histogram with saturation present
in one of the channels.

Regards,
Don F
Anonymous
January 25, 2005 3:27:10 PM

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

Ken Tough wrote:

> OK, so I've rtfm'd, and have an idea of the basics, but any tips on
> the histogram? I gather horizontal axis is brightness and vertical
> is nr of pixels. (Not actually described in the manual). I suppose
> you want the 'centroid' to be reasonably centred, and fairly well
> spread but with not too much area in the left or right tails.
> Any good primers?

If your scene is mainly white, you would want the histogram to show up mostly to
the right. If your scene is mainly dark, your histogram would be mostly to the
left. It's a histogram, not an exposure meter. If you see, for example that it
is likely that there is more information 'rightwards' of the historgram then
likely you over exposed... If there is a lot of blank space between the histo
and the right side, and you know there are white elements in the scene ... you
underexposed.


>
> I also gather that the blown highlight display lets me see what
> parts of the pic are clipped, and I have a few options:
>
> - knock exposure down manually and "burn"/"dodge" in an off-line prog
> - reduce contrast in image optimisation (JPG)
> - switch to NEF, where I'll have more bits to recover detail by
> doing manual adjustments later off-line
>
> Is that basically right? What am I missing?

RAW (perhaps NEF) to conserve maximum information for post edit. If you see
that areas of scene clipped high, then you must reduce the exposure to conserve
detail. If the clipped areas are minor, or deliberately there (lights, some
reflections), then leave them.

Experiment.


--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.
Related resources
Anonymous
January 25, 2005 3:27:10 PM

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

"I found, is that each camera may assign a preference to one of the RGB
channels in the histogram display."

Would looking at a histogram help you determine if you have your white
levels set correctly?
January 25, 2005 3:27:10 PM

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

My understanding is that the only real reason to examine the histogram
is to see if shaddows are clipped (moving off the top left). I shoot
with the highlights screen & darken if there is any flashing burnt
highlights. Further adjustments can then be done in photoshop. If the
shadows are clipped a second shot to overlay/merge might be needed in
extreme cases.

If shooting jpeg that makes sense to see if a contrast adjustment was
needed to spread it out or tighten it up.
Anonymous
January 25, 2005 3:42:21 PM

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

Aldo Pignotti wrote:

> "I found, is that each camera may assign a preference to one of the RGB
> channels in the histogram display."
>
> Would looking at a histogram help you determine if you have your white
> levels set correctly?

I don't think so. The histogram shows how much 'lightness' there is in the
image and are mostly an aid to placing the exposure properly.

White levels go to the color temp of the light source.



--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.
January 26, 2005 2:19:49 AM

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

On Tue, 25 Jan 2005 12:27:09 +0200, Ken Tough <ken@objectech.co.uk> wrote:

>
>OK, so I've rtfm'd, and have an idea of the basics, but any tips on
>the histogram? I gather horizontal axis is brightness and vertical
>is nr of pixels. (Not actually described in the manual). I suppose
>you want the 'centroid' to be reasonably centred, and fairly well
>spread but with not too much area in the left or right tails.
>Any good primers?

The histogram shows you the range of pixel numbers verses brightness, but it may
be useless data!

For example, a night shot is going to be mostly dark, and a snow scene mostly
white, so the histogram will look skewed, but so what?

What you really want to see in the histogram is whether or not there are 'clear'
areas at one or both ends. If there are, it is an indication that you can change
the exposure to take advantage of this range. However, you may find that an
increased range is not necessarily a good picture! Lots of times I've adjusted a
portrait to get full range only to find its made the face too contrasting.
Sometimes limited range is good!

For an other example, if you take a snow scene and see that there are no pixels
at the dark end, you can drop the exposure down and maybe get more detail in the
snow. However, if you see in the next histogram that there is a 'bulge' that
looks clipped off at that end, then you know you went too far, and you have
pixels lost in the black.

It's a bit of hard work using the histogram to take picture exposure info,
because it changes for each picture. But if you really want to maximize your
range, you can shoot a series of bracketed pics and watch the histogram to get
an idea of where you are.

My main use of the histogram is to see if I have any unused space in the
exposure that I can use. Sometimes an automatic expose reading will be a bit
wrong, and you will see it right away by a lack of pixels at one end. It's now
easy to dial in some compensation to use the missing range.

I also find it easier to adj on a 19" monitor rather then in a 1" camera screen!

>I also gather that the blown highlight display lets me see what
>parts of the pic are clipped, and I have a few options:
>
> - knock exposure down manually and "burn"/"dodge" in an off-line prog
> - reduce contrast in image optimisation (JPG)
> - switch to NEF, where I'll have more bits to recover detail by
> doing manual adjustments later off-line
>
>Is that basically right? What am I missing?
>
January 26, 2005 2:19:50 AM

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

The PS Camera Raw Plug-in (CRP) has an RGB histogram and so does
BreezeBrowser which is sort of interesting, that that I necessarily know
what to do with that either... but the cool thing about the CRP is that
you can adjust exposure compensation, brighness, contrast & shadows and
of course WB & watch what that does to the histogram as you tinker.

Hold down alt while sliding exposure or shadows & it shows the areas
being clipped (not apparent on the histogram). The brightness & contrast
dials supposedly don't have this risk of clipping but I noticed
increasing contrast sometimes drops the hump on the histogram so it
looks pretty wimpy. Maybe that's OK too, it just means the highs & lows
are more balanced & less middle tones. It is a funny contradiction
though that a bold high contrast image has a flat looking histogram.

The histogram can also be watched while adjusting all these to see if
parts extend off the top and to expand the image to fill unused left &
right areas though that's not always desireable.

Such complicated interesting stuff!
Anonymous
January 28, 2005 3:26:12 PM

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

Don F <donf11@NOSPAMhome.com> wrote:

> There is a good description of the histogram here:
>http://luminous-landscape.com/
>
>Use the pull down menu found on the "Understanding Series" button.
>
> The only thing noteworthy (other than the tutorial), I found, is that
....

Thanks for this, and for all the other helpful replies.

--
Ken Tough
Anonymous
January 28, 2005 3:32:25 PM

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

paul <paul@not.net> wrote:

>The brightness & contrast
>dials supposedly don't have this risk of clipping but I noticed
>increasing contrast sometimes drops the hump on the histogram so it
>looks pretty wimpy. Maybe that's OK too, it just means the highs & lows
>are more balanced & less middle tones. It is a funny contradiction
>though that a bold high contrast image has a flat looking histogram.

True, it seems counter-intuitive at first glance. Thinking about
that, though, will give me a nice feel as to how 'contrasty' the
image is. It doesn't seem nice to lose contrast range just to
keep a few highlights in though. I suppose that's where your own
custom non-linear contrast map could come in useful (one I left off
my list of potential fixes). Who knows, I might get around to that
one day, but as yet I'm not even printing much.

--
Ken Tough
January 28, 2005 3:32:26 PM

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

Ken Tough wrote:

> ...It doesn't seem nice to lose contrast range just to
> keep a few highlights in though. I suppose that's where your own
> custom non-linear contrast map could come in useful (one I left off
> my list of potential fixes). Who knows, I might get around to that
> one day, but as yet I'm not even printing much.

Are you talking about loading a custom curve into the camera? That might
be helpful if you didn't want to shoot RAW. AFAIK it's only possible to
load one curve though it would be nice to have a low contrast curve for
bright sky situations, etc.

I've come to the conclusion that I really need to bracket for those
bright sky shots & merge the two. I had really bad results shooting the
other day trying to underexpose to save highlights my shots were
terribly underexposed, even with RAW I could not recover them
acceptably. For the amount of work involved to do all that it might well
be wise to load a custom curve instead.
Anonymous
January 30, 2005 7:10:17 PM

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

paul <paul@not.net> wrote:

>Ken Tough wrote:
>> ...It doesn't seem nice to lose contrast range just to
>> keep a few highlights in though. I suppose that's where your own
>> custom non-linear contrast map could come in useful (one I left off
>> my list of potential fixes). Who knows, I might get around to that
>> one day, but as yet I'm not even printing much.

>Are you talking about loading a custom curve into the camera? That might
>be helpful if you didn't want to shoot RAW. AFAIK it's only possible to
>load one curve though it would be nice to have a low contrast curve for
>bright sky situations, etc.

Yeah, exactly. That's what I was thinking of.

>I've come to the conclusion that I really need to bracket for those
>bright sky shots & merge the two. I had really bad results shooting the
>other day trying to underexpose to save highlights my shots were
>terribly underexposed, even with RAW I could not recover them
>acceptably. For the amount of work involved to do all that it might well
>be wise to load a custom curve instead.

The page DonF recommended (http://luminous-landscape.com/) has
mention of the merging for high-contrast situations. I would
love to see the impact of such a curve, since I have been a
bit disappointed at trying to take dramatic sky shots along
with landscape.

--
Ken Tough
January 30, 2005 7:10:18 PM

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

Ken Tough wrote:

> paul <paul@not.net> wrote:
>
>
>>Ken Tough wrote:
>>
>>>...It doesn't seem nice to lose contrast range just to
>>>keep a few highlights in though. I suppose that's where your own
>>>custom non-linear contrast map could come in useful (one I left off
>>>my list of potential fixes). Who knows, I might get around to that
>>>one day, but as yet I'm not even printing much.
>
>
>>Are you talking about loading a custom curve into the camera? That might
>>be helpful if you didn't want to shoot RAW. AFAIK it's only possible to
>>load one curve though it would be nice to have a low contrast curve for
>>bright sky situations, etc.
>
>
> Yeah, exactly. That's what I was thinking of.
>
>
>>I've come to the conclusion that I really need to bracket for those
>>bright sky shots & merge the two. I had really bad results shooting the
>>other day trying to underexpose to save highlights my shots were
>>terribly underexposed, even with RAW I could not recover them
>>acceptably. For the amount of work involved to do all that it might well
>>be wise to load a custom curve instead.
>
>
> The page DonF recommended (http://luminous-landscape.com/) has
> mention of the merging for high-contrast situations. I would
> love to see the impact of such a curve, since I have been a
> bit disappointed at trying to take dramatic sky shots along
> with landscape.
>
Check out Photomatx.

Jan
January 30, 2005 7:10:19 PM

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

Jan wrote:
> Ken Tough wrote:
>
>> paul <paul@not.net> wrote:
>>
>>
>>> Ken Tough wrote:
>>>
>>>> ...It doesn't seem nice to lose contrast range just to keep a few
>>>> highlights in though. I suppose that's where your own
>>>> custom non-linear contrast map could come in useful (one I left off
>>>> my list of potential fixes). Who knows, I might get around to that
>>>> one day, but as yet I'm not even printing much.
>>
>>
>>
>>> Are you talking about loading a custom curve into the camera? That
>>> might be helpful if you didn't want to shoot RAW. AFAIK it's only
>>> possible to load one curve though it would be nice to have a low
>>> contrast curve for bright sky situations, etc.
>>
>>
>>
>> Yeah, exactly. That's what I was thinking of.
>>
>>
>>> I've come to the conclusion that I really need to bracket for those
>>> bright sky shots & merge the two. I had really bad results shooting
>>> the other day trying to underexpose to save highlights my shots were
>>> terribly underexposed, even with RAW I could not recover them
>>> acceptably. For the amount of work involved to do all that it might
>>> well be wise to load a custom curve instead.
>>
>>
>>
>> The page DonF recommended (http://luminous-landscape.com/) has
>> mention of the merging for high-contrast situations. I would
>> love to see the impact of such a curve, since I have been a
>> bit disappointed at trying to take dramatic sky shots along
>> with landscape.
>>
> Check out Photomatx.


Hmmm... http://www.hdrsoft.com/

" Saving time in post-processing
Photomatix Pro is designed for productivity -- automatic blending,
unlimited stacking, easy comparison of results and batch processing save
hours of masking and layers work in image editing softwares."
!