How to properly interpret a Histogram?

[Sonny]

I would like to better undersand how to do this. Can you post any tips, advice, or articles you guys might have.

Also, am I able to post the histogram information from my 20d (kinda like the EXIF data)?

[JohnT]

Here's a decent article on understanding histograms. It's entitled "Understanding Histograms."

http://www.luminous-landscape.com/tu...stograms.shtml

[Skutty2Shots]

thanks for the link Im excited to put what i learned into practice!

[ThePhilosopher]

A hump to the left with a tail to the right means an image with more darks than lights; photoshop is pretty good at report statistical information - how and where that information is photoshop cannot tell you (nor if it is correct).

[donlfaulkner]

Thanks, John, for the link, very informative. And thanks Sonny for the question.

[tertius]

Originally Posted by Skutty2Shots

thanks for the link Im excited to put what i learned into practice!

Thanks for the 4 year bump, I was just thinking about this last night.

[Fishn2photog]

Thanks guys. That was the most understanding I've gotten out of a tutorial for Histograms yet.
Good information never grows old. :)

[neyekon]

In my opinion the biggest thing to consider when analyzing the histogram for an image, because depending on the light source and subject a histogram can look any which way and be correct for that exposure, is the far left margin and the far right margin. Far left is complete black (no detail in that area) and the far right is complete white(no detail in that area), so if your histogram shows a spike and especially a thick spike on the far left(shadow) or far right(highlight) you have NO DETAIL! in that part of your image, so are you ok with that?... is what you have to ask yourself. You can also view your highlights indicator in most DSLR's to see where those BLOWN HIGHLIGHTS are, they will flash in solid white. Once you expose an image with blown highlights or black shadows no levels adjustment, dodge or burn in photoshop(PP) will bring any detail back. You often see blown highlights in the form of glare on water, metal and any shiny subject that reflects strong light, sometimes leaves on trees on a sunny day.
The way I decide how to expose an image is to mostly keep an eye on the highlights indicator and bracket(taking several exposures at adjacent settings, +,_). I adjust my exposure settings(aperture, shutter speed) till I get blown highlights (blinking white areas) in my highlights indicator, then I pull back 1/2 stop at a time till I have no blown highlights. This is the lightest I can capture this scene with FULL DETAIL in the lighter areas. As for the shadows well I have to zoom in on my LCD and view those areas and look for detail in the darkest areas. Then it becomes a matter of compromise, what detail is more important to my scene? Because when you shift to improve the detail in your highlights you damage the detail in your shadows and vise versa. This is especially true in a HIGH CONTRAST scene, the higher the contrast between light and dark the harder it is to get a well exposed image, that is why photos at high noon on a sunny clear day are difficult to expose well. I personally like PARTLY CLOUDY days to shoot because I use the clouds covering the sun as a filter, I shoot a scene in full sunlight when the sun is out then I adjust my settings and wait for a cloud to cover the sun and expose the same scene again at a lower contrast, I later decide which is the better exposure.
Ansel Adam's Zone System is based on the scientific method of shifting the various zones(levels of luminance) to achieve optimal exposure, he was the master. He worked with film(silver halide).Complete black is zone I and complete white is zone X, mid grey is zone V. Adams used Roman numerals.
The human eye is able to distinguish between something like 15 levels of luminance(zones).
A digital camera can only record between 5 and 7 levels (zones), so this is what you see in your histogram.
The histogram is not an instrument that tells you whether your image is rightly or wrongly exposed...it is a tool to help you decide how to expose your image. It is a graphical representation of your exposure.

[Gambit]

I won't disagree with what's said before - 'cause it's good - but just offer a suggestion:

I've found that playing around with shooting on a sunny snowscape or sandscape is a good way to practice analyzing histogram + image, at least on the bright end. If you let the camera autoexpose for the scene then your actual subject (person, object, whatever) is too dark. So you make manual adjustments and get used to seeing the spike to the right and saying - oh, that's OK, because my subject is this little bump here near the middle. :) You can do the same thing with a properly-lit subject against a dark background like a night sky. (Leave out the flash since that's a whole other twist.) Note that if you let your subject fill the frame then that alters the exercise.

A Christmas tree can be a lot of fun to play with.

[Fishn2photog]

Thanks Ricardo for the detailed info. Very helpful.
I have never experimented with bracketing. I would like to, but I don't have a program
that would then blend them together.
I am hoping to get Lightroom in the next month, but as of right now I am limited to using Gimp.
Which program do you suggest for blending, or stacking these bracketed shots?

Thanks again.

Kelly

[neyekon]

Originally Posted by Fishn2photog

Thanks Ricardo for the detailed info. Very helpful.
I have never experimented with bracketing. I would like to, but I don't have a program
that would then blend them together.
I am hoping to get Lightroom in the next month, but as of right now I am limited to using Gimp.
Which program do you suggest for blending, or stacking these bracketed shots?

Thanks again.

Kelly

Kelly, I bracket to ensure that I have an exposure that I am pleased with (can work with) and not really to blend or stack later in PP. I can't advices on that subject but here is what I often do. After bracketing I may pick an exposure that has the right amount of detail in the shadows but slightly over exposed highlights(blown highlights), so in PP I will adjust levels slightly, dodge and burn where needed and then CLONE out the blown highlights. Cloning requires some practice to get right but it is easy to do on skies, grass and trees...on skin you need to match the skin tone well. I use Photoshop CS and I can keep an eye on the histogram for that image as I work on it and make adjustments.

[Fishn2photog]

ok, great. I have never thought about attempting to clone the sky for blown out areas. Thank you for the advice it is really appreciated.

[jeffclow]

Originally Posted by Fishn2photog

Thanks Ricardo for the detailed info. Very helpful.
I have never experimented with bracketing. I would like to, but I don't have a program
that would then blend them together.
I am hoping to get Lightroom in the next month, but as of right now I am limited to using Gimp.
Which program do you suggest for blending, or stacking these bracketed shots?

Thanks again.

Kelly

Two good programs for use in blending bracketed shots are Photomatix and Dynamic Photo HDR .... both offer full functional free trial downloads.