The Sleeping Giant's Sea Lion

by Jakub

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68

While there may not be a "right" answer to this question, there are "correct" answers. A histogram is a powerful tool, and when you understand how to use it effectively, it can greatly help your photography. As you mentioned, a histogram is a representation of tonal range and distribution in a photo. The basic mechanics are as such: A histogram represents ...


19

For myself the easiest way to understand UniWB was the following. Most current digital cameras have twice as much green light sensors as they have reds and blues (referenced as RGBG). Now to achieve neutral gray by changing white balance, usually the red and blue channels need to be amplified more than green. Just a few examples (for Canon 350D): ...


15

You might read this histogram like this: There's nothing wrong with you image. (At most, this histogram says there are "unused" bright tones, so you could maybe expose the photo a bit more, to "move" the histogram a bit to the right -- e.g. use more you your dynamic range to get more of the spider's dark area. But moving to the right might get you ...


15

Yes, it's possible to select by pixels' intensity range. Step-by-step Make a copy of the layer (Layer → Duplicate Layer) Select the duplicate layer, apply threshold (Colors → Threshold) to select the range of intensities. In Layer → Mask → Add Layer Mask (or right click in the list of layers). Select “Grayscale copy of layer” and “Invert mask”. idem: Mask ...


15

Simple: the color of the sky is comprised of the mix of all three channels. If it were gray, there would be equal amounts of red, green, and blue. It's not, though — there's a lot more blue, a little less green, and very little red. Pretty much like this: Check out how the arrows on the slider are pretty much exactly at the same percentages as the spikes ...


15

Well for starters, using the zone system allows you to obtain the correct exposure before you take the photograph. I'm a big fan of getting it right first time - if you take a photo, check the histogram, adjust settings, take another photo, check the histogram etc. you are using up valuable time, especially if you are shooting something time sensitive. I ...


12

In short, there's no useful connection. The histogram shows a certain view of the information in an image, and it's useful for avoiding some specific problems and can be used in image analysis, but without referring to the original image, you can't really tell if a particular histogram shape is good or bad (or even if things which look like they might be ...


11

To add to jrista's excellent answer, an histogram is god-send in bright situations where your LCD is very hard to read (eg: at noon in a field of snow, for example).


11

Most camera bodies (afiak) that display an image histogram, presents a histogram that is based on the JPEG representation of the RAW data captured by the camera sensor. If you do your post processing work with RAW images (and you should ;) ), and you use the camera's histogram display as a guide when taking pictures, then the discrepancy between the ...


11

In the old fashioned darkroom we had a tool called the densitometer. It measured the density (how much light is blocked when you shine a light through) of the negative or slide. It was a bulky and expensive device, and of course it required the film to be developed so it wasn't very practical for use in the field. But we could use it in testing to ...


11

The general rules for histograms still apply, it's just that most of the "weight" of your histogram will be leaning to the left: Your aim will be the same: keep as much of the data in the histogram from clipping at the right hand edge, without leaving too much way down the left hand side. You should be able to see some data reaching all the way across ...


10

The height of each individual, vertical line in a histogram indicates how much of that particular tone your image has, or the tones intensity. As tones in a histogram progress from left (black and shades) to right (brights and highlights), where a particular vertical line lies indicates how intense the tones represented by that line are. If one particular ...


9

I'm not a technical photographer and never made much use of the histograms that I've been seeing for the last 5 or 6 years, until this summer. I went to Israel with family this summer, and as the goal of the group was to see a lot of sites, not to be in various places with ideal photographic lighting, I took a lot of photos in midday sun. To make matters ...


6

Without referencing a white object in your photo, we cannot decide which one has a better white balance. In short, white balance is process of removing unrealistic color cast on your image, i.e., correct the white area in your image that captured as gray. So it cannot be judged by histogram. If you know what part of your image should be white and the image ...


6

I don't think this technique is used widely if at all. Aside from giving broad information about exposure, the particular shape of the histogram is very specific to the image content, so forcing an image to conform to the histogram of a different image would be pointless and quite likely eliminate detail in certain areas. The only possible use would be if ...


5

There is a plugin called Adagio Range Selection that does pretty much what you want. You can't select from the histogram directly, but you can select the upper and lower boundaries.


5

As Alan says, it's a way to get an in-camera histogram that more accurately represents the raw capture. So, the times when you would use it are when you are unsatisfied with the histograms you're getting. The very long and detailed explanation from Guillermo Luijk is here: http://www.guillermoluijk.com/tutorial/uniwb/index_en.htm


5

The histogram in Lightroom 3 does change. Here's an example: Full frame Cropped You'll note that the cropped image has more image information in the top third of the histogram, whereas the uncropped one has more in the lower third. That's what you would expect. So the question is, why aren't you observing this? Are you using Lightroom 3?


4

I decomposed your image into its component colors in the GIMP with Color | Components | Decompose, to Color model: RGB and with 'Decompose to layers' checked. When I look at the individual layers, this is what I see: I guess that the bulk of each "color" is going into painting the background; the red layer is making the background all-black, which is ...


4

For having more contrast in an image, it's good to have a wide range of light intensities in a picture; and for keeping details, neither highlights nor shadows should be clipped. That's about it. You cannot calculate what's aesthetically pleasing, thus I recommend looking at the picture instead of the histogram.


4

The basic thing I use it for is telling at a quick glance if there is enough light. If the histogram is all on the left, it is too dark and at best you will need to do some post-processing tweaks to get a usable photo. If it is all to the right, it will probably be washed out. Note that you can recover somewhat from both of these in post-processing, but you ...


4

There's a maximum contrast ratio a sensor can record. It's usually better to minimise contrast with lighting and boost it in post if necessary. The best histogram shape depends on the subject, again when I'm shooting a studio setup with lights I aim for a flat histogram to maximize the options for post processing.


4

The human eye is more sensitive to green light than red or blue. For that reason, digital sensors have twice as many green photosites than red or blue. The overall luminance of an image, then, is more dependent on the green channel than red or blue. So the luminance histogram will look most like the green histogram. So if the dominant colours in the ...


4

Simple answer: You can't tell how the photographer exposed the images and you won't learn anything about that from looking at the histograms of the processed photos. Chances are that the photographer is shooting in RAW and that the photos are post processed quite a bit. In post you can drag the exposure (that results in a pushed histogram to the left or ...


3

Ansel Adams, who invented the Zone System is still a clever chappy. The zone system is a way of categorising the tones that we can see. A digital camera can only see about +/- 2 zones from what you're metered for. So you have to make a choice on what you want to meter for, what you're willing to turn black or burn out. For me, it's about pre-visualising ...


3

There are several aspects of the zone system which can still be useful, and which the histogram doesn't represent. First, you can use it as an aid to visualization of a scene before you take a picture. This is useful for any case where you care about composition, and this kind of forethought and planning will usually pay off with better results than ...


3

The zone system tells you what to base metering on in a scene of higher dynamic range than your camera could capture, and what you will gain and lose when changing the exposure either way - by adjusting exposure for a higher zone, you will push all the other zones down and lose your lowest zone (and vice versa for underexposing). For example, what was ...


2

If the histogram shows everything bunched up at one end, then have either a very dark or very light image. If the histogram is bunched at the right this means you have a very light image - most of the pixels have recorded lots of light, and lots of pixels will have the maximum value. This is often referred to as blown highlights. While there are some ...



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