Tag: histogram

Histograms: get to understand them and improve your photography

Today I want to talk about one of the most helpful features of the camera- the histogram. Don’t think I always liked histograms. When I started, I found them complicated to understand and in fact, I totally ignored them for a while.  However, once I saw the point of the histogram, I started checking them on the screen of my camera every time I was taking a shot. Trust me; the time invested in understanding histograms is totally worth it. They will become one of the best tools you will have, both in the field and in post-processing.

Histogram

What is a histogram?

The histogram is a graph that shows the range of tones in your photo, in other words, it tells you which shades you have in the photo you just took.

Check the histogram in the field

You can set your camera to show you the histogram in its screen each time you take a photo. This is quite handy, especially at the beginning when you are still not used to checking it and you might forget to ask for it. In my Nikon camera, in order to see the histograms in the playback, I needed to check the Histogram in the menu of the Display mode. If you have another type of camera, have a look at the Manual and check how you can set it. It will probably be something similar to what I explained for the Nikon.

Most cameras also have the option to show you the RGB histogram. In fact, this is a group of three histograms, each one showing you the histogram of colors Red, Green and Blue. Today I am going to focus in the general Histogram, but I just want you to know that you have the option to use it by the 3 colors as well, should you choose to do so.

Histogram

Check the histogram in Lightroom

Once you import a photo to Lightroom, you can automatically check the histogram from the Library and Develop modules.

Histogram

Getting familiar with the histogram

Histograms can look a bit scary at first, but once you know what to look for, they are quite friendly. The histogram is a graph with a horizontal axis which represents the shades you have in your photo. On the left edge you have the pure blacks and as you go to the right on the axis you have lighter and lighter tones until you reach to the pure white in the right edge. I have a little trick to remember where are the blacks and whites in the histogram. I always think the histogram is like “B&W photography”, black is first (in the left) and whites after them (in the right). For this trick to work you have to think from a left-to-right writing mode.

OK, so now we know what the horizontal axis means. What about the height of the histogram? It tells you how much of each shade you have in the photo. The basic principle of reading the histogram is the same; the more peaks you have in one area on the horizontal axis and the higher they are means that these are the tones and shades that are the most dominant in the photo.

Histogram

Let’s see this in a real photo:

Histogram

 

The histogram is a great tool for getting well-exposed images. A general rule of thumb is to have the histogram stretched all over the horizontal axis and avoiding having strong peaks (spikes) at the extreme left and/or right of the axis.

Histogram
This photo is quite balanced, you can see that the histogram stretches almost all over the horizontal axis, the most dominant colors here are bright and for that reason, we see higher peaks on the right side of the histogram (but not at the edge)

A photo with too many picks in the blacks means that it is too dark or underexposed. To correct the exposure, you will need to increase the light of your image by, for example, using a wider aperture or increasing the ISO.

Histogram
This photo was under-exposed, that is why it is so dark and the histogram stretches only over the left-hand side of the axis, and we see that the peaks (which are high enough to be called spikes) are concentrated at the left-hand edge

On the other hand, if the photo has a lot of high picks in the white, it means that it is overexposed or even burnt. This time, to correct the exposure, you will need to decrease the light of your image by, for example, using a smaller aperture or a lower ISO.

Histogram
This photo has been over exposed and parts of it are even burnt, the histogram shows just that; we see the graph is very low the most part of the axis and only towards the right-hand edge of the axis the histogram rises sharply

 

Now you know! If you see that your histogram is too much in the blacks or in the whites, this means that you MIGHT need to correct the exposure of the image. Notice that I said MIGHT. Why? Because as photography is a creative craft, it might happen that having a underexposed or overexposed photo is exactly what you are aiming for. You need to think what do you need in your final image and then see if the histogram you have matches what you are looking for. I will show you with a little game!

Let’s play the histogram game!

I am going to show you a histogram and you need to decide which kind of photo might correspond to it. Spoiler alert! Don’t scroll down too far or you will see the answer! Let’s see the first one:

Histogram 1

 

 

histogram-correfocs

Options:

  1. A boiled egg on a white table
  2. A night photography of a street event
  3. A chess board
  4. A multi-color chicken

Solution: Number 2! In night photography you will get histograms with a lot of pick in the blacks area. But this is normal because night is dark and black is what we expect to find in the frame.

Histogram

Histogram 2

 

histogram-egg-white

Options:

  1. A boiled egg on a white plate
  2. A beach at night
  3. A chess board
  4. A gray cat on a brown sofa

Solution: Number 1! We got a histogram with a lot of whites because the image is mostly white!

Histogram

Histogram 3

histogram-egg-black

Options:

  1. A polar bear in the snow
  2. A groom in black sitting in a black car
  3. A multicolor bouquet of flowers
  4. Eggs in a white plate on a black table

Solution: Number 4! Here the histogram shows picks in both blacks and whites and almost no middle tones because the photo has high contrast: white and black are the main colors.

egg-in-black-1

Histogram 4

Histogram

  1. A cat in the middle of the night
  2. A bride in the snow
  3. A colorful house with a sunburst
  4. A colorful patchwork blanket

Solution: Number 3! The beautiful Gaudi House and the most part of the photo is well exposed, so the histogram has a lot of middle tones. However, the sun-star makes the whites in the histogram quite high. Exactly what I wanted!

Histogram

What do you think about histograms now? Still scary? I hope not! It takes a bit of practice to get used to them, but believe me, it is totally worth it! Grab your camera and tell me how it goes! Have a happy shooting!

Histograms – From your camera to Photoshop

In this post I want to take a detailed look at one of the most basic tools used in image processing and that is sometimes overlooked by photographers. I am talking about histograms, an incredible useful way of looking at the data contained in an image that can give a lot of information both during the capture of an image with your camera and during the post-processing using an image processing software such as Photoshop.

What Is a Histogram in Photography?

But let’s first take a look at what a histogram is. A histogram is a graphical representation of any type of information, it does not have to be an image. In formal terms, a histogram is a bar plot that represents the number of occurrences (y-axis) of a given event (x-axis). This could be, for instance, the number of people with a given age within a group. Imagine, for instance, a photography club where the members have different ages as follows:

  • 20 years old: 3 members
  • 21 years old: 1 member
  • 22 years old: 1 member
  • 23 years old: 4 members
  • 24 years old: 1 member
  • 25 years old: 6 members
  • 26 years old: 0 members
  • 27 years old: 2 members

A histogram representing the values above would look like the following figure.

hist1You can see the age range represented on the x-axis and the number of members with a given age on the y-axis. This way of presenting the information is very simple and easy to interpret and hence the widespread use of histograms in all branches of data analysis.

When talking about photography, the x-axis will represent the intensity or brightness (which can go from 0 to 255 on an 8-bit image) and the y-axis will represent the number of pixels with that given brightness. In the case of a grayscale image, a single histogram contains all the information of the image while in the case of a color image three separate histograms are needed, one for each of the basic colors.

Notice that given an image, a histogram can be constructed, but given a histogram, an image cannot be constructed. In other words, when a histogram is created, important information is lost and thus histograms cannot be used as compressing algorithms. This is because the histogram tells us how many pixels have a given brightness level, but it does not give any information on the location of those pixels within the image.

So what information can we get from a histogram? This is related to a rule of thumb according to which the more spread among all values a histogram is (i.e. flat) the more balanced the image will be. Now, when applying this rule, you need to take into account what type of image you are dealing with.

Take, for instance, the following black and white image of the Charles Bridge in Prague together with the histogram (highlighted with a red rectangle) as shown in Photoshop.

hist2

There are a couple of things that we can learn from this image. First of all, the scene looks rather dark, and that is why almost all the pixels are on the lower (leftmost) half of the histogram. The histogram is ordered from left to right, with the darkest value (0) on the left and the brightest one (255 when working with an 8-bit image) on the right.

In addition to this overall distribution of the brightness values, it is also noticeable that there are two main peaks with a valley in between. In this particular image, the reason for these two peaks is that both the water and the bridge itself are rather dark while the rest of the buildings and the overcast sky are lighter. This means that the scene itself lacks of mid tones and hence the gap in the histogram.

If we improve the image by increasing the brightness and the contrast, we end up with a much flatter histogram that also covers a wider range of brightness values.

hist3

Now you can see how the center of the bulk of pixels moved to the right and it lies much closer to the center of the histogram. At the same time (and as a consequence of this), the image looks much more balanced than before.

If you look closely to the histogram, especially on darkest pixels, you can see that the bars are now much more disperse than before with a lot of variations and low values intertwined with high values. This is actually a consequence of the algorithm used to increase the contrast in Photoshop, which is similar to a histogram equalization.

Now, what happens if your image was intended to be dark? Good photos are not necessarily those that comply with all the rules known like for instance a flat histogram, completely in-focus or well balanced in colors. After all, that is why automatic modes do not always produce the images we are looking for.

The image below, once again from Prague, is a backlit scene that was intended to be dark in order to create a high contrast photo as a result.

hist4

Notice how the histogram shows most of the pixels on the left side with a relatively high peak on the far right side. This is the result of having the Sun on the image which, even though small, is very bright while the rest of the scene is underexposed to capture the silhouettes and shadows. Trying to get a flatter histogram with this image would render a completely different (and unwanted) result.

Finally, the image below, from the Red Square in Moscow, is a much more balanced one, something the is reflected on a histogram centered at the mid tones. Even though there is a high concentration of pixels on the middle, the overall distribution is symmetric and has a good coverage of all the values without getting into the extremes (under or overexposed areas). This is also a natural consequence of the scene being captured, with no strong shadows or light sources included.

hist5

Notice that even though this is a color image, the histogram I am showing is the luminosity one. This is because what we are interested on here is the exposure balance of the picture, so the full color histogram will not yield any useful information for our purposes.

As you can see, in general, the use of a histogram can be very useful, but you need to get used to the particularities of each image in order to correctly read it. When capturing an image, it is useful to look at the histogram for a couple of reasons. First, the back screen of your camera can be brighter or darker than the average monitor. This means that you could get disappointed when you get back home and open your images with your computer. Also, if the ambient light is too strong, the contrast of the camera screen might no be good enough to distinguish whether your image is properly exposed or not. However, a histogram will always be visible and, as long as you stay away from the extremes (unless that’s your intention!), once you get back home you will at least be able to do a good job with post-processing, since your image will not have completely dark or burnt out areas.

Something similar goes with post-processing. No matter how bright or dark your monitor is, looking at the histogram will always give you an objective assessment of the exposure of your final image. This way you will avoid the problem of publishing a photo that looks too dark or too bright in other people’s monitors.

I hope this post was useful to you. Next time you are out making photos, look at the histograms of the photos that you take and I am sure that with some time you will incorporate this great tool in your workflow. And as usual, if you have any question, just write me an email!

Lightrooms Histogram

In this tutorial I want to take a good look at Lightroom‘s Histogram and explain to you how to use it to help with your images and make them look spectacular.

You can see the Histogram both in the Library Module and the Develop Module, but you can only really use it for the Develop Module.

So, click on Develop.

histo

You will see it at the Top Right hand corner.

histo1

You can also access it by pressing (Ctrl+0) that’s Control + Zero, or on a Mac it will be Command + Zero.

So we could go super in depth here talking about the Histogram, but that is really not necessary to learn how to use it and get great results.

The Histogram is really just a Graph plotting out all the pixels on your image.

In the image below, where I have highlighted you will notice R G B with percentages on it, and you will notice how this changes as you hover over areas on your image. This is useful when you are checking areas and you think it looks a little too “Red” or whatever, and you start to change the colours up trying to balance it out, you can use these percentages as a guide for that.

histo2

You’ll understand more as I go along.

You will also notice when you hover over the Graph it is split up into 5 sections.

Blacks

Shadows 

Exposure

Highlights

Whites

By clicking and holding on these individual areas you can you can then manipulate your images.

Play around with each one for a few minutes and when you are familiar, Press Ctrl Z to undo until you are back at the start.

For Photography we would mostly use the Highlights and Shadows area, we would also play around with exposure, but the first two would be our main focus so we’re not losing much detail. For example, a bright Sun or edge of a cloud may be far too bright and you’d want to bring that down just a touch.

The same goes for the opposite , like Black Wheels on a Black Car, you may want to take it back a little and show a bit more detail.

So as an example, we’ll take my starter image below.

20140920-IMGL6900-2

As you can see it’s a little Dark due to the exposure, the Highlights aren’t great and it’s a little saturated with colour.

To Fix this, I’m first going to Click on Highlights and slide it to the Right a little, to give a bit of life to the models.

Then I’m going to do the same with my Shadows, only this time I’m going to slide to the left a little to bring out those Darks more in the Eyes, Background and Hair.

And Finally, I’m just going to play with the Exposure a little, it’s not really necessary, but it is good to have a look and see if I can balance the image just a little and see if I can make any further improvements.

You can also play with the Blacks and The Whites too, I found that by sliding the Black area to the right it gave me a little bit more colour.

Now you will notice on the Histogram, there are two upward facing triangles.

histo3

When you click on them, what they indicate are the areas in my image that is absolute Black or absolute White, my whites were fine which means my Highlights are all good and the Blue Dots Highlighted in the Image above are true Black, on this occasion those true Blacks are fine, there’s no problem there. But as mentioned before, you may lose some detail in the Shadow areas, you’d then have to play with Black, sliding back and forth to try to fix it as best as you can.

In my image the Blacks are spot on, no problems with those as they’re deep in the Shadows.

To check back and forth instead of clicking on them all the time, you can press (J) to show both Whites and Blacks, Whites will be in Red and Blacks in Blue.

So I hope that has enlightened you a little on the Histogram, it looks scary but it really isn’t.

20140920-IMGL6900-2

So if you like our Tutorials and want to get more into Lightroom check out or Lightroom Products

We also have some FREE Lightroom Presets which are awesome! Enjoy 🙂

Recovering blown out images in Lightroom

Fall can be a great time to capture many different looks, because of the constant change in weather and colors. On the day of the photo, I wanted to be able to move around quickly and did not want to lug around a bunch of equipment that would get wet and dirty, so all that I used was my camera and tripod. Only using natural light saved me from having to bring extra gear, but also presented a problem. On this day it was very rainy, misty and foggy which gives me the atmosphere I am looking for, but it often times looks washed out in the raw file. If you have ever shot in fog, you know that it can be hard to capture enough detail in the distance and keep your subject properly exposed. All of the moisture in the air catches the light and often times gives you blown out the part in the image.

In this tutorial I am going to walk you through what you need to know to be able to recover an image in Lightroom, that may be blown out.

1. Temperature

This is what the RAW file looks like straight from the camera. The only difference I made was turning down the temperature slightly, as I had my original at around 5500. Now you may be wondering, how do you know where to set the temperature and in reality I don’t. All of these adjustments are not in an exact order, there is a lot of jumping back and forth, from section to section and tweaking until you find what you like. I turned down the temperature knowing that I wanted a cooler and more moody feeling to the image. I wanted to bring out the cold and lonely feeling of someone in a world of their own.

Before we go to the next step take a look at the Histogram and notice the lack of detail in the sky portion of my image.

RecoveringBlownOutImages1

2. Exposure

This is where we are going to make the adjustments to be able to recover some of that sky. I mentioned earlier that shooting in this kind of weather becomes hard to expose properly because the dynamic range can be so vast. When I was shooting, my objective was to set my camera so that I could get as much information in one exposure as possible. There were other ways I could have set the camera (like boosting the ISO) to capture more info, but I kept getting the little island blown out, so I stuck with the settings you see (right under the histogram).

I boosted the shadows/blacks and brought down the highlights/whites. I normally would not do such harsh adjustments, but I needed to in this situation, to achieve my end result. If you compare the histogram of the 1st image with the one below, you will notice that not as much of the right side (white/highlights) of the histogram is clipping.

We can now see that there are some clouds in the sky (slight as they may be) and it is not all white, with no information. This is not enough, though, we have information in the sky, but the image looks bland and the color still does not fit the mood we set out to create originally. The next few steps will be more about editing the color.

RecoveringBlownOutImages2

3. Color

Steps 3,4 and 5 are a peek into some of the color editing decisions I made to pop the subject out at the same time as showing some of the background information we recovered, using the previous steps. I will be doing a color editing tutorial in the future, but in the meantime check out our tutorial for giving your photos a retro feel. In the previous step we recovered the highlight and shadow details, but in the process, we flattened out the image. To fix those adjustments one way to add contrast and color adjustments to your photos, is to use the Tone Curve.

RecoveringBlownOutImages3

4. Color

Next, I played around the HSL (Hue/Saturation/Luminance), again just a peek at your own photos will ask for different settings.

RecoveringBlownOutImages4

5. Split Tone

Then I added more of a cool color to my shadows, using the Split Toning.

RecoveringBlownOutImages5

6. Final Steps

After getting the color  I was going for, I did some light spot removal and added some noise. I do have to mention that for the color work mentioned above, I did use a preset as a starting point and then tweaked it to fit my needs. If you want some presets to speed up your process or to just get you going in a direction, check out the presets available by Sleeklens.

7. Additional Tips

Like many things, when it comes to editing photos in Lightroom/Photoshop there are many ways to get to the final result. If you need to be more precise using tools like the adjustment brush or graduated filter, it will help you get results to specific areas and not have to worry about affecting the whole image.

RecoveringBlownOutImages6

8. Conclusion

Remember, the best way to set yourself up for success in your post processing is to have an idea of what you want your final image to look like. Shooting to capture all of the information in the raw file will help you later.