Exposure Histogram, It's Your Friend!

This is the second post in this “How to craft better photos” Series. I will be talking about the basic concepts of photography exposure histogram.  Follow this link to read the first article titled Understanding Exposure Will Help to Improve Your Photo.

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                                                              Taking proper exposed images matter!

Using the histogram in you camera’s image viewing LCD will help you to take a much higher number of well exposed images.  I will cover this feature with enough detail to give you a working knowledge of how to use the histogram to make better pictures.   I do not pretend to cover everything on histogram but I will present enough knowledge to improve your proper exposure technique immediately.

Human Eye and the Camera Sensor

The human eye can cope with an enormous brightness range.  For example on a bright day we can see in to the deep shadows cast by a tree at the same time we can see details in the lightest part of a white cloud directly over the tree and lit by the sun.

The camera’s sensor can only capture a more limited brightness range in a single exposure.  If you want to record the subtle detail in the lightest part of the cloud then detail will be lost in the shadow areas of the image. Similarly if you set exposure to reveal full detail of subjects in shade then you will end up with "washed out" highlight detail where light tones become featureless white.

To make easier the understanding of this, I will use the term “f-stops” to represent the quantity of light  that can be capture.  The human eye retina has an static contrast ratio of around 100:1 that is about 8 1/2 f-stops. Today’s digital cameras are capable of  “see” about  5 or so usable f-stops of light.  Unfortunately, many of the higher contract subjects we shoot can contain up to 12 f-stops of light values, this is more than it is possible to capture with a digital sensor today.  That is why it is important to understand how your digital camera records light, so that you can better control the quality of the captured image.

 

What is the histogram

Histogram is a topic that we could spend a lot of time talking about but I will give you an answer that will help you to understand it better, the simple one.

The histogram is a graphical representation of the exposure of an image.  Exposure refers to the amount of light that strikes the camera’s sensor to form the photography image.  Therefore, the histogram is a representation of how much light and tones the image has.

The image at the left is a typical histogram.  I will explain the meaning of its part.  Click here to have a better view of it while a explain.

The graph has two axes: across the bottom (the x axis) go all the distinct values your data can have, and up the side (the y axis) you plot how many times each value occurs. In a digital camera, values in 8-bit mode range from 0 through 255 for x axis. (0 = Pure Black, and 255 = Pure White).
The subject brightness range we can capture in any given image and still retain detail is about five f-stops as I said before. We can therefore divide a scale of image brightness into fifths and consider each one to be about a stop. These divisions can be referred to as very dark, dark, medium, bright, or very bright. This becomes the x axis of our histogram.

On the left hand end is black (zero) and on the right is white (255), with every other possible brightness spread in between. Eighteen percent medium gray would be dead center.

If we count how many pixels within our image have each distinct brightness value and plot this on the y axis, we get our histogram.  The top of the histogram (top of mountain peak, y axis values) represents the number of pixels of color in that x range, a value you cannot control, so it is for your information only. We are mostly concerned with the left and right side values of the histogram, since we do have much control over those. (Dark vs. Light)

 

How interpret a the histogram

A “correct” exposure can be regarded as one where the most important areas of the image looks “right” with its details.  Therefore, there is not a perfect exposure histogram.  
A dark, low-key image will have a histogram that clusters mainly around the left end. The histogram of a bright, high-key image will tend towards the right. The one form an image with a more "average" character will likely be spread more evenly across the spectrum ( as a mountain).

	Underexposed Image Histogram This histogram is clipped off on the left (dark) side which means that the image is generally too dark .  In fact , the light range in this histogram shows that exceeds the capability of the camera’s sensor which means that shadows details are lost.
	“Correct” Exposed Image Histogram This histogram contains almost a full range of light that the camera’s digital sensor can record.  The light range is represented by a graph like a mountain peak.  This is a “correct”exposure, since the histogram is not clipped off to the left or the right.  If you can make your image histogram look like this, you will have good images.
	Overexposed Image Histogram This histogram like the one at the left is clipped off on the right side of the histogram  (white area) which means that the image is generally too white .  In fact , the light range in this histogram shows that exceeds the capability of the camera’s sensor which means that highlight details are missed.

Here are three different exposures of the same image and their corresponding histograms.

The underexposed one is starting to clip on the shadow end which may or may not be an issue.  It depends on what we want. Deep shadows and silhouettes are supposed to come out this way. Given the subject matter though, not having any pixels over medium would definitely be considered a problem.

 

 

 

 

The histogram for correctly exposed one shows a subject clustered near medium, with no completely black or white pixels (no clipped to the left or the right).

 

 

 

 

 

 

 

The overexposed version clearly shows clipping in the highlights. We have lost data here that can not be recovered later since we never captured it in the first place when the image was shot.  Unlike on the shadow end, burned out white is rarely desirable.

 

 

 

Since our eye tends to know that shadows are black, and expects that, it is usually better to expose for the highlights. If you see dark shadows, that seems normal.

So, in a worse case scenario, expose the image so that the right side of the histogram graph just touches the right side of the histogram window, and the image will look more normal.  This technique is commonly referred to as "exposing to the right" and can work on all types of images, providing we adjust the exposure after the fact after uploading these images to our computer.

 

Homework - Using the histogram While Shooting

So now you know what a histogram is – grab your digital camera’s manual and work out how to switch it on in playback mode. This will enable you to see both the picture and the histogram when reviewing shots after taking them.

Keep an eye out for histograms with dramatic spikes to the extreme ends of either side of the spectrum. This indicates that you have a lot of pixels that are either pure black or pure white. While this might be what you’re after remember that those sections of the image probably have very little detail – this is a hint that your image could be either over or under exposed.

Histograms are the best way to assess the accuracy of an exposure because they represent the exposure in a graphical form that is unaffected by viewing conditions.

 

Hopefully this will give you some understanding of how to read the histogram for an image. Clearly the best way to learn what a histogram can tell you though is to go out and shoot some images of your own, paying attention to the histograms after each shot.  When you know how to interpret a histogram you have a much better method to check exposure.

I will love to see comments about your experiences…    You may share them with us in the comment area.

 

Read the Full Series

This post is part of a series on “How to craft better photos” . It will be all the more powerful if you taken in context of the full series which looks at 5 points of how to improve your photography and do it in a creative way.  Start reading this series here.

If you need to return just subscribe to our RSS

How to Protect Your Business in Today’s Marketplace

When the economy took a dramatic nosedive at the beginning of 2009 , many businesses, including photography studios and photographers, were caught off guard.  Since then, smarts photographers have made significant changes in how the run their businesses. Among those who have taken a proactive approach to keeping their businesses on track are photographer like me and may be you.  I may said that “2009 season was half full, but we could see what was happening in the local economy and knew we were in for a very bad position in 2010.  Our bookings dropped by two thirds, customers and clients interested in my high quality photography started making decisions based on prices.  Facing this reality, I made substantial adjustments in how I run my business.  I’ve eliminated staff, fixed expenses and paid down business debt with personal savings”.

One thing I haven’t eliminated is marketing. In fact I poured considerable effort and resources into getting the word out about my business.  Instead of pay advertising , this year I made a conscious decision to avoid pay advertising and to spend my time, not my money , on marketing.

Here some Marketing ideas to follow;

1. Display your work locally – There are shops, restaurants, museum, even libraries that will showcase your work for free.
2. Identify worthy pro bono project – Photographing a local non-profit organization or two at no charge every year is a win-win arrangement.  I had been doing it for several years, giving my expertise and free time to organizations as “LA Fondita De Jesus”.  By doing this work , my business has caught attention of people who associate themselves with this causes.
3. Think of Catching Promotions – Give away something that is in as a IPod to the first booking job for the month, or a 11” x 16” free.
4. Consider Business + Home as a good investment – Instead of  expend money in remodeling your studio or paying rent, prepare your home as your studio and save that money.
5. Generate Buzz online – Publishing your latest work , photos, schedule activities on timely bases on your blog or web site expand your reach and keep your business name in clients and prospect mind.

Bucket List: Create A List of Things To Do Before You Die

Currently in theaters there’s a movie entitled The Bucket List. A bucket list is a list of all the things you’d like to do before you die. Have you ever made a “bucket list” ? and  stop putting off your dreams for "someday".

How many people do? Those who do, usually do it far to late. It’s not macabre; it’s actually enjoyable and extremely useful.

Take inspiration from the movie "The Bucket List" and ask yourself: If I had one year left to live, what would I be sure to do?

By creating a list of 100 things ( more or less) you want to do before you die or before you "kick the bucket", you can begin focusing your life on what really matters to you.

So, what should you include on your bucket list? Maybe you want to . . .

1. Witness a solar eclipse
2. Ride a gondola in Venice.
3. Parachute trip
4. Do stand-up comedy…

There are several things you can do to make the list more useful.

1. Prioritize it. Find the most important things on the list. Find the things you can accomplish readily and with the least amount of effort.
2. Make a plan. List the steps necessary to accomplish specific items. (You might do this for all of the items, but just doing it for the most important and easiest will get you started.)
3. Act on it.
4. Repeat the process.

 

It's never too early or too late to create a bucket list. So, whether you're 10 or 98, use this lensfor inspiration and for guidelines on how to get started creating your list of things to do before you die.

 

Reference: http://www.squidoo.com/100things

Understanding Exposure Will Help to Improve Your Photos!

Understanding exposure makes you a better photographer

This is my first post in this “How to craft better photos” Series. I will be talking about the basic concepts of photography exposure.

                              Taking proper exposed images matter!

Today the digital cameras can handle exposure very well in automatic and semi automatic modes, but understanding exposure properly can certainly help to improve your photography.

Let's start by thinking about what's happening with light when you take a picture. The light passes through the lens and then through the shutter before it arrives at either a sensor or a frame of film. The camera's lens and shutter control how much light gets to that sensor or film frame.

 

Exposure is all about how much light go into the camera sensor or film.

Too much light, and your photos will be washed out, too little and they will be too dark.

 

Overexposed Image	Proper Exposed Image	Underexposed Image

 

5 Reason to have control of the exposure

1. If you overexposed (too much light) you will end up with blown highlights and you can never recover details in these areas of the image, never.
2. If you underexposed (too little light) same happens, there is not data recorded in dark areas and you can never recover them.
3. Poorly exposed images have low contrast
4. Poorly exposed images don’t have good color saturation
5. Light meter in cameras can be (and the often are) fooled by certain lighting conditions

Therefore, is a most to have an understanding of exposure before you press the shutter!

What Affects Exposure?

There are three things related to exposure.  The relationship between aperture, shutter speed and ISO is what make an exposure. Those three are closely connected, and that connection is the basis of every photograph.
Two of those involve how much light comes into the camera; the third is the sensitiveness to light of the film or sensor of your camera.

• The shutter Speed
• The Aperture
• The ISO (light sensitivity)

Understanding Exposure – The Shutter Speed

To understand exposure , you need to understand shutter speed. The camera’s shutter controls  how long the the light coming through the lens gets to hit the media; film or sensor.

The shutter works as your eyelid.  It is normally closed, when you press the shutter , it open for a fraction of second to allow the light to get the media. Controlling the shutter speed means controlling the time the eyelid is opened.

The longer it stays open, the more light enters. If it’s open for too long, the photo will be overexposed. Not open for long enough and your photo will be too dark.

 

Understanding Exposure – The Aperture

The other part of the exposure equation is the aperture.  What the heel is that?

To understand exposure you need to know what the aperture is and  does.  As with shutter speed, the aperture is also a way of controlling how much light enters the camera.

The aperture is an adjustable hole in the lens. It can open to allow more light in. Or it can close to become just a tiny hole, stopping so much light from entering.  It behaves as your eye iris.

 

So aperture and shutter speed work together to create an exposure. There is just one combination between the shutter speed and the aperture that will resulted in a proper exposed image.

Therefore, if you have a slow shutter speed (to let more light in) you have to close the aperture to compensate. And visa versa – if you have a fast shutter speed (letting less light in) you have to open the aperture to allow in more light to compensate.

 

Understanding Exposure – The ISO

There is one more key element in the equation, ISO which refers to the light sensitivity of the sensor (or film) inside the camera.  The lower the ISO, 100 for example the more light we need to get the proper exposure.  The higher the number, let say 800, less light we need.

Since we need less light with a higher ISO, you might be tempted to use a high ISO all the time, Be Careful, as we go up in sensitivity, we tend to lose color saturation and gain noise, which gives images a grainy look (speckling effect on photos).

 

So..

So it's our job to manage exposure to get the sharp, clear photos we want. The key thing to remember is that the three elements—aperture, shutter speed and ISO—are always linked. For photographers it's a balancing act, and so we're always adjusting the shutter speed and aperture for the right exposure and the effect we want.

Of course, you can bypass all of the above simply by setting your camera for auto or program mode and letting the built-in computer do the work. Still, understanding the relationship of aperture, shutter speed and ISO will give you a greater understanding of how to take control of your photography.

Remember :

Shutter Speed + Aperture + ISO = Proper Exposure

 

Homework

Homework for this lesson is fairly simple. Set your camera to manual mode.  Keeping always the same ISO setting. Take a photo.  Then, change one of the elements, aperture for example to a higher setting, and take a photo.

How the exposure change? It is lighter or darker?

Now change the other element (shutter speed in this case) to compensate the first element changed - to a faster shutter speed.  Now you get same exposure than the first taken photo.  Why? Because you set the relationship between aperture and shutter speed to the same as the original photo.

I will love to see comments about your experiences…    You may share them with us in the comment area.    You may subscribe to our RSS too!

 

Read the Full Series

This post is part of a series on “How to craft better photos” . It will be all the more powerful if you taken in context of the full series which looks at 5 points of how to improve your photography and do it in a creative way.  Start reading this series here.

How To “Craft” Better Photos – The Series

This week I will start a series of posts that will walk you through a complete tutorial about how to take control of your photo exposure. If there’s one lesson that I have learnt about photography it’s that a key element to be a successful photographer is the domain of photography exposure.

An entire photographic industry has been built convincing consumers that the subject of the photo exposure is mysterious, difficult and impossible to understand, so it’s more convenient to let technology decide for you.

The fact is that the concept of photographic exposure is extremely simple. It can be mastered by anyone who can multiply or divide by two. All you need to know will be included it in this series.

I will help you to understand: What is photography exposure, how it can be used to improve your photos, how to use it in a creative way, and how to control the exposure on any lighting condition.

Below is the list of posts that will be published during the following days or weeks, stay tuned! Subscribe to our RSS or to our newsletter.

1. Understanding Exposure will help you to improve your photos!
   Next 07/14/2010
   Get the basic terms of exposure, its key elements and its relationship.
2. Exposure Histogram, Your Friend! Next 07/16/2010
   Learn how to interpreted the histogram and use it to check the exposure every time you shoot.
3. Creative Exposure – Making the Difference!
   Learn about depth of field, shooter speed, how to use them to make your photography a piece of art.
4. Sunny 16 Rule – To the Rescue!
   Learn all you need to know to use your camera in manual mode.
5. Bracketing, How and Why?
   What is bracketing and how to use it ?

I included a poll about the use of the camera histogram to control exposure, feel free to vote.

I will love to know what you need to know about exposure… You may share them with us in the comment area.

Cropping to Print for Popular Sizes – Free Photoshop Actions

After trying to crop a photo to the correct aspect ratio for the size I was printing on my Epson 9800, I decided to find a way to automate this.  The problem I have ( and I am sure many of you too) is that oftentimes the aspect ratio our cameras shoot in doesn’t fit popular printing sizes as 8 X 10”, 4 X 6” and 5 X 7”.

At then end,  cropping will happen.  Here is how to do the post processing and  the actions that I already did to solve this problem, free for download.

First I will explain to you the easier manual way to do it.  After that I will teach you how to use the action tool to  automate it.

 

Step One:

Locate and open the photo you like to print in Photoshop©. Go to Image > Duplicate to keep safe the original image and crop an exact copy of it.   Photoshop will assign the same name as the original image and add the word copy at the end, you may keep this name or change as you want.

Step Two:

Select the cropping tool at the tool panel or type the letter C.

Once you have the cropping tool selected, go to the preset options tool ( see right image ) and select the size preset you need.

Now your cropping tool will keep the aspect ratio of the selected size for you.  Just click and drag the cropping tool to frame the image as you want.

 

 

Step Three:

Now with the photo frame by the cropping tool, you may re-size the frame, rotate it to compose the image as you need.   After that press Enter and the final cropped image will be shown.You will need to do every single step above for every image you want to print in a popular aspect ratio or size.

After asking around I realized that lot of other people have had this size problem too, so I decided to turn this in to an action to make it easier for us in the future.

 

 

The “Cropping Create” Action

I provide here a Photoshop© action file in two different compressed formats ( zip & rar) for your convenience. The action file has three actions: Create 8 X10”, 4 X 6” and 5 X 7”.

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One Time Setup:

To download it, please select the appropriate format link for you, un-compress it and double click the file to be opened in Photoshop.

CroppingToPrint.rar

CroppingToPrint.zip

Once you had completed the above step, your Photoshop working space should look like the one at the right, including actions for 8 X10” , 5 X 7”,
and 4 X 6” .  To open the action panel go to Window > Action.

Step One:

We’ll start from scratch again.  Open a photo you want to turn in to a 8 X 10” , then go to the action panel (Window > Action), Select the action “Create 8 x 10”, then click on the play selection button ( the triangle one at the bottom of the panel, see image).

Step Two:

This will run the action for you.  The action will automatically duplicate the original image for you, then will configure the cropping tool to the aspect ratio you need ( in this case 8 X 10 “) and will allow you to correct the cropping framing as needed, will crop, will save the cropped image and will close it for you. This is really fast & easy. 

Below are the two screens that will pop up during the process, the first one will advice you that in the next step you may correct the frame and must press enter to continue, click continue on this window. 

The second one will allow you to select the saving options , once  you are ready press save.

 

 

 

 

Will you share your best Cropping techniques with Us?

The above technique to crop at the right aspect ratio are just one of them, you are free to use the provide action to make your post processing easier and faster.

What other techniques do you use to crop your images? Share with us, leave your comments.

How to Buy a Digital Camera

Selecting the right camera for you should start before the purchasing.  A mistake I often see some digital camera buyers making is that they select a camera way beyond of what they really need and should pay.

Some question to ask yourself and some things to do before you go to shopping:

1. What do you do with your photos? What do you need the camera for?
   The answer to this will give you an idea of how many megapixels, what type of camera, format and size.
2. What experience level do you have with photography cameras?
   Depending of the experience you will select some of the camera features you need and the type of camera.
3. What type of photography will you be doing? Landscapes, portraits, macro, sports, weddings, indoors, outdoors, low light ambient etc.
4. Are you looking to learn the art of photography?  or Are you just interested to point and shoot?
5. The size and portability matter to you?
   I some time prefer to bring with me a point and shoot camera than my professional SLR due to the fact of small size and portability, especially when I am going to capture photos of family activities.

Answer these questions and you will be in better position to make the right selection of camera for your needs and budget.

Do your research, read the reviews, and don’t buy on name brand alone.  Let me give you some hints!

 

Megapixels means less than sensor size

One of the sale person’s favorite feature used to sell digital cameras is how many megapixels it has.  Three to five years ago it was an important criteria to  make a right selection,  however these days, with must new cameras with in the range of  5 to 12 or more megapixels it is not so critical.

More megapixels means bigger photo file sizes and more computer storage and processor needs.  A right balance between  good resolution, storage space and sensor size is better criteria to do the right selection.

Knowing the final use for your photos will give you an idea of the maximum resolution you need.  Why pay for megapixels you will not need?

I will go a little deep in the technical part of it, just to give you the tools to understand why. 
Usually for paper printed photos you will need 150-300 pixel per inch, for electronic media 72-100 pixels per inches is enough.  Taking this in consideration then if you will use your photos for share them with friend thru social networks and print them in 5” x 7 “ paper you just need a 3 megapixel camera.   If the use of your photos are for print them in high quality magazines covers and sizes up to 16” x 20 “ then you need a 12 megapixel camera.  See table below

Megapixels Camera	Paper Print Size	Electronic media Size
2 MP	3” X 5 “	8” X 12“
3 MP	4” X 6”	11” x 14”
4 MP	5” X 7”	16” x 20“
6 MP	8” x 10”	24” x 32”
8 MP	11” X 14”	28” X 42”

Besides, other photo quality indicator is the sensor size of the camera, bigger is better.  Image sensor range size from 5,76 by 4.29 mm for point and shoot to 50.7 by 39 mm for high end SLR cameras.

Select from the above table how many megapixels you need for your photo use, the bigger sensor and you will end with high quality images, an affordable price that comply wit your needs.

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Optical Zoom vs. Digital Zoom

Other feature the sale person will used to sell the camera to you will be the zoom.  There are to type of zoom; the optical and the digital zoom.  Optical zoom is the critical one and it is the second criteria you should used to select your camera.

The optical zoom is given by the lens glasses of the camera and it does not affect the image quality as the digital zoom does.  The digital zoom is given by the camera software that crop and re-size the image to a bigger size, at the end of this process the image lost its quality.  The optical zoom range goes from 3X to 12X for high end point and shoot cameras.

 

Don't overlook the LCD

More and more compact camera manufacturers are forgoing traditional viewfinders in favor of LCDs for framing shots. If you do manage to find a model with a viewfinder, it's likely to be a very small one with limited usefulness, so it's more important to focus on getting the best LCD you can find. For point-and-shoot cameras, LCD sizes start at 2.5 inches and go all the way up to 3.5 inches, but there aren't many 3.5-inchers, and the ones we've seen are typically expensive. Currently, the sweet spot for screen size is 2.7 or 3 inches. Resolution on the LCD is measured in dots—the higher the number of dots, the more detail you'll see, and the resolution is independent of the display's physical size. A decent camera LCD should have at least 230,000 dots.

 

Pay attention to must-have features

Image stabilization, which helps reduce the blur that can come from shaky hands, is an important feature to have. If a camera has digital image stabilization, that's fine, but it should have optical or sensor-shift stabilization as well. Virtually all modern cameras include face-detection technology, which detects and focuses on faces in the frame and improves the image's overall composition and quality by optimizing the color and white balance. Just make sure you turn it on before you shoot portraits or group photos.

 

Size matter but not for everyone

One of the major benefits of a point-and-shoot camera is its compactness, but some models are more pocket able than others. Thinner cameras are typically more expensive and sometimes sacrifice features. Unless you plan to keep your camera in a jeans pocket, there's no need to spend a premium on a super-slim camera. With a larger camera, it will still fit in a jacket pocket, but you'll likely get a larger LCD, a longer zoom lens, and easier-to-manipulate controls.

If your answer to the type of photography you want to do is commercial or learn the art of photography then you should go with a SLR camera. As the P & S, some SLR models are more portables than other, that is why hands on experience it is so important.

 

Keep in Mind

Do you remember the looking “grains” of the film photography, grains like the ones you see when look close to the TV. Well in digital photography that happen too.  It is know as “noise”.  Looks for noise specifications of the camera. It is direct related to ISO, more ISO – more noise.  Select a camera that will produce less noise level in a given ISO.

ISO is like ASA in film photography.  It is the measuring of light sensitiveness. For low light conditions you need a higher ISO.

 

Now you are ready to do your re-search online looking for the best price, read the reviews of your potential selections and be ready for the shopping day.

 

Hands on experience

Once you’ve narrowed down your search to a handful of cameras head into your local digital camera shop and ask to see and play with them. There’s nothing like having the camera in your hands to work out whether it suits your needs.

When I shop for a camera I generally use the web to find reviews, then I go to the local store to see it, ask the sale person a demo of the camera,  I also get to play with it and get a feel for which one I like better.

Make The Deal

Ones you’ve selected the right camera for you it is time to find the best price.

I generally start online and do some searches to find the most competitive prices on the models  I am interested in. With these in hand I am able to negotiate in person with local stores or with online stores.

 

Help with your tips

Based on my own experience of buying several cameras since 1985, these are some hints I can provide you, but I am sure others will have useful advice to add, fell free to add your tips on how to buy a digital camera in the comment area below.

 

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