All Tutorials

July 4, 2012

How To – Get the Correct Exposure With Your Digital Camera

How-to

There is a lot to learn when it comes to digital photography, and one of the best topics to start with is Exposure. This tutorial will go over all the key factors that relate to exposure and give tons of sample photos illustrating the How, and Why.

Exposure in it’s simplest form is controlling the light. A combination of Aperture, Shutter Speed, and ISO are the tools we have as photographers to control the light with a digital camera. A “good” exposure is the correct blend of all three tools depending on the given situation, and what effect the photographer was going for. This is a very important concept to understand!! As the photographer your in control of the exposure, so you can tell the camera to do things that Auto Mode would never allow!! Therefore, the “correct” exposure could be totally different with the same exact scene, depending on camera settings, filters, off camera lighting, etc.

Your digital camera when set to an Auto Mode will figure out the exposure on it’s own using it’s built in light meter and a variety of other criteria that help it determine the correct exposure.

Be sure to click the image for the 1200px Crisp Version!!

Correct Exposure - +1 exp/comp with Spot Metering Enabled!!

Correct Exposure – +1 exp/comp with Spot Metering Enabled!!

 
exposure-triangle

The Exposure Triangle – Click For Larger Version!

 

How Exposure Actually Works

When you point your camera at any given scene in Auto Mode the advanced scene recognition technology will take over, face recognition technology possible kicks in depending on the camera,  and then the camera will make a educated guess on the exposure. It will chose a blend the three exposure tools available!! (Aperture, Shutter Speed, ISO).

Amazingly the camera produces a solid exposure most of the time these days!! Sony in particular has taken it to the next level with it’s facial recognition technology(it’s been around for some time). Basically, if the camera see’s a face it prioritizes focus, exposure, and other effects if enabled, towards a portrait type exposure and then takes the shot. The Sony’s do such a good job they almost asks you to leave it on auto !! The camera actually said that to me ;)

In-camera light metering works awesome with most subjects in most lighting situations, but there are tricky scenes that will fool your in camera occasionally!! Snow is a classic example of this. Cameras notoriously under-expose snow scenes, because your cameras light meter is not looking for pure white and does what it thinks it should do with the scene, underexpose.

The latest Sony cameras have really advanced scene recognition software built in!! Superior Intelligent Auto Mode in particular which is found on the Nex-F3, A57, and A37, you can bet the camera will actually get it correct almost all of the time. This super advanced auto mode really is incredible and I used it on the Sony A57 for quite a while with total amazement at the results.

 

Dandelion

Sony A57 w/ 24-70mm f/2.8 Carl Zeiss Lens @ f/2.8, 1/1250sec, 70mm, ISO 100, Handheld, Jpeg Fine

Sony A57 w/ 24-70mm f/2.8 Carl Zeiss Lens @ Superior Auto Mode – f/2.8, 1/1250sec, 70mm, ISO 100, Handheld, Jpeg Fine

 

Light Flow

Light Flow

How the Exposure Actually Happens

Check out the illustration on the left, and notice how the Light travels through the optics and relates to each element of the exposure process. ISO is controlled on the sensor,  but notice how the Shutter and Aperture work in tandem with the sensor and lens! They all work together and relate to one another is the concept you need to grasp here. Basically the light travels thru the lens optics and gets shaped into what the sensor, and photographer wants to see. The optical quality of the lens basically determines how good the light gets shaped and controlled before it hits the shutter. The Aperture changes the angle at which the light is focused and sent to the sensor. The shutter then simple controls the amount of time the sensor is exposed to the light source.

Aperture

F-Stop Chart

F-Stop Chart

Aperture is the tool that controls the light flowing though your lens in increments know as f-stops. Aperture also controls Depth of Field which we will discuss later ;) Basically the light travels through the lens like water through a pipe. The Aperture is the valve the can slow the flow of water or in our case light ;) Check out the illustration on the right, see what I mean? f/16 is barley letting any light thru, and f1.4 is pretty much wide open!!

Aperture settings are called f-stops and indicate the size of the actual aperture opening. Each f-stop lets in half as much light in as the next larger opening and twice as much light as the next smaller opening. It’s a circle, so the math involves pie if your wondering.

Shutter Speed

The shutter is what controls how long the Sensor is exposed to the light source. Basically the time of the exposure is all the shutter has to do. The longer the shutter is open, the more Light that can flow in to fill up that sensor with information. In a dark scene the shutter will need to be open longer than in a bright scene.

Shutter Speed also has standard values for Full Stop Increments just like the Aperture and ISO!

1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8. 1/4, 1/2, and 1 full second

montgomery_falls_2

 

ISO

The ISO is basically how sensitive the camera sensor is to light. The higher the ISO the more sensitive, and the lower the less sedative. A great analogy about ISO I read once by Bryan Paterson. his analogy was to picture the ISO as worker bees. At ISO 100 you have 100 worker bees on your side trying to grab up all the light coming in. At ISO 200 you have twice as many worker bees trying to capture the light, therefore it will take 1/2 the time. So in other words lets say I have my camera set-up to take a picture and the I’m at f/4 1/250sec ISO 100. Now I change the ISO to 200 and something needs to adjust to get the correct exposure. So I scroll on the shutter speed and guess where the correct exposure winds up at?? 1/500sec!! Exactly half the time is required to get the same exposure with ISO 200, because it has twice the sensitivity, or worker bees ;)

High ISO is usually needed to get a good shot in low light. New cameras these days are coming out with ISO as high as 25,600! That right ISO 25,600 or even higher. Another factor of ISO that is important to remember is noise. The higher the ISO the more Noise you will get in your images. This is caused by the sensor sensitivity (voltage/ power) being raised therefore it’s more susceptible to noise.

ISO also has full stop increments:

ISO 50 100 200 400 800 1600 3200 6400 12800 25600

Be sure to click the image for the 1200px Crisp Version!!

Smiling Fish

Smiling Fish -

 

Recognizing Your Scene is Key!!

Recognizing the scenes in advance is key to getting more consist and accurate exposure’s!! Knowing that the camera is going to struggle in various conditions due to the limitations of the in-camera  metering system is critical, and takes some work and experience on your part!! This will give you the fore-thought to adjust the camera in advance and get a much better exposure in those tough situations.

Sample “Correct” exposures

Below are a few examples of exposures that would normal not look very good, but because I know how the camera metering system works, I can adjust accordingly and get the “correct” exposure.

I took this image in the bright sun behind my brothers house. I new that Sadie’s white fur would want to blow out, so I used partial metering and focused on here eye/ face. That will tell the camera sensor “hey there is some info here we need to expose for” otherwise the camera would average out the scene and take into account for all the green. The result would have been Sadie’s white fur slightly overexposed. I wanted to get all the detail/ texture of the fur.

Canon 5D Mark II, Canon 70-200mm f/2.8 L IS, @ f/2.8 1/5000sec, ISO 200, Highlight Tone Priority enabled.

get the correct exposure

 

Notice how bright the background is on the image below of the roaring sea lion. If I shot this in Auto mode, the Sea Lion would be underexposed for sure!! Knowing this from experience, I used the Exposure Compensation while in Av (Aperture Priority mode) and added +2/3 exp/comp. That raised the exposure so I got the “correct” exposure!!

get the correct exposure

 

In this tug boat scene below the lighting was at it’s harshest, and from experience I knew the camera was going to under expose the bright white tug as illustrated in the image below.

getthe correct exposure

White Tug boat, Normal Exposure on average metering mode

By simply adding a little exposure compensation (+1/2), I was able to get the “correct” exposure of the bright white tug!

get the correct exposure

White Tug Boat, + 1/2 stop exposure compensation

 

Here is another example of a photo that your camera will screw up every single time!

Be sure to click the image for the 1200px Crisp Version!!

Niagara Falls, NY Side

Niagara Falls, NY Side

Michele and I went to Niagara falls a last year and knowing that white waterfall water will fool the camera sensor is critical to getting the “correct” exposure. I set the camera’s exposure compensation to +1.5ev, and this brought the water back to almost white as apposed to gray.

 

Take a look at these three exposure’s below:

This is what the camera decided was a “correct” exposure when using evaluate metering mode in a really tough scene like Niagara Falls.

Niagara_0ev

Niagara Falls- Standard Camera exposure

So I added +1 to the exposure comp and I got this: f/16 @ 2sec ISO 50, SO by adding 1 full stop of exposure bias the camera added 1 full second to the shutter speed for me, therefore doubling the amount of time the shutter is open and yielding a much better result.

niagara_+1ev

Niagara Falls- Standard Camera exposure +1 exposure comp

+1 was still not enough though so I went with + 1.5 and got this “correct exposure”

Niagara_+1.5ev

Niagara Falls, NY +1.5ev

 

In this next image, the sky was incredible and I knew I wanted to get a pretty long exposure in order to capture the taillights. I did not have any filters to help slow the shutter down, so I set the camera to f/20 or so, and the lowest ISO setting, which gave me the longest exposure possible. Michele drove ;) If I were in auto mode, the camera would have froze everything and probably put the flash up. Would that picture be be cool? I doubt it.

Taking control of the exposure is the name of the game if you want to get creative photos like this one below.

Streaking Tailights

 

Closing Remarks

As you can see, getting the “correct” exposure is often not as simple as just pointing and shooting in auto mode. Although that does work really well, it’s not taking control of the exposure, and that is what photography is all about! You are in charge no the camera. The camera is just a tool to help you capture moments, and as the photographer, it’s your job to create the exposure!!

I hope you all got something out of this Article, and have a great 4th of July!!!

Jay

Happy 4th of July!!

 

Some Photography Reference Material


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Thanks,
Jay

 

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About the Author

Jay
Hello, I'm the owner and operator of SonyAlphaLab.com. Please check out the About page for a full background on myself and the Lab ;) Google+ | Twitter | RSS-feed | Email Updates!!




3 Comments


  1. Kevin

    Jay,

    I been following your website for a couple of weeks now. I am new to photography (Less than 1 year) and I did have a couple of questions for you.

    I notice that most of your very sharp shots (Such as the one with Sadie) are taken with your Cannon Camera.

    1. What is most important to get such sharp shots the Camera or the lens?

    2. Does exposure have a direct correlation to sharpness of the subject?

    I currently have a Nex-5N with the 18-55mm kit lens and also the 16mm pancake lens.

    I’ve taken some decent photos but I still feel they are no where near the sharpness of the photos I would like to take and frame.

    Also do you have any suggestions regarding Lens for sharp photo’s of people cars and buildings.

    Thanks for your help keep up the awesome work.

    -Kevin


    • Jay

      Hey Kevin,

      You really need an Award for one of the best questions asked to date on SonyAlphaLab.com!! How about a Gold Star?? lol

      Jay,

      I been following your website for a couple of weeks now. I am new to photography (Less than 1 year) and I did have a couple of questions for you.

      I notice that most of your very sharp shots (Such as the one with Sadie) are taken with your Cannon Camera.

      1. What is most important to get such sharp shots the Camera or the lens?

      2. Does exposure have a direct correlation to sharpness of the subject?

      1. The lens is the most important factor in getting a sharp shot. The sensor also has a lot to do with it however, and so does the processing of the data that the camera captures. So, it’s the camera, the software on the camera, and the Lens!!

      Now, that Sadie picture was taking with a top of the line Pro-Grade Canon lens, and a top quality Pro Grade camera!! The 5D mark II Sensor also has no Anti-Aliasing filter, which tends to slightly soften images at the cost of fixing some other flaws. They drop it off on really high end model cameras, and that does help significantly with sharpness.

      Also the Lens has a sweet spot, and you want to use it for the sharpest, and best contrast results. Shooting wide open is fun but it does not yield the sharpest results. Also going above f/16 is going to introduce a bit of diffraction which, again will cause some softness.

      2. In my opinion yes, but technically I’m not 100% sure. When you nail the exposure your image is going to looks its best overall. The contrast will be super accurate, and hence yield a nice crisp contrasty edge, which to the human eye relates to sharpness.

      Sadie’s white fur for example looks sharp in the shot above, but if the exposure was slightly higher it would have no detail because it was blown out. The rest of the fur would still look sharp though. So technically it didn’t effect sharpness, but it got rid of detail in the image which creates the sharpness that our eye sees. I hope that makes sense ;)

      3. As far as getting the sharpest shot possible, their are a few things you can do:
      Use a tri-pod, Use the sharpest aperture your lens possible, Make sure your focus on the correct spot 1/3rd of the way into the scene for landscapes. If it’s a building I would focus on what you want to have most the detail, Use the self time ensure you get no camera shake from hitting the shutter button, If you are hand holding, make sure your shutter is fast enough.

      I hope this helps Kevin!!

      Jay


  2. […] The Sony A7 and A7r are a professional grade cameras, and using manual mode is really easy with the three physical control dials at your finger tips. The exposure triangle consisting of Shutter Speed (upper thumb dial), Aperture (front pointer finger dial), and ISO (rear thumb control ring). With these controls you can dial in the shutter speed to what ever you need while watching the on camera meter. That tells you if the exposure is + or – ideal per the camera. More on the basics of exposure in this article (Click Here) […]



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