Tag: exposure

Exposure Compensation And Bias Are Your Friends – Photography Basics

I have some bad news.

Your camera is not perfect.

Don’t worry though, none of them are. The saving grace to this dilemma is the Exposure Compensation (sometimes called Exposure Bias) feature on DSLRs, smartphones, mirrorless cameras, drones and a lot of point and shoot cameras. It is a little button that looks like this.

Exposure Compensation

The exposure compensation button works by forcing the camera to over expose or under expose, according to its current settings, by a set number of stops. Hence the symbol for it is the + and – signs.

Typically the range is -3 to +3 stops but some cameras will have a -5 to +5 range. Cameras are pretty similar in how the setting actives; simply press or hold down the button and then turn one of the camera dials. On phones you will typically tap the screen to set exposure then drag up or down to change it.

Your user manual explains exactly how your exposure compensation feature works.

How Handy is Exposure Compensation?

Exposure Compensation can be helpful when you know your camera is going to mess up or is already messing up. As explained in the Metering Modes post, your camera is not perfect and can only meter a limited area of the view. Plus, your camera has to make decisions about what’s important in the frame and try to make everything come out all average. But it makes mistakes.

We’ll use an image of a tugboat on Puget Sound from Seattle as an example of a challenging shot where exposure compensation helps.

Program mode, ISO 100, f/11, 1/500 – The camera is doing all the exposure calculations here:

This is with the camera’s default setting using evaluative metering. I could switch to spot metering and point it at the tugboat. Instead, I use a camera dial to selectively over expose by one stop.

Over Exposing

Here’s the same shot over exposed by one stop.

Getting better. The tug is a little more visible.

Below are shots over exposed by two stops and then three stops.

As the exposure gets higher and higher, we can see the tugboat more and more, although we lose detail in the background.

I chose this image because these types of decisions come up all the time when shooting sunrise or sunset.

Now For Under Exposing

Swinging the other direction, we’ll under exposed by one, two and three stops.

We get more detail in the clouds lit by the setting sun, but we lose our main subject along the way.

As you can see, there is a big difference in exposures across a swath of seven stops of light (-3 to +3 stops). What is most pleasing to some, in this case, might not be pleasing to others.

How is it Useful?

The over/under exposure compensation is a quick way to correct your camera’s wrongheaded bias towards too harsh or too dull of light. In this example, the shot that was underexposed by one stop has a good chance of being salvaged and enhanced in a computer.

This quick setting can also help insure faces aren’t hidden in darkness by shadow when all around them is bright light. It’s better to blow out the details in the surroundings than leave a face too dark.

On Your Phone

To use exposure compensation on a phone, tap the screen and move your finger up or down to over or under exposure. It’s super easy.

Tomorrow we’ll cover Histograms!

Questions? Pop ’em like Pez in the comments section below. or email me at peter@peterwestcarey.com.

Photography Basics – A 43 Day Adventure, and its companion 40 Photography Experiments, are series written by professional photographer Peter West Carey. The series are designed to unravel the mysteries of photography, helping you can take better pictures. Subscribe here to receive all the updates and bonus material. Your comments are always welcome.

If you enjoy the series, consider learning photography first-hand on a professionally led international photo tour in Nepal or Bhutan. More information can be found at Far Horizon Photo Tours.

October 17, 2018
The Exposure Triangle – Photography Basics
With our law and rules finished, let’s jump into how to make a photo.

The Exposure Triangle

First, there is The Exposure Triangle. It balances all things. Makes things right in the Universe. Or maybe it is just a handy metaphor.

To be honest, the Exposure Triangle, to me, is better explained as two Teeter-Totters, which isn’t nearly as sexy as a triangle. What the Exposure Triangle is trying to tell you, is there are three things which have an impact on proper exposure of an image on film or on a camera sensor:
- Shutter Speed
- Aperture
- ISO
We’ll be going over each of those in more detail in the following days.

Shutter Speed

Tree Amongst Rock Formations, Bryce Canyon National Park, Utah, USA, North America

Essentially, this is how fast your camera blinks. Remember the days of film and how you were never, ever, ever, ever supposed to open the back of the camera while the film was loaded? That’s because film reacts to light and if you don’t control how much light hits it, it freaks out and exposes EVERYTHING. Much cursing typically ensued.

So the shutter does the blinking of the camera (from closed to open and back to closed). Everything is dark inside the camera and then “BLINK”, the shutter lets in how ever much light it is told to. More on this tomorrow.

Aperture

The Aperture is analogous to the pupil in your eye. It’s a hole that lets in light and can be changed in most cameras and even some smartphones.

Let’s use an analogy. It’s pitch-black inside this room the is 20′ x 20′ and you are standing in the center. Outside the room is daylight. Are you with me?

Next to you is a 40 ton, 8′ wide wrecking ball. You’ve been working out and are feeling destructive so you swing the ball forward and BAM! 8′ wide hole in your wall. How much light do you think is coming in right now? Tons.

Now back up and let’s do this again. Instead of a wrecking ball, let’s use a 1” wide drill bit on that wall. POP! Hole is in and, if you are standing back 10′, how brightly lit is the room now?

Can you see now how Aperture affects how much light comes into the room? More on how the aperture does other cool stuff on Friday.

ISO

The ferry boat Kittitas approaches a dock in a high key photograph

People often ask what ISO stands for; International Standards Organization. I get blank looks after that answer or “Oh, ok” looks followed by, “Huh?”. Wikipedia has thousands of words on ISO as it relates to photography, but in short, we’re talking about sensitivity here.

It’s the exact same sensitivity as if I punch you. If you’re a body builder, you’re not that sensitive to a punch. But if you’re….oh jeeze, now I need to come up with an example where I punch something sensitive…a cute, fluffy bunny. Sorry bunnies. Chances are, with the same punch the bunnies would yelp and jump a mile because of the guns I’m packing on this 6’1” frame. (sorry, obscure, and sometimes old, pop culture internet references may come up this month)

Better yet, let’s go back to the wrecking ball analogy. You’re in the pitch black room before the ball smashes an 8′ hole in the wall. If you’ve been in the pitch black room for an hour, your eyes are far more sensitive to light, aren’t they? Your pupils are open wide, trying to gather as much light as they can.

BAM! The ball smashes a hole and ARGGHHH!! You sensitive eyes don’t like all that light.

Same scenario but this time, before the ball strikes, we’ve been holding a flashlight pointed into your eyes for 10 minutes. By ‘we’ I mean me and the bunny you made me punch. Your eyes are now constricted and not so sensitive, are they?

BAM! Hole in the wall and you think, “Eh, not so bright”. Your eyes were less sensitive.

ISO will be covered on next Monday.

Got all that? Shutter speed = how long light hits your camera sensor. Aperture = how wide is the hole letting in light. ISO = how sensitive the sensor is to light.

Visualize

Here’s where the triangle comes in. Visualize it like this:

Except for the bunny, it’s a nice balanced triangle. However, the moment one of those corners changes, let’s say you change the ISO from 100 to 400, then the triangle gets all fuddled up and is not in balance any more.

If one, or both, of the other variables aren’t moved as well, the bunny picture won’t come out properly exposed. And by properly exposed I’m talking about an ideal here. After you learn the rules through these 43 days, you’re welcome to break them as mentioned yesterday. But until then, we’re shooting for properly exposed images.

Revisualize

Another way to think of it is:

With the Exposure Teeter Totters Of Doom, if ISO wants to move up or down, one of his buddies (or possibly both) needs to go in the opposite direction to make all things even. This is all in regards to the amount of light hitting the camera sensor. Any of the three could be in the middle and if it is changed, one or both of the other two needs to change to keep exposure proper and level.

Silhouette of mountain with trees at sunset – East Africa – Tanzania

Currently a lot of smartphones, action cameras and drones have a fixed Aperture, so you only have two settings to play with; ISO and Shutter Speed. Most DSLRs and point-and-shoot cameras can adjust all three.

That’s it!! That’s the Exposure Triangle. It’s not a huge mystery, really. It is simply an attempt to keep all things in balance for a proper exposure. Those three things, explained more fully over the coming days, are what determine a proper exposure. ISO, Shutter Speed and Aperture.

Experiment With It

Here are a few practical experiments you can try at home to help the concepts take form:
- ISO Limits Of Your Camera
- Depth Of Field – Changing Aperture
- Look At The Light
Tomorrow we will cover How Your Camera Works.

Questions? Pop ’em like Pez in the comments section below. or email me at peter@peterwestcarey.com.

Photography Basics – A 43 Day Adventure, and its companion 40 Photography Experiments, are series written by professional photographer Peter West Carey. The series are designed to unravel the mysteries of photography, helping you can take better pictures. Subscribe here to receive all the updates and bonus material. Your comments are always welcome.

If you enjoy the series, consider learning photography first-hand on a professionally led international photo tour in Nepal or Bhutan. More information can be found at Far Horizon Photo Tours.
October 3, 2018