How Your DSLR Camera Works

Automatic vs. Manual Settings

Many cameras have automatic settings. They have ways to select simple options, like “sports” or pictures with fast shutter speeds, "landscapes" with wide depth of field, “portraits” or “close-ups” with a bigger aperture, so that the main subject is in focus and everything else is blurry around it, “night time” with longer shutter speeds, or “inside” which compensates for the color of indoor lighting.   It is fine, and you can get great results by using these predetermined settings.   I mean that.  Don't wait to start taking pictures.  Automatic settings can help you relax about the technical side and develop your eye.  That's a very important part of making pictures that have life in them. 

The manual settings transfer the control of what is happening in the camera to you.  They allow you to achieve and refine specific effects.  Learning to use the manual settings on a camera is like learning to play a musical instrument.  It is good to get the concepts and maybe practice some scales until the skills are automatic.  Then you can play written music... follow prescribed formulas for achieving predetermined results, or you can improvise... access your skills, but follow your heart and instincts. 

Some people love the technical mastery that is possible with photography and some people are totally baffled by it.  I've seen incredibly bright people who can do many other technical things get stuck about cameras.  It was a shame because it almost stopped them from doing photography.  So don't let that happen.  Use the automatic settings all day long, use them forever if you want to, and if you want to venture into the technical side, know that you can do it.  There are a few basic concepts which are not that hard to understand in themselves, they are just swimming in technical language.  It's the lingo that's tricky - especially when you are hearing and trying to work with everything at once.  There are only so many concepts the brain can process at the same time, and they tend to jam up in there.   I know because they jammed up on me.  Just slow down and work with them.  At some point, the light will go on and then it will seem like the simplest thing. 

I will try to explain:

How Cameras Collect Light:  Aperture, Shutter Speed and ISO

Your camera is a box for collecting light.  It controls the amount of light it collects in three ways:  by the sensitivity of the film or sensor collecting light, by the size of the opening for collecting light, and by the amount of time it is open.   We are just going to talk about two of them at first, "aperture" and "shutter speed".

Think of it like watering a garden.  If you use a big stream you will water the garden quickly.  If you cut the stream back, it will take more time.   You want a specific amount of water, so you play with those variables…the size of the stream and the duration of time that it’s running.  If your only objective were to water the garden quickly, you would use the biggest stream possible, but there would be reasons (like not destroying your plants) to control what you are doing.  The same is true with cameras.  You want a specific amount of light, but have a choice of how big an opening you use and how long you keep it open.  In camera language, the size of the opening for the "stream" of light is called the "aperture" and the amount of time the stream is running is called the "shutter speed".

Cameras have “f-stops” to designate the size of the opening or aperture.   It takes a little getting used to, because the higher the f-stop number the smaller the aperture, but that’s because the f-stop is actually the denominator in a fraction.  You can think of it more simply.  Aperture is like watering your garden with measuring cups.  ½ cup is larger than ¼ cup, that's all.  They don't usually talk about that in camera land.  They just say the denominator and throw an "f" in front of it... 1/2 becomes "f/2", and 1/4 becomes "f/4".  They actually complicate it further because the fractions for f-stops are f/2.8, f/4, f/5.6, f/8, f/22.   They do that to make us insane.  Or actually they do that because it's a mathematical result.  It's actually the (focal) length of the lens divided by the opening of the lens.  This is part of the geeky side of cameras that some people joyfully embrace, and the best of them can use these terms in sentences.  (As in, "I "pushed" the aperture a quarter of a stop.")  You don't have to talk that way.  You really don't, and you can still take amazing pictures.  The funny thing is that after doing this a while it will actually sound normal and then welcome to the club.

In this long exposure, moving water blurs into smoke.

In this long exposure, moving water blurs into smoke.

Cameras also have stops for designating time or “shutter speed”.  Stops for aperture and shutter speed stand in “reciprocal” relationship to each other.  That means, to collect a given amount of light, if you go up one stop in aperture you go down one stop in shutter speed.  Think of it like a seesaw.  They go up and down at exactly the same rate.  Or back to a garden.  Imagine an irrigation system that had two controls, one for the amount of water flowing in the system and one for the amount of time it is flowing.  To deliver 10 gallons of water to a garden you could create the same relationship.  More time, less water flowing - less time, more water flowing... like that.


Fast shutter speeds freeze motion.

Fast shutter speeds allow you to freeze motion.  They are great for sports and moving water, and birds flying by.  The trade-off is that to collect enough light with a very fast high shutter speed, you have to use a big aperture.  Big apertures, especially combined with telephoto lenses, create a narrow “depth of field”.  Look out your window and notice that you can see close and far away and everything is in focus.  That’s a wide depth of field.  Narrow depth of field means that only subjects at a certain distance away will be in focus.  Depth of field depends on a combination of things…  your aperture, your distance from the subject, and the size or “focal length” of your lens. Long story short, you will want control over your depth of field.

A narrow depth of field can be created with the "flower" or "portrait" settings on your camera, or by using a larger aperture, a longer focal length, and being closer to your subject.

Because I used a large aperture, and because I was very close to this leaf, there is a very narrow depth of field.  Only the front of the leaf is in focus.  I did not take an “accurate” picture, in sharp focus for the entire image, but I achieved my objective, which was to show the detail on the leaf, and the beautiful fall colors.  You can exploit the difference between how the camera works to look at something in a new way, to focus attention on what is most beautiful or meaningful to you.

There is one more thing within our control in the manual functions of a camera, and that is called   “ISO”.  It is the abbreviation for “Industry Standards Organization” and is the term used to identify the sensitivity of the film you would use in a film camera.  The term has carried into the digital world.  At higher ISO, the film or the camera sensor is extremely sensitive to light.   So when you need to collect light quickly or where light is not readily available, you can use a higher ISO.   To talk about the garden again, ISO is like the soil.  The water that you deliver will do its work differently depending on how your soil absorbs water.  You would have to pay attention to that, and match the rate at which water is delivered and the velocity of water that's delivered to the characteristics of the soil.

It helps me to think about this separately because of the way I do my photography.  I'm always taking pictures of waves.  I usually want to freeze their motion which means I want fast shutter speeds.  That means I need a big aperture, and a big aperture combined with a telephoto lens would tend to reduce my depth of field...but I want a big depth of field, so the only thing left for me to do is push my ISO. 

Once again, there is a trade-off.  At high ISO’s your film or sensor will indeed record the light very quickly, but because of that sensitivity it will react to everything, creating extra information on the image, called “noise”.  This is the visual equivalent of static.  It looks a little like snow or fog on the image.  Many new cameras are built to correct to some degree for this problem.  You can use Photoshop or other special software that can help with that, but once again, it is a balancing act.  You want to remove noise without reducing sharpness. 

You will always be playing with aperture, shutter speed and ISO.  Each variable has its strengths and trade-offs, so you get to choose what is most important to you in each situation, what strengths you want to use, and how to work around the trade-offs.

How Your Sight is Different than a Camera

Dynamic Range

Dynamic range is the range of light to dark in which you will see detail in an image.  People see in a wider dynamic range than a camera.  That means for example, to name one of the more classic and difficult situations, you could have a bride in her white dress and a groom in his black tux standing next to each other.  If you are not careful, you will either “blow out”, or over-expose, and lose the details of the dress, and under expose the details in the tux.  What to do?  Your options:  Know your priorities (in this case, I would go for the dress), find an optimal balance between the two, where you get enough of the tux and still get what you need from the dress.  Underexpose the entire image slightly, because using Photoshop or other software, you can always “pull out” details that are darker than they should be.  But you can never recover details that are so overexposed that they were never recorded.  You can also shoot “raw” files.  That means files that are not processed and reduced in size by the camera.  They contain every bit of information that your camera could possibly collect, and make it possible for you to recover quite a bit of detail from your image. 

You will encounter the same situation if you have to take a picture of someone standing in a window.  Again, you will either overexpose the window and underexpose the person or visa versa.  The same techniques apply.  You will probably want to expose for the person perhaps slightly underexposing the image to compensate for the light blasting in the window, and deal with it further in post processing. 

People can see details in both light and dark at the same time, but cameras usually can't.  Unless you are doing HDR photography, sometimes you have to choose.

There are times when you can exploit the narrower dynamic range of the camera.  In this picture of a sunset on Great Salt Pond, the individual trees were lost in shadow.  But the important part of the picture was the color of the sky reflected in the water. 

Finally, there is HDR or High Dynamic Range photography.  In this technique you take multiple pictures of the same scene at different levels of exposure.  You can do this by setting up a tripod and manually changing the exposures, or some new cameras have this built in as one of their features.  Then you use software to combine the images together.  In this way, you can show all the details at every exposure level.  Sometimes the effect is very rich and amazing and sometimes it's a bit surreal.  You get to decide what you like and what you are trying to demonstrate.

Leading the Eye

You can use lines and shapes within a picture to draw the eye.

People constantly tell me that they took a picture at sunset when color overwhelmed the sky.  When they looked at the picture, they found instead, a little pinprick on the horizon.  There are reasons for this.  Your eye sees about 55 degrees of information.  In other words, if you turned in a circle and saw everything all around you, that would be 360 degrees.  If you just look in one place, you see 55 degrees, or between 1/6th and 1/7th of the full circle.  A camera can “see” much more or less than 55 degrees, depending on the lens that you use.  So the part that you saw, could have gotten lost as only a portion of the picture.

The biggest reason is the way your eye works together with your mind.  Your mind interprets the objective information received through your eyes.  If something is important to you - a charging buffalo, a beautiful sight, your child wandering into the road, for example, your mind will bring you to it.  You will see that and only that, as if there was nothing else in the picture.  The camera is entirely objective.  It makes no decisions about what is important.  It does not emphasize anything at the expense of anything else.  So your task is to develop your own techniques - to replicate the activity of the mind. 

You can use dynamic range and depth of field to focus attention on a particular part of the image.  You can zoom in with your telephoto lens.  You can use lines and shapes within the picture to draw the eye to what you want to emphasize.  You can do the same thing by positioning within the picture.  A subject placed like a bull’s eye in the middle of a picture will cause the eye to land on that spot and stay there.  A subject placed to the sides will cause the eye to travel.  That’s the reason for certain techniques in photographic composition, like the “rule of thirds”, where you imagine a “tic-tack-toe” grid on the scene and place the important part of the picture at the intersections of the grid.  You can also use other composition tools like golden ratios.  There is even software to help you do that.  In reality, you will develop your eye, and you will feel the best compositions, both in taking the pictures and in processing later. 

Unless you stage a picture, you will be dealing with what is there, so again, it is a matter of optimization.  You decide what you want to show, what information is important to the story or feeling you are trying to convey.  You can work with what is there, experiment with different focal lengths, exposures and shutter speeds.  You can balance content, and line, and texture and position, until you are happy with what you’ve done. 


You can make enhancements in Photoshop and other software.  Learning about software is a course in itself.  Your options are so varied and powerful that you can radically alter the picture from what was actually there.  In that case, you have created digital art, a derivation, rather than a representation of your original picture.  It’s fun, and can be very effective, but to be honorable, when you use techniques like that should say so if you are intending to sell picture.  

My goal with the pictures I take is to be true to the natural scene and the native abilities of the camera.  I very seldom add artificial light.  I do not spray flowers with water to simulate dew or rain.  I do not disturb nesting wildlife.  I do not move things around.  You can do all these things (except disturb wildlife) and it’s fine.  People construct and photograph the most amazing things and the construction itself is part of the art.  But in my particular case, when it comes to nature photography it is important to me personally, to see the world as it presents itself.   I don’t want to control what I am taking.  I want to learn and be surprised.  That’s what I feel right now. That’s what does it for me.  In a year it might be something else.  

When I post-process in the computer, I try to limit myself to adjustments that compensate for the change in medium.  I am changing from a luminous, three-dimensional world to a flat piece of fine art paper and in my case, a mat finish.  So I might make changes a little bit, not much.  I may change saturation or vibrance by 3%, apply a warming or cooling filter for 3 or 5%, sharpen all or a part of a picture by 3%, pull some detail out of the bright parts and shadowed parts of the picture, reduce noise a little bit.  The key, when faced with such powerful tools, is restraint.  You may still spend a lot of time, as it takes time to try different things, and stay in control of the result.  The truth if you are like me, is that you may get a tiny bit obsessed. 

The ideal is that you will use the optimal settings at the time of taking the picture, but you can correct your mistakes or refine images that were taken under difficult conditions, to a certain extent, in post-processing.  Again, you will learn over time and improve your techniques, both in taking the pictures and in working with them afterward. 

I don’t want to alter the picture, only allow it to truly reflect my memory and experience of what was there.  For the most part, I limit myself to techniques that approximate those a film photographer could use in a darkroom.  There are exceptions to this, like combining images for high dynamic range photography or stitching images together for a panoramic shot.  In that case, I clearly describe the technique in pencil, on the back of the image.  Another exception is restoration.  I worked on a picture of my sister, taken by my father more than 40 years ago.  The slide was completely discolored and it had big blotches and scratches all over the picture.  I used lots of techniques available in Photoshop to restore the image to what was there when my father took the picture.  I could only guess what the original colors might have been.  The changes took several hours and they were pretty radical, but it was clear that I was restoring rather than trying to change the image. 

If there is any doubt about a technique, if it changes the picture too much, unless the change is obvious and clearly noted for a particular purpose, I don’t use it.   That’s for my fine art work.  If I’m fooling around, making cards or something for friends, then that’s a different situation.  I’ll do anything.

An outstanding painter in our gallery, and a good friend commented about how much more time it takes to make a painting than a photograph.   At first, I agreed with him, but then I thought about it.  I go out for many days, taking hundreds or thousands of pictures to get the ones I want, take them home and spend hours or days in post processing.  I experiment with several versions to get the print to be perfect…  So I guess it depends on the picture and on the painting.  It’s just a different process.