An Introduction To My Talking Points

September 24, 2012  •  Leave a Comment

An Introduction To My Talking Points

Recently, I was asked to give some photography pointers to a local high school's yearbook staff. So, one of the first things I did to prepare for this little soirée, after calming down, and breathing deeply to lower my blood pressure, was to start writing down some talking points. This was going to be a question and answer session, and maybe explaining how some of my equipment works. Having no idea what kind of photography background any of the kids possessed, I figured I would start by talking about the first thing that would come into my head. Knowing me, I knew my mind would suddenly go blank the second I entered the classroom, if not sooner.  With that, and having a poor memory to begin with, some talking points for reference were really in order. At first they were going to be short single line sentences, but as I started jotting them down, I found myself writing a few short paragraphs from time to time. My next thought was to flesh it out a bit more, and finally I just decided to make the whole thing into a blog posting. That way, in the future I could always pull it up if I were to do this again. As an additional bonus, I would be able to keep current by updating the posting. Also, anyone else would to be able to retrieve it at any time. But first I feel the need to explain a few basic photography concepts dealing with light and what a DSLR camera is trying to do.

Photography is all about dealing with light and how it is recorded. To do this, there are three main controls on a camera that you can set and use for taking photos. These are the aperture size, the shutter speed and the ISO value. All interact with each other in controlling how long the light will be used to record/create the photo, and how the photo will look.

Before getting to them, I need to explain one other photography concept. Stops. Stops are how everything is measured and related to when it comes the amount of light entering a camera. The difference in the amount of light between one full stop to the next full stop is either doubled or decreased by half. The entering light is controlled by the shutter speed and aperture size.

The aperture and f stops have to do with numbers you see on a lens or in a camera that may have a lower case “f” with them. The aperture is the opening inside the lens that light entering the lens must pass though on it way to the sensor or focal plane. The size of it is usually set with the camera. These sizes are called f stops. They are mathematical factions and equations that rounded off. Remembering the explanation of Stops, the opening size in a full f stop to the next will be either doubled or decreased by half. For example, if you have your camera set to a f4 sized opening and you want to change the opening size one full f stop, the next full f stop opening would be either f2.8 or f5.6.

Now that you have that concept down (yeah I know, this next part may spin your head a bit faster). The smaller the f stop number is the larger the aperture opening will be. Conversely, the larger the f stop number, the smaller the aperture opening. So, using the example from above, the f2.8 opening will be double the size of the f4 and the f5.6 opening will be half the size of the f4. Maybe to better understand this concept, remember these are fractions, but not written that way. So add the “1/” to the f stop value. Now the f stops look like this, 1/2.8, 1/4, 1/5.6, etc.  (As she is reading through this, The Lovely Kath is thinking, “Ahah! So THAT is how that works!”. Light bulb moment.)

To add a bit more confusion into the mix, there are smaller increases and decreases of f stops in between a full f stop. Most commonly, they are 1/3 or 1/2 of a full f stop. This is where the f stops called f3.2, f5, f6.3, etc come from. These then only change the size of the opening by a 1/3 or half of a full f stop either up or down. Last, remember changing your f stop setting by a full f stop is either doubling or decreasing by half the size of the current f stop opening/setting. There is a full f stop between f3.5 and f5.

Now you are thinking, nice, great, but what does all of that have to do with taking a photo? Your choice of an f stop has two impacts on your photo. One has to do with the shutter speed used when taking the photo, and the other has to do with what is called “the depth of field” that will be in the photo. I'll get to the shutter speed in just a bit. The depth of field in a photograph is that part of it that appears to be in “acceptable” focus and how “deep” into the photo it appears to go. From here, things can get really deep in to the weeds, no pun intended, so I'll stay away from that. If you don't believe me just click on this Depth of Field link to Wikipedia. What you really need to know and understand is this, the larger the f stop, f2.8, the shorter the depth of field will be. A photo taken with f8 will appear to have more in focus deeper into a photo then one taken with f2.8. Also, a photo taken with f8 will have an overall look of being sharper than one taken with f2.8. Using f2.8 is one way to be able to isolate your subject by having a short depth of field by causing your background to become blurry, and also your foreground depending on where or what you focus the lens on. It has to with the physics of optics.

The ISO value. This number is fairly easy to understand. It is a measurement of how fast the camera's recording method is, be it film or sensor. The smaller the number the slower the camera will be in capturing the light. The higher the number the faster the camera will do this. Now, here comes the problem that must be dealt with, or at least kept in mind. The problem is the same with both a fast ISO film and a fast ISO sensor setting. A fast or high ISO setting will create more “noise” in the digital photo and “grain” in a film photo. There is always noise and grain in a photo, but the higher the ISO, the more it will become visible. The dark areas will have more noise then the light areas. Last, ISO values are also measured in stops. So a setting of 400 will be twice as fast at recording the light than a setting of 200 but half the speed of a setting of 800. Again there are 1/3 and 1/2 stop ISO values, 250, 320, etc.

The shutter speed. This also easy to understand. It is the time the shutter inside the camera is open allowing light to strike the camera's recording method, be it film or sensor. So, a speed of 1/4000 of a second will be a very fast amount of time allowing for only a very short period for the light to enter. Where a speed 1/2 second is slow allowing a good amount of light in. Yes, again all these speeds are set up using the stop organization. So 1/200 of a second will let light in twice as long as 1/400. A photo taken with 1/800 will allow the light in for half the time of a photo taken with 1/400. Last, there are also 1/3 and 1/2 stop shutter speeds.

Now that all this is as clear as mud, here is how it all comes together and in a nutshell and how I shoot. I'm making a few assumptions now. The first is that you are a using a modern DSLR camera and the second is that it has not been set to Manual mode. I shoot mostly in Av mode, Canon term, which means I am controlling the aperture and thus the amount of background/foreground blur. I will also set the ISO as well. When I take a photo, these two elements have already been set; leaving the camera to figure out what the needed shutter speed will be based on how much light the camera is reading to get a properly exposed photo. The camera needs a starting point to calculate this, so it has been programmed to think whatever it is looking at, the whole scene must exposed so that a color called “18% grey” is created over the whole photo.  Just go with me on this name. The concept is, if you took all the colors in that scene, placed them in a blender and turned it on, the resulting color would be this 18% grey color. For the photo to come out in this 18% grey, the camera comes up with a shutter speed it thinks will give the photo this color, thus a properly exposed photo in the camera's mind.

Using the camera in Tv mode, Canon term, means you are setting the shutter speed. From there the camera calculates what it thinks the correct aperture should be to achieve this 18% grey color, again for what the camera thinks will result in a properly exposed photo.

The right ISO value is needed to get the shutter speed and aperture size you are using to expose correctly.

The right shutter speed is needed to get the ISO value and aperture size you are using to expose correctly.

The right aperture size is needed to get the shutter speed and ISO value you are using to expose correctly.

I know, it all sounds like all you will be doing is running in circles! This is why some understanding of what is happening and a little practice are very important so you will be able to develop your own starting point. Set a few things and then let the camera calculate out the rest. After a while, your own style of shooting will develop. For me, I love blurry backgrounds.

A first example. If I’m out and about taking photos and shooting in my usual method, in Av mode, I might have my camera set up in this manner; the aperture set to f2.8 and the ISO value set to 400. The camera could be calculating the shutter speed to be 1/400 of a second. This is allowing in an amount of light I’ll call “X”. Everything is coming out fine, and the exposures are looking good. Now if I were to change my aperture down by one full stop, it would become f4. I have just cut the amount of light entering the camera by 1/2. So to compensate for this drop in light and regain allowing in this “X” amount of light, the camera would change to using a shutter speed of 1/200 of a second, thus holding the shutter open twice as long the previous speed of 1/400 of a second. If I was shooting in Manual mode where I would be in charge of all three controls, I would have also had to change my shutter speed to 1/200 of a second after changing to f4 or else the photos would be coming out dark.

A second example. When I go to shoot a soccer game, I will set my camera to Av and dial in f2.8. Next, I'll dial in an ISO speed, maybe 400. Then I'll take a photo of what I will be shooting and see what shutter speed was used. If it was not fast enough, say I wanted to be around 1/640, I then would bump up my ISO a bit more. By doing this, the sensor will now need a shorter time of light hitting it so the shutter speeds can be made faster. Then, I'll take another photo and see if that gives me the speed needed. From there, the camera will be using my f stop and ISO and picking the shutter speeds. Some speeds used will be faster and some slower than what I may have first gotten, but they will be generally around this starting point. I am always checking my histogram to see if the photos are becoming too bright or dark as the light may be changing.

A third example. Again shooting in Av mode and setting the ISO value for shooting at an evening football game. I'll start by setting up my camera just like I did in the second example for the soccer game above.

At the start of the game with the sun still up and the lights turned on my ISO might be 800. As the night wears on and the sun sets it will get darker on the field to the camera. Your eyes will compensate for this falling light level so you never really notice it. The camera isn't faring as well. It is trying to maintain the same amount of incoming light hitting the sensor as there was at the start of the game. To do this it is adjusting the shutter speeds to be longer and longer. At the start of the game it might have been using a speed of 1/800 but by the end of the first quarter it could be using a speed of 1/400. Unwanted blur could now be showing up in the photos and they could also start looking a bit dark now. What to do?

You can't add anymore light by increasing the aperture, it is already at the lenses’ maximum opening. The camera is choosing the shutter speeds and they are getting slower, not what you wanted. There is only one option left, other than going home, and that is to start increasing your ISO value to make it more sensitive to light. Yes! The shutter speeds are back! The trade off is with these higher ISO values comes “noise” in the photos. Now the question is, how much noise is acceptable? Or, how much blur is acceptable if I drop my ISO value back a bit?

One last adjustment you might also have to make because of the falling light levels is to increase the exposure compensation in the camera. This will have the camera make the exposures bit brighter. See below.

There are other ways to achieve the same result and they work fine, but this what I have always done. I have a friend and fellow photographer who mainly does weddings and portraits, and she shoots in Manual mode. This means she is choosing the ISO, shutter speed and aperture. She has learned what works for her, but she is always checking her histogram to make sure the exposures are coming out correctly.

Exposure Compensation. In your camera there is an adjustment you can make called exposure compensation. With this adjustment, you can set the camera to make your exposures brighter or darker. This goes back to the 18% grey color that the camera is trying to achieve; well sometimes achieving this is a bad thing. As an example, if you take a photo with lots of white snow in it, the resulting photo could have the snow looking a bit grey, or under exposed. By bumping up the exposure compensation a stop or so, the photo will be exposed a bit brighter resulting in whiter snow. The same concept goes the other way for a photo that could contain many dark elements that you want to stay dark. If you have set the camera to Manual mode then you will have to make the needed adjustments yourself.

Now without any further ado, here are my talking points. I hope they are helpful!

Talking Points

Talking Points Mark II

Doug


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