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Author Topic: Wildlife photography, Part 2 Exposure/Composition (1of2)  (Read 1953 times)

Offline popeshawnpaul

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Wildlife photography, Part 2 Exposure/Composition (1of2)
« on: January 05, 2009, 08:00:10 PM »
So now you have that camera and you want to get some images.  I'm going to try and focus this discussion on nature photography but these principals will apply to other types of photography as well.  You can learn a lot of this from any site, however I'll try to tell you some of this information and relate it to nature and wildlife photography.

Understanding Exposure

This is the most important part of photography in my opinion.  If you aren't a real technical person then just try and figure this one principal out as it is the basis for photography no matter if you use film, digital, or a point and shoot camera.  Let's go over each one and then we can discuss how each one affects the other one.

Aperture/f-stop

Your camera lens is a glass tube that takes light and displays it on the film or sensor in the back of the camera.  Sometimes you want to let more or less light into the lens.  There are little blades that close inside the lens to let less light in when you tell the lens to do so.  If the lens blades aren't closed down at all, then the lens is "wide open".  Some lenses are faster than others and can display more light to the film or sensor.  The fastest lenses shoot at f1.  F-stops range from 1, 1.2, 1.4, 1.8, 2.8, 4, 5.6, 8, 11, 16, 22, and 32.  Every time you go up one of these numbers you are going up one stop of light.  Each step up lets half as much light in as the number just below it.  So if you go from f1 to f1.2, you are letting half the light in that you would be if you left the lens at f1.  This is called stopping the lens down.  If you keep the lens at the fastest setting you are shooting wide open. 

Shutter Speed


The camera determines how long the film or sensor will be exposed to the light coming from the lens.  There is a little shutter curtain in front of the film or sensor that opens in the camera and lets the light from the lens hit the sensor.  It will open and close depending on how you set the shutter speed.  Shutter speeds vary on a camera from 30 seconds to 1/8000th of a second.  That means that the camera at the lowest shutter speed of 30 seconds will open and expose light to the sensor for 30 seconds.  At the fastest speed of 1/8000th of a second it opens and closes so quick that the sensor only gets 1/8000th of a second worth of light. 

ISO

We use to call this ASA to rate film speed in the old days but ISO is the digital equivalent to film speed.  Remember shooting asa 400 film in the old days?  That's just like setting your camera to ISO 400 these days with a digital camera.  The ISO changes how sensitive the sensor is to light.  In the old days of film you had to change the type of film speed you were using by changing to a different roll.  These days you can just tell the sensor what speed to shoot at and dial it in.  You can go from shooting the slowest sensitivity of ISO 100 to the faster speeds of ISO 3200 from one shot to the next.  ISO ranges or speeds are as follows:  100, 200, 400, 800, 1600, 3200, 6400, 12800, 25600.  Each time you double the number you are making that sensor twice as sensitive to light. 

Aperture vs Shutter Speed vs ISO

Each one of these affects the others.  If you change one setting on any of these 3 the other 2 must compensate.  If you let half as much light through your lens by stopping it down 1 stop, you need to slow the shutter down so that it is open twice as long to compensate for half the light getting to the sensor.  Or you could keep the shutter speed the same and change the ISO up one stop and the sensor will now be twice as sensitive and quick at gathering light.  I think of aperture, shutter speed, and ISO like a hose filling a bucket with water.  The hose diameter is the lens, the water is the light, and the bucket is the sensor.  If I send water to a bucket with a 1 inch hose I can fill the 2 gallon bucket in a minute.  If I use a hose that is twice as wide, say 2 inches then it will let twice the amount of water through and so you only need to leave the hose on for half as long to fill the 2 gallon bucket.  That is like opening up the aperture on your lens.  If you let it put twice as much light through it then your shutter speed only needs to be open half as long.  The bucket size really determines how long you need to keep the hose on.  If your bucket is twice the size then you need to keep the hose on twice as long or make the hose twice as wide.  Either way will accomplish the goal of filling the bucket.  The different sized buckets are the equivalent to different ISO settings. 

Let's illustrate this with a couple examples.  If I'm shooting and my camera light meter is indicating that at ISO 400 and f4, I need 1/250th of a second shutter speed.  If I decide to lower my f-stop to f2.8, then I need to keep the shutter open half as long to get the same amount of light.  Therefore, my shutter speed will need to be 1/500th of a second.  If I stop down my lens to f5.6, then my sensor is getting half the light it was at f4 and now I need to keep my shutter open twice as long, so 1/125th of a second.  Now let's add in ISO and see how that affects things.  If I decide I want to shoot at ISO 200 instead of 400, it's going to take twice as long to fill that sensor up with light.  The sensor is half as sensitive to light as it was at ISO 400.  So if I was shooting f4 @ 1/250th at ISO 400 and then I change that to ISO 200, I need to give that sensor twice as much light because it's half as sensitive to light.  Therefore, I need to either open the aperture one stop to f2.8 or slow my shutter speed down to 1/125th of a second.  Either way will accomplish the goal of getting twice as much light to the sensor.  This is really complicated stuff.  If it isn't making sense maybe go and try to read further about this on the internet.  Once you have this it is a good basis for which to have in your photo career.

What Aperture To Select

This depends on your subject.  I showed a series of 7 photos with a deer and various apertures ranging from f4 to f32 in part 1 of this series.  Here are those photos again:

F4


F5.6


F8


F11


F16


F22


F32


The wide open aperture of f4 on those shots blur the background and have the least depth of field, meaning only the deer is in focus and not much else in front or behind the deer.  Then go up and look at f16 and see how the grass directly behind the deer is now in focus and the background is in focus.  The higher the aperture, the more stuff in your photo that will be in focus.  That being said, depth of field is usually not good in a wildlife photo.  I like a narrow depth of field so that background is blurred nicely and that buck pops out of the photo.  See how that deer stands out in the f4 photo?  That is desireable to me.  You need to decide what is desireable to you in a photo and pick an aperture that suits your needs.

So I generally pick the wide open or fastest aperture on a lens when shooting birds and wildlife, but what do you do when you are trying to shoot a landscape image?  Well, I do the opposite.  I set my aperture for the highest setting possible and that will maximize depth of field.  Now that tree in the foreground will be in focus as well as the mountain in the background.  Just be sure you always focus on the nearest object you want in focus as distant objects will stay in focus behind your foreground if you are picking a high enough aperture.

Let's complicate things...if I'm shooting 2 sheep on a mountain and one is standing in front of the other, now I have a problem.  If I shoot at wide open at f4 and have a narrow depth of field and that 2nd sheep that I'm not focusing on will not be in focus.  If I select too high of an aperture, everything including both sheep and the background will be in focus.  That is not desireable.  In this situation I would stop the lens down a stop or two to f5.6 or f8 and hope I now have enough depth of field to get both sheep in focus but not the background.  One check of your lcd screen after taking a test photo will show you if you got both in focus.

As a general rule, if you are shooting pictures of people you want a shallow depth of field and want to shoot wide open.  However, if it is Christmas time and you want to take a group shot of people, you may want to stop down and get more than just one person in focus. 

What Shutter Speed to Select

For wildlife we use a simple formula.  We just take the focal length of the lens we are using and put 1 over that.  So if I'm using a 200mm lens then I shoot at least as fast as 1/200th of a second.  If I'm shooting with a 400mm lens then I shoot at least as fast as 1/400th of a second.  If I'm shooting a 50mm lens then I use a shutter speed of 1/50th of a second.  Now let's factor in IS to this equation.  IS systems can vary from 2 stop to 5 stop IS.  A 2 stop IS would allow you to go below this 1/focal length rule by 2 stops of light.  So if your 200mm lens has 2 stop IS then you could go from 1/200th of a second to 1/50th of a second.  (1/200 to 1/100 to 1/50th)  If your lens has 5 stop IS then you could go all the way down to 1/6th of a second.  (1/200 to 1/100 to 1/50th to 1/25th to 1/12th to 1/6th)  This can give you a big advantage in low light.  As a general rule, no matter if I have IS or not I try and shoot at 1/250th or higher.  This is because animals move and it takes a speed of at least that much to stop most action.  If I can afford the light I prefer to shoot at 1/500th or 1/1000th of a second.

What ISO TO Select

This depends on how much light is out there.  If it is nighttime, you need the fastest speed you can get.  On my 40D that is ISO 3200.  The images will be grainy at this high ISO but that may be the only way you can get the shot.  Generally just after dark I can start shooting deer or wildlife at ISO 1600 and get at least 1/250th of a second shutter speed.  As the day progresses and there is more and more light, you can lower your ISO as the day goes along.  By mid day I'm usually shooting at ISO 100 or 200.  I do this because lower ISO speeds mean less grain and noise in my images.  However, at dawn and dusk I'll take a grainy/noisy photo over no photo at all.  This is where a point and shoot camera fails at wildlife photography.  Dawn and dusk is usually the best time to take pictures though so it's a catch 22 really.  Point and shoot cameras are really noisy at ISO speeds of 400 or higher.  This means you can't get enough shutter speed and those shots of the deer or elk are blurry.  I think we have all experienced that.  Like I said though, a noisy shot is better than no shot so you guys with point and shoot cameras set your ISO to the highest setting and hope some turn out when there is no light.

Each camera will vary in quality from ISO to ISO.  My camera looks really good up to ISO 400.  Some of the new full frame cameras look really good up to ISO 1600.  Point and shoot cameras only look good at the slowest speed of ISO 100.  It varies with the camera and size of the sensor.  The more megapixels you pack into a small sensor, the more noise the pictures will have in them.  Do you really want that 15 megapixel point and shoot that is noisy as heck?  I'll take less megapixels and less noisy pictures any day.

Real World Exposure

Ok, enough theory that you should know.  In practice I personally use aperture priority for 95% of what I do.  The other 5% is manual mode.  I use aperture priority for 2 reasons.  First, I like to select the aperture or f-stop as it will determine how much depth of field I will have in a photo.  Second, light can vary and I want my camera meter to be constantly metering the situation in case the light changes.  If I'm in manual mode you must select the shutter speed and the aperture.  In aperture priority you select the aperture and the camera selects the shutter speed.  So if you are shooting a deer and the sun suddenly goes behind a cloud and gets darker, the camera will detect there is less light and slow the shutter speed down.  If you are in manual mode you may not notice the subtle changes in light.  The only time I use manual mode is when I'm shooting a subject in difficult light.  A good example would be a black bear on snow.  The dark bear and snow will fool the meter and the bear will either be in proper exposure and the snow will be blown out or the snow will be in proper exposure and you won't see any detail in the bear.  In this instance you select a setting inbetween both extremes and lock it in so it won't change on you.  These instances are very rare.

One word of advise, don't use the P or auto mode ever.  It is a lazy way of doing things and you won't learn anything.  Besides, your camera doesn't know how much depth of field you need, only you can determine that.  Having that knowledge and control will give you more power over your photos and you will have better results.  There is a reason why pro cameras don't have these modes...

Composition

This is a challenging subject.  Framing a deer or bird can be very challenging.  There are general rules though.  You generally want your subject looking into the frame and you don't want to center your subject often.  I use the rule of thirds a lot.  You split a photo into thirds each way and where they intersect is a power point.  I try and put my subject or the center of focus on a power point.  Putting an eye on a tightly framed subject on a power point is usually the best. 

Continued on (2of2)...

Offline Todd_ID

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Re: Wildlife photography, Part 2 Exposure/Composition (1of2)
« Reply #1 on: January 14, 2009, 12:15:56 AM »
This is simply too good to let languish on page 2!
Bring a GPS!  It's awkward to have to eat your buddies!

 

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