aperture

All posts tagged aperture

Exposure Rules

Posted by JUST PhotographIN' on May 8, 2018
Posted in: Thoughts, Tips and Tricks. Tagged: , , , , , , , , . Leave a comment

Today is a nice sunny day.  I was just out with my camera trying to capture some birds.  How did I select my exposure settings?  In a previous post, I discussed the exposure triangle.  Aperture, shutter speed and ISO make up a trio of settings that combine to create the proper exposure.  There are a couple basic exposure rules that can get in the ball park of the proper exposure in certain situations.

As I mentioned, today is a nice sunny day.  The first exposure rule is called Sunny 16.  This is where the aperture is set to f/16 and the shutter speed and ISO are set to the same value.  Back in the film days, ASA (now ISO) was a constant for the roll of film.  If I had a roll of ASA 100 film, that is the same as saying ISO 100 for a digital camera.  ISO is an international standard measurement for exposure.

On a sunny day, like today, I can get a proper exposure by simply placing my camera settings to f/16, 1/100, ISO 100.  This may be good for landscapes and still objects.  However, I was hand holding my 400mm lens while trying to capture a moving object.  This means that I need to adjust my exposure settings to compensate for these variables.

The general rule of thumb for getting a sharp image while hand holding a lens is to use a shutter speed equivalent to the focal length of the lens.  For my 400mm lens, this means that I need to use a shutter speed of 1/400 or faster to stop any motion induced by myself.  Keep in mind that I am still shooting the same bright sunny scene.

I want to keep the same exposure reading I had when I was at f/16, 1/100, ISO 100 with a new shutter speed of 1/400 to compensate for hand holding a 400mm lens.  My options are f/8, 1/400, ISO 100 or f/16, 1/400, ISO 400.  There are actually more combinations of the exposure triangle that achieve the same equivalent exposure value.  It is up to me to decide how to balance the equation.

Perhaps the clouds build.  This reduces the scene’s luminance.  There is also an overcast 8 rule that looks like f/8, 1/400, ISO 400.  I used ISO 400 because 400 speed film was a more typical all purpose film speed.  However, f/8, 1/100, ISO 100 gives the same reading on the light meter.

Digital cameras have taken away some of these really good basics.  I say that, because a camera can do all the thinking for a person and achieve a good exposure.  Back in the film days, it took a little extra thought process before the shutter button was released.  Yet, all the same fundamentals still apply and can be used in digital photography.

I shoot almost exclusively on manual mode.  Automatic modes have purposes.  They can speed up the process of taking a photograph.  I just rely more on the fundamentals to get me where I want to be.  In a way, I am challenging photographers to think more before they take a photograph.

Ask: what is the lighting of the scene?  On the next bright sunny day, set the camera to manual with f/16, 1/100, ISO 100 and see how well it exposes the scene.  Said with slight sarcasm: maybe automatic mode will become a thing of the past!  Photography is more fun when it is not so automatic.  So, remember the sunny 16 and cloudy 8 rules. Give them a try!

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Introduction to Exposure

Posted by JUST PhotographIN' on May 8, 2018
Posted in: Geeky, Thoughts, Tips and Tricks. Tagged: , , , , , . 1 Comment

I have been wrestling with how to present this information, because there is so much already available.  It is photography 101, the basics, plain and simple.  My goal is to present some more in depth, deep dive information to really get people thinking about photography in a different way.  I am going to start by introducing exposure value.

The exposure: what is it?  How is it controlled?  Most cameras have some form of a light meter to gauge how much light is in a scene.  Another way to express this is with the words: luminance or exposure value.  These are essentially measurements of how bright or dark a scene is.  A camera can capture a certain range before things are completely black or completely white.  Somewhere in between completely black and completely white is middle tone grey.  The actual value for middle tone grey is 18% grey.

Exposure value (EV) is based on this scale of luminance.  A camera is essentially trying to make everything a middle tone grey.  The range of a scene, however, can vary anywhere from pure black to pure white.  Digital cameras show this information in the histogram.  A light meter has a scale of plus EV and minus EV with the middle being zero.  This zero point is where the exposure value is calibrated to achieve middle tone grey.

Underexposed scenes will tend to lose information in shadows and blacks.  This is referred to as clipping.  Clipping is when the exposure value is insufficient to capture information.  Overexposing a scene can also result in clipping in highlights and whites.  The goal is to have the sensor capture a scene that is not completely black nor completely white, rather more toward the middle tone grey range.  Again, this is where the needle reads zero on the scale.

There are essentially three ways to control the exposure value: aperture, shutter speed, and ISO.  Each one of these settings controls how much light reaches the sensor to create the exposure.  Aperture is the physical opening of the lens that light passes through to reach the sensor.  Shutter speed is the duration (time value) that light is allowed to reach the sensor.  ISO (was referred to as ASA for film speeds) is an increase of the sensor’s sensitivity to light.

The combination of aperture, shutter speed, and ISO is often called the exposure triangle.  This is due to the balancing act of changing these settings to achieve the correct exposure value.  The exposure triangle can also be used to create certain aesthetics in photographs.  I will be doing a series of posts that dive deeper into each setting over the next couple weeks.  Stay tuned!

Introduction to Lenses

Posted by JUST PhotographIN' on February 14, 2018
Posted in: Thoughts, Tips and Tricks. Tagged: , , , , , , , . Leave a comment

As I was beginning to get more serious about photography, I started asking other photographers for advice about equipment.  I looked at what they were using and tested out different camera bodies from different manufacturers.  There was one piece of advice that I heard several times: get good lenses (often referred to as glass).  I am glad I followed this advice, and have reciprocated the advice to other folks who ask me about equipment.

There are several reasons why I think it is important to get good quality glass.  The lens is what actually creates the image.  A high-end, expensive camera with the best sensor only captures what it is seeing through the glass that is placed in front of it.  Meaning, if the quality of the lens is poor, the image will be poor regardless of how good the sensor in the camera may be.

Lenses can have different specifications.  They can be wide-angle, normal, or telephoto.  This changes the perspective of what the lens can see.  Some lenses can zoom between focal lengths to change the angle of view more quickly without having to change the lens.  Other lenses have a fixed focal length (referred to as prime lenses). There are fast lenses and slow lenses, which is a reference to the aperture of the lens and how much light it will let pass through to the sensor.

Wide-angle lenses are lenses that see a greater angle of view from side to side.  They are lenses with focal lengths less than 50mm.  I have a 16-35mm super wide-angle zoom lens that I use for landscapes and astrophotography.  It is also a fast lens with a f/2.8 aperture that lets in a lot of light for low light situations.

Normal lenses are typically 50-85mm.  These are good for portrait photography.  I do not take many portraits.  However, I know a lot of portrait photographers who use something in this range.  People are rendered nicely by these focal lengths.

Telephoto lenses are going to range anywhere between 70-400mm.  I use a 70-200mm zoom lens for portrait work as well as some wildlife and landscape photography.  This is my go to lens if I want to carry one lens that will cover a wide range of possible distances.  I tend to get more questions with this lens, as well.  Longer lenses tend to attract more attention.

Speaking of longer lenses, the final category is the super telephoto, which is basically anything 400mm or higher.  These lenses are great for wildlife and sports.  They are probably the most recognizable lenses out there due to their size.  People often migrate toward me when I have my 400mm f/5.6 lens on.  They are intrigued to ask what I am shooting or make a comment like: “I wish I had that camera (they really mean lens).”

Last year, I added a spotting scope to my lenses.  It is a 1250mm focal length, f/10 aperture, Celestron C5 spotting scope.  Again, people migrate toward me when I am using this lens.  It is unique for photography, and offers a slightly different perspective.

Lenses impact the photographs that can be created.  My challenge for this week is: take a look at the lens.  Find out what the technical specifications are: what is the focal length of the lens?  What is the aperture range?  Is it a prime lens or zoom lens?  Next week, I will be going more in depth about aperture with a video to demonstrate how it works.

Spotting Scope Photography

Posted by JUST PhotographIN' on March 22, 2017
Posted in: Thoughts. Tagged: , , , , , , , , , , . 3 Comments

On Monday, I took my new Celestron C5 spotting scope out to view a nesting Great Horned Owl.  The scope kit comes with a standard eye piece for optical viewing.  However, they also offer an adapter that allows a camera to mount to the scope for use as a super telephoto lens.  This was my main objective when I bought the scope.

Monday was my first time setting up the scope with the camera mounted on it.  There are some technical details to take into consideration when photographing with a long focal length.  I also use a 400mm lens that has similar issues, although not as exaggerated.

File Mar 22, 12 13 22

This is looking into the front of the Celestron C5 spotting scope.  The technical specs are shown around the perimeter: focal length of 1250mm with an aperture of f/10 making the primary mirror diameter 127mm.  There is also no image stabilization.

File Mar 22, 13 54 52

The owls have nested around this location for several years.  I setup the scope with the eye piece to get the scope pointed at the right location.  Then, removed the eye piece and attached the camera on the adapter.

File Mar 22, 12 35 03

The above photo is with the camera on “live view” mode.  I ran into a few issues with live view.  First, there was glare from the ambient light on the screen.  Second, in order to view anything on the screen, I had to adjust the shutter speed to a  much longer exposure than was required for the actual exposure.  I am guessing this is due to the camera not having the aperture information to calculate the overall exposure when displaying the image on the screen.  The camera is more than likely reading the light within the scope itself, which is much darker than the ambient light within the scene.

As I mentioned in the technical information about the scope, the aperture is fixed at f/10.  This means I am controlling the exposure with adjustments to shutter speed and ISO.  The general rule of thumb to freeze camera motion is to use a shutter speed equivalent to or greater than the focal length.  In this case, that means faster than 1/1250th of a second.  This is where having a camera with good high ISO performance comes in handy.  It turns out that the rule of thumb of placing ISO and shutter speed equivalent to each other gave me the proper exposure for the scene.  I went with ISO 1600 and shutter speed of 1/1600 at the fixed aperture of f/10 provided from the scope.

This may sound like over kill.  Yes, I could have used ISO 1250 and shutter speed of 1/1250.  However, there was a slight breeze which added motion to everything, and I wanted to make sure I was getting the fastest shutter speed to freeze the motion as much as possible.  This is not talking about the owl movement, which would have been frozen at a much slower shutter speed of possibly down to 1/500th or slower (since she was not moving that much).  I am strictly speaking about the subtle shake in the camera setup on the scope.

Eyes On

This is the resulting image.  There are a few more tricks to reduce camera shake.  I already mentioned one of them above: shoot with live view.  Live view inherently locks the mirror up which reduces the “mirror slap” that occurs during a normal exposure.  The camera also has a mirror lock up function, which is the mode I ultimately used to take the photos.  Mirror lock up requires a double press of the shutter release button.  The first press locks the mirror up.  The second exposes the image.

There are drawbacks to this, as the timing of events in the scene may change by the time the photo is exposed.  I did not time the actual sequence, but I am guessing there was around a two second delay between the first shutter click and the second shutter click to allow for the shake to minimize from the mirror flipping up.

Owl Blink

After the mirror flips up, I can no longer visibly see what is in the view finder.  This means things can change in the time it takes to hit the shutter to expose the image.  For example, when I started the process for this image, the owls eyes were open.  By the time I hit the shutter to expose the image, she was blinking.  It was an odd coincidence to capture this moment.  Had I seen her blink, it would have been too late to capture the moment, due to the delay from the mirror locking up and hitting the shutter release the second time to expose the image.

This can be reduced by shooting the images with live view.  However, the exposure setting to view anything on the screen was not appropriate for the exposure of the scene.  This resulted in a blank image full of white pixels since everything was overexposed.  Again, I am unsure if this is due to the camera not having the aperture information to assist with calculating the exposure to display on the screen.  Canon EF lenses communicate aperture information with the camera body.

Lastly, I was also using a remote trigger for the shutter release.  This allowed for hands free operation of the camera to further reduce motion of the camera.  Using the shutter release button on the camera requires a press which in turn induces motion into the setup.  The remote shutter release removes this induced motion.

At any rate, I was thrilled with the results from my first attempt to use the Canon 5DIII mounted on the Celestron C5 spotting scope!  I am looking forward to more trips out into the field with the setup.  I am sure I will get more familiar with the intricacy of shooting with the setup.