Aperture, is quite simply, the hole where light travels through.  If you look through your lens, you’ll see a hole formed by a bunch of little blades.  The size of the hole is expressed in f-stops, which is a ratio between focal length and the diameter of the hole.  That’s why the numbers seem to be pretty weird.  I won’t bore you with the math because, quite frankly, it bores me too!  If you are so inclined, however, you can can look at this Wikipedia link that explains it much better than I can.

The aperture is expressed as a number prefixed with ‘f’ or ‘f/’ for “focal” (again, referring to that ratio).  In the image of the camera above, it’s the number on the top right of the LCD that’s prefixed with the ‘F’.  So, what is important for our discussion is this:  the smaller the number, the bigger the hole; conversely, the larger the number, the smaller the hole.

You may have come across the term ‘fast lens’ at some point.  That term refers to the widest maximum aperture (smallest number) that the lens can use.  With a fast lens, the aperture is so wide that it allows the shutter speed to be really fast because so much light can go through the lens.  Lenses that have a maximum aperture of f/2.8 or less (remember: the smaller the number, the bigger the hole) are generally considered fast lenses.  These types of lenses aren’t cheap though!  Many are priced in the thousands, some specialized ones are in the tens of thousands.

So why spend all that money?  Why would anyone want a fast lens?  Well, for a couple of reasons:

It gives you the ability to shoot in darker conditions

I shot the above photo in a very dark  church at ISO1250, 1/25, f/2.8.  If everything but that f/2.8 didn’t make any sense to you, suffice to say, it was really dark in there!

It gives you the ability to isolate the subject by reducing the depth of field

The size of the aperture is one of the biggest contributing factors to depth of field (DOF).  A wide aperture (small f/ number) reduces the depth of field, whereas a small aperture (large f/ number) increases the depth of field.  With a small DOF, a thin portion the scene in front of you will be in focus.  As your DOF increases, more and more of the background comes into focus.  I know all of these inverse relationships can get confusing, so I’ll let some pictures do the explaining:

small DOF (wide aperture; small f/ number)

f/2.8

f/4.0

f/5.6

f/8.0

f/11

f/16

large DOF (small aperture; bigger f/ number)

Now that you (hopefully) have a better idea of how to use aperture, you can apply the settings to your camera by switching to ‘A’ mode (or ‘Tv’ mode for you Canon users) on your camera and dialing in the desired aperture based on the DOF you want.  Notice that the other number (that’s the shutter speed) changes whenever you change the aperture.  That’s because aperture is only one of three components to exposure (shutter speed and ISO are the other two).  Each of these components must be balanced and there are tradeoffs to be made when changing settings.  Stay tuned and I’ll demystify the other settings in a further blog post.

Until then, keep shooting and share your work!

]]> http://www.johncruzphotography.com/2010/10/demystifying-camera-settings-aperture/feed/ 0 http://www.johncruzphotography.com/2010/06/going-going-gnd/ http://www.johncruzphotography.com/2010/06/going-going-gnd/#comments Wed, 02 Jun 2010 23:39:50 +0000 John Cruz http://www.johncruzphotography.com/?p=51 In the days of powerful image editing software such as Photoshop, Paint Shop Pro, GIMP, and others, some people may argue that things like filters are obsolete.  Certainly, in some cases, with digital photography’s auto-white-balance, and shooting in RAW makes things like color correction filters not as useful as they once were, there are still some things that can’t be replicated as easily in an image editor.  One of these effects is from the Graduated Neutral Density (GND) filter.

What is that, exactly?  To answer that question, let’s look at the component parts of the name.  A Neutral Density (ND) filter is an accessory that mounts onto the filter mount screw at the front of your lens.  It cuts down the amount of light that will hit the sensor without distorting or discoloring the image (that’s where the ‘Neutral’ part comes in).  Think of it as looking through tinted windows in your car.  How much light it cuts down is dependent upon what type of ND filter you use.  This can typically be determined by looking at the number beside the ‘ND’ in the filter.  Below is a simple table that describes how many stops of light a particular ND filter will reduce:

The ‘Graduated’ part of the name simply means that the filter (usually rectangular in shape) is coated with the specified ND strength in a graduated pattern (darker to lighter).  As you can see from the photo below, the top part of the filter is quite dark, and gradually gets lighter in the bottom.  The filter system by Cokin that I have comes in three parts: a ring that mounts onto the filter screws on the lens, the filter holder that slides onto the ring, then the filter itself, which slides into one of three tracks of the filter holder.  Personally, I like this system a lot for a couple reasons:  because it can be transferred between lenses of different sizes simply by purchasing the appropriate ring size, and also because it allows me to stack filters if I decide to (admittedly, I haven’t done that yet, but I like that I have the choice to when I do!)

So what can we do with this little contraption that we can’t do in our fancy schmancy image editor?   Well, one of the most common things the GND is used for is to control exposure between the sky and the ground.  Without the GND filter, we have to make a choice between having a well-exposed ground, but a blown-out white sky, or a nicely exposed sky, but a dark ground.  For me, at least, I want it all!   Have you ever looked at that sky and thought, if that sky was about 3 stops darker,  the sky and the ground would look great together!  Okay…  If you’ve ever thought that, consider yourself addicted to photography!  To solve our problem, all we have to do is slap on an GND8 and, based on our table above, we’ve dropped the sky down 3 stops, and now the sky and the ground can live together in perfect harmony in your frame.  If I lost you in the geekiness of it all, the bottom line is that the GND8 will allow you to capture things like the the deep blue hues of the sky and the texture of the clouds.  Without the GND filter, the detail in the clouds will be blown out beyond all recovery.  Short of pasting in, or brushing in, a new set of clouds, the blown out patch of white will remain white.  With the GND, you no longer have to compromise — you get beautiful tone throughout the image.  Below is a comparison picture of the final result (GND on the left, no GND on the right).  No Photoshop here, except for a mild saturation bump.

Well, that’s it for now.  Hopefully, with the GND, you can graduate the level of of your landscape photos!

Many people who begin their journey down the path of learning more about photography often start looking at photos taken by others and, more often than not, someone will ask, “what settings did you use?”  It’s a fair question, but it’s a fairly limiting one because, you see, there are many “right settings” that the photographer could have used, but for any given photo, only one was selected, and in some cases, the “right setting” wasn’t used for a particular reason!  Have I confused you yet?  Good, because the answer to that question is, “it doesn’t matter!”  Really.

Unless it was a controlled, consistent environment, shot at approximately the same time of day, in the same time of year, in the same type of weather, and for the same composition, those settings may no longer be valid.  To put it simply, all those settings do is tell your camera how to record the light that is available in the place that you’re aiming at.  Depending on the selected settings, you, the photographer, can influence how that light is recorded, and use it to communicate your message.

As you can probably already figure out, even if you went out to the very spot where a great photo was taken, the lighting conditions could be wildly different.  And when you get there, you may decide to tell a different story.

The bottom line is: don’t rely on other photos, or other photographers’ “right settings” to get you great images.  Know your camera and know what you want your photo to say.  These two things will tell you what the “right setting” is to use.

Teaching you how to figuring out the “right setting for what you want your photo to say” is what this site is about, so if you need help with that, stick around, and I’ll try to cover those topics.  Until then, I suggest you read Bryan Peterson’s book, Understanding Exposure: How to Shoot Great Photographs with a Film Or Digital Camera.  For under 20 bucks, it’s an easy read that will help you get beyond, “what settings did you use?”