f-stop

All posts tagged f-stop


Welcome back all and Happy New Year, I know it’s been a while since there’s been a blog post but I’ve been very tied up with new photo shoots. I thought we would touch on a topic that is fast becoming a “very big thing” in the photo community for both hobbyists and professionals alike. HDR Photography…it’s a term that I’m sure you’ve heard tossed around, but many people aren’t sure what it is, and what it can do for your photos.

HDR stands for High Dynamic Range. Have you ever tried to take a photo of a landscape with lots of trees and a nice bright blue sky only to discover that the photo doesn’t look like the scene in front of you at all? Perhaps the sky is perfectly exposed but the trees are all dark. Or maybe the trees look perfect but the sky is so blown out it almost looks white. What happened?

Perfect sky, dark shadows

Overexposed sky, nice shadows

You think perhaps something is wrong with your camera? Or those damn kids tinkered with your settings again? Rest assured your camera is working just as it should. The real problem is eyes. “The kids have been tinkering with my eyes?” No, you see the human eye is the best camera ever invented. It can see and properly expose a very wide range of light. Wider than any camera ever made.

Think about a night scene, you’re walking along a street, there are very bright street lights, headlights of cars, but when you look up at the sky you can still see the stars and even perhaps a blue tint to the sky. This is because the human eye can actually see a range of over 24 f-stops of light. This range of light is referred to as “dynamic range”. It is the difference between the minimum and maximum amount of light that can be seen at the same time. The very wide dynamic range of the human eye allows us to clearly discern both the bright street lights and the very dim stars all at the same time.

Unfortunately, we’re not so lucky with our cameras. Even the best digital cameras made only have a dynamic range of 10-14 f-stops. This makes our camera’s almost 1000x less sensitive than our eyes. This is why when you try to shoot the same scene with a wide dynamic range of light with your camera it doesn’t look anything like it did when you were looking at the scene through your own eyes. So what can we do to fix this? Do we have to take everyone we know with us when we travel somewhere so they can all see the same scene with their own eyes?

As awesome as that would be, although I imagine it would be tough to coordinate all of those schedules, this is where HDR photography comes in, or High Dynamic Range. HDR Photography allows you to shoot a particular scene with 3 or 5 different exposures and then using special software combine all those photos into one that has the best exposed parts of each individual photo. So now you can shoot that sky and tree scene exposing for the sky in one photo, the trees in another, and all the other pieces in between. Then combine them into one beautifully exposed photo throughout.

The last time I was at Disney’s Animal Kingdom I took these 5 photos of the “Tree of Life”. Each one is exposed slightly differently so that the set covers the full dynamic range of light present in the scene.

Tree of Life -2 exposure

Tree of Life -1 exposure

Tree of Life 0 exposure

Tree of Life +1 exposure

Tree of Life +2 exposure

When we combine all of these together using software capable of creating HDR photos such as Photoshop or Topaz Adjust, the software picks the best exposed parts of each photo to create a single one that represents the entire dynamic range of light that was in the scene. It makes a High Dynamic Range photo which looks like this:

Tree of Life HDR Photo

As you can see this photo now shows everything from the sky to the ground to the tree perfectly exposed. I’ve actually just started toying with HDR photography and it takes quite a bit of practice to get good at it. I’ll be the first to admit that I have quite a ways to go. Like with anything else though practice makes perfect! So the next time you find yourself shooting and the scene doesn’t look quite the same in your camera as it does in person, think about creating an HDR photo.

I’ve barely scratched the surface of HDR Photography in this blog post. It was really meant to be an overview of the process rather than an in-depth how to. There are many people who do this type of work better than I so it would be worth it for you to check out some of their pages and their awesome photography.

The website “Stuck in Customs” is an awesome site created by Trey Ratcliff with a great free tutorial on how to create HDR photos. Don’t forget to check out his awesome gallery as well here. After looking at these photos one thing is clear, you can’t help but be “wowed” by a good HDR photo.

As always please feel free to post your results, leave comments, and ask questions. Happy Shooting!

Scott Dengrove is a professional photographer from the NYC area. Scott’s work has been featured in many national photography competitions and published in several nationally circulated magazines and publications. In addition, his work can currently be seen in 3 exhibits at Cosi® restaurants in New York and Connecticut. For more information, and to see more of Scott’s work visit his website at www.dengrovestudios.com and connect with him on his Facebook page at www.facebook.com/dengrovestudios

I’d like to continue our series on exposure modes. I know it’s been a while, I was just waiting for your comments and photos from the last post. It’s ok, I forgive you, I know you were just waiting until we got to the manual exposure modes so your creative juices can flow free 🙂 So we pick up where we left off with Aperture Priority Mode (A).

Aperture Priority Mode is the first semi-manual mode that we’ll discuss. This is the first opportunity for you to have some say on how your camera sets it’s exposure. So let’s get to it. What is Aperture Priority Mode?

Aperture Priority Mode allows you to manually set the aperture on the camera and then have the camera set the shutter speed automatically. As you recall from our previous discussions, aperture, controls the size of the opening of the shutter, or how much light is allowed to hit your film or digital sensor during the time the shutter is open. It is measured in f-stops. So why would you want to set your aperture manually when your camera does a perfectly good job of setting it in P-Mode?

Well, you may recall that aperture not only controls the amount light entering the shutter, but also has the side effect of controlling your….come on, you know this one, depth-of-field! This is an excellent reason to override the camera’s settings and set the aperture yourself. Say your taking a portrait of a beautiful model in a lovely woodland setting…what’s that? No models around you say? No problem, let’s say you’re taking a portrait of your cute as can be 10 year old in a lovely woodland setting. Huh? No woods near you….hmmm ok you’re taking a portrait of your cute as can be 10 year old in a very crowded city park.

This situation is even better, you have all these other people around, and even worse they are in the background of this lovely photo that you are trying to take! What are you to do? You turn to Aperture Priority Mode (A) of course. By manually taking over control of the aperture and using a very large aperture setting of say f/1.8 or f/2.8 you can take that beautiful photo of your cute 10 year old and have all those people in the background become just a blur, so the cuteness of your subject shines right through. Like in the example below:

Bird with shallow depth-of-field

Bird with shallow depth-of-field f/2.8

Ok so my cute 10 year old happens to be a bird 🙂 The point is that this photo has a very shallow depth-of-field and a lovely blurred background because of the large aperture setting of f/2.8 that was used. Working with the camera in Aperture Priority Mode (A) allowed me to manually set the aperture to f/2.8 and ensure that setting is what the camera would use when it took the photo.

Now those of you have been reading carefully, might think I’ve made a mistake about something. You might even think I’ve completely lost it, because it seems I’ve made that mistake in more than one place. You may be thinking, “dingus over here doesn’t know that 2.8 is a small number..he keeps saying that f/2.8 is a large aperture, how can that be??!!” Let me assure you it is no mistake, and it is something that does take getting used to.

You can think of it like fractions, 1/2 is bigger than 1/10 even though 10 is a larger number. It turns out that aperture numbers work the same way. The larger the f-stop value the smaller the aperture size. You can see an example of this below:

Aperture sizes and depth-of-field (Courtesy of http://howtotakepics.blogspot.com/2009/03/basics-terms-of-dslr-photography.html)

Aperture sizes and depth-of-field (Courtesy of http://howtotakepics.blogspot.com/2009/03/basics-terms-of-dslr-photography.html)

The diagram above clearly illustrates that the larger the aperture, the smaller the f-stop number. You can also see that the larger the aperture, the more shallow your depth-of-field becomes. This is why photographers love to get lenses with the largest aperture possible. Since a larger aperture lets more light in, this allows you to use a faster shutter-speed when shooting in low-light (remember reciprocity from our previous discussion). For those of you that own DSLR cameras, you may have noticed that the lens that is included has an aperture range of approx. f/3.5 – f/5.6. This means that the largest aperture that can be set is f/3.5 and as you “rack-out” your zoom the largest aperture your lens can achieve is only f/5.6. By the way, to rack-out, means to zoom your lens out to the maximum focal length.

This is why camera companies can afford to include these lenses in the kit with your camera. As you can see they do not have a particularly large aperture. Or as we say in the industry, they are not very “fast” lenses. A lens that has a larger aperture compared to another lens is referred to as “faster”. The faster a lens is, the larger the aperture setting that can be used, and also the more expensive it is! You will find that most people who shoot with the lens that came with their camera always feel they cannot get great photos in low-light situations. This is because as we’ve seen before the kit lens is usually not very fast, or the camera companies wouldn’t be able to afford to give it away. It is not uncommon for a photographer to buy a faster lens, either an f/2.8 or f/1.4 after shooting with the kit lens for a while.

We’ve learned before that when shooting portraits a large aperture is usually used to achieve a nice shallow depth-of-field. So what if we’re shooting landscapes? Well for that we want just the opposite, we want to use a very small aperture like f/16 or f/22 (remember small aperture, large f-stop). This will give us a very large depth-of-field or high degree of sharpness throughout the photo. This is exactly what we want for landscapes. Picture a beautiful mountain scene with water, hills, trees, in a photo like this we want to make sure that everything in the scene from the water in front to the mountains in the distance are nice and sharp. How do we do this? With a small aperture of course!  Take a look at the example below:

Reservoir, large depth-of-field, f/16

Reservoir, large depth-of-field, f/16

Wow, look at that, not only is everything in the photo nice and sharp because of the small aperture we used, but the content of the photo actually matches what I was describing, how unusual 🙂 By the way when we want to refer to an area in the photo which stretches on as far as the eye can see past the horizon, such as the one above, we refer to that point as infinity. So for a photo like this you would actually set your focus to infinity when taking the shot.

Now that you have a new creative tool under your belt, go out and start shooting! Don’t be afraid to experiment with your aperture settings. Try out what we talked about above, or mix it up a bit. Sometimes using an unconventional aperture setting can create some very interesting results. Shooting in Aperture Priority Mode (A) really opens up a whole new world of creative possibilities. I actually find that I shoot in Aperture Priority Mode about 90% of the time. And don’t forget that the camera still sets the shutter speed automatically, so the camera still ensures that you get a nice even exposure. That is until next time when we discuss Shutter Priority Mode (S).

Until then, please feel free to comment, ask questions, and absolutely send or post some results!