Photography Experiments: Aperture, Focal Length, and Sensor Size

Just a quick photography experiment to demonstrate the effects that aperture, focal length, and sensor size can have on depth of field (i.e., how much you can blur the background of a photo.)
It snowed here recently, so I took a photo of a branch with some snow on it, which came out decently enough, but it prompted me to think: what would this look like at different apertures – or even different sensor sizes? So I decided to perform a little photography experiment to find out, and these were the results.

snow on pine tree branch - f5.6First is the original photo – taken at f/5.6, at max zoom (200mm, equivalent to 400mm on a full-frame camera) using my Lumix G2 camera. Even on my smaller micro four-thirds sensor, you can see that the background is completely blurred out – even more so than I could’ve gotten with my f/1.7 lens!

The depth of field in this photo is very shallow – if you look closely at the bottom right of the photo, you can see the bottom part of the branch is slightly out of focus (because it was angled slightly towards me). This gives you an idea of how thin a “slice” of the scene was in focus.

snow on pine tree branch - f22Next, I changed the aperture to f/22, but kept everything else the same. As you can see above, the background is still blurred out, but not as much. It is still blurred somewhat because I was focusing on a branch just a few feet in front of me, while the background is easily another hundred feet beyond that.

Compared to the first photo, you can see that the bottom bit of the branch is in focus – meaning the depth of field was greater, and a thicker “slice” of the scene was in focus.

snow on pine tree branch - f5.9 (compact camera)Finally, for this last picture I switched to a different camera – a compact Canon PowerShot ELPH 320. The aperture here is f/5.9, nearly the same as my very first shot, but as you can see the background is hardly blurred at all! The depth of field here is very deep – a very large portion of the scene is in focus.

Unfortunately, the little compact camera I was using couldn’t zoom to the same focal length – so this photo is at the equivalent of 255mm, instead of 400mm, and that contributes to the greater depth of field as well.

However, the smaller sensor size also has a significant impact – because the sensor is so small, there’s less room for the light to be “smeared out” (as it were), and so less of the background can be blurred.

So, what did we learn from all this? All else being equal:

  • A larger aperture (a smaller f-number) provides less depth of field and allows for a more blurred background.
  • A longer focal length (zoomed in more) provides less depth of field and allows for a more blurred background.
  • A larger sensor allows for less depth of field, which allows for a more blurred background.

This is why compact & cell phone cameras – which usually don’t have large apertures, don’t have long focal lengths, and have small sensors – are at a serious disadvantage when it comes to getting shallow depth of field & that nice blurred-out background look.

Nothing here is terribly ground-breaking in itself, and all of this should be basic “photography 101” stuff, but I still think that actually performing photography experiments like this can be incredibly useful, in the same way that performing physics or chemistry experiments can be useful even if you already know the theory behind it.

As for myself, experiments like this help me develop an intuitive “feel” for how all the different settings and elements work together, so that I can just take the photos I want to take, without having to spend too much time thinking about which setting affects which aspect of the photo.

Perhaps this experiment will help you in the same way, or perhaps it will inspire you to perform your own photography experiments. Either way, I hope it’s been helpful, or at least enjoyable!

Fun in the Snow

Okay, I admit it, I’m a sucker for snow – especially when there’s lots of it.
Okay, I admit it, I’m a sucker for snow – especially when there’s lots of it.

I dropped off Amanda at the YMCA (gym) today around 1pm, and then I decided to go for a “drive.” At this point, there’s like 5 inches of snow in most places – give or take 1 or 2 inches – and the roads are pretty bad because it’s coming down so fast that the plows can’t keep up with it. Perfect conditions for some joy riding!

After driving up (and down) most of the big hills in Fitchburg (my street being one of them), I headed up route 12 towards Ashburnham. The roads were slick, but I never noticed. Along the way, in West Fitchburg, I came across an accident that had just taken place. The police were there, and the tow truck was just arriving, so the road was blocked for a few minutes, and I had plenty of time to observe.

A middle-aged guy driving a Chevy Suburban had smashed into a telephone pole at a corner – interestingly, he hit the pole on the inside of the corner. (How he did this I’m not sure, but I’m certain that “bad driving” had something to do with it.) So I watched this with some amusement until they moved the truck to the side of the road where the flat-bed tow truck could get to it.

After reaching Ashburnham, I turned onto 110 (I think it’s 110, maybe 101? I forget.) This was a fun road, because out this far the plows are scarce compared to Fitchburg – and there’s more snow up there, too. Eventually this merged with Rindge Road – which leads back to Fitchburg. THIS was a challenge. It had NOT been plowed AT ALL. All I had to go on were a pair of tire-tracks on my side of the road, with snow piled 6″ deep everywhere else. Even with AWD and snow tires, it was a bit tough. Especially since I was traveling at between 35 and 40 MPH. However, as most regular readers of this blog will know, I’m an excelent driver. Some concentration, both hands on the wheel, and judicious use of engine braking allowed me to remain in control the entire way. But it was FUN. 🙂

Back in Fitchburg, the main roads had improved somewhat, and it was almost time to pick up Amanda from the YMCA. So, I went home to wait out the last half hour (and obviously, to write this entry) and once again, found the only problem I have in the snow. Ironically, it occurs when I’m turning a sharp corner that’s got a lot of snow on it. My speed is usually like 3 MPH (yes, 3), and the Keithmobile just kind of… slips. Sideways. Sometimes the front doesn’t turn (understeer), and sometimes the back end whips out a bit (oversteer). It’s a little annoying; but what can you do? Snow tires give less traction side to side (as opposed to forwards & backwards), and let’s face it, at only 3,500 lbs., the Keithmobile isn’t that heavy. So it slides from time to time, if you’re not careful (or if conditions are nasty). Still, all it takes is some quick steering input to correct (for oversteer), or, alternatively, a light jab to the throttle (for understeer). So it’s all good. (I love my car!)

Well, I gotta get to the YMCA now – drive safely everyone, and enjoy the snow, if you can!

I Love Winter

I love winter, because I can do things like this:
I love winter, because I can do things like this:

The Beauty of All-Wheel Drive* (and snow tires)

Can I just say how great AWD is? Okay, okay, I know I’ve probably said it a million times, but c’mon – it’s great fun.
*(With apologies to Subaru’s advertising department)

Can I just say how great AWD is? Okay, okay, I know I’ve probably said it a million times, but c’mon – it’s great fun. And snow tires really round out this killer combination.

Last night, as anyone who lives in mid-New England knows, was a nice little snowstorm. We got about, oh, 6 inches (or so) here in Fitchburg. I drove around in it as much as I could, of course – before the roads were plowed, etc. Up Mt. Vernon Street, up side hills, through unplowed parking lots, all over the place. As long as you’re alert and know your limits (i.e. you have a good grasp of the physics of car driving) you can have a lot of fun in the snow. And you can have a lot more fun with AWD and snow tires. Whee!

Last night when they finally plowed my driveway, I moved my car up the street a bit and sat there while they plowed. Of course the plow could not get down to the pavement (it’s very uneven) so the driveway was now just a sheet of tightly packed snow just about a half an inch thick. And along side the driveway, in an unused parcel of land (that doesn’t get plowed) was a lot of snow, and some piles made from the plowing.

If you’ve been around my house for a while, or if you’ve ever driven with me to my house, you know that I like to pull in straight and turn up into that unused section so that I can back down into the driveway – leaving the car pointed straight out, for an easy exit. I do this because backing into the driveway from the street is hard (it’s a narrow street) and it’s just not as much fun. Especially when there’s snow up on the unused lot. I just drive right into it, full bore, and climb up as far as I can go (there’s a car from across the street that parks at the far end of the plot, so I can’t go far when he’s there). Then, I reverse down.

Now, when it’s dry this is no big deal. But when there’s 6 or 7 inches of snow (packed snow by now) that I’m driving through, it’s lots of fun. Of course, any more snow than that and I’m starting to reach my limits – the Keithmobile-D only has a maximum of 8 inches of ground clearance – once you get into snow that deep, the bottom of the car starts to catch, and you can get stuck. But as long as there’s less snow than that, I just run up & reverse out. It’s fun on another level because no one else in the house (with one exception – the people upstairs drive an older Subaru) has AWD (or even snow tires, from what I can see). So I just know they’re gawking at me. (I know this for certain because when they were plowing last night, the people downstairs were out on the steps, and I backed right into the driveway right in front of them. This would not have been possible for them; the driveway was very slick, and it’s got a bit of a steep incline for the first two or three feet where it meets the street.)

Other than that, it was just fun driving around in the snow. I miss driving sometimes – although not enough to start couriering again!! (Never again, I swear!!) Still, I enjoy driving, and I enjoy a challenge, and driving in the snow is always a challenge. When it snows out, it’s almost like regular roads become “off-road,” and since I like off-roading… well, you get the idea. 😉