Photography - Experimenting with Aperture in Manual Mode

I'm an absolute novice at taking pictures in manual mode, so I wasn't even thinking of writing a post on it. I just started using this mode less than a week back and am still trying to understand all the nuances involved. However, when I came across this post by Aparna of My Diverse Kitchen, a fellow Goan, an ardent blogger and a fervent  photographer, I decided to take one step ahead and take part in her exercise.

So here's the picture. The camera I used is a Canon EOS Rebel T3i. I don't have a 50mm f/1.8 lens (hint hint to my hubby), so I stuck to my 18-55mm kit lens and as suggested by Aparna, set the focal length to 24mm. I set the ISO to 100, changed the aperture to f/4.0 (unfortunately it doesn't go any higher in my lens) and experimented a bit with the shutter speed. Here's one where the shutter speed is 1/15s.

If whatever I said went right above your head, then let me try to explain whatever little I've understood. Just look closely at the photograph. The orange and lemons look sharper while the rest of the items look a little blurred.

You may have seen some amazing food photos in food blogs or restaurant menus where a plate of succulent kebabs, a neatly cut piece of chocolate cake or a bowl of luscious ice-cream look so tantalizing against a wonderfully blurry background. And you may have wondered how it is possible to make one aspect shine so much, while toning down the backdrop. This is where aperture plays a major role.

Aperture is basically the opening in your lens through which light comes in. The bigger the opening, the more the light coming in. The smaller the opening, less light comes in.

Aperture is measured in F-stop numbers. Example  f/2.0, f/5.6, f/22 etc.  The smaller the F-stop number, the larger the aperture. The bigger the F-stop number, the smaller the aperture. I know, it's counter-intuitive (because it's a fraction) but you will get the hang of it very soon.
Once again - smaller the F-stop number, more light comes in. Larger the F-stop number, less light comes in.
Example - f/4.0 has MORE light coming in than f/22.
All this when you thought you were done with school and exams. Sigh..

So why not always shoot with a wider aperture? More light gives better pictures, eh?
This is where DOF comes in. DOF (Depth of field) is the area in your photo that you want sharp or blurred. Remember the gorgeous photos with the blurry background I was talking about? [Something I need to really work on, now that I'm actually talking about it]. Those pictures have a shallow DOF. What that means is, the main subject (read yummilicous food) is sharp and in-focus, while the background and all the pretty decorations are blurred. Same goes to portrait pictures where a child or a bunch of people are the "stars" who stand out against a blurry backdrop.
Compare this to a beautiful scenery. You want all the elements - the trees, the clouds, the mountains, the lake and whatever else you have in there, to be given equal importance. Which means, the depth of field should be greater because everyone's the star in there and all elements should be clearly in focus.

So what is the connection between aperture and DOF? Aperture decides the DOF. Or rather, depending on what DOF you want your picture to have, you set the aperture accordingly.
A wider aperture (bigger opening, more light, smaller F-stop number ) focuses on the main subject which results in a shallow DOF. A smaller aperture (less light) gives a greater DOF. No, I'm not going any deeper into that, because I don't want to pull my hair out. Just remember that a smaller F-stop number (say f/2.0) gives a shallow DOF (more blurry background) compared to a larger F-stop number (say f11).

Here are two pictures for comparison. [My lens doesn't have a lower F-stop number, so this is just about what I could manage in terms of blurry background]. The picture on the left has a bigger aperture (f/4.0), hence a shallower depth of field. The oranges and lemons look sharp, while the coffee mugs and rest of the cast look blurred. The picture on the right has a smaller aperture(f/10), hence a wider depth of field. The mugs et al, look clearer.

Larger aperture (smaller F-stop number) = shallower DOF (more background blur).

One more term to remember when changing the aperture is "shutter speed"- the duration taken for the shutter to open and close. When the aperture is bigger, more light comes through the lens, hence the shutter speed should be faster, otherwise the picture will be overexposed. Likewise, when the aperture is smaller, less light comes through, so the shutter speed should be slower in order for the required light to come in.

Take a deep breath. It's not as confusing as it looks. Just remember that a smaller F-stop number should have a faster shutter speed.

In the above pictures for example, for the wider aperture (f/4.0), I set the shutter speed to 1/15s (0.066 seconds). For the smaller aperture (f/10) I set the speed to 0"3 s ( 0.3s).

Here's another example. The first picture was taken with an aperture of f/4.0 and shutter speed of 1/250s. The second picture was taken with an aperture of  f/14 and a shutter speed of 1/5s.

See the difference?

The first picture (wider aperture) has a shallow depth of field (more background blur).
Since the aperture was wider than that of the second picture, it was taken at a much faster shutter speed. [ I did not use a tripod for any of these pictures, so there may be some differences in the position.]

Keep varying and experimenting with the shutter speed till you get the picture you envision. Ofcourse, the light source and time of day can affect the quality of the picture. So also could ISO which determines the sensitivity of the camera's sensor to light. I don't want to go deeper into that,  because it will leave me more confused than you, so let's stick to whatever I just explained. All I can say is if your picture appears too dark, increase ISO and if too bright, decrease it (or just set ISO to Auto if you are not sure what the heck is happening). If ISO is way too high then the picture will be grainy ("noisy" in camera jargon).

So that's about how much I know. I'm all set to explore the "Av" (aperture priority) and "Tv" (shutter priority) modes next. As of now, I'm sung as a bug in a rug with the "Auto" mode, but since I've stretched myself a little bit to understand what some terms means, I'm hoping I will soon be comfortable clicking pics of my dishes in manual (or Av) mode.

Until then, Happy Clicking!!

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