Hands off the auto-mode, really I mean it!

APERTURE

This post is the first of four in series on switching off the 'autopilot', meaning learning to use and be comfortable with the manual settings of your camera. The first post is on aperture and the next posts will cover shutter speed and ISO.

So what is the auto-mode really? It's sort of a plane's autopilot. A great feature that will get you safely from A to B, but what if the autopilot is programmed for Phoenix and you really wanted to go to Ft. Lauderdale? Sure you'll get somewhere warm, but it was not the destination you intended.

What is aperture?
It is actually really simple. If you take the lens off your camera and look straight through it, you will see a set of diaphragm blades forming a circular hole. If you have a lens with an aperture ring (such as the Nikkor 50mm f1.8 AF D) you can actually see the diaphragm blades opening and closing. This is essentially what allows more or less light into the lens and onto the image sensor.

↓ Showing the lens' aperture openings: f1.4 - f5.6 - f16 (left to right)

↑ Images taken of a map at a 45 degree andgle to provide a foreground and background. Aperture used: f1.4 - f5.6 - f16 (left to right)

Notice how the three (rather boring) map images get sharper and sharper from foreground to background as the aperture hole gets smaller. This effect is referred to as the depth of field in the picture, i.e. the overall foreground and background sharpness. A good analogy is, to squint your eyes. If you have mild myopia this will improve your vision slightly yielding it less 'blurry'. Go ahead and try. The same thing goes for your camera, the smaller the diaphragm hole, the sharper the overall picture is foreground to background. Now to the confusing part: the smaller the hole in the diaphragm, the larger the aperture number, or f-stop number as it is also called. The reason why is not relevant here, but what is important is the reverse relationship. To this day, I still get confused about it. So I always remember the 'squinting eyes' analogy.

Background blur
With the depth of field in mind I hope it is clear that the lower you set the lens' f-stop number, the bigger the aperture opening and consequenlty the less depth of field and the more background 'blur' or de-focus.

↑ Images taken @ f2 - f2.8 - f2.8 (left to right)

↑ Images taken @ f2

Unfortunately, most of the lenses that come with entry-level DSLRs is a 18-55mm lens with a f4-5.6 aperture. Meaning they do not have to ability to produce the low f-stop number background blur. But not to worry, there are a couple of tricks to produce similar results.

↓ Images taken @ f7.1 - f5.6 - f7.1 (left to right)

↑ Images taken at f5 - f7.1 (left to right)

The shots above were captured by increasing the distance between the subject and the background. I was also weary to pick a uniform looking background in pattern and color. This will usually give you a nice, smooth background despite the larger aperture number.

Landscape sharpness
When shooting landscape photography or large group portraits, you generally want good foreground and background sharpness producing an overall sharp image. This is done by closing the aperture diaphragm, by squinting your eyes so to speak, to around f11-22.

↓ Images taken @ f11 - f13 - f11 (left to right)

↓ Images taken @ f20 - f11 (left to right)

↑ Macro images taken (with ring flash) at f11

If you've ever heard the phrase that a lens is better "stopped down" this what it means. That some lenses perform better sharpness-wise and quality wise if there are not at their maximum aperture opening. Mind you this is more due to the poor quality control and/or build of the lens than a physical characteristic, and my recommend is to return your lens that needs to be "stopped down" for a better working copy.

Squeeze the light
I am sure there has been situations where you have thought, "wow, I sure which there was more light available". Trying to take the photo anyway, it usually turns out blurry and grainy. This is where a low f-stop number lens, such as a 50mm f1.8 comes in handy. Such a lens is able to 'squeeze' through two and a half times more light to the image sensor than the run-of-the-mill 18-55mm starter lens. A real lifesaver.

↑ Images taken @ aperture f1.4 - f1.8 - f2.8 (left to right)

The images taken at the Metropolitan Museum of Art in New York, the Ciragan Palace in Istanbul and the Vancouver Aqurium would have been nearly impossible to take without a lens with a large aperture opening due to the very little available light. If I happened to have a tripod with me, I could have used that to allow for a smaller aperture opening when taking the photos in New York and Istanbul, but I did not. A tripod would not have helped me taking the photo of the jellyfish since that was moving, so I either needed some elaborate lighting equipment (which I do not carry aruound) or a lens with a large aperture opening.

Take the same images on auto-mode, and you would just have triggered the flash and produced an entirely different set of images that would not come close to what you had envisioned. More on why the on-board camera flash is no good in a later post.

So turn off the auto-mode, possibly invest in an in-expensive 50mm f1.8 lens (for Canon / for Nikon) and get aperture-creative. I hope the images have been inspiring and the text have shown you part of the way. A word of advice though: switching the 'autopilot' off is not easy, and will not yield the results you envision the first couple of times. Keep practicing and you will soon be able to capture what you envision with a little aperture creativity.

Read second part of series on shutter speed, and don't miss the third post on ISO.

For the technically interested: Shots taken with the Canon 30D and Nikon D300. Lenses for the Canon are Canon 17-40mm f4 L and 100-400mm f4.5-5.6 IS L, and Sigma 24mm f1.8. For the Nikon the Nikkor 105mm f2.8 VR Micro and 50mm f1.4 G AF-S lenses were used.