If we were to shoot a portrait – just a simple head and shoulders then we'd want to blur the background in order to place all the attention on our subject. Even if the background isn't distracting, then a shallow depth of field is quite flattering or simply more interesting to the eye.
Taking our shot of Katie as our example. By using an aperture of f/2.8 and focusing directly on the right eye (as you look at the shot) with an 85mm lens all the attention is directed to her gaze – just as it should be.
Katie's jacket, shoulders and the background (a road and stone wall) become diffuse and don't distract. The eyes are sharp but the drop-off from crystal clarity is really very quick, so you get that pleasing softness around the edges. Overall, the perspective and limited depth of field makes this quite flattering for the person being photographed – although Katie doesn't need much help as she's young and attractive anyway - unlike Rousey and I!
Of course, there are pros and cons to using very shallow depth of field. One of the pros is that because the aperture is wide open it is letting in a lot of light and this helps us in lower light situations because it allows us to achieve a faster shutter speed without the need to push ISO higher.
If you're a total newcomer and are now asking shutter what? ISO what? This is something we'll come back to again and again. In fact, the three-way relationship between aperture, shutter speed, and ISO is the basis of exposure. It's a reciprocal relationship that you'll need to understand to get those exposures right. Let's side step it for now or it'll take over this article. Remember we're concentrating for now on the effect of changing aperture.
I love shooting at wide apertures. Portraits, still life, even nature pictures can sometimes really come to life and feel more evocative when the sharpness is limited. Of course you've got to know where the sharpness needs to be in order to make the most of the blur!
If you get it wrong then the photograph can look pants. In fact, this brings me to one of the cons of shooting at very wide apertures and that is focusing. When there is so little area that is likely to be sharp, then precise focusing is even more essential. So if you are shooting a portrait at f/1.4 then you have to make certain the focus point is precisely on the eyes and believe me, it's easy to get wrong.
I remember the first time I used a lens with an ultra wide aperture. It was an 85mm f/1.2L Canon and it was a lovely bit of kit (at nearly £1,400 it needed to be). I got all excited and snapped my model using the widest f/1.2. It looked superb on the LCD and then I downloaded the images. I couldn't work out if anything was sharp! Lesson learned. When you are working at any extreme, your technique has to be spot on.
Well, if you use a compact camera or a compact system camera with a sensor that is a fraction of the size of a full-frame DSLR's sensor, again you'll find that depth of field is different. Even at wider apertures there is greater sharpness through the image that makes it difficult to get the really cool shallow focus look you may be after. It's fine for those landscapes but you might struggle if you want a limited focus portrait.
Again, let's not get bogged down in the science but because the size of the aperture and the focal length of the lens together determine depth of field, it follows that the shorter focal lengths that go with a smaller sensor mean greater depth of field. The science of this is well documented online if you want a more geeky explanation. If you do, I'll get your white boffin's coat for you. If you can wait, we'll perhaps come back to this in a future fotoBuzz article.
However, it should be noted that the new generation of Compact System Cameras, such as the X-Series cameras produced by Fujifilm, do allow you to use limited depth of field. Incidentally, you'll often hear the phrase 'bokeh' used in connection with a sharp subject and diffused background. This is simply taken from the Japanese word bokeh - which refers to the aesthetic quality of the blur! So, for bokeh, read creative blur!
The image you can see here is a portrait I took using the Fuji X-M1 – a camera that is considered an entry-level CSC by the manufacturer. By using exactly the same aperture principles as explained already, I was able to take this portrait at a wide aperture and make the background diffuse. I used a 60mm lens and an aperture of f/2.8. If you look at the farm building in the background you can see that this aperture has knocked it right out of focus.
So whatever type of subject you want to shoot, you can choose the right aperture to suit it and your creative vision. And on that note, let's find out how our resident wildlife pro, Andy Rouse, uses aperture when he is out in the field...
Let's find out how our resident award-winning wildlife ace, Andy Rouse, uses aperture when he's out in the field.