Uma explicação que encontrei muito boa e facílima de entender sobre abertura para o user que disse que não está muito familiarizado com isto:
"As with Exposure,
aperture is related to shutter speed in a similar way. If the aperture is small, you’ll need to have a slower shutter speed to have enough light to create the proper exposure. If the aperture is large however, you’ll need to have a faster shutter speed to create the same effect. Basically, shutter speed affects exposure and clarity. Faster shutter speeds are good for shooting subjects that are moving quickly. (Fast Shutter = Frozen Subject.) Slow shutter speeds are good when you want to blur the action. (Slow Shutter = Blurred Subject – subject moving.) This is good if you want to show for example the movement of water or streaks of light at night.
Secondary Effects of Aperture: Small aperture not only allows less light to reach the image sensor but it also makes the entire scene appear sharper and more in focus. This results in what is known as a “long depth of field” (everything is in focus), which is particularly useful when you want everything in the viewfinder to be sharp and in focus. A large aperture has the opposite effect, as only your selected subject will be in focus (this is also referred to as a “short depth of field”). A good example of this is portrait photography, which uses a short depth of field extensively because it focuses attention on the subject.
One last photographic concept –
Aperture and Shutter Stops: (This is where I have to read slowly, out loud and sometimes even trail my finger along the words to understand – and even then well, it’s a challenge..sigh.) Both aperture and shutter speed are measured in standard units called stops. Opening the aperture by one stop doubles the light that reaches the sensor. Similarly, speeding up the shutter by one stop will cut the amount of light that reaches the sensor in half. By opening the aperture one stop and speeding up the shutter one stop, you’ll keep the exposure constant. Opening aperture by 2 or 3 stops and slowing down the shutter speed by 2 or 3 stops will have the same effect on exposure. The amount of light that reaches the sensor will remain constant and the pictures will be just as light or dark as before. Exposure is kept constant by changing shutter speed and aperture the same number of stops.
So what changes then? The depth of field and the moving object will either be frozen or blurred. It’s understanding this depth of field concept that will give you more creative control over your photography and the know how to take your pictures to an advanced level.
(Or so say the experts.) ;-)
While I do hope to understand all this and definitely want to improve my photographic technique, I’m thinking it’s going to take longer than just watching a DVD or reading this information over and over. Mostly though, it’s just gonna take “real world” experience.
But in all honesty, there’s nothing wrong with the beginner level – it’s warm and cozy like a favourite blanket, and it doesn’t mock your remaining brain cells...oops sorry...my brain cells. (Translation: me thinks I’ll be a beginner for a long long time.)
To get another perspective on Exposure, Aperture and Shutter Speed, I received this email from Ron Klutts (thanks Ron!) who wrote:
Yeah that's a good example to understand it. Now to take it to the next level, if you open the f-stop by 1 stop you are letting in double the light, so the time (shutter speed) needs to be half as fast; i.e. bigger hose means less time to fill it. Each full number on the aperture is doubling the amount of light. Each whole bigger number on the shutter speed is half as much light; i.e. 125 to 250 is half the time. So it makes making manual adjustments easy.
But what effect does the aperture size have on the photo? That controls how much else is in focus, in distance fore and aft of the focus point. Huh? So a smaller aperture i.e. f16, f32, will have a greater depth of field. That is the area just in front of and behind the area you focus on that will also appear to be in focus. So it's a neat way to blur the background or make it in focus. Try it shoot the same subject with an exposure of f2.8 @ 1/1000 sec say and then again at f16 @ 1/30 sec. You'll see the difference. Also try shooting things close up and at medium distance to see the effect.
It's good to know that there’s not just one way to explain the mechanics of photography since we all absorb this information differently. Hopefully, if you’re a beginner like me, you aren’t feeling completely lost (I have to admit that my mind is still flailing through much of it). That’s why it’s good to not only read about the different settings and techniques, but to also experiment as Ron suggests, and which is why I can’t recommend enough Scott Kelby’s
"The Digital Photography Book", not only for beginners but for those who want to experiment shooting different subjects in various scenarios. And as we learned on last week’s show, the sequel to this book is about to be released – I think I’ll put that one on my Christmas list. ;-)"
Bom, pelo que vi nas propriedades da foto, o moço usou os seguintes valores: f5.6, exposição 1.3 segundos e ISO 200...
As minhas foram tiradas com valores piores ainda (f ainda menor, exposição também menor a ISO 400) e ficaram um pouco escuras
Se percebi bem o que disseste, deveria ter ido para valores, por exemplo, de f8.0, mantendo a mesma exposição e o ISO a 200, correcto?
Exactamente. F8 sería uma boa opção. De qualquer forma escolhe a prioridade à abertura para a máquina ajustar automáticamente a velocidade de obturação. Não tens de te preocupar com o ISO se estiveres a usar tripé. Quanto mais baixo o ISO mais nítida fica a tua foto, pois o aumento do ISO introduz ruído, especialmente em fotografia nocturna (mais ainda numa compacta).
Só tenho pena de não ter tido tempo de fazer este tipo de experiências antes das comemorações da Marinha aqui em Aveiro.
