Newby Question about Aperture...

roxysmom · Jun 21, 2007

I am in a class learning about aperture and shutter speed but I'm still very confused! I'm not confused as to what they are but how to use them when taking pictures.

For example....I want to take a picture of my son with the background blurred. I thought to do this I needed to set my aperture high. But when I took the picture for one everything was dark. Then I used my flash and it was not any better. What am I doing wrong? I am in the VERY early basic stages of this!

I have a Nikon D-80 and I'm using a 18-135mm lens.

Thank you!

Groupcaptainbonzo · Jun 21, 2007

Set a good ISO (100 or 200). Put the camera in apperture priority (Usually labled AV). Set a wide apperture anything wider than f4.5 (f4.. f2.8... f1.?...). and let the camera meter for your apperture setting. make sure that there is some space behind your subject before the background. To keep background in focus try f11 ... f16... f22 etc. If you are getting a very long exposure time (anything over 1/60th second. Use a tripod... or a bean bag).

Big Mike · Jun 21, 2007

You can't just input the setting you want, without considering the other settings. For example, when you 'set your aperture high', you were probably setting it very small, which didn't let in enough light and you got a a dark image. When using a small aperture like that, you need to compensate by keeping the shutter open longer. This is why the camera has a meter built into it.

Firstly, let's correct your mistake. When you want to get a blurred background (shallow Depth of Field), you will want to use a large aperture. The larger the aperture, the smaller the F number. So you would want to set the lowest F number that you can, to blurr the background.

Now, it's sort of important to understand the relationship between shutter speed and aperture. Think of it like filling a bucket of water with a hose. You could fill the bucket very quickly with a large hose...but if you use a smaller hose, it will take longer. If you cut the size of the hose in half, it will take twice as long to fill. It's the same with light coming into the lens/camera. If you make the aperture smaller (higher F number), the shutter must stay open longer...in order to make the exposure.

So going back to the camera...there are obviously different modes. In Auto mode, the camera reads the light and gives you a shutter speed and aperture that will give you a medium exposure for the light it's seeing. If you want to choose a specific setting (say, a large aperture)...then you can use the priority modes; A or T. You choose the priority setting and the camera gives you the other setting, based on the light that it sees. Lastly, there is Manual mode. In this mode, you have to adjust both the shutter speed and aperture...but you still need to read the light. The camera will have a scale in the viewfinder & on the top screen. When in manual mode, you should adjust the settings until the 'needle' lines up with the centre mark '0'. You can then deviate from that setting to change the exposure, but the meter gives you a place to start.

The third variable is ISO. A higher ISO means you need less light for the exposure...but it gives more noise. It's best to leave the ISO as low as possible unless you need a faster shutter speed to freeze camera or subject movement.

Mike_E · Jun 21, 2007

Hi Roxysmom, If I read your post correctly, what you may have done is an age old trap of thinking that, naturally, the bigger the number the larger the thing.

So, if you were going for a high aperture and the photo came out dark then you most likely were using a high number.

If this is so then you just need to remember about the numbers being opposite of the actual size of the opening. (think of a seesaw, push the number down and the aperture goes up)

The smaller the aperture the less light getting into the camera and the darker the photo. To tie in the Depth of Field, just remember that it is on your side so that the smaller the number (on the lens) the smaller the DoF.

And if I misread your post...never mind

mike

nomade · Jun 21, 2007

Big aperture means a smaller number for example 1.8, 2, 2.8...Small aperture means a bigger number 8 11 16 22...A bit reversed I understand your confusion.

junray · Jun 21, 2007

Big Mike said:
..but you still need to read the light. The camera will have a scale in the viewfinder & on the top screen. When in manual mode, you should adjust the settings until the 'needle' lines up with the centre mark '0'. You can then deviate from that setting to change the exposure, but the meter gives you a place to start.

Big Mike,

Thanks for the explanation and a great analogy overall. It really helped me understand a little bit more about the light meter on my camera. I just have a Canon Digital Rebel which I'm trying to learn using the manual settings. Believe it or not, I had this camera when it first came out about 3-5 years ago and I'm just now trying to learn to use the manual setting. I think it's because I'm more of a videographer and have been doing it for over 10 years. Anyway, I'm trying to learn more about photography in hopes of crossing over to the still format.

By the way, I stumble unto this website and figure I register.

Ray