I have a question about the Nikon D3100

PineappleDood · Sep 23, 2013

Im new here and its my first time posting. I bought this Nikon D3100 a while back but have just started getting into it for real. I have a question about the shutter speed, aperture size and the lighting. I want to take pics with long shutter speed so that the picture have a motion/blurring effect but every time I try, the pic is completely white or pretty much all white. I want the speed to be 2 seconds or longer but whenever its that long, the aperture size changes with the speed and I cant figure out how to separate the two. I need some photographers help.

pixmedic · Sep 23, 2013

what mode are you shooting in? you might want to consider shooting in manual for longer shutter speeds so you can set you ISO low, your aperture small, and still keep your shutter speed long. if you are shooting in aperture, shutter priority, or AUTO, the camera will automatically adjust the other settings for what it considers proper exposure. the only way to control all three settings yourself is to shoot in manual.

amolitor · Sep 23, 2013

You're probably shooting in some program mode, right? Maybe you have the dial on "S" so you can set the shutter speed, and the camera sets the aperture to match?

At some point the camera is going to have the aperture squeezed down all the way, it cannot make the opening any smaller. At this point, your shutter speed is still too long -- it's going to let in light for such a long TIME that even though the aperture is very small, too much light will fall on the sensor. The picture will be over-exposed.

Step 1: make sure that your ISO is set to the lowest sensitivity, 100 on the D3100. This will set the sensor up to be able to take as much light as possible before overexposing.
Step 2: adjust your shutter speed down until the pictures start looking better.
Step 3: will that suit you? Is the shutter speed long enough?

Just as a check, try shooting in manual (M). Set the aperture to as large a number as possible:

- hold down the +/- button on top of the camera, and turn the wheel left-to-right. Watch in the finder and make sure the numbers are going up. When they stop going up:
- set the shutter speed to 2 seconds of whatever
- fire off a frame

If the frame is white, you still have too much light. Look into buying a neutral density filter, which simply cuts out a bunch of light.
If the frame is black, you don't have enough light, open the aperture up a bit. Also, learn to use the meter display in the viewfinder.

KmH · Sep 23, 2013

Camera Exposure: Aperture, ISO & Shutter Speed

2 seconds is a really long exposure. Your shots are over exposed. To much light is getting in the camera.
If you put the camera in manual mode (see page 73 of the D3100 users manual (PDF file on the software disc)) you can set the shutter speed, lens aperture, and ISO separately.
With a 2 second shutter speed you will likely need to set the lens aperture to it's smallest setting (f/22 is a fraction, so it's a small lens aperture setting).

If the scene you are shooting is lit by direct sunlight, a small lens aperture may still let in to much light, and you'll need a Neutral Density filter on the front of your lens to cut down the amount of light getting to the image sensor.

In manual mode the 3 adjustments - shutter speed, lens aperture, and ISO have a relationship called a 'stop' of exposure.

A 1 second shutter speed lets is 1/2 as much light (1 stop less light) as a 2 second shutter speed does. 1/400 lets in 1/2 as much (1 stop less light) light as 1/200 does. 1/2000 lets in 1/2 as much (1 stop less light) light as 1/1000 does.
So, changing the shutter speed from 2 seconds to 1 second is 1 stop less light. Changing the shutter speed from 2 seconds to 1/2 second is 2 stops less lightand only 1/4 as much light gets in.
Going the other way, changing the shutter speed from 1/2 seconds to 2 seconds is 2 stops more and 4x as much light gets in.

It's the same for ISO and the ISO numbers are a bit different. ISO 100 makes the image sensor 1/2 as sensitive to light (1 stop less light) than ISO 200 does. ISO 600 is 1/2 as sensitive to light (1 stop less light) than ISO 1200 is.

F-number - Wikipedia, the free encyclopedia
When lens aperture is changed, we have to consider the area of the opening, not just the diameter of the opening.
So to halve or double the area we can't just use x2 or /2, we have to use the square root of 2 - 1.4142.
So f/4 lets in 2x more light than f/5.6 does. f/4 is a bigger lens aperture than f/5.6 is.

Typical one-third-stop f-number scale (The light green numbers are classic full stops, but f/3.5 to f/5.0 is also a full stop change in lens aperture.)

f/No.	0.7	0.8	0.9	1.0	1.1	1.2	1.4	1.6	1.8	2	2.2	2.5	2.8	3.2	3.5	4	4.5	5.0	5.6	6.3	7.1	8	9	10	11	13	14	16	18	20	22

MartinCrabtree · Sep 23, 2013

I took this with my D90 with a SB-400 flash. Camera setting was flash>slow>rear. I'm not real happy with it but it illustrates what can be done. The flash settings are the same as your D3100 has. I have a D3100 too. Exposure was ISO 200 @1/10 second f4.5. I would stop it down to maybe f8 to do it again.