I need someone to explain things to me!

[scrutiny1]

-Aperture
-Shutter Speed
-Sensitivity

Those are three things I DO NOT understand! When do I use those things and what is their relationship? Also, how do I manually adjust the shutter speed on my Nikon D-70s? If you could explain those I would be sincerely greatful.

Also, I do not understand how the mm on lenses work. So if you feel like making my day, explain.

THANK YOU!

 

[terri]

Welcome to TPF!

Check out the Articles forum towards the top; specifically, you might find this series very useful. I think the part on shutter speeds and aperture is Part Two.

Hope this helps!

 

[fmw]

You need to do some basic reading but here's is a really quick definition.

Aperture is the size of the hole the light passes through to reach the film or sensor. Adjusting it affects the volume or brightness of light that reaches the sensitive material.

The shutter is a door that opens for a given amount of time and adjusting it affects how long the sensitive material is exposed to that volume of light.

Sensitivity is the sensitivity to light of the sensitive material.

These three things in combination affect many things in the final image. The most important one for the beginner is that the combination affects how light or dark the image appears to the eye.

 

[ksmattfish]

Aperture controls exposure and depth of field. Aperture is written as f/#. The formula is lens focal length divided by the actual size of the aperture = f/#, but you don't have to remember that as long as you know that a smaller f/# is actually a larger hole, and a large f/# is a small hole. A smaller hole (larger #) gives less exposure than a larger hole (small number).

Depth of field is how much of the image is in acceptable sharp focus. Typical examples would be a landscape photograph where everything is in focus has a deep DOF. A portrait where the subject is in focus, but the background out of focus has a shallow DOF. DOF is controlled by several factors, but as far as aperture goes a larger f/# means deeper DOF than a small f/#.

Shutter controls exposure and the rendering of time and motion. A fast shutter speed freezes action, while a slow shutter speed would allow for blurring, streaking, etc... There is a minimum shutter speed that is usually required for hand holding a camera and avoiding camera shake (blurring because you are wiggling the camera). Shutter speed is usually written as a number such as "125", but it stands for the reciprocal (1/#), meaning 1/125th of a second. 1/30th of a second is half the exposure of 1/15th of a sec, and twice the exposure of 1/60th of a sec.

ISO is how sensitive to light your materials are. ISO 200 is twice as sensitive as ISO 100. ISO 400 is twice as sensitive as ISO 200, and so on. Typically the less sensitivity (lower #), the higher the quality, less noise/grain, etc... What ISO to use is usually determined by the lighting conditions. In general ISO 100 for bright outdoors, ISO 400 for indoor flash, ISO 1600 or 3200 for very low light conditions.

ISO, aperture, and shutter are all balanced together to get correct exposure. If you need more exposure you can open the aperture (smaller #), decrease the shutter speed, or increase the ISO. If you need less exposure you can close down the aperture (higher #), increase the shutter speed, or decrease the ISO. If you need the same exposure, but needed more DOF (larger f/#), you could close down the aperture (decreasing exposure) to get the DOF you need, and the either decrease the shutter speed or increase the ISO, or both (increasing exposure). As you decrease/increase the exposure with one setting, you must compensate with one or both of the other settings.

Focal length is the distance between the film/sensor plane and the rear nodal point of the lens. Mainly remember that a short focal length gives a wide angle of view and less magnification, and a long focal length gives a narrow angle of view and more magnification.

 

[scrutiny1]

Thanks! That was a HUGE help!

 

[JIP]

One nice thing about your camera (and I guess most DSLRs for that matter) is the data that comes with your picture so if you shoot lots of pictures and just use your program you can go back later and look at the decisions the camera made for you like shutter speed and aperture.