Aperture+Shutter Speed+ISO=Confused

[momma_morris]

Hello I'm new to this forum so I hope I'm posting in the right place! I've been taking pic's for a while with just a point and shoot camera, recently I purchased my first DSLR. I'd love to learn more about Aperture, Shutter Speed, ISO. I've found alot of sites just by using goggle but I'm so confused with it all! Is there a good site out there for beginning?
Thanks,
Christina

 

[Overread]

Understanding Exposure by Bryan Peterson

It's a book rather than a website but its well written and idealy suited to teaching you how to start using ISO, shutter speed and apertures both to achieve a correct exposure and going further to using the settings in a creative manner.

 

[MisplacedAngler]

What kind of photography are you into? If you're shooting mostly outdoor pics, then your ISO will typically be really low thus removing one variable from your equation and there is a direct relationship between your last two variables shutter speed and apature size.

BTW, the book Overread recommended is good, but I learned most of what was in the book online before I ever bought it.

 

[edouble]

ISO directly affects your shutter speed. Higher ISO = faster shutter speed. There as a trade off with dslr and high ISO though. Higher ISO more noise (grain) in the picture.

Aperature is related to the size of "hole" that light travels through to the sensor. The bigger the "hole" (smaller f number) the more light can travel to the sensor. More light going to the sensor = faster shutter speed. The smaller the aperture (large f number) less light travels to the sensor = longer shutter speed. A large aperature like f/2.8 gives a narrow depth of field (dof). A small aperture like f/22 gives you wide depth of field (dof).

DOF is used to isolate a subject like a single flower (small f number). Or DOF is used to have an entire scene in focus like a flower garden (large f mumber).

This is a very broad subject and requires pages of text and examples to fully explain.

 

[Babs]

Understanding Exposure by Bryan Peterson

+1

I've bought that book on the basis of a recommendation from this forum, and it's great. Really well laid out, well written, and online support too (not that I've looked at that yet :blushing

 

[Rekd]

ISO directly affects your shutter speed. Higher ISO = faster shutter speed. There as a trade off with dslr and high ISO though. Higher ISO more noise (grain) in the picture.

Aperature is related to the size of "hole" that light travels through to the sensor. The bigger the "hole" (smaller f number) the more light can travel to the sensor. More light going to the sensor = faster shutter speed. The smaller the aperture (large f number) less light travels to the sensor = longer shutter speed. A large aperature like f/2.8 gives a narrow depth of field (dof). A small aperture like f/22 gives you wide depth of field (dof).

DOF is used to isolate a subject like a single flower (small f number). Or DOF is used to have an entire scene in focus like a flower garden (large f mumber).

This is a very broad subject and requires pages of text and examples to fully explane.

What he meant to say was;

If you want to stop motion use a faster shutter speed.

If it's dark out you'll want higher ISO and big aperture (small number), especially if you want to stop motion. (Hi ISO lets in more light, similar to a bigger aperture, but a high shutter speed kind of counter-acts that) The darker it is the more noise you'll get from higher ISO.

If you want to focus both near and far away, use higher aperture. If you want to focus on a very specific area and blur everything else (Depth of Focus, DOF), use a lower aperture.

I would suggest using Aperture Priority or Shutter Priority for a while to get used to how they work together. (For sports/action stuff, use shutter priority).

I'm just bustin' edouble's chops. He gave a great explanation that you may be able to understand better after a few months of shooting and getting to know your camera.

 

[farmerj]

SLR Simulator | Simulates a digital SLR camera

try that out.

 

[KmH]

The 3 - shutter speed - lens aperture - ISO - are inter-related and are known as the Exposure Triad.

Some call it a triangle, but that is really a poor analogy.

DSLR cameras have a built-in reflected light meter. We can center the light meter reading by adjusting one or more of the 3 parts of the exposure triad to make a properly exposed image.

In a short time we discover that once we have centered the light meter we can keep it there by adjusting any 2 of the 3 exposure triad settings. The key is that if one setting is increased, the second setting must be decreased.

As an example, if we let in more light by making the lens opening larger (larger aperture), we can get the same exposure by adjusting the shutter speed so it opens for a shorter period of time.

Another similar example would be again letting in more light with a larger lens opening (larger aperture) but adjusting the ISO so the image sensor is less sensitive to light, instead of adjusting to a faster shutter speed.

Aperture is one of the things that can affect if the foreground and background of a photo are in focus. That is known as depth-of-field, or DOF. In general, large lens openings are used to make the DOF shallow with the subject sharply focused but the foreground and background blurred. That's really good for making a portrait type photo, but not good for a landscape type photo where we want the entire photo in focus.

Shutter speed can control if things are motion blurred or not. The longer the shutter is left open, the more chance things can move while the picture is being taken.
So, if we want to take pictures of runners we use a fast shutter speed to stop the motion. For a photo of a flower arrangement made inside, we can use a much slower shutter speed because nothing in the frame is moving.

ISO is just an adjustment that adjusts how sensitive to light the image sensor is. As the ISO setting gets higher, so does the amount of electronic nosie ther is in the image. The ISO setting has a bearing on what shutter speeds you can use. As the amount of available light goes down, we can increase the ISO to keep the shutter speed the same.

 

[table1349]

Understanding Exposure by Bryan Peterson

It's a book rather than a website but its well written and idealy suited to teaching you how to start using ISO, shutter speed and apertures both to achieve a correct exposure and going further to using the settings in a creative manner.

:thumbup::thumbup:
You can't go wrong with this book.

 

[shan35mm]

Hi momma_morris,

My website has posts that explain the very basics for each of these topics. It might be just what your looking for to clear the confusion.

I'm not a spammer, so I won't post the address here. If you would like the address, just send me a message and I will send it over to you.

 

[prodigy2k7]

Ugh better read the websites and books, found 2 errors is what people said above.. 95% correct though

 

[prodigy2k7]

ISO directly affects your shutter speed. Higher ISO = faster shutter speed.

No. Changing your ISO only under or over exposes your photo. You compensate with changing aperture or shutter speed. For example: If you are in Tv mode, you are set to 1/500 and you change your ISO from 100 to 200, your aperture changes, not your shutter.

If it's dark out you'll want higher ISO and big aperture (small number), especially if you want to stop motion. (Hi ISO lets in more light, similar to a bigger aperture, but a high shutter speed kind of counter-acts that) The darker it is the more noise you'll get from higher ISO.

This is a little misleading. A higher ISO can seem to give the photo more light exposure physically but no more light is actually entering the lens. Im pretty sure you already know this but want to clear that up for readers. ISO simply amplifies the signal the signal. The sensor receives the same amount of light depending on the shutter and aperture only.

 

[edouble]

ISO directly affects your shutter speed. Higher ISO = faster shutter speed.

No. Changing your ISO only under or over exposes your photo. You compensate with changing aperture or shutter speed. For example: If you are in Tv mode, you are set to 1/500 and you change your ISO from 100 to 200, your aperture changes, not your shutter.

Wow, that is the most absurd definition of ISO that I have ever heard. "ISO only under or over exposes your photo" - wrong wrong wrong wrong!!!! Changing ISO increases or decreases the sensitivity of the camera's sensor. Increasing or decreasing this sensitivity directly affects shutter speed.

Is you shoot in a shutter priority mode then yes the aperature would change. A high ISO is 99.9999% of the time used for faster shutter speeds.

Know what you are talking about before you tell others they are wrong ldman:

From wikipedia "Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. Relatively insensitive film, with a correspondingly lower speed index requires more exposure to light to produce the same image density as a more sensitive film, and is thus commonly termed a slow film. Highly sensitive films are correspondingly termed fast films. A closely related ISO system is used to measure the sensitivity of digital imaging systems. In both digital and film photography, the reduction of exposure corresponding to use of higher sensitivities generally leads to reduced image quality (via coarser film grainimage noise of other types). Basically, the higher the film speed, the worse the photo quality." or higher

 

[Proteus617]

This stuff gets easier if you think of it in terms of "stops".
Aperture (F-stop) relates to the size of the iris in the lens
Speed is the shutter speed
ISO is the sensitivity of the film

Here's the sequence
F-stop: 1 1.4 2 2.4 4 5.8 8 11....
Speed: 1sec 1/2 1/4 1/8 1/15 1/30...
ISO: 3200 1600 800 400 200 100...

Don't worry about the above numbers, think of them as units on a number line. Each unit is one stop apart. On any of the three scales, moving one number to the left doubles your sensitivity to light, one number to the right halves it.

For example: your camera is in auto and suggests ISO 100, F8, 1/100. Want to increase your exposure one stop? Move any one of those values one stop to the left. Want to open up your aperture to F4 but keep the exposure the same? F8 to F4 is +2 stops. so you have to change your shutter speed or ISO -2 stops to compensate.

 

[RSPhotography]

wow, there are so many wrong definitions of ISO on this thread!!

it's not surprising you're confused because it appear's that lots of others are too!!

Did you ever have a film camera? If you did then you may remember that you could purchase film with different ISO numbers. They referred to how sensitive the film was to light. The higher the number, the less light was needed to 'expose' a photograph.

The same applies to digital. Your DSLR has a sensor in it that reacts to light. The sensor is actually analog (i.e. not digital) and you can increasse or decrease the sensitivity (gain) by adjusting the ISO number.
generally you want the lowest number you can afford as increasing the number adds more noise to the picture. (Think of 'gain' as volume - you increase the sound but you also increase the background noise)

However, most of the time you'll have to increase the ISO speed in order to capture enough light.

I think aperture and shutter speed have been covered rather well... (aperture = size of hole, shutter speed = length of time the shutter is open to capture a pic)