A book on Aperture and ISO?

[BabsS]

I spent 3 hours at Borders yesterday going through photography books trying to decide on the best one.
I finally choose Canon EOS Rebel Sxi/450D Digital Field Guide by Charlotte K. Lowrie.
When I got it home I realized that it didn't go enough in detail about ISO and Aperture for me to understand the concepts.
It is a great book for learning the in and outs of the Canon Rebel (which I need to do!) ..not so much for learning photography.
If anyone has a great book to recommend that will teach me what the heck ISO and Aperture is and how to use it..I would love to hear about it!
I learn more by doing..not reading
the problem is..I don't' know where to begin on the doing part!
I have no clue where to start!

[amberskies]

Start with the tutorials on this site:
Digital Photography Tips and Tutorials

They are hugely helpful!

Nikon also has video tutorials:
Digitutor | Global Site | Nikon Imaging

There are whole books on Exposure. I've seen this one in the store but haven't read it:
chapters.indigo.ca: Understanding Exposure: How to Shoot Great Photographs with a Film or Digital Camera: Bryan Peterson: Books

[inkista]

Bryan Peterson.Understanding Exposure. That'll get you through the basics of "the exposure triangle" of iso, aperture, and shutter speed.

The only blind alley he leads you down is thinking that f/22 is a be-all end-all cure for sharpness/focus, without ever mentioning that you'll lose some sharpness at very small apertures to diffraction effect--which has become more visible with digital sensors because we've got higher resolution than film did and the ability to examine digital images at extreme magnification. The common wisdom with a crop-body sensor is not to go smaller than f/16 unless you're willing to make the compromise.

Other than that, that book is great. You may also want to follow it up with his Learning to See Creatively which is about basic composition.

[PowerPix]

Well, I was going to recommend our own infamous "Inkista" as some good reading material.......but she beat me to it. Plus, she talks (you know, good for explanations and stuff). You should really do some reading up on her, lots of good info!!!!!

[PowerPix]

Anyway, I'll try to explain:

ISO
What ISO denotes is how sensitive the image sensor is to the amount of light present. The higher the ISO, the more sensitive the image sensor and therefore the possibility to take pictures in low-light situations. Although, there are detriments to high ISO. I will explain further.


ISO speed affects the shutter speed / aperture combinations you can use to obtain correct exposure.

Suppose your digital camera's light meter warns you there is not enough light to correctly expose a scene. You could use the on-board flash, but let's suppose again it's not allowed (like in a concert or indoors recital). You would then need to use a higher ISO, which increases light sensitivity. Set on "ISO Auto" mode, your digital camera will automatically select a higher ISO. Otherwise, you can manually select the next higher ISO and see if the increased sensitivity allows you to obtain a correctly exposed picture. If it does, you can now take a correctly exposed picture.

Similarly, if you find the camera is using a shutter speed that is too slow (1/60 sec. and slower) to handhold the camera steady and shake-free (thus resulting in blurred pictures), and you cannot open up the aperture anymore, and you do not have a tripod or other means to hold the camera steady, and you want to capture the action, etc. etc. -- then you might select the next higher ISO which will then allow you to select a faster shutter speed.

However, all this increase in sensitivity does not come free. There is a price to pay: that is your image appearing more noisy (or grainy). Meaning there will appear to be static in the image.

See, when you boost the sensitivity of your image sensor by selecting a higher ISO, the image sensor is now able to record a fainter light signal. However, it is also true now that it will record fainter noise, where noise is any signal that is not attributed to the light from your subject. The increased sensitivity allows the image sensor to record more light signal and more noise. The ratio of light signal to noise (S/N ratio) determines the "noise" in your resultant image. Generally noise starts getting really noticeable at ISO 800 and up. But this varies per camera. Some are not noticeable until around ISO 1600.

An image sensor is usually calibrated so that it gives the best image quality (greatest S/N ratio) at its lowest possible ISO speed. For most consumer digital cameras, this value will be expressed as ISO 50, ISO 64 or ISO 100. A few digital cameras use ISO 200 as their lowest ISO speed. The lower the ISO speed, the less noise you will have in the image, therefore clarity!

The size of the image sensor determines the ISO speed range that a digital camera can use without suffering from undue noise. One reason for this is because the pixels on the larger image sensor can be larger and therefore receive more light, and thus have a greater signal-to-noise (S/N) ratio.



Aperture

The main function of a camera lens is to collect light. The aperture of a lens is the diameter of the lens opening and is usually controlled by an iris. The larger the diameter of the aperture, the more light reaches the image sensor.

Aperture is expressed as F-stop, e.g. F2.8 or f/2.8. The smaller the F-stop number (or f/value), the larger the lens opening (aperture). Ok so smaller #, larger opening and vice versa.

A "fast" lens is one that has a large maximum aperture (e.g. F/2.8 etc.)

A large maximum aperture is preferable to a smaller one since it gives the photographer more latitude in the kind of pictures that can be taken.

For example, it is pretty obvious that the larger the aperture (smaller #), the better your digital camera will perform in low-light situations, since a larger lens opening is able to admit more light than a smaller lens opening. And therefore allowing lower ISO.

A larger max. aperture (smaller #) also allows you to use a faster shutter speed to freeze action.


Kind of hard to wrap your head around all of it but just something to get you started on what each means. Hope that helps a little.

[BabsS]

oh Wow! Thank you all so much! I have ordered the book on Amazon! Can't wait to dive into it!
And now I'm going to read all the articles you suggested. And then, I'm going to play with my camera )
I'll never learn anything if I don't get enough courage to change a setting!
You all are so helpful!

[Digidave]

Put your camera in "Manual" mode. Then experiment & then experiment some more. When you have complete control over your aperture, shutter speed, & ISO you can't help but learn what each one does to exposure & how they effect each other.

[WVCoalMiner]

Anything written by Scott Kelby