ISO and F-stop

[vthondaboi]

What effect does ISO have really?

Also how about the F-stop. I read that it has something to do with depth of field. Allowing more light in, but seems like decreasing shutter speed does that.

Seems like the most useful thing is shutter speed....

 

[jwedehase]

ISO represents the film's sensitivity to light. In a digital camera, it's the CCD or CMOS (or whatever) sensor instead of film. Higher numbers mean more sensitive. This translates to faster shutter speeds but less photo quality.

The f-stop is the size of the aperture opening, inside the lens, that allows light in. An aperture that is wider open (lower f-number)will offer less depth of field, but faster shutter speeds. A tighter aperture (higher f-stop number) makes for slower shutter speeds but more DOF.

Shutter speed is not related to DOF in any way.

Think of it like a bucket you have to fill with water through a hose. Aperture is the size of the hose, shutter speed is how long the hose runs, and ISO is the size of the bucket. You should then be able to see how they all relate. Assuming ISO stays the same, that means aperture (f-stop) and shutter speed will react in an opposite manner to each other.

GHO has some really awesome tutorials here:

http://www.ximinasphotography.com/lessons/

 

[llpoolej]

Shutter speed is a useful thing, but, if you want control over your photo, all things must work together. If you are doing a portrait, you usually want the background blurred, so you use a large Fstop(small , numer=bigger aperture= less depth of field)

The larger the aperture, the faster the shutter speed. If the shutter speed is still not fast enough, raising the ISO will increase it.

If you are doing macros, you want a larger depth of field. If you are doing scenics you want a large depth of field. Portraits and sports events usually call for a shallow depth of field.

So, aperture to *me* is the most important value, as it controls the entire scene. ISO and shutterspeed are also very important depending on what you are shooting

There is a reason people pay big money for fast lenses(F2.8 and faster) Which is the ability to control the scene and shoot in lower light situations

 

[funloven]

I can't seem to find anything that says f-stop on my camera.
My digital is a Casoi w/ 5.0 Mega Pixels. When I go into the menu I have something that is called Record Mode and if you choose Best Shot it lets you pick from 23 different photo setting possibilities. Do you think that is what sets the f-stop on my camera?

 

[llpoolej]

On digicams it is a little more difficult to say how to adjust it. If it has an "A" mode, which stands for aperture priority, it may be easier to adjust. Hard to tell you without knowing how to work that camera

On point and shoots, the depth of field is so large, due to the small sensor size, that it is almost impossible to achieve a shallow depth of field.

 

[funloven]

I could still use a bit more advice. I hope this doesn't get to be burdensome. My Record Mode - BESTSHOT gives me 23 options to choose from. Here are some examples:
1. Portrait - blurs background
2. Infinity - Hard sharpness and High Saturation
3. Candlelight - Soft sharpness, and daylight white balance.
4. Party - High sensitivity
5. Macro - High saturation
6. Sundown - Infinity focus, Red filter, and daylight white balance
7. Night Scene - Slow shutter, daylight white balance
8. Text - Macro mode, hard sharpness, high contrast
9. Twilight - High Color saturation and magenta color filter.

So what is the opinion about which of these would work best for 1. full tank pics, and 2. for individual fish/coral?

Also, is it recommended to wait until night to take pics with lights out, during the day with drapes drawn, or daytime w/ natural light?

Boy, this was a mouth full! :eek2:

 

[gregr]

Given those choices (some of those are pretty nutty) I'd go with Text for the individual corals and Portrait or Party for the fish and full tank pics.
vthondaboi- This Reefkeeping Magazine article describes how you can manipulate the aperture to get the type of picture you're looking for. There are example photos of the same shot taken with different apertures too.
Greg