ISO and shutter speed questions

[coreymcl]

OK I know this is a stupid question but I'm guessing somebody besides me also wants to know this. Is there a cheat sheet to tells me when is a good time to use certain ISO settings? Like ISO 100 for ..., ISO 200 for ... and so on? The reason I am asking is I took some pictures at a basketball game for my son and they have a lot of noise. I know I have read if you use to high of an ISO then you will get noise. On my 20D I can only adjust the ISO and aperture. Well at least that I have found.

Thanks for the help.

[brad]

My general rule of thumb...

Always use the absolute lowest ISO you can get away with.

In other words, when trying to find the right settings for the exposure, bump that ISO up to the next level only as a last resort.. do what you can with f stop and shutter, first.

Now, that said.. and having just come from a basketball game myself in which I have found myself very frustrated with the results... basketball.. don't go slower than 1/125 and use an f-stop as wide as your lens can handle sharply (which should be f/2.8 for that nice IS 70-200mm f/2.8L you have)... then push the ISO only as far as you have to in order to get the right exposure...

(I was shooting f/4.5 and 1/90 at 1600 ISO on my 10D.. was still a stop under exposed .. and I'm grumbling looking at the shots.. out of a dozen, only one is decent and its a rather boring shot of a single player dribbling slowly... bleh)

[engstrom]

ISO, aperture, and shutter speed are the triumvirate of exposure. In general you want to use as low an ISO as possible and still get the shutter speed/aperture you want. If you are shooting for a particular shutter speed, for example, and have opened up your aperture all that you can/want to then increasing your ISO is all that you have left. If you have any questions about what I've said let me know.

[engstrom]

Oh, and by the way, there is no such thing as a stupid question here!

[coreymcl]

OK I read through my manual I know I shouldn't do that but I did. I don't see a way in manual to set all three: ISO, Aperture, and Shutter Speed. What gives?

[coreymcl]

Also what good is a histograph? How do I read this. I have no idea what this means to me.

[markperez]

here is a couple of links on histograms. To find some more links goto google and type in +histogram +camera

http://www.pcmag.com/article2/0,1759,1658619,00.asp

http://www.luminous-landscape.com/tu...tograms.shtml-

[brad]

First off, you have to abandon the "automatic" settings on the camera.. essentially, you should be shooting in either M, Av, or Tv... these give you the most control.

ISO -- when you're in one of those modes, you can set the ISO by pressing the button on top of the 20D that says DRIVE-ISO .. the big wheel on the back changes the ISO setting.

f-stop.. when you are in Av or M mode, you set the f-stop with the wheel by the shutter button... in Av mode, the camera's light meter will read the scene and based on the selected f-stop and ISO, it will choose a shutter speed for the proper exposure.. watch this number carefully to make sure it is appropriate for the scene..

Shutter speed.. when you are in Tv mode, it is adjusted by the wheel by the shutter button, when you are in M mode, it is adjusted by the wheel on the back... in Tv mode, it does the same thing I described in the Av section above, only the camera chooses f-stop based on shutter speed..

When you are in Tv or Av mode, the wheel on the back will "push" or "pull" the exposure... you can tell it to overexpose (pulled to the right) or underexpose (pushed to the left) up to two stops either direction.

Clear as mud? If you want, we live close enough, we could meet for an afternoon of shooting and I can show you what I'm talking about.

[coreymcl]

I would like to meet and clear this up. Let me know when you have some free time. Also I have been shooting in M not automatic.

[markperez]

welcome for the links

[coreymcl]

Sorry yes thanks for the links!

[CaptainTom]

I guarantee that once you understand the relationship between ISO (sensitivity), F-stop (aperture), and shutter speed (shutter speed), your photography will improve by leaps and bounds.

The entire concept is based on the amount of light that reaches the sensor.

aperture is the hole that the light comes through. The bigger the hole, the more light will come through.

shutter speed is the amount of time the hole is open to let light in.
longer shutter speeds let in more light than shorter shutter speeds.

ISO is an adjustment as to how sensitive the camera is to the light.

If a proper exposure reading is i.e. F8 at 1/2 second at ISO 400
you have a certain amount of light going through the hole (f8) for 1/2 a second, and the sensor is more sensitive to the light than if it were set to ISO 200 or ISO 100.

If you close the hole by half (change the aperture to f11), in order to let in the same amount of light as before, you have to now either let the light in for twice as long (1 second), or increase the sensitivity of the sensor (ISO 800).

This same relationship works if you change the shutter speed, you have to adjust the aperture, or if you change the ISO , etc.

The point is ; the correct exposure will happen when X amount of light reaches the sensor. You control the light by adjusting the f-stop (aperture) and the shutter speed. You can adjust the ISO if your f-stop and shutter speed adjustments don't get you what you need.

It is late and I am tired, so this may all be back wards or something (caveat emptor).


Or, you could search Google for aperture fstop

[brad]

Just to add to what was said above about ISO/Shutter/F-stop being a triumvirate...

Imagine an exposure for a minute at ISO 100, f/16 and 1/125 shutter. This is a set of elements that describes the exposure and the amount of light that reaches the sensor/film... if you were to change the f stop to f/8.0, the aperature would let in twice as much light so to get the same amount of light on the sensor, you would have to speed up the shutter to 1/250.. make it f/4.0 and you'd have to double the shutter again to 1/500. (The same works in reverse, f/32 lets half as much light in, so you'd have to slow the shutter down to 1/60.)

Now take that f/4.0 and 1/500 .. let's say you needed to get 1/1000 for a shutter speed, but cannot open up the f-stop any further... instead of letting twice as much light in, your only other choice is to make the sensor twice as sensitive, so you would bump up the ISO from 100 to 200 ... bump it up to 400 and you could get 1/2000 shutter or you could go back to f/8.0

Starting to make some sense?

[brad]

LOL Tom.. you and I are on the same wavelength. (Pun intended)

[gpbusa316]

Just want to clarify one thing and add another... In M (Manual) mode on the 20D, the wheel by the shutter release (called the "Main Dial" in the manual) will adjust the shutter speed and the wheel on the back ("Quick Control Dial") adjusts the aperture value.

As Brad mentioned, in "Tv" (shutter priority) mode, the "Main Dial" by the shutter release, adjusts the shutter speed... and in "Av" (aperture priority) mode, the "Main Dial" by the shutter release, adjusts the aperture value.

Also, the on/off switch must be all the way up in the last position (above "On"), or the "Quick Control Dial" on the back WILL NOT function.

Tony