Use for Aperature Mode ?

New to this, electronic, photography. Can anybody give me a case..or cases..where you would set your F-Stop and let the camera 'find' the 'correct' shutter speed?

When you need a specific DOF. Or when you need to keep a fast lens open for background highlights. Or when you want to preserve a sharpness sweet spot in a lens and shutter speed is not important.

On a 300D it's the only way to get ETTL to work right.

there will be additions to this list....

I tend to spend a lot of my time in AV mode as often the main thing I want to control is my aperture! I set the aperture depending on the type of shot I am doing and what sort of DOF I am looking to achieve, then look at the shutterspeed I am getting and if necessary adjust the ISO so the shutterspeed is appropriate for the shot.

You want some cases where I would want to adjust the aperture? OK, here's some off the top of my head...

Portraiture with a nicely blurred background, I will select a large aperture, say f2.8-f4.
Landscape with a sharp foreground and a sharp background, I will select a small aperture, say f13 or lower.
Macro photography where I want to maximise my DOF at high magnifications, again I will select a small aperture, say f11-f16.
Scenario where I want a very slow shutterspeed for something like blurring a waterfall for example, I will stop down to a very small aperture, perhaps the smallest the lens will go to (depending on lighting).
Scenario where I want the fastest possible shutterspeed under the given lighting conditions I will shoot wide open.

Hopefully you get the idea.

PS. Sorry forgot to say "Welcome!" GTO-Guy!

Hmmm...Do the G series cameras have a 'fast lens' ? If it isn't beyond the scope of this posting, what IS a 'sharpness sweet spot' ?

:o I am afraid I don't know what a ETTL is, and the only '300D' I know about is a pretty slow car!

And thanks for those examples. DOF, I do understand. Yeah, I get the idea now. I'll have to do some learning about that..

Thanks... Neat cameras, these.

The G series does have a relatively fast lens. I was impressed with that.

All lenses have a sweet spot where they perform best. It is usually not wide open or steppd down all the way. "F/8 and be there" is an old saying that you can take to heart. Set the aperture to F/8 and you can be guaranteed the lens will be most likely in its' sharpness "zone".

ETTL is a flash function of measuring and firing off the right amount of light for the composed shot.

300D is a Digital Rebel.

Take your camera to Neah Bay in the summer...

GTO-Guy,

Just take a picture in Av mode at different apertures, so start at 2.0 and work your way up, you'll notice the depth of field get wider as you go up.

do a google search for aperture or f-stop and experiment.

What Cosworth and nitsch are saying is somewhat correct. Since you posted in the G series forum, I'm assuming you have a G series camera. Their advice is based on dSLR lenses.

A G6 has an aperture range of 2.0 to 8.0. 8.0 is completely stopped down, so nitsch's advice of F13 does not really mean anything. When Cosworth talks about F8 bieng a "sweet spot", he is refering to a lens that goes to F22 or so. On a G series camera F8 is completely stopped down and is nowhere near a sweet spot.

I appreciate the advice of those with lots of experience, but if you are going to lurk in this forum, I wish you would make your comments "forum topic specific".

There are 3 controllable modes, M, Av andTv. M lets you set both Av and Tv and then check exposure with a half press. Let's not dwell on M.

That leaves Av and Tv. When you use Av, you set the Aperture and the exposure compensation and the camera sets the shutter speed. Tv, you set the shutter speed and exp and the camera sets the aperture. Doesn't really matter which you use as long as the setting you use will result in the correct exposure. The problem is that for many possible shutter speeds, there is no correct matching aperture. There are more possible shutter speeds than aperture values. Say for instance you are in low light and want a fast shutter speed. If you open the aperture to the max, 2.0 that will give you the maximum shutter speed that is properly exposed. Of course, everything has tradeoffs and wide apertures affect depth of field. If you are in bright sunlight and want to slow down the shutter, close the aperture and that will require the camera to select a slower speed.

That is the value of Av over Tv. In most situations, if you choose a reasonable Av value, there will be a corresponding shutter speed to make a correct exposure.

If you do want to use Tv, or even sometimes Av, be sure to turn on Safety Shift in the menu. Then, if you set a value for which there is no corresponding value, the camera will adjust your value to make sure the shot is exposed properly. Conversly, if you are trying to do something tricky and want to override the camera's exposure compensation, turn it off or go to M.

"F8 and being there" was just an aperture reference. Yes, it may be lost on someone who does not have an understanding of lens apertures (regardless of body type). I meant no "mudding" of the issue, just to say that a lens (any lens) has a subjective sweet spot and that Av mode can lock you into it. I was intending to stay "forum topic specific" and it may have been misinterpreted. My apologies if I wasn't clear enough.

No problem. I'm not trying to start anything. But "F8 and being there" just does not apply to a G series camera no matter how much you know about anything. Most dSLR lenses are not their sharpest wide open or completely closed down, hence the F8 reference which means somewhere in the middle. But on a G series camera F8 is completely opposite, the equivalent of saying F22 is the sweet spot. A little like extoling the virtues of a certain kind of antifreeze to an air cooled VW forum.

I've heard the sweet spot theory, which on a G6 would be 4.5 or 5.0. However, this means that the lens is sharpest at that aperture point and does not address lighting or other factors. It is relevant in that, if you have a situation where you can achieve proper exposure and there are no other factors (like slowing the shutter speed down too much on low light hand held shots), it would be a good idea to go toward the sweet spot. IMHO, the sweet spot theory is only one of the many factors to take in to account.

Ah, yes... Oh, I'm not much for Neah Bay these days. I 'used to' enjoy going out there, if you know anything about 'our' local politics.
But I have taken a few (hundred) up on Hurric ane Ridge.

Yesss... I have G-1. Great little camera, thanks to my Son-in-Law who likes carrying around my old large, heavy, bulky camera bag! He gave me this one, which I think is...great. He bought it new in 2001 and it is perking right along...with a box full of various batteries.

And YES, the only minor problem I am finding is the f=8.0 smallest 'light hole'. Occassionally I shoot a 1/250th shot that turns out very overexposed. I'll dabble with the Av mode more, now... and maybe get a fix for that little problem.

I was a little annoyed to find that my polaroid lens was basically unusable ...in the LCD. But I find that if I turn 'the dot' towards the Sun..where ever it is, I do alright. Better than holding an old Sun-Glass over the G-1 lens.

To tell you the truth, I can't think of what would make me go back to...THAT BAG...
but then, I'm not a 'pro'...

Thanks for the info.....

Sure you can.

Like he says, "Sure you can"... But my light meter went off with The Kid. Travelling light, these days.

Thanks, all of you...very much.