Question about D40 exposure modes

I have a question about the differences between Program, App Priority, and Shutter Priority. Aren't they essentially the same thing? In Program mode, the f stop and speed move together, in App Priority you change the f stop and the speed moves with it, in Shutter Priority you change the speed and the fstop moves. However, you wind up with exactly the same parings.

As I was typing this it occured to me that the camera might "remember" different adjustment settings for each mode. If it does, that's really cool and my question is answered. I could wait to get home and see but I figured to put the question to the forum anyway in case there are other differences.

mgshn1 said:

I have a question about the differences between Program, App
Priority, and Shutter Priority. Aren't they essentially the same
thing? In Program mode, the f stop and speed move together, in App
Priority you change the f stop and the speed moves with it, in
Shutter Priority you change the speed and the fstop moves.
However, you wind up with exactly the same parings.

Click to expand...

For a given scene and a specific light level that you want, there can only be one correct ev reading. And for a given ev reading, all the shutter/aperture/ISO combinations will result in the same effective exposure. So yes, all three exposure modes should have the same pairings or triplings (if you add auto-ISO into the mix).

The reason to use A instead of S really comes down to whether or not the aperture used is more important to you than the shutter speed used. And vice versa. With P mode, you let the camera come up with what it thinks is a suitable aperture and shutter speed. All three allow you to change the settings if you need to.

larsbc

You are correct in that Program, Aperture priority and Shutter priority
should all result in the same exposure, but they will not necesarily
result in the same aperture/shutter combination.

Example:
Say you shoot a sceen in A mode and you select f/8. Assume the
camera determines that 1/250s is the correct shutter speed.

If you shoot the same sceen in S mode, and set the shutter speed
to 1/1000s, the camera should pick f/4 as the correct aperture.

f/8 with 1/250s gives the same exposure as f/4 with 1/1000s, but
the DOF is different.

--
ToeKnee44 (aka Tony)
'The Constitution only guarantees the American people the right to pursue
happiness. You have to catch it yourself.' Benjamin Franklin

Sorry, maybe I wasn't clear with my original question... For any scene there is one ev level that is correct. That EV level is met go a number of apeture/shutter pairings.

From what I can tell, it doesn't matter which of the three modes you use (P,A,S), any of them will allow you to cycle through all the same "suitable" combinations.

If that is the case I'm wondering what is the benefit of using one mode over the other.

Every lens has a "sweet spot" and it is usually stopped down, not wide open. Also, depth of field increases as a lens is stopped down. So if you are more interested in the sharpest image, or more depth of field, you would use A mode where you can select the best aperture and let the shutter speed fall wherever. If stopping action is more important to your shot then you would want to use S mode where you can select a shutter speed high enough to freeze your subject and let the aperture fall where it may. If you don't want to think or don't care, then you can use P mode and let the camera select whatever speed and aperture the firmware thinks is appropriate. The exposure may be the same but certainly not the resulting image.

basically you are right but i use Aperture priority when i know i want a nice blurred background (small dof) widest aperture.or in the case of landscapes high number F narrow aperture. I guess it is a matter of what you think is important. if you have a moving subject you need a high shutter speed so then use S mode. I like to use manual mode which also can give you the same results and is a great way to practice so you can see which shutter speeds and apertures go together. Also with M mode its easy to over or under expose as you sometimes need to.

I think as you work with your camera you get to know what A, S or M settings you need for the effect you want.
i really never use P or auto modes.
--not an expert and a d70s user

http://www.pbase.com/arev
Vera

mgshn1 said:

Sorry, maybe I wasn't clear with my original question... For any
scene there is one ev level that is correct. That EV level is
met go a number of apeture/shutter pairings.

From what I can tell, it doesn't matter which of the three modes
you use (P,A,S), any of them will allow you to cycle through all
the same "suitable" combinations.

If that is the case I'm wondering what is the benefit of using one
mode over the other.

Click to expand...

If you want the aperture in all your shots to be at f/2.8, which makes more sense:

1) Using A mode and setting it to f/2.8 and letting the camera make changes to the shutter speed as the lighting conditions change.

2) Using S mode and changing it every time the lighting changes so that the camera ends up choosing f/2.8.

Obviously, A mode makes more sense in this scenario since you only need to set one parameter one time.

larsbc

in A mode the camera remembers what you set the appiture to and it will always be that until you change it. The shutter speed will change as dictated by the meter but A stays fixed. In S mode the shutter speed remains fixed and it's the appiture that changes with the available light.

In P mode the f stop and shutter speed are initially "picked" by the camera. Starting from there you can move the pairing in either direction (wider/faster or smaller/slower). However, when you go to take the next picture, even though the setting will still tend to be the way you set it there's no telling exactly where the fstop or speed will start. Also, when you move from P to anything else and back to P the adjustment you previously made is lost.

Thank you all for helping me understand the true use of the A, S, and P settings.

(What a remarkable camera this is!)