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When I am in aperture mode in my d90 camera, I have noticed I can also change my shutter speed by clicking the rear wheel.
Is that a bug? How is it possible?

If it is not a bug, how do I know the original shutter speed that my camera initially chose for that aperture ?

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Welcome to the site, stam! There's no need to surround your for greetings — it's a Q/A site, so it's not rude to just jump right in and ask. :) –  mattdm Apr 9 '11 at 20:35

2 Answers 2

up vote 3 down vote accepted

You may be changing the aperture in Shutter Priority mode (or the shutter speed in Aperture Priority mode) indirectly by actually changing the ISO. Look at custom menu setting d3 (Show ISO/Easy ISO) -- if that is turned on, the "unused" dial for your priority mode becomes the ISO dial -- you don't have to hit the ISO button to make a change.

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I knew I should have read my manual, 2 books and other documentation better! Now, if only this would work in manual mode as its the only complaint I have with my D90. But that's what the 300s and higher models are for and look forward to my next purchase. –  Wayne Apr 10 '11 at 3:37
    
N-I-C-E !!! Now this is the answer. Thanks a lot. Now that I got it - its pretty useful –  stam Apr 10 '11 at 22:19

{My bad - probably a lack of sleep made me write the previous nonsense}

Update:

This is your way of doing Auto Exposure Compensation. You can tell what is the original (neutral) speed by looking at the AEC indicator on your camera. If the indicator is at 0, that this is the standard exposure. Otherwise, you are compensating.

Update 2:

When shooting in an auto or semi-auto mode (like the Aperture mode), the camera sets the 3 exposure parameters (Aperture, Speed, ISO) so as to get a "standard" amount of brightness in the metered area. In the semi-auto modes, you set one or two of the parameters, and the camera then calculates the 3rd.

Sometimes, the standard exposure (Auto Exposure) is not giving the right exposure to the scene. For example, when shooting snow, the AE will generate a dark (gray) image instead of bright white. You can then tell the camera to make your scene brighter and look like it was actually was. This is the AE Compensation, or AEC. This is done by means of overriding the automatically calculated value of the 2nd or 3rd parameter. In this case they are the speed and ISO.

I am not familiar with Nikon systems, but I assume you can tell the camera to fix the ISO at a constant value, then the speed is the only variable left.

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Wait, (btw: thanks for the reply) . what is the AEC ? is there a way to lock it from being changed ? when I change the shutter speed, why is my exposure comensation still 0? –  stam Apr 9 '11 at 13:19
    
and why is the iso also changing when i rotate the wheel ? –  stam Apr 9 '11 at 13:21
    
BTW - welcome to the community. –  ysap Apr 9 '11 at 13:28
    
Hi, thanks for the elaborate answer . but my question was different . Let me re-explain. I know that I can fix the expossure compansation using the +/- button and that will change my shutter speed. I think I did something different with my factory settings . cause now I can also move it by changing the shutter speed wheel . and then the AEC sign doesnt change and i dont know what was the original shutter speed was. now lets say i am stopping down after rotating the shutter wheel. Is the new shutter compensated or not. I didnt do it through the AEC feature so is is not showing anywhere. 10x –  stam Apr 9 '11 at 13:34
    
@stam - If I understand correctly, then this is exactly the case where you change one of the 2 variables (the speed), and the camera recalculates the 3rd (ISO) so the exposure remain constant. Is it that the ISO is going up when the speed gets higher? The original speed is not so important as long as you have the exposure you want. Of course, you have side effects of more/less noise or motion blur. –  ysap Apr 9 '11 at 13:43

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