I have a used Nikon d40x and I'm just learning how to use it. I understand the A mode allows you to choose different apertures and adjusts shutter speed for optimal exposure. The problem is, I've tried different apertures and lighting situations and the shutter speed is not changing. Am I missing something? This problem doesn't occur in other modes as far as I can tell.
Several settings could be causing your D40X to demonstrate the behavior you are describing when you are also using the built in flash.
- Check Custom Setting 10. If it is set to 'On' and the Minimum Shutter Speed is set to '1/60 sec', then the camera will increase the ISO rather than allow the shutter to be slower than 1/60 sec (see page 76 of the D40X Manual).
- The following shutter speeds are available when the built in flash is used in Auto, Portrait, Child, P, and A mode: 1/200 - 160 sec (page 117 of the D40X Manual).
- If the flash control mode is set to TTL while shooting in Aperture Priority (A) mode and flash mode is set to Fill, then the minimum shutter speed allowed will be 1/60 sec. To allow slower shutter speeds select slow sync, rear curtain, or slow sync + rear curtain flash mode or use Manual shooting mode to control shutter speed as well as aperture.
Many camera bodies from major manufacturers offer the ability to have "slow sync" flash in A/Av mode capture ambient light during a flash exposure, and it sounds like yours might be set to allow that. On Canon's 50D body, for example, you can set a fixed 1/250th shutter speed - netting you maximum sync - or allow an automatically set shutter speed from 1/60th to 1/250th. Check your manual to see what it says about flash and A/Av mode, and adjust the setting accordingly.