When I am using D7000 with 18-105 lents, Aperture priority mode, Digitec TTL flash, I usually experience that photos are under exposed and the shutter speed gets limited to 1/60 or 1/30. I do not know why? Can it be increased? Even similar problem occurs when in Manual mofe. The photos turn out to be under. The result is not consistent. Shall I require to change the flash to Nikon make only. Pl suggest. Thanks in advance
One qualifier first, camera Auto mode is fully auto, it does everything as it pleases, and may not be adjustable in any way (compensation maybe). Below is speaking of camera modes A,S,P,M.
1/60 second is the default 'minimum shutter speed with flash' used in camera A or P modes. We use flash in dim places, which meter slower, like perhaps 1/4 second shutter (for one example). But we don't need 1/4 second because we are instead using flash. So automation can set it faster.
If you wanted to use the 1/4 second (whatever it meters), you can set Slow Sync mode, which will use it (whatever it meters). Or Rear Curtain sync will do the same (on Nikons).
Or your D7000 menu E2 allows other slower Minimum speeds, but 1/60 second is default menu "Minimum shutter speed with flash", A or P modes.
To make it be a faster shutter in A or P modes, you either have to go out into brighter ambient that will meter higher, or you can use camera M or S mode and set any shutter speed you wish (up to Maximum shutter speed with flash, menu E1). More at http://www.scantips.com/lights/flashbasics4.html about these choices.
Check the Flash Shutter Speed setting in the settings section. You can set the minimum shutter speed that the camera uses when a flash is attached to a higher shutter speed.
Also, when using a flash, you might as well just use manual mode on the camera. Just keep your shutter speed at or below the maximum sync speed (I think it's 1/250s for the Nikon D7000). The flash exposure is affected by aperture, not shutter speed. Slower shutter speeds will let you capture more of the ambient light, something which is nice to be able to control.