The control layout is basically identical to the Optio A30 and several previous Pentax ultra-compacts. The power button and shutter release are on the top panel, while on the back are the D-pad, playback and menu buttons, the zoom control and the Green Button, the instant easy-mode control found on all of the Optio range. The zoom control is a relatively chunky rocker switch positioned under the right thumb, but it is stiff enough that it isn't easy to operate it accidentally. It's not the most sensitive control in the world though, and the zoom is stepped with seven positions from wide to telephoto, so precise framing is going to mean some moving backwards and forwards.
In common with most high-spec compacts the A40 offers some manual exposure control, in the form of shutter priority or full manual modes. The only available aperture settings in manual exposure mode are minimum and maximum (f/8.0-f/15.4), although shutter speeds from four seconds to 1/2000th of a second are available in 1/3EV increments, so there is some room for creativity. The menu does also offer some degree of picture control, with adjustable contrast, saturation and sharpness, but there is no control over noise reduction. It does offer some other creative features though, including multiple exposures on the same frame, and a wide range of scene modes.

The Dynamic Range Adjustment feature is similar in function to Sony's DRO system. It proportionally increases the sensor gain in darker areas and reduces in in highlights, reducing the occurrence of black featureless shadows and burned-out highlights in high contrast shots. It has four settings; off, weak, strong and automatic. I found that it didn't do much about the highlights, but was able to pull out about a stop and a half of extra shadow detail without significantly increasing image noise, which should go some way towards alleviating the inherent dynamic range limitations of the 12MP 1/1.8-inch sensor.

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