Aperture and DOF in live-view (with Pentax K-30)

About the issue

It seems that during live-view the aperture used is neither the maximum aperture the lens is capable of (like it happens while using the optical view-finder), nor the chosen aperture value (either manually in M / A or automatically in S / P / scene modes).

After a quick experimentation I came to the conclusion that it's somewhere between 4 and 5.6.

Solutions

However one can easily preview the depth-of-field by using either:

• the optical DOF preview feature, which, while still in live view, once the preview button is pressed will set the aperture to the chosen value, and will keep it as such until the preview button is released; (apparently in order to achieve this the camera will quickly swing the mirror before and after the preview, probably to trigger the aperture;) unfortunately during the preview you can't use magnification, but you can use focus peaking;
• the digital DOF preview feature, which will in essence make an exposure (i.e. take a photo) and allow one to inspect it just like with a normal image in preview mode, providing histograms, over- / underexposure blinkers, magnification, etc.; moreover if the image is acceptable one has the option to save it; on the down-side, because this feature actually makes an exposure, the time needed to obtain the preview is the same as the time value, thus rendering this feature cumbersome with long exposures (say more than a second);

Either of these features can be assigned to the RAW/Fx button.

Links

• Focus Adjust the K-5 and Pentax AF Lenses with Live View (mentions in the beginning the aperture issue in live-view);

• Pentax Forums -- K3 Live view question (discusses exactly the same issue, but for Pentax K-3);