"Igfx" refers to the Intel Graphics Media Accelerator, an onboard graphics chip. If a message appears in the notification area informing you that the driver has crashed, the software may be outdated or corrupted.
What is Dvmt total GFX mem?
DVMT Total GFX Memory = set to MAX. you could experiment with this amount. be aware that it shares memory with your system RAM so setting a higher amount with 4GB RAM might leave you with less RAM available. you'd have to actually be running a game for the memory to be used.
What is a good aperture?
The best aperture for individual portraits is f/2 to f/2.8. If you're shooting two people, use f/4. For more than two people, shoot at f/5.6.