Sigma 10-20mm is an ultra wide angle (UWA) lens, with an angle view of 60 degrees. It can focus up to 24cm, which is less than a feet for those who are still thinking in British system. It has a 77mm diameter filter thread. The result is that the Pentax K7 pop up flash will not work as the light will cast a shadown of the lens onto the photo. The Pentax 540AF is the top of the range of flash. A direct (90 degree) flash will provide a poorly lighted photo on the side of the photo. After some experiments, a 180 degree flash to the ceiling bounced back the light, and the picture now is more acceptable. However, it will need a reflected ceiling. I will need a diffuser, if I were to shoot direct. I have not tried this yet as I don't have one to start with. I find that using the Auto mode of the flash is better than P-TTL (Through The Lens). I need to remember that Sigma is a 3rd party lens, and it meters using the "center weighted" and not the 77 segments. Photography is all a...
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