我想問,點先可影到張相係四個角的位置呈現黑色,我有圖.

我睇你張相都唔係四隻角全黑,
唔使搞咁多野既~
只要利用一支燈, 光唔可以散開既,
好似大口徑既電筒, 舊式枱燈 (即係有個杯加個燈膽果隻)
用黎做照明, 房間會全黑, 必要時加上黑色 (或深色) 背景紙,
(夠大張既圖畫紙就OK)
咁叫佢唔開閃燈影相就OK~ 小心手震, 最好用腳架.
另外利用DSLR專用既鏡頭插落普通SLR時,
亦會出現 "暗角" 位, 呢個係因為DLSR既感光片比較細,
所以用係SLR時出黎個影像就唔夠大而變成圓形.
呢個效果就一定要配件勒.
另外利用極端細既光圈亦可做出四角位 "比較暗",
不過呢個係鏡頭設計問題,
依家大部份鏡頭都唔會咁.

This effect called "Dark corner" or vignetting in purpose to create more focus
on the center ...

there is 2 way to make that effect :

1. PHOTOSHOP POST PROCESSING !!! ( I know you dont want this)

2. in DSLR it is very easy, I just apply a special filter or stack up couple
filters to do this.

In your case, you can try this :
use a black piece of thick paper, and make a small hole in the middle of it
and make sure the circle is slight smaller than the lens size ...
and use it to wrap around your camera when taking photo ...
it need to be adjusted since lens come in and out I think in your case ...

But I still recommend you do photoshop or get a DSLR with a lens system.

Good luck

alien