Queries from new pentax k-x owner

[ssxdots]

Hi, I've gotten my pentax k-x from SLR revol along with a Sigma 17-70mm f/2.8-4 lens.

Had some test shots with it, but I have some newbie questions here.

I shoot in Aperture priority mode but the aperture displayed on the screen only starts with f/4.0 and above. Why is this so? Shouldn't I be adjusting from 2.8 - 4 instead?

Also, are there any tips on how to reduce graininess under low-light condition? (See third photo below)

Test shots:

 

[evolutioner]

it starts from f4 because u've zoomed in quite a lot..
f2.8 works at 17mm where u have zoomed out to the widest..

wats the ISO settings of ur 3rd photo?
a way to reduce noise for high ISO would be to shoot raw and then convert + PP with photoshop
but i never bother to use that as it's too troublesome for me

 

[airconvent]

yup...the f rating denotes the fastest setting for both ends of the zoom (i.e. wide to tele).
So f/2.8 is only at the 17mm end and progressively closes to f/4 at the 70mm end.

 

[hitendra]

at 70 mm, the max aperture you'll get is f/4 only... you'll get f/2.8 when you go to 17 mm

 

[ssxdots]

Thanks for the help guys! I see what you mean now. Still love the lens!

 

[ssxdots]

Hey guys, here's another newbie question. What kind of lenses produce such DOF?

Sorry man, I am an amateur at these stuffs still.

 

[airconvent]

Well, the exif data indicated a 100mm lens at f/2.8
But a 50mm lens at f/1.4 or f/1.7 should be able to give you good bokeh too.

 

[pinholecam]

EXIF data from the photo.

Camera Maker: Canon
Camera Model: Canon EOS 5D Mark II
Image Date: 2010-07-08 17:25:01 +0800
Focal Length: 100.0mm
Aperture: f/2.8
Exposure Time: 0.0040 s (1/250)
ISO equiv: 100
Exposure Bias: none
White Balance: Auto
Flash Fired: No (Manual)
Color Space: sRGB


Use your lens at 70mm f4 and focus closer. See what it can give you.

 

[ssxdots]

:sweat::sweat::sweat:

I should have checked the EXIF data first. Thanks!