Tips for using my 10-20mm

Youstolemyname · 27 Oct 2008 at 23:22

Well I just got my 10-20 back from sigma and it does seem a lot sharper but only in really good light. So I guess it's going to be tripod time, which is fine.

But when I am shooting a landscape, where should I be focussing? Manually and setting the focus ring to infinity? Or on auto and seeing what the camera picks up?

I did a few test shots on full auto mode and they were pin sharp. When I go manual they are soft as butter!

Any info and help greatly appreciated.

Pho · 27 Oct 2008 at 23:43

You probably want to use the hyperfocal distance.

http://www.dofmaster.com/ - download the program to generate spinny wheels

.
http://www.lensplay.com/lenses/lens_depth_of_field3.php
http://www.aguntherphotography.com/tutorials/depth-of-field-hyperfocal-distance.html

I still have issues understanding it mind.

aztechnology · 28 Oct 2008 at 00:16

Where you need to focus depends on what you are taking pictures of.

You can work out hyperfocal distances if you like, but the rule of thumb is that depth of field extends about twice as far beyond the point of focus as is does in front. So work out what you want sharp, find an aperture that is suitable (use a focus chart if you must, guess if you can't be bothered) then focus about a 1/3rd into that field.

if you post details of the bad landscapes then we can have a guess where you are going wrong.

Youstolemyname · 28 Oct 2008 at 00:28

thanks guys. I will post some pics when i get back from cornwall. But from using those charts, at F16 on a 10mm focal length I should be focussing about 24cm into the scene? My maths must be totally funked up there or something as that seems really wrong.

(Based on focal length squared divided by fstop times frame crop co-efficient of 0.0254 for the 400d)

aztechnology · 28 Oct 2008 at 14:21

nearly.. but not quite?

as you are using a 10-20, you will likely be using a 1.6crop sensor. My hyperfocal calculator puts Hyperfocal distances as 34ish cm (0.344m). At that distance, everything from 0.17m to infinity will be in focus, my calculator uses a circle of confusion of 18.75 microns for 1.6 crops.