Aperture value on lens???

[skeletonman]

Not sure if this is the correct place to post my question? Just a few days back, I bought an Olympus 11mm-22mm 2.8-3.5 lens.

I have a question here, so when at the wide end its aperture is f2.8 and at zoom its aperture is f3.5? Am I right to say so? Please correct me if I am wrong.

And if i have set the aperture to anything more than f3.5 or more like f22 on my cam(E510), the image will not longer be sharp and focus like when its aperture is in the limted range (f2.8-f3.5)?

Please kindly enlighten me on this issue. Thanks all in advance

For your info - I have tested a few images with the landscape mode to see what is the f value used by the cam. Its like f3 to f4. And this is based on the calculation of the cam.

 

[Digital Matt]

I have a question here, so when at the wide end its aperture is f2.8 and at zoom its aperture is f3.5? Am I right to say so? Please correct me if I am wrong.

This statement is correct, but you might want to do a little reading. You are not quite getting everything yet.

The more you stop down your aperture (larger numbers), the more of the image will become in focus, or within the depth of field. Sharpness, is really a function of the quality of the lens. There are a lot of factors involved, but it is generally safe to assume that a lens will at its sharpest, 2-3 stops down from it's max. In the case of your lens, at 11mm, 2.8 being max, it should be sharpest by f/5.6, or f/8. Don't worry about what the camera does in auto. It has no idea what you are trying to do.

http://photonotes.org/cgi-bin/entry.pl?id=Aperture

http://luminous-landscape.com/tutorials/understanding-series/dof.shtml

 

[skeletonman]

This statement is correct, but you might want to do a little reading. You are not quite getting everything yet.

The more you stop down your aperture (larger numbers), the more of the image will become in focus, or within the depth of field. Sharpness, is really a function of the quality of the lens. There are a lot of factors involved, but it is generally safe to assume that a lens will at its sharpest, 2-3 stops down from it's max. In the case of your lens, at 11mm, 2.8 being max, it should be sharpest by f/5.6, or f/8. Don't worry about what the camera does in auto. It has no idea what you are trying to do.

http://photonotes.org/cgi-bin/entry.pl?id=Aperture

http://luminous-landscape.com/tutorials/understanding-series/dof.shtml

Hi Digital Matt, thanks alot for the reply. So does it mean that for any particular given type of lenses at any given f values. It is generally safe to assumed that we can step down by 2-3 f values (increasing the f values).

Example for 40-150mm 4.0-5.6 lens, we can step down (increasing the f values) by maybe like 6-8 in order to achieve the desire results?

For my case I would like to achieve a landscape image where everything is sharp and focus. Sorry for posting so many questions.

 

[Alex_B]

For my case I would like to achieve a landscape image where everything is sharp and focus. Sorry for posting so many questions.

Depending on the scene, you would then go smaller apertures, say f/8 or even f/16.

On 35mm medium I usually go to f/8 if nothing is in the foreground ... and f/16 or beyond if there are objects in the foreground.

 

[Alex_B]

keep in mind though, that for very small apertures (f/16 or f/22) your lens might already show diffraction effects which lowers overall image quality. But this really depends on the lens.

 

[skeletonman]

Thanks for for the replies...I will continue to play around and hope I can get it right.