Hi,
I have a Sigma 10-20mm f/4-5.6 EX DC HSM canon mounted lens, when ever i shooting with this lens for landscape get it that setting f/8 for aperture giving me sharpest results, also in blur index of this lens we can see the sharp result come with f/8-f/11 in whole range (http://www.slrgear.com/reviews/showproduct.php/product/171/cat/31).
but when i see photos of photographer in journals, they use f/16 or f/22 for landscape with this lens.
I just want to know just because of DOF they use this numbers for their aperture or something else?!!
thanks.

High aperture values can also be applied for keeping the exposure time as long as possible in the given circumstances, ie for dreamy flowing water, or to eliminate passersby on the image (in combination with ND filters).

In the case of flowing water yes but what about using high value to take photo from forest or desert or forest with the lake front it?

I use the Sigma 10-20mm lens extensively and never consider the lens sharpness characteristics. For me the aperture selection is based on what DOF I want to achieve and what creative effects I am after (shutter speed). With these two criteria in mind I select the desired aperture and it can vary between f/4 to f/32 but is usually around f/11 to f/22 range. I don't notice any discernable difference in sharpness throughout it's aperture range, I may have an excellent copy of this lens.

For me personally I don't pay too much attention to most of the recommendations concerning photography, lens sharpness being one, I shoot, process and output exclusively in sRGB when advised that Adobe RGB is better, I never sharpen an image in PP just being content with max sharpness set by camera and I use a polariser at 10mm when the physics says not to.

I understand that lens sharpness can be a very important issue for some folk but I personally would much rather worry if I had the sunrise times correct to be in with a chance to get a decent shot. ;-)))

JP

Hi john, thanks for your guiding
you say set max sharpness in your camera,that is create noise,is that? how do you decrease the noise?

for instance i see your beautiful photo in this link(http://1x.com/v2/#photos/member/14617/29862/) that take with sigma 10-20
can you please say the aperture value for this shot?
thank you

ss

No its not to create noise, it is simply to have the sharpness set in the file in camera so I don't have to worry about it in PP, I like to keep things very simple in processing and just use a few basic techniques or I could be lazy...

The noise of the file is not affected as far as I can see by setting the camera's sharpness setting.

JP

f/16 and I focussed on the rock edge about 3 metres in front of where I was stood.

JP

It means you set high aperture value to have DOF and zoom in some place near you stood,right?

I set f/16 and focused about 3 metres in front of me to obtain a large DOF in this instance, the zoom was set on my lens to get the desired scene before I focused.

As you probably know, DOF is a function of lens focal length, aperture and point of focus, a good online calculator is http://www.dofmaster.com/dofjs.html but in practice I can predict large DOFs easily as I use very short focal lengths most of the time and even f/8 and less produces acceptable results.

JP

For me the other use of aperture is the speed of the shutter I want to achieve. If I want a 1/4 of a second to motion blur water this is how I would go about it.

I do all my exposures manually, the camera isn't all that clever in reality as it doesn't know what I'm thinking....

I would set ISO to lowest setting 100 equivalent in case of D300.

Set a base aperture of f/16, meter the scene in spot mode. Adjust the shutter speed to desired setting of 0.5 or 0.7 underexposed, if I am able to achieve desired shutter speed at f/16 then I am fine but I may need to increase or decrease aperture to accommodate my desired shutter speed and I will do this as long as I can still maintain my desired DOF (bit of experience and guesswork as I don't actually calculate DOF in the field) and this isn't usually a problem as slow shutter speeds are usually obtainable with smaller apertures giving greater DOFs.
If I can't achieve my desired Shutter speed then I will have to put a bit of black resin plastic in front of my lens.....

JP

That is so constructive, thank you john
Best regards

ss