Having trouble focusing wide angle lens for big DOF

[rambler4466]

10-22mm lens (crop factor camera, not full frame) 1. Turn off auto focus. 2. Set Aperture at f/22 3. Focus on something 1 meter away (around 3 feet)

DoF should be 14" to infinity

If you do have a DoF scale on the lens, do not focus on anything! Look at rpcrowe's image of the scale. At f/22 everything between 3 meters and infinity should be in focus. Set the focus ring with the 3 just above the orange line and shoot.

Alas, none of my lenses have that scale.

[chauncey]

Matt, you might want to check the MTF Characteristics of your lens...http://www.canon-europe.com/Support/...ork_iii_en.asp
Go to page 213 to find your lens and note the severe drop-off at the image edges.
I use those tables as a first stop reference for lens purchases. High @ straight is better.

As good as you are...don't rule out gear.

[Polar01]

Frank: I would look at your info again, The distances you state are correct if on a full frame camera, however if using a crop framed camera at your setting then under and including 19mm would work, but for 20-22mm this would not be true. If using a full frame camera than 10-22mm at your f/22 and focused on something 3ft away then your DOF would be 15.96" to infinity.
With some of the DOF calculators it is hard to tell which is for crop cameras and full frame cameras, if I chose Nikon or Canon DSLR than that is a crop camera, if Nikon D3 or Canon 5D than those are full frame. Another thing you have to watch out for is your state focus on something 1 meter away (around 3 feet), if you were to focus on something 1 meter away that is only 3.37 inches longer than 3 feet (36") that changes being able to now go up to using 10-20mm instead of 10-19mm all for only 3.37 inches. One last thing never ever use the DoF scale on the lens it is to only give you an idea, either autofocus on something a known distance away then turn off or manual focus do not assume that the DoF scale is correct. I carry a small tape measure with me for 12 feet, if shooting with something close in the fore ground I measure for the centre of the tripod to the object and then good to go.

Cheers:

Allan

[woof woof]

I almost never use very small apertures.

I think that sometimes people use them in an attempt to get front to back DoF which will could well exceed the scene. For example with a 20mm lens on an APS-C camera f22 will give DoF of under 2ft to infinity but if there's nothing within 5ft of the camera you could open the aperture to f8 and still get about 4 1/2ft to infinity and be more likely to avoid any possible diffraction issues.

If shooting at the wider end of the zoom range at something like 10-12mm or there abouts even f4 could get you under 4ft to infinity.

Another method worth trying is the Merklinger (Google if not familiar, it's an easy method...) method which avoids having to memorise DoF tables or carry them with you.

[Hero]

Why on earth would you use such a small aperture on anything other than something very very close-up? It will only give you major headaches in the shutterspeed and diffraction departments (although the latter one is quite susceptible to sharpening) Both of which are major causes for softness in your images.

[Colin Southern]

Why on earth would you use such a small aperture on anything other than something very very close-up? It will only give you major headaches in the shutterspeed and diffraction departments (although the latter one is quite susceptible to sharpening) Both of which are major causes for softness in your images.

I wouldn't say it necessarily "causes a headache" shutterspeed wise -- in many cases it's the long shutterspeed that we're after, and even with copious quantities of ND filter a narrow aperture is still required to get an exposure into the "several minutes" realm.

In terms of diffraction - as far as I'm concerned, it can be ignored most of the time. Yes, diffraction is real, but the effects are only visible at high magnifications, so doesn't really affect a real-world image unless it's printed VERY large. And - as you pointed out - it responds pretty well to sharpening anyway.