depth of field

[russebarre9]

I have a tamron 18-270mm zoom/macro. I read an article where this person acheived maxium depth of field looks like from his nose or 2 feet to a great depth by focusing via the distance scale. The lens has a distance scale like a depth of field ring that you can use to focus. Does anybody have any ideas on this or can you tellmy how to acheive a maxium depth of field do you focus 1/3 up in your scene?

[dcclark]

What you are looking for is hyperfocal distance. Here's an article about it here on DPS -- or google around, it's a topic with a lot of articles on the web.

[kencaleno]

So what is Hyperfocal Distance? It is the point of focus that will give you the greatest acceptable sharpness from a point near your camera on out to infinity. (Up to prints size 11 x 14 inches) The near point is half the distance to your HFD. The wider your lens and the smaller the aperture, the larger the area of acceptable sharpness. Here is a chart I made for 18-55 and 70-300 kit lenses-

Depth of field appears to be the most confusing of focus elements. Depth of field is a range of acceptable sharpness in an image, from near to far. Three factors control Depth of field: Aperture: The wider the aperture, the shallower the depth of field. Focal length of lens, The longer the focal length of the lens, the shallower the depth of field will be. and Distance from subject, Landscape images have great depth of field, whereas Macro (extreme close-up) images have very shallow depth of field. Concerning depth of field, Hyperfocal distance seems to be even more confusing -Hyperfocal distance is a point of focus where at a certain aperture, Half the distance from that point to Infinity, (which starts at 30 feet, and extends to as far as you are able to see)) will be in acceptable focus, The best lenses for hyperfocal distance are 80mm or wider ; telephoto lenses, because of their relative short depth of field, are rarely used. (Prime lenses have a scale on them for this, zooms do not) Using a 18mm setting on your zoom lens at f11, Hyperfocal distance is somewhere around 5 feet (1500mm), so depth of field at this aperture would be from 2 1/2 feet ( 750mm) to infinity, when focused at 5 feet. A good guideline for great depth of field for landscapes is to use the bottom focusing marker in your DSLR viewfinder, (either horizontal, or vertical) as this will focus 1/3 of the way into the distance, (It is on the lower third imaginary “Rule of Thirds” gridline!) ,as is usually recommended. [ NOTE: Unless your camera has depth of field preview, looking through the viewfinder all will not be in focus, because your lens, until you press the shutter button to make the shot, will be open at full aperture.]
Ken