Depth of Field guides on my lens

len20

Ok, so this is a little embarrassing, but I want/need to finally understand how to control the depth of field in every shot.

How do I read the guide on my lenses? My older lenses had two markers to show me the range (eg. 2 ft - 14 ft.) of what will be in focus. But some of my lenses have only one dash. I don't understand how to read them.

Please help.

alexf

Might depend on the lens. This happens in older MF lenses. Generally you have an aperture ring you can change and a focusing ring. Colored lines show the distance between two lines of the same color, for different apertures. So the distance between two vertical lines of the same color will be much bigger at f/22 than at f/2.8. The lines will also point (to the min and max focus distance (in meters and feet).

For example (this changes on every lens as it depends on its characteristics and focal length), if you focus on a subject at say 3 meters (9ft), at f/22 you might get a depth of focus (DOF) with everything in focus between 2 meters and close to infinity. At f/2.8 the same focus point will be much narrower, maybe between 2.8 meters and 3.6 meters.

Whenever you change aperture, DOF changes. The bigger the aperture (smaller number - e.g. 2.8), the narrower the DOF. When you focus at a certain distance, you actually get everything in focus that is a little closer than the focus distance and more behind (further) than the focus distance. How much depends on the aperture. HTH

len20

I really do understand the concept of dof and how it relates to aperture. I've even done some studying of the nifty diagrams. I just want to be able to glance down at my lens after finding my focal point and know where my dof begins and ends without doing the math.

My canon 70-200 mm 2.8L has only one slash on the guide, not two. I just don't know how to read that guide.

pathfinder

Many of the "modern" lenses with AF, especially zooms, no longer have the two depth of field markers on them, like the Canon EF-S 17-55 f2.8 IS has no dof marks at all

SO you can use a table depth of field guide or a program like DOF master. I know there are Apps for the iPhone that will display depth of field as well.

Or do what I do, use the depth of field preview button on the side of your camera that will stop down your lens to the actual planned shooting aperture. It will look real dark at first as the aperture stops down, but if you are patient, and wait 10-15 seconds, your eye will begin to dark adapt, and then you will begin to actually see the depth of field through your viewfinder.