Front/Back Focus vs DOF= 1/3:2/3?

jmg257 · 01-09-2012, 06:52 PM

I see numerous methods for testing lens/camera for front/back focus. They seem to all say that the resultant focused area should be equally distributed front and back of the focus point. But then I read that typical DOF extends 1/3:2/3 around the point of focus.
About Photography

Are these notions in conflict?

Thanks!

twitch · 01-09-2012, 07:31 PM

Try it for yourself in this link

The answer though is that it is not a fixed proportion, it varies depending on a few different factors (eg the focal length, the aperture and the subject distance).

jmg257 · 01-09-2012, 09:04 PM

Great info...thanks Twitch!

**Lowell Goudge** · 01-10-2012, 04:57 AM

The short answer is that at infinity it is split 1/3-2/3. It moves a little toward 50/50 as you focus in I think the absolute measure is based upon the ratio of subject / focal length

Anvh · 01-10-2012, 01:47 PM

Originally posted by Lowell Goudge

The short answer is that at infinity it is split 1/3-2/3. It moves a little toward 50/50 as you focus in I think the absolute measure is based upon the ratio of subject / focal length

lol

You do know what infinity means right?

At macro the focus distribution is 1:1 and past the hyper-focal distance the focus is 1:infinity

Depth of field

01-09-2012, 06:52 PM	#1
jmg257 Inactive Account Join Date: Jan 2012 Posts: 202	Front/Back Focus vs DOF= 1/3:2/3? I see numerous methods for testing lens/camera for front/back focus. They seem to all say that the resultant focused area should be equally distributed front and back of the focus point. But then I read that typical DOF extends 1/3:2/3 around the point of focus. About Photography Are these notions in conflict? Thanks!

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01-09-2012, 07:31 PM	#2
twitch Veteran Member Join Date: Nov 2009 Posts: 4,571	Try it for yourself in this link The answer though is that it is not a fixed proportion, it varies depending on a few different factors (eg the focal length, the aperture and the subject distance).

01-09-2012, 09:04 PM	#3
jmg257 Inactive Account Join Date: Jan 2012 Posts: 202 Original Poster	Great info...thanks Twitch!

01-10-2012, 04:57 AM	#4
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,887	The short answer is that at infinity it is split 1/3-2/3. It moves a little toward 50/50 as you focus in I think the absolute measure is based upon the ratio of subject / focal length

01-10-2012, 01:47 PM	#5
Anvh Veteran Member Join Date: Sep 2011 Posts: 4,616	Originally posted by Lowell Goudge The short answer is that at infinity it is split 1/3-2/3. It moves a little toward 50/50 as you focus in I think the absolute measure is based upon the ratio of subject / focal length lol You do know what infinity means right? At macro the focus distribution is 1:1 and past the hyper-focal distance the focus is 1:infinity Depth of field