Depth of field (Page 3): I use this formula A LOT in my computer vision designs... But it is only an approximation and assumes that the lens is infinitely short. In practice, that...

jlg1000 Loc: Uruguay / South America

TriX wrote:

Yes, assuming the same aperture, distance to subje... (show quote)

I use this formula A LOT in my computer vision designs... But it is only an approximation and assumes that the lens is infinitely short.
In practice, that means that the lens length can be neglected next to the distance to the target.

So, in the case of teles shooting at very log distances, it is true... But a zoom and a prime with the same aperture will differ il length, so if you do portraiture, this effect cannot be neglected

As a sidenote, the correct DOF formula is akin to a transmission line... It has infinite terms.

jlg1000 Loc: Uruguay / South America

User ID wrote:

Yes.
A prime lens is just a zoom thaz been locked at one focal length. Acoarst some mechanical parts are omitted by design.

Yeah right... and a wall is a door locked at one position. Also, some mechanical parts are omitted by design.

Please do yourself a favor, read some book on theoretical optics.

tcthome Loc: NJ

sippyjug104 wrote:

My favorite pastime is tabletop micro/macro focus ... (show quote)

Thanks for the explanation on what N & M are.

StRoch Loc: New Orleans

Ditto, ROTFLMAO. I come here for laughs and I’m never disappointed.

Craig Meyer Loc: Sparks, NV

Just reviewing the posts, and not referring to texts, let's understand that Depth of Field may be a calculated property. BUT, (Sorry admin!) the quality of Depth of field is also called Depth of "Apparent" focus. And the close observation of the image looks for "Circles of confusion." With such subjective criteria set forth, begging for a precise answer to such a hypothetical question, actually begs the question.

The simple assumption is that on the same camera, a 35mm prime and a zoom set to 35mm and the same aperture and capturing the same scene/subject will yield largely the same DOF. it would be certainly good for a starting point.
After that it is up to the photographer to produce the image that was pre-visualized. You DO pre-visualize.................
Smile,
C

Gdelvecc Loc: Dallas, TX

Thank you for a clear and concise answer!!

Craig Meyer Loc: Sparks, NV

Gdelvecc wrote:

Thank you for a clear and concise answer!!

Thanks,
C

User ID

TriX wrote:

You got a problem with science?

It is you who have the "problem with science". But its not just you alone, so nothing personal here. The problem is Hogsters toss it out to just muddy the waters (and try to look really smart).

Acoarst youre all just observing UHH Sacred Tradition. After all, it plainly comes with the territory.

gwilliams6

Rongnongno wrote:

Actually NO. br br Each lens is build for a purpo... (show quote)

Sorry you are not correct Ron.

Three things determine depth of field. 1) lens aperture; 2) lens focal length: 3) distance from subject to lens

If two lenses are truly both 35mm as listed (many lenses actually vary a bit in focal length from their listed focal length) then the depth of field at the exact SAME lens focal length, SAME aperture, and at the SAME distance from subject to lens, would have the same amount of depth of field.

Differences in the optical quality of the glass, distortion, etc. have NOTHING to do with depth of field at all. Lens compression and lens perspective doesn't factor in depth of field.

You need to know the science here. As a Professor of Photographer at a state university I have to know and teach this to my photography students .Decades as a pro and with my Masters Degree in Digital Photography, I know the optical science here.

Adorama TV's Mark Wallace has an easy to understand video on depth of field:

https://www.youtube.com/watch?v=95Igz6QM7Ag

Cheers

TriX Loc: Raleigh, NC

User ID wrote:

It is you who have the "problem with science". But its not just you alone, so nothing personal here. The problem is Hogsters toss it out to just muddy the waters (and try to look really smart).

Acoarst youre all just observing UHH Sacred Tradition. After all, it plainly comes with the territory.

And your issue with the DOF formula and definition (not from me, from Wiki) is? Please tell us why understanding the components/drivers of DOF is not useful. Maybe you could instruct Mr. Williams (above)?

Harry0 Loc: Gardena, Cal

Craig Meyer wrote:

Just reviewing the posts, and not referring to tex... (show quote)

Another point to this is tat most AF lenses will pit the subject @ 2/3 away.
So @ 1/3 behind the subject, and 2/3 foreground will be in focus.
I like manual focus.
I can take my lens at f:1.8, and get the batter and the catcher in focus. Or just the batter.
I used MF film cameras, and I'm used to shooting at f:8. Nice DofF range.
That I can move back and forth and create different shots.
From pitcher, batter and catcher to batter catcher and faces behind the backstop.
I never did get into just getting the eyeball skin in focus....

Ysarex Loc: St. Louis

Harry0 wrote:

Another point to this is tat most AF lenses will pit the subject @ 2/3 away.
So @ 1/3 behind the subject, and 2/3 foreground will be in focus.

This is incorrect. Most AF lenses will focus on the subject.
DOF distributes unequally around the focus plane such that more is in focus behind the subject than in front. DOF does not necessarily distribute in a 1/3 -- 2/3 proportion around the focus plane.

frankraney Loc: Clovis, Ca.

Ysarex wrote:

This is incorrect. Most AF lenses will focus on the subject.
DOF distributes unequally around the focus plane such that more is in focus behind the subject than in front. DOF does not necessarily distribute in a 1/3 -- 2/3 proportion around the focus plane.

User ID

Harry0 wrote:

Another point to this is tat most AF lenses will pit the subject @ 2/3 away.
So @ 1/3 behind the subject, and 2/3 foreground will be in focus.
..........

Typical UHH mythology from an apparent nonuser of the systems discussed.

Harry0 Loc: Gardena, Cal

User ID wrote:

Typical UHH mythology from an apparent nonuser of the systems discussed.

I shoot Nikon, and most of my lenses will do this when in auto focus.
Subject and foreground in focus, backgriound fades to bokeh bits.
By design.
"Father, they doth knowest not ..."