Online Depth Of Field Calculator

[nulla]

Not sure if this site has been posted before or if I should have posted this in another thread... so mods please move if so.

I found this site very helpful.

Online Depth of Field Calculator

Its a depth of field calculator.

Select Camera, Lens, Focal Lenth and bingo


Neil

[Damn Brit]

It has been posted before Neil but it doesn't hurt to revive it, in fact I think I'll put it in the article section.
Thanks for bringing it up again. I'll change the title and make it a sticky.

[fs999]

Thank you for the tip !

[pilgrim02360]

Thanks for the info. F.Y.I. this site can be accessed with a PDA/Smartphone (whatever you call these things). I use a Palm Treo 755p and the site works with no problem.

[code4code5]

iPhone users, try this. It's only $0.99 at the app store and works great. Camera and US/Metric are customizable.

iTunes Store

[systemA]

Very nice!

[falconeye]

Originally Posted by code4code5

iPhone users, try this. It's only $0.99 at the app store and works great. Camera and US/Metric are customizable.

Nice, as the title says, "Simple DoF Calculator".

I found this program useful too:

Photocalc

has a couple additional features which I personally like.

[Matthew]

I have a problem with the Online Depth of Field Calculator web site.
If you change between sensor sizes, it changes the depth of field figures.
Surely depth of field stays constant for a given lens at a given aperture and focal distance. After all, if you change sensor size you are only cropping (or uncropping the image).
Now I understand that if I want to shoot the same subject at the same size with a different sensor size, I will need to change my camera-subject distance (and thus focusing distance) or change my focal length and this will change my depth of field if using the same aperture. However this is not what the Online Depth of Field Calculator is claiming to do.
Any thoughts?
Have I missed some important point?
Do I not understand what the term "depth of field" means?

[falconeye]

Originally Posted by Matthew

Do I not understand what the term "depth of field" means?

Yes, you don't.

Cropping or approaching a printed photo hanging on a wall for closer inspection both changes the DoF.

You can find endless debates about the topic elsewhere in the forum and please go there to learn more about all this.

Google: "depth of field" sensor site:pentaxforums.com

[Matthew]

Originally Posted by falconeye

Yes, you don't.

Done my reading now, even though I hate being told to do a Google search that does not improve the signal to noise ratio.
It would seem that the definition has been reworked.

Macquarie Dictionary: "depth of field, n. Optics. The range of distances along the axis of a camera or other optical instrument, in which an object will produce a reasonably clear image."

Depth of field - Wikipedia, the free encyclopedia "The DOF is determined by the subject distance (that is, the distance to the plane that is perfectly in focus), the lens focal length, and the lens f-number (relative aperture)."

In many places on the web this definition has been extended to include other practical factors as Falk has pointed out. I think that using a new term or appending a qualifier to the term would make things much clearer. The original definition still has merit on its own. After all, the lens is still projecting exactly the same image on exactly the same area of sensor no matter what it is mounted on. What you and the sensor do with the image, or extra image area afterwards is another matter.

[falconeye]

Originally Posted by Matthew

Macquarie Dictionary: "depth of field, n. Optics. The range of distances along the axis of a camera or other optical instrument, in which an object will produce a reasonably clear image."
[...]
After all, the lens is still projecting exactly the same image on exactly the same area of sensor

With this bit of preparation, the core idea of the definition of DoF can easily be worked out (and I don't agree that the term's meaning has changed over the past 100 years -- it is carved in stone and teached in optics classes; the interweb sometimes has problems to keep simple things simple ).

1. Lens projecting exactly the same image: Yes, and out of context, DoF would always be zero. Optically, only one subject plane is in focus and all other parts of a subject are not sharp.

2. Therefore, reasonably sharp is the keyword here.

3. As this term needed a precise definition, an otherwise sharp point is allowed to smear out over a finite-sized area, the Circle of Confusion (CoC). And its size matches the human eye's capabilities. Typically, the Zeiss formula is used:
CoC = image diagonal / 1730


So, whenever the image diagonal changes (e.g., when cropping), so does DoF. Note that pixelpeeping is cropping because your monitor is limited in size.



If you go thru all the math, you'll see that independently from sensor size, focal length and everything else, DoF only depends on three factors:
- The distance to the subject [m]
- The physical diameter of the lens' aperture in millimeter [mm]
- The Field of View (FoV) of the image, in degrees [°]

Of course, the 2 parameters, FoV and lens' aperture in millimeter can be computed from 3 variables (sensor size, focal length and f-stop). However, this obscures things and sometimes leads to endless debates

[jstevewhite]

Originally Posted by falconeye

1. Lens projecting exactly the same image: Yes, and out of context, DoF would always be zero. Optically, only one subject plane is in focus and all other parts of a subject are not sharp.

2. Therefore, reasonably sharp is the keyword here.

3. As this term needed a precise definition, an otherwise sharp point is allowed to smear out over a finite-sized area, the Circle of Confusion (CoC). And its size matches the human eye's capabilities. Typically, the Zeiss formula is used:
CoC = image diagonal / 1730

Based on the capabilities of a theoretical human eye, that is. The Zeiss formula is based on assumptions involving final magnification, visual acuity, and assumed viewing distance. This leads to the inescapable, counter-intuitive, and fractious reality that if you have better vision, you'll get less depth of field, and the converse. And such gems as: "If you don't have enough DOF, step back from the image."

So, whenever the image diagonal changes (e.g., when cropping), so does DoF. Note that pixelpeeping is cropping because your monitor is limited in size.

If you go thru all the math, you'll see that independently from sensor size, focal length and everything else, DoF only depends on three factors:
- The distance to the subject [m]
- The physical diameter of the lens' aperture in millimeter [mm]
- The Field of View (FoV) of the image, in degrees [°]

Of course, the 2 parameters, FoV and lens' aperture in millimeter can be computed from 3 variables (sensor size, focal length and f-stop). However, this obscures things and sometimes leads to endless debates

Hehe - you pointed out the pig-in-a-poke, above, then did some hand waving to turn the subjective ( "reasonably sharp" and "visual acuity" ) into precise-sounding math. The reason this subject generates so much debate is that the foundational assumptions are completely subjective. These debates raged back in the days of film. We can all see *something* is going on, but it's really tricky to actually quantify from an experiential standpoint. The math certainly means something, but it's at least one layer of abstraction away from what we're looking at, as, likely as not, you and I would see different DOF in a print at 8x10.

I'm not disagreeing with your post, I'm just pointing out that there are gotchas in there that make it impossible to remove the contentiousness from this topic.

One note: One place where "The lens projects the same image" is an accurate description of affairs is in Macro applications. 1:1 is 1:1, no matter who's leg you're pulling, and the DOF is constant across sensors, and dependent on the visual acuity of the viewer.

[falconeye]

Originally Posted by jstevewhite

I'm not disagreeing with your post, I'm just pointing out that there are gotchas in there that make it impossible to remove the contentiousness from this topic.

This thread was opened by somebody who was completely misled as probably is the majority of people discussing the topic.

So, this thread was opened as "DoF for beginners". And I think we already made good progress here.

Your post clearly belongs into category "DoF, advanced topics".

I don't disagree with what you have written. I am just not sure that it helps to grasp the very idea what DoF actually means.

[Duck Dodgers]

I just noticed the iphone screenshot. WTH? Focus point in the example is 5ft 26in? Isn't that the same as 7ft 2in? Or 86 inches? What kind of weird, illogical, un-intuitive interface is that?

[Pentax_XTC]

http://iphone.dofmaster.com/

It's the same as the paid app, which is $1.99 USD, but if you have a data connection available there is no charge!