RichJ207 Loc: Sammamish, WA

Looking through photography books about DOF, they describe the distance from the object as the distance measured from the lens. I’m using a 16-35mm lens at 35mm, taking close up pictures of jewelry using autofocus and attempting to have a few inches of DOF. Is the distance really measured from the front element of the lens, the point closest to the object being photographed? It makes a big difference, when I enter information into a DOF calculator, whether I measure from the shutter plane or the front element of the lens. Thanks for clarification!

ORpilot Loc: Prineville, Or

I don't know how your calculator is set up but in the film days it was measured from the film plane which was always marked on top of the camera. Most mirrorless cameras have "focus peaking" this lets you visually see what will be in focus. You can always do a manual check. You put a ruler, tape measure down, in your studio setting, shoot the photo at several zoom settings with several F-stops and then you can actually see on your ruler what is in focus. Where it starts and where it stops. If you are using an old film lens and some newer manual lenses, they have the DOF scales on them. There is always more than one way to skin a cat.

Najataagihe

Calculator???

Rulers???

Angst???

Just bracket and chimp!

CHG_CANON Loc: the Windy City

The FAQ of a popular online DOF calculator seems to address:

http://www.dofmaster.com/faq.html

Is the 'subject distance' measured from the front of the lens or from the film plane?

This question is relevant only for close-up and macro photography. For other photography, any error caused by measuring subject distance from the wrong location is neglible.

The depth of field equations are derived from the "thin lens" equation, which assumes a single lens element with no thickness. And, subject distance is measured from the thin lens. So, technically, subject distance is measured from the front of a lens.

However, that doesn't apply directly to a photographic lens. These lenses have many elements, and the front of a lens isn't necessarily the location that subject distance is measured from. The actual location is something called the "front nodal point" of the lens. The location of the front nodal point isn't documented by lens manufacturers, nor is it easy to find experimentally.

I measure subject distance from the front of the lens. I believe that the nodal point would actually be somewhere between the front and rear elements. But, by assuming it is at the front of the lens, I get a conservative estimate of the depth of field from the calculator. In other words, the depth of field calculation shows less depth of field than will actually be seen in the photo.

bleirer

It is from the sensor. Here is a good'n for close up and macro https://www.photopills.com/calculators/dof-macro

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Sensor plane.

bleirer

Now i am not so sure. You need a pc to run the applet but the explanation is clear. https://graphics.stanford.edu/courses/cs178/applets/dof.html

bleirer

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GoofyNewfie Loc: Kansas City

Measure from the focal plane indicator circled in yellow below.

(Download)

bleirer

Great article https://www.photopills.com/articles/depth-of-field-guide

From their glossary of terms: Subject Distance - The distance between the lens of a camera and a subject being photographed.

RichJ207 Loc: Sammamish, WA

Thanks to all of you who responded to the DOF question that I was really hesitant to ask. Now, since it looks like there may be two approaches, it seems like I would need to know what approach was used by the author of any DOF calculator before I know how to apply it to my close-up photo application. The front of the 16-35F4 lens is about 16” away from the jewelry object that has a depth of about 4”, so the distance from the front of the lens to the sensor plane in the camera body brought up the question of what reference point was meaningful for the calculator. Thanks again for the inputs!

User ID

Forget those parroting “film plane” and “focal plane”. You are calculating DoF, not magnification.

You can reasonably measure from the “thin lens” already described earlier. OK now, THIS is where you need to use that film plane marker .... you’ll use it to locate where, inside your complex lens, is the position of the virtual thin lens.

Inside the bulk of your complex lens the location of the virtual thin lens is, natcherly enuf, 1 FL forward of the film plane when focus to infinity.

With zooms you’ll usually know only an approximate FL, but DoF is more subjective than scientific, so obsessive accuracy is pointless anywho.

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The virtual thin lens is seldom near the middle of a complex zoom. Even with primes it can get weird. Put that big bulky 20mm prime on your SLR and location of the virtual thin lens is way inside the camera, not inside the lens barrel at all. OTOH with a compact 135/2.8 prime the virtual thin lens can be hovering in space outside the lens barrel somewhere within the lens hood ... cuz the lens hood is often 135mm from the film plane. It’s magic.

kymarto Loc: Portland OR and Milan Italy

I'm not understanding why the numbers are important to you when you can see exactly what you going to get by looking through the viewfinder. If your DOF is too shallow you might consider focus stacking, which can give you exactly how much you want in focus while maintaining a nicely blurred background.

bleirer

After thinking on it a bit, and playing with the applet I posted above that shows and uses the formula and the impact of the variables, there are two distances and their ratio involved. One from the subject to the lens (whatever it's virtual position is in a complex lens) called subject distance or focusing distance and one from the lens or its virtual position to the sensor. Moving the lens farther from the sensor by focusing makes the sensor to lens distance larger while making the lens to subject distance smaller (this is the subject distance typed into the calculator), allowing you to focus on closer objects. Making the lens to sensor distance shorter makes the lens to subject distance longer, allowing focus on farther objects. Until the rays entering are parallel, which is infinity focus.

Here is a proof of concept: type a number in a dof calculator smaller than any lens minimum focusing distance, one inch for example. The calculator still gives a result. This would be impossible if was using the sensor to subject distance. Since the subject would be inside the camera or lens.

Notorious T.O.D. Loc: Harrisburg, North Carolina

Yes, I assume there is a good reason for the focal plane being marked on my DSLR camera bodies...