I thought the following photograph represents depth of field (or lack thereof).

 

This was taken on a Canon 5D MKII using the Canon 100L macro lens with an attached SMC diopter at :

1/250

ISO 200

f/22

 

Even at f/22, DoF is so thin that the subject's left eye is OoF. 

 

The purpose of this thread is to illustrate the effects of aperture and DoF at such close ranges.

 

I wonder if the diopter also affected DoF? Does anyone have any information or articles on this?

 

 

 

Edited June 17, 20241 yr by hedonist222

 

 

Edited June 17, 20241 yr by hedonist222

My thinking is that with tele (macro) lenses the focus plane is much less curvy than with wide angle lenses. And so the effect of closing down the aperture with macro lens will be much less pronounced than that with wide angle.

 

In another angle the focus plane filling the sensor will be shape of globe with wide angle while just a sliver of it with macro. And therefore the effect of aperture relative to relative size of DOF will be limited.

Hi @hedonist222 - nice find and image!
 

A focal plane can be thought of as a percentage of distance depth in the entire scene.  In short, the smaller the overall scene being photographed, the smaller the distance in focus, or thinner the focal plane.  The thinner the focal plane, the smaller the aperture required for depth of field sharpness. 
 

Typically we use a macro lens to make a tiny creature or detail fill the sensor.  This reduces the overall scene size and greatly reduces the depth of the focal plane due to less physical distance from the front to back of the scene.  When shrinking the overall scene even further via diopters or super macro lenses, the distance in the focal plane decrease even more quickly requiring a much smaller aperture to compensate.
 

As an example, a wide reefscape or wreck can easily be photographed at f/11 or f/13 with DoF basically to infinity.  This is because it is a very large scene with a relatively large difference in the focal plane distances.  Details in the far distance naturally fall out of our eyes ability to see which makes the focus falloff appear normal.  
 

A small macro scene, however, will often require a minimum of f/16 to achieve a deep enough DoF that looks natural to our eyes.  This also results in out of focus areas being much more easily seen, again due to the thin focal planes.  The addition of a super macro tool further shrinks the scene thus requiring f/22, or beyond.  (Obviously different apertures for creative desires).  
 

Due to the thin focal plane, the angle and positioning of the camera becomes equally critical.  If you wanted both eyes to be in focus in your example, another solution is to rotate the camera slightly so both eyes are on the same ultra thin focal plane. 

An environment based on mm’s of distance is what makes macro, especially super macro, such a challenging and rewarding type of uw photography.  

 

Edited June 17, 20241 yr by ChipBPhoto

The diopter (which SMC was it?) will certainly change DoF, as it reduces the working distance. DoF depends on (i) focal length, (ii) aperture and (iii) working distance.

See e.g. the table in the link: https://www.photopills.com/calculators/dof-table

 

The table is for use over the water. For a lens behind a planport, the focal length increases by approx. 33% ("diving mask effect"). There are other inexactness as well, but the table + corrected focal length will give you a reasonable approximation...

 

Wolfgang

 

Edited June 17, 20241 yr by Architeuthis

2 hours ago, Architeuthis said:

The diopter (which SMC was it?) will certainly change DoF, as it reduces the working distance. DoF depends on (i) focal length, (ii) aperture and (iii) working distance.

See e.g. the table in the link: https://www.photopills.com/calculators/dof-table

 

The table is for use over the water. For a lens behind a planport, the focal length increases by approx. 33% ("diving mask effect"). There are other inexactness as well, but the table + corrected focal length will give you a reasonable approximation...

 

Wolfgang

 

SMC-1

2 hours ago, Architeuthis said:

The diopter (which SMC was it?) will certainly change DoF, as it reduces the working distance. DoF depends on (i) focal length, (ii) aperture and (iii) working distance.

See e.g. the table in the link: https://www.photopills.com/calculators/dof-table

 

The table is for use over the water. For a lens behind a planport, the focal length increases by approx. 33% ("diving mask effect"). There are other inexactness as well, but the table + corrected focal length will give you a reasonable approximation...

 

Wolfgang

 

Actually depth of field is down to magnification and aperture and to me this is the best way to think of it.  Focal length changes DOF due to a change in magnification.  The problem with focal length is it is not constant in most macro lenses - it reduces as you focus closer.  For pretty much all normal lenses DOF is constant at a given magnification and aperture.

 

There are of course special cases such as it appears the the new FCP which does some funky stuff with the image to feed it into a macro lens where it appears the DOF is thinner than equivalent magnification in a fisheye lens.

 

On the original question about shallow DOF yes diopters reduce DOF because they increase magnification.  In this sort of photography getting the right angle of approach and picking exactly what bits you want in focus is a large part of getting a pleasing image.  YOu have to think about how you will approach the critter to get the focal plane where you want it.

 

THis is the curse and challenge of macro photography.   I've recently started focus stacking on land and it rapidly teaches you how thin the DOF is at high magnification and how many shots you need to take to get a 3D object all in focus - it's a lot and I'm using a m43 sensor which has more DOF as you need less magnification to fill the frame.