Depth of Field Calculator | With 35mm Equivalency

Depth of Field Calculator with Camera Equivalency Calculator

 

The depth of field calculator allows you to find the depth of field of any aperture of any lens at any distance. The depth of field calculator also includes a 35mm equivalency calculation so you can see equivalent lens crop and depth of a given aperture on smaller or larger sensor cameras compared to full frame 35mm. 

 

 

You may notice that depth of field gets shallower as you use smaller sensors. This is because the calculator assumes all of the sensors are of the same resolution. As you move to a smaller sensor, the viewing or printed resolution stays the same, but you will see a cropped image by a crop factor of the given sensor.

A 50mm APS-C lens will have a cropped field of view of 75mm. If you compare a full frame 24 megapixel sensor to a 24 megapixel APS-C camera shooting the same image at the same distance, you’ll be looking at that 1.5x cropped depth of field of the APS-C image with much more resolution which results in shallower perceived depth of field.

What this means is, higher resolutions cameras technically produce shallower depth of field because you get a more detailed view of the circle of confusion. However, if you were to stand back and look at the images in Lightroom without cropping in, the perceived depth would be the same.

These calculations are based off a circle of confusion of standard photo viewing distances.

 

Circle Of Confusion Sensor Values

Medium Format = 0.05mm
Full Frame = 0.03mm
APS-C = 0.02mm
APS-C Canon = 0.019mm
Micro 4/3 = 0.015mm
1″ = 0.011mm

 

These values are adequate for the sake of calculations, but depth of field and resolution isn’t that simple of course.

These values are standard values based off un-cropped images at a standard viewing distance and these numbers come from and are used by the camera manufacturers themselves.

 

Calculating DoF Based On Sensor Resolution

If you wanted to see a more defined depth of field of your camera based on sensor resolution without the subjectivity of viewing distance and print size, you would have to take a value of 2x the sensors pixel pitch to produce a circle of confusion of a given sensor. However, the reason we don’t do this is because you would also have to calculate the effects of diffraction of different aperture values based on the pixel pitch of the sensor. Diffraction will affect the size of a lenses Airy disc based on aperture, which will affect the total resolution output of a lens.

 

The calculator below allows you to enter you own circle of confusion, so that you can play around with the resolution of different sensors.

To find the circle of confusion of your camera, you would calculate 2x (pixel pitch) in mm. 

For example the Sony A7III has a pixel pitch of 5.91 microns. 5.91 / 1000 = 0.00591mm. 0.00591 x 2 = 0.01181 or 0.012. 

You could say the Sony A7III has a possible CoC between 0.012 and 0.03 based on subjectivity of viewing. Program in 0.012 into the CoC of the calculator will give you a much shallower depth of field. 

 

 

Circle of confusion = the disc or cone of light a lens produces that is considered acceptably sharp or in focus.

 

The Real Science Of Lens Equivalency | Exposing The Myth

The above information is all based off a viewing distance and subjectivity of human perception and the assumption that we all have 20/20 vision. It also assumes that as you move to a smaller sensor, you increase the resolution.

In reality, based on the physics of light, an f1 lens always produces the same depth no matter what sensor you stick behind it. A lens doesn’t care about crop factor or the circle of confusion of a sensors pixel pitch. An f1 lens produces the same depth on a full frame camera as it would on a APS-C camera. That is just the laws of physics, it’s not magically changing its cone of focus because of a different sensor.

As an example, what if we were to shoot the Sony A7rIII full frame with a given lens, a 50mm f1, then shoot in APS-C crop mode with the same lens 50mm f1. We would have the same pixel pitch and same circle of confusion but a different perspective of 75mm.

So we could calculate in the maximum circle of confusion of the A7rIII, 2 x 4.51microns = 0.009mm. This gives us an actual circle of confusion of the Sony A7rIII if we were to crop or view close. 

This gives us a depth of field value of: 2.59″

This means the Sony A7rIII has a maximum depth of field of 2.59″ regardless of viewing subjectivity.

Now, we can do our APS-C crop with 18 megapixels, but since we don’t have any more megapixels to crop into, we can use the standard CoC given by APS-C sensors with a value of 0.02mm with a 75mm crop factor.

This gives us a depth of field of 2.54″

So the A7rIII full frame no crop with maximum CoC value produces a result of 2.59″

The A7rIII 18megapixel APS-C with a standard CoC value produces 2.54″

They are nearly identical.

 

Depth of Field Equivalency | Conclusions

 

A lens always produces the same depth of field regardless of the sensor you put behind it, but as you move to larger or smaller sensors, you will have to change your lens focal length or distance to match perspective and this will change the depth of field of a lens.

For real world use, I added a 35mm lens equivalency and aperture value that would produce the same results at the same distance to help settle any confusion. You would have to adjust exposure with shutter or ISO to compensate for the different aperture because no matter what camera you use, an f1 lens will always allow more light in than an f1.5 lens as long as their light transmittance value is the same.

Which expels another myth, “bigger sensor gather more light.”