Calling all portrait photographers!

[Destin]

This is wrong.

Nope.

We've been through this before and I've provided the math that proves this is wrong.

Again nope.

If you believe there is some math out there thave proves that if you take an AF-S 50mm f1.8 and depending upon if you use it on an APS-C or a full frame sensor the DoF will change with the sensor size then I'm sorry but you're not understanding the math or the math is wrong.

The sensor size doesn’t change the DOF directly.

The lens will have the same DOF at the same focus distance on any sensor.

But the sensor size indirectly changes the depth of field because to get the same field of view with a full frame sensor, you’re closer to the subject. And shooting sports, you’ll have to use a longer focal length to achieve the same field of view, again, effectively giving you a thinner depth of field.

Therefore: Sensor size is a direct variable in the depth of field equation. There’s a reason that professional photographers choose full frame bodies, and this is one of the big ones.

So yes, sensor size does change your depth of field.

 

[Designer]

There must be some purpose in the DOF calculator for asking what camera. Other than figuring the relative size of the sensor, I can think of no other reason.

 

[Destin]

There must be some purpose in the DOF calculator for asking what camera. Other than figuring the relative size of the sensor, I can think of no other reason.

That’s exactly why. Some only specify Brand and sensor size.

 

[Ysarex]

There must be some purpose in the DOF calculator for asking what camera. Other than figuring the relative size of the sensor, I can think of no other reason.

You are correct. A DOF calculator requires the sensor size in order to complete the calculations. There is no other reason to require it be entered.

Joe

 

[Ysarex]

This is wrong.

Nope.

We've been through this before and I've provided the math that proves this is wrong.

Again nope.

If you believe there is some math out there thave proves that if you take an AF-S 50mm f1.8 and depending upon if you use it on an APS-C or a full frame sensor the DoF will change with the sensor size then I'm sorry but you're not understanding the math or the math is wrong.

The sensor size doesn’t change the DOF directly.

Yes it does.

The lens will have the same DOF at the same focus distance on any sensor.

No. The same lens at the same f/stop and same focus distance will have different DOF on different size sensors -- see illustration:

The illustration uses the DOF calculator at DOF Master. Don Fleming has his math right.

Joe

But the sensor size indirectly changes the depth of field because to get the same field of view with a full frame sensor, you’re closer to the subject. And shooting sports, you’ll have to use a longer focal length to achieve the same field of view, again, effectively giving you a thinner depth of field.

Therefore: Sensor size is a direct variable in the depth of field equation. There’s a reason that professional photographers choose full frame bodies, and this is one of the big ones.

So yes, sensor size does change your depth of field.

 

[Destin]

This is wrong.

Nope.

We've been through this before and I've provided the math that proves this is wrong.

Again nope.

If you believe there is some math out there thave proves that if you take an AF-S 50mm f1.8 and depending upon if you use it on an APS-C or a full frame sensor the DoF will change with the sensor size then I'm sorry but you're not understanding the math or the math is wrong.

The sensor size doesn’t change the DOF directly.

Yes it does.

The lens will have the same DOF at the same focus distance on any sensor.

No. The same lens at the same f/stop and same focus distance will have different DOF on different size sensors -- see illustration:

View attachment 148084

The illustration uses the DOF calculator at DOF Master. Don Fleming has his math right.

Joe

But the sensor size indirectly changes the depth of field because to get the same field of view with a full frame sensor, you’re closer to the subject. And shooting sports, you’ll have to use a longer focal length to achieve the same field of view, again, effectively giving you a thinner depth of field.

Therefore: Sensor size is a direct variable in the depth of field equation. There’s a reason that professional photographers choose full frame bodies, and this is one of the big ones.

So yes, sensor size does change your depth of field.

That makes no sense whatsoever.

You’re telling me that taking my 50mm 1.8 off of my D500 and putting it onto my D750 is going to magically change the optical formula of the lens?

This makes zero sense whatsoever and I will not believe it until someone can explain the actual physics to me. The DOF calculator has to be wrong here because the physics of how a lens manipulates light don’t just magically change when you put it on a different camera body.

The only reason full frame sensors provide a thinner depth of field is that they force you to get closer to the subject with the same focal length.

I’ll be going home to test this out after work for sure. But I have a pretty damn good understanding of physics, and that’s not how it works.

 

[Ysarex]

This is wrong.

Nope.

We've been through this before and I've provided the math that proves this is wrong.

Again nope.

If you believe there is some math out there thave proves that if you take an AF-S 50mm f1.8 and depending upon if you use it on an APS-C or a full frame sensor the DoF will change with the sensor size then I'm sorry but you're not understanding the math or the math is wrong.

Don Fleming doesn't have his math wrong. (DOF Master)

Sean McHugh doesn't have his math wrong. (Cambridge in Colour)

Those are two highly respected authorities whose calculators demonstrate that you're wrong. The burden then is on you to reference DOF calculations that support your position -- a link to a DOF calculator please or the math formulas. Until you do you've been proven wrong.

Joe

 

[Ysarex]

This is wrong.

Nope.

We've been through this before and I've provided the math that proves this is wrong.

Again nope.

If you believe there is some math out there thave proves that if you take an AF-S 50mm f1.8 and depending upon if you use it on an APS-C or a full frame sensor the DoF will change with the sensor size then I'm sorry but you're not understanding the math or the math is wrong.

The sensor size doesn’t change the DOF directly.

Yes it does.

The lens will have the same DOF at the same focus distance on any sensor.

No. The same lens at the same f/stop and same focus distance will have different DOF on different size sensors -- see illustration:

View attachment 148084

The illustration uses the DOF calculator at DOF Master. Don Fleming has his math right.

Joe

But the sensor size indirectly changes the depth of field because to get the same field of view with a full frame sensor, you’re closer to the subject. And shooting sports, you’ll have to use a longer focal length to achieve the same field of view, again, effectively giving you a thinner depth of field.

Therefore: Sensor size is a direct variable in the depth of field equation. There’s a reason that professional photographers choose full frame bodies, and this is one of the big ones.

So yes, sensor size does change your depth of field.

That makes no sense whatsoever.

You’re telling me that taking my 50mm 1.8 off of my D500 and putting it onto my D750 is going to magically change the optical formula of the lens?

Nope -- not suggesting anything of the kind.

This makes zero sense whatsoever and I will not believe it until someone can explain the actual physics to me. The DOF calculator has to be wrong here because the physics of how a lens manipulates light don’t just magically change when you put it on a different camera body.

The calculator is correct and you are correct about the behavior of optics. The problem results from you're thinking that DOF is measured or defined at the film or sensor plane. That's not how DOF is defined and unless we want to change what we're talking about we have to work with the long established (older than us) and industry accepted definition of DOF. DOF is defined as a characteristic of human visual perception measured when we view a print (final image). So there is no standard measurement of DOF that occurs for example at the sensor. When all of the variables are accounted for in the process toward realizing the final viewing image the sensor or recording media size is taken into consideration as a determinant variable. It's a value in the math formulas. I think that's proof enough.

The only reason full frame sensors provide a thinner depth of field is that they force you to get closer to the subject with the same focal length.

This is a bad way to think about the comparison. To make an appropriate comparison between cameras of different sensor size you need to compare the result when both cameras are used to take the same photograph. Otherwise it's not really a comparison.

Joe

I’ll be going home to test this out after work for sure. But I have a pretty damn good understanding of physics, and that’s not how it works.

 

[snowbear]

When a Nikon full frame camera is switched to crop (DX) mode, is only the portion of the sensor matching the size of the APS-C sensor being used, or is the just the full frame image cropped to the APS-C sized via software/firmware? If the sensor's zone of activation changes, that may be a real way to test (or demonstrate) it.

 

[Ysarex]

When a Nikon full frame camera is switched to crop (DX) mode, is only the portion of the sensor matching the size of the APS-C sensor being used, or is the just the full frame image cropped to the APS-C sized via software/firmware? If the sensor's zone of activation changes, that may be a real way to test (or demonstrate) it.

The whole point is to be able to use a DX lens on an FX body so the only thing that makes sense is that the smaller sensor area is used -- hardware not software -- so yes that works as a testing methodology. It's important to stress however that the only test to conduct that makes any sense is to use the two sensor sizes (cameras) to take the same photo.

Joe

 

[snowbear]

I would think the DX-moded sensor on any FX body would have the same CoC as any DX body (0.019mm). Something to try in the next day or so.

 

[Destin]

When a Nikon full frame camera is switched to crop (DX) mode, is only the portion of the sensor matching the size of the APS-C sensor being used, or is the just the full frame image cropped to the APS-C sized via software/firmware? If the sensor's zone of activation changes, that may be a real way to test (or demonstrate) it.

The zone of activation changes, which is how the crop factor is formed. The camera essentially just crops the image in software after you press the shutter but before you save it.

That’s exactly how I’ll test it on my D750 when I get home.

If I take an image in Fx mode and then crop it to match an image taken in Dx mode, I’m guaranteeing that I’ll get the same exact image. And I’ll take the same image with my D500 as a safety net to compare.

Extremely interested to see the results. I’ll post them when I can.

I’d theres a visible difference in depth of field I’ll compeltley admit that I’m wrong.

 

[Derrel]

85mm lens. Desired: 8.47 foot tall field of view, to show a man and woman, standing, full-length, with some space below their feet, and above their heads.

With a Full Frame sensor, this field of view height (8.47 feet) is achieved at 20 feet camera-to-subject distance; with a 1.6 x APS-C sensor it's right around 34.5 feet distant, to get the same, exact height (a 1.53x Nikon or Sony sensor is a little,tiny bit closer).

Soooooo: guess what! Moving the APS-C camera BACK, farther from the subject, causes the depth of field to increase, compared to the 20.0 foot camera-to-subject distance that the full-frame camera requires; that distance change causes 1) a greater (longer) camera-to-subject distance, and 2)tends to alter how far behind the background is in relation to the camera's sensor and 3) moves the focus distance closer to the Hyperfocal Distance.

The smaller the sensor is, the CLOSER the camera-to-subject distance is at the range where background objects move into a fairly deep DOF range. At the closest ranges, DOF is skimpy; as camera-to-subject distances increase, to say, beyond 20 feet, DOF increases at a VERY rapid rate. DOF is NOT a linear thing!

There's a point where the full-frame 24x36mm sensor and normal, common lenses like 50mm, 70-200, 85mm, 100mm, 135mm, offer a combination of shallow DOF and a high degree of background blurring, which can be utilized for creative effects. What happens with smaller sensors, like m4/3, APS-C, and smaller, is that there is a LOT of depth of field beginning in the 10- to 20-foot camera-to-subject range; the toughest thing to wrap one's head around when using on-line DOF calculators is this: DOF is easy to quantify with numbers,and it might seem that there's little difference between one format size and another, but the quality of the out of focus (meaning the degree of de-focus, not the bokeh quality) in the background is tricky to describe or to delineat or to define with numbers; the problem is that the human brain and eye can "recognize" many things in a backdrop, unless that backdrop is really,really defocused.

A second problem relating to DOF is that with smaller sensors, the wider-angle focal lengths are VERY short! This means shooting at 17,18,19mm on APS-C gives almost totally hyperfocal focus at CLOSE ranges, and means that getting OOF backdrops on wide-angle shots is impossible, or very difficult, or requires crazy-short, crazy-fast wide-angle lenses to get OOF backdrops.

There are basically three DOF ranges: close-in, moderate, and longer-range. DOF does NOT behave in a linear, perfect manner. Small-sensor cameras CAN create some (note: 'some') shallow DOF effects at macro and close-up ranges, but at medium ranges, and at longer range, small-sensor cameras tend toward deep DOF and easily-recongizable backdrops; Medium and larger-format (6x6,6x7,6x8,6x9 cm images being Medium format, and 4x5,5x7,and 8x10 inch being Large Format) cameras create images with shallow DOF to incredibly shallow DOF.

The FORMAT's SIZE, and the lenses that are used to make each and every Picture Angle of View, or ever single Picture Frame Size, have a MAJOR influence on the DOF, in most cases in the close-up to medium-range situations.

Seriously....listen to me..listen to Ysarex...this has been covered here a dozen times or more, over a decade...listen to Ysarex, not idiots on YouTube who cannot tell the difference between an APS-C shot and an iPhone shot and a Medium Format film shot. If you have ***ever*** shot a 6x6 cm film camera, you KNOW that format size can play a HUGE part in the kind of DOF you get, and the types of images you can create.

Bob Atkins has some fantastic articles on-line, that show the differences between FX (FF) and APS-C cameras, in regards to DOF. As well as an excellent field of view and DOF calculator.

 

[snowbear]

Destin: I'll do the same as a control - D750, AF 50mm f/1.8D Nikkor.

Darryl: Destin and I are looking at this from different angles - I believe the sensor size has a direct affect on DoF, while Destin believes it is indirect. I will make my shots tomorrow evening. I think we've hijacked this thread enough so we should probably post results in a new thread .

 

[Ysarex]

When a Nikon full frame camera is switched to crop (DX) mode, is only the portion of the sensor matching the size of the APS-C sensor being used, or is the just the full frame image cropped to the APS-C sized via software/firmware? If the sensor's zone of activation changes, that may be a real way to test (or demonstrate) it.

The zone of activation changes, which is how the crop factor is formed. The camera essentially just crops the image in software after you press the shutter but before you save it.

That’s exactly how I’ll test it on my D750 when I get home.

If I take an image in Fx mode and then crop it to match an image taken in Dx mode, I’m guaranteeing that I’ll get the same exact image.

You can't crop the FX image! If you do then it's not an FX image is it?
When you do your testing: It's not a valid comparison if you don't use the two sensor sizes to take the same photograph. If you take different photos with the different sensor sizes you have no comparison. If you crop an FX image to DX size then it's a DX image, duuuuh! Again you are thinking about DOF as though it is something that occurs or is defined on the sensor. It is not. Both sensors must be used without cropping to take the same photograph.

Joe

And I’ll take the same image with my D500 as a safety net to compare.

Extremely interested to see the results. I’ll post them when I can.

I’d theres a visible difference in depth of field I’ll compeltley admit that I’m wrong.