FF DOF

[gerardo2068]

Can somebody clarify to me how DOF change in a FF camera from DX?

Thanks

 

[mjhoward]

You're DOF is effected by the fact that you'll have different distance to subject to achieve the same magnification for the same focal length.

 

[gerardo2068]

So, is the space of acceptable DOF is greater in a FF camera than in a DX camera?

if a shoot a person with at 50mm on a DX camera and I frame it to fit the person from the tip of the head to the tip of the feet only,

and I composed for the same exact frame (tip of head to tip of feet) on a FF camera will I get a wider DOF in the FF?

I would even have have to use longer focal length on a FF right? like 85mm to make it comparable to the DX?

By using a specific focal length on a DX and a longer focal length on a FF relative to the DX version, would't that close the difference in DOF between both formats??

Thanks

 

[o hey tyler]

If the framing is the same, meaing the subject appears the same size in the frame, with the same focal length/aperture... The DoF on a FF camera will be shallower, not larger. Because you can get closer to your subject to frame the same shot due to the lack of magnification of an APS-C sensor.

 

[Rephargotohp]

Actually, It is because as sensor size increases so does the Circle of confusion. So even compensating for Distance and crop (Framing), a FF Sensor will have a shallower DOF than a crop sensor, which in turn has a shallower DOF than a P & S

The larger the circle of confusion, the sooner it becomes apparemt a "Point" is now a Blur spot and becomes visible to the eye...or the best way I can explain it in less than 1500 words

 

[gerardo2068]

If the framing is the same, meaing the subject appears the same size in the frame, with the same focal length/aperture... The DoF on a FF camera will be shallower, not larger. Because you can get closer to your subject to frame the same shot due to the lack of magnification of an APS-C sensor.

But if me or the subject don't move the position and all, wouldn't I need a longer focal length in a FF to archive the same size in the frame of the subject? in that case, how would that affect the DOF in relation to the DX?

 

[Ysarex]

If the framing is the same, meaing the subject appears the same size in the frame, with the same focal length/aperture... The DoF on a FF camera will be shallower, not larger. Because you can get closer to your subject to frame the same shot due to the lack of magnification of an APS-C sensor.

But if me or the subject don't move the position and all, wouldn't I need a longer focal length in a FF to archive the same size in the frame of the subject? in that case, how would that affect the DOF in relation to the DX?

less DOF with the FF.

Joe

 

[gerardo2068]

Actually, It is because as sensor size increases so does the Circle of confusion. So even compensating for Distance and crop (Framing), a FF Sensor will have a shallower DOF than a crop sensor, which in turn has a shallower DOF than a P & S

The larger the circle of confusion, the sooner it becomes apparemt a "Point" is now a Blur spot and becomes visible to the eye...or the best way I can explain it in less than 1500 words

LOL yeah, I'm in the circle of confusion all right! I read about it but I need to refresh.


So, in a simpler term the larger the sensor, the easier is to get a shallower DOF given the same frame, size of subject in the photo, and same aperture ?

 

[analog.universe]

If the framing is the same, meaing the subject appears the same size in the frame, with the same focal length/aperture... The DoF on a FF camera will be shallower, not larger. Because you can get closer to your subject to frame the same shot due to the lack of magnification of an APS-C sensor.

But if me or the subject don't move the position and all, wouldn't I need a longer focal length in a FF to archive the same size in the frame of the subject? in that case, how would that affect the DOF in relation to the DX?

If you don't move, and the subject doesn't move, so you instead use a longer focal length to achieve the same framing, your depth of field will be more shallow at a given aperture on FF than at that same aperture with a shorter focal length on APS-C.

 

[analog.universe]

So, in a simpler term the larger the sensor, the easier is to get a shallower DOF given the same frame, size of subject in the photo, and same aperture ?

:thumbup:

 

[Rephargotohp]

Actually, It is because as sensor size increases so does the Circle of confusion. So even compensating for Distance and crop (Framing), a FF Sensor will have a shallower DOF than a crop sensor, which in turn has a shallower DOF than a P & S

The larger the circle of confusion, the sooner it becomes apparemt a "Point" is now a Blur spot and becomes visible to the eye...or the best way I can explain it in less than 1500 words

LOL yeah, I'm in the circle of confusion all right! I read about it but I need to refresh.


So, in a simpler term the larger the sensor, the easier is to get a shallower DOF given the same frame, size of subject in the photo, and same aperture ?

Simple answer yes, Even given same Framing (magnification) a FF will have a shallower DOF, as would a Medium format above that

 

[gerardo2068]

Thanks everybody for the info!

 

[Helen B]

Actually, It is because as sensor size increases so does the Circle of confusion. So even compensating for Distance and crop (Framing), a FF Sensor will have a shallower DOF than a crop sensor, which in turn has a shallower DOF than a P & S

The larger the circle of confusion, the sooner it becomes apparemt a "Point" is now a Blur spot and becomes visible to the eye...or the best way I can explain it in less than 1500 words

Sorry to reanimate the monster of DoF, but none of that is correct.

The format has no effect whatsoever on the circle of confusion. Why should it? Does a lens magically change its properties when it is mounted on cameras of different formats? The size of the circle of confusion depends on the lens' focal length and aperture, distance to the plane in focus and distance to the object point under consideration. It does not depend on the format.

What does depend on the format is the maximum acceptable circle of confusion (I'll call it the MACC). The larger the format, the larger the MACC, because of the lower magnification from the recorded image to the final viewed image. The larger the MACC, the more out-of-focus the image of a point can be before it appears to be out of focus on the final viewed image (eg on a print) - that's how MACC is defined. Therefore the larger the format, the more blurred the image of a point can be before it looks out of focus when the final image is viewed. (All this assumes that the final viewed image is the same size for all formats - a standard assumption but one that should be remembered.)

This means that DoF is greater for large formats when the lens focal length, aperture and focused distance are all held constant. The smaller DoF that larger formats are known for comes about by holding the angle of view the same - ie increasing the focal length compared to smaller formats, or moving closer and holding the lens focal length the same.

The increase in focal length as the format gets larger (holding the angle of view the same) has a greater effect on DoF than the increase in MACC, therefore the increase in focal length wins and the larger format has less DoF than the smaller.

In that sense, the shallower DoF of larger formats is because of the change in focal length, and definitely not because of the MACC - because the MACC alone would mean that larger formats had deeper focus than smaller formats.

 

[Josh66]

Actually, It is because as sensor size increases so does the Circle of confusion. So even compensating for Distance and crop (Framing), a FF Sensor will have a shallower DOF than a crop sensor, which in turn has a shallower DOF than a P & S

The larger the circle of confusion, the sooner it becomes apparemt a "Point" is now a Blur spot and becomes visible to the eye...or the best way I can explain it in less than 1500 words

Sorry to reanimate the monster of DoF, but none of that is correct.

The format has no effect whatsoever on the circle of confusion. Why should it? Does a lens magically change its properties when it is mounted on cameras of different formats? The size of the circle of confusion depends on the lens' focal length and aperture, distance to the plane in focus and distance to the object point under consideration. It does not depend on the format.

What does depend on the format is the maximum acceptable circle of confusion (I'll call it the MACC). The larger the format, the larger the MACC, because of the lower magnification from the recorded image to the final viewed image. The larger the MACC, the more out-of-focus the image of a point can be before it appears to be out of focus on the final viewed image (eg on a print) - that's how MACC is defined. Therefore the larger the format, the more blurred the image of a point can be before it looks out of focus when the final image is viewed. (All this assumes that the final viewed image is the same size for all formats - a standard assumption but one that should be remembered.)

This means that DoF is greater for large formats when the lens focal length, aperture and focused distance are all held constant. The smaller DoF that larger formats are known for comes about by holding the angle of view the same - ie increasing the focal length compared to smaller formats, or moving closer and holding the lens focal length the same.

The increase in focal length as the format gets larger (holding the angle of view the same) has a greater effect on DoF than the increase in MACC, therefore the increase in focal length wins and the larger format has less DoF than the smaller.

In that sense, the shallower DoF of larger formats is because of the change in focal length, and definitely not because of the MACC - because the MACC alone would mean that larger formats had deeper focus than smaller formats.

Thanks.

That was probably the most brief, and yet informative description I have read on why larger formats have less DoF.