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Depth of Field (DOF), background blur, and bokeh are related, but different concepts. There is also subject-background isolation/separation.

• Depth of field is based on focal length, aperture, distance, and a predefined acceptable sharpness level. It is concerned with what parts of the image are expected to be sharp, not what parts of the image will be blurry, or how blurry unsharp portions of the image will be.

• Background blur – How blurry is the background? I think of it as something that can be quantified. How big are bokeh balls a given distance from the lens? Different lenses with the same focal lengths, apertures, and distances can create different, though similar, amounts of blur because of different amounts of distortion, aberration, and field curvature. (There's also foreground blur, but people tend to be less interested.)

• Bokeh is a qualitative description of the blur that is produced. Are the bokeh balls round? Do they vary in shape throughout the frame? Are they smooth? Do they have edge highlights? Are they smeared? Some people refer to how lenses "render" images.

• Subject-background isolation refers to (subjectively) how well the subject stands out from the background. This can be achieved with depth of field and background blur, as well as appropriate lighting (such as rim lighting and creative use of "glow"). The common formula is to try to use narrow depth of field with high background blur. However, some types of bokeh can achieve good subject isolation with high depth of field and low background blur. For instance, Sonnar lenses create bokeh balls with an edge highlight toward the center of the frame, but a smear toward the edge of the frame. This tends to emphasize the sharpness of the subject toward the center, while also emphasizing the blurriness of the background toward the periphery.

Depth of Field and Background Blur tend to be inversely related. To minimize DOF and maximize background blur:

• Use a longer focal length.
• Use a larger aperture.
• Use a smaller camera-subject distance (or larger subject-background distance).

To illustrate DOF vs bokeh, consider images taken at F2.8 on four different lenses: 35/2.8 (x2), 35/1.4, and 35/1.7. They were taken handheld from the same standing position. DOF is approximately the same in all of the images, which you can see by examining the flower for sharpness. (Try to ignore the glow, which affects perceived sharpness.)

However, note that:

• They have different amounts of background blur (differently sized bokeh balls).
• One has a noticeably shorter focal length than the others.
• Three exhibit a "swirl" (oval shaped bokeh along the edge of the frame).
• One has a one-sided edge highlight.
• Two have medial edge highlights.
• One has a lateral "fade".
• One has a mild lateral "smear".
• One is very smooth.

Lenses: Focal/Cimko 35/2.8; Hansa 35/2.8; FujiFilm XF 35/1.4; Fujian 35/1.7 (c-mount)

Here are the FujiFilm XF 35/1.4 and Fujian 35/1.7 wide open:

Depth of Field (DOF), background blur, and bokeh are related, but different concepts. There is also subject-background isolation/separation.

• Depth of field is based on focal length, aperture, distance, and a predefined acceptable sharpness level. It is concerned with what parts of the image are expected to be sharp, not what parts of the image will be blurry, or how blurry unsharp portions of the image will be.

• Background blur – How blurry is the background? I think of it as something that can be quantified. How big are bokeh balls a given distance from the lens? Different lenses with the same focal lengths, apertures, and distances can create different, though similar, amounts of blur because of different amounts of distortion, aberration, and field curvature. (There's also foreground blur, but people tend to be less interested.)

• Bokeh is a qualitative description of the blur that is produced. Are the bokeh balls round? Do they vary in shape throughout the frame? Are they smooth? Do they have edge highlights? Are they smeared? Some people refer to how lenses "render" images.

• Subject-background isolation refers to (subjectively) how well the subject stands out from the background. This can be achieved with depth of field and background blur, as well as appropriate lighting (such as rim lighting and creative use of "glow"). The common formula is to try to use narrow depth of field with high background blur. However, some types of bokeh can achieve good subject isolation with high depth of field and low background blur. For instance, Sonnar lenses create bokeh balls with an edge highlight toward the center of the frame, but a smear toward the edge of the frame. This tends to emphasize the sharpness of the subject toward the center, while also emphasizing the blurriness of the background toward the periphery.

Depth of Field and Background Blur tend to be inversely related. To minimize DOF and maximize background blur:

• Use a longer focal length.
• Use a larger aperture.
• Use a smaller camera-subject distance (or larger subject-background distance).

Depth of Field (DOF), background blur, and bokeh are related, but different concepts. There is also subject-background isolation/separation.

• Depth of field is based on focal length, aperture, distance, and a predefined acceptable sharpness level. It is concerned with what parts of the image are expected to be sharp, not what parts of the image will be blurry, or how blurry unsharp portions of the image will be.

• Background blur – How blurry is the background? I think of it as something that can be quantified. How big are bokeh balls a given distance from the lens? Different lenses with the same focal lengths, apertures, and distances can create different, though similar, amounts of blur because of different amounts of distortion, aberration, and field curvature. (There's also foreground blur, but people tend to be less interested.)

• Bokeh is a qualitative description of the blur that is produced. Are the bokeh balls round? Do they vary in shape throughout the frame? Are they smooth? Do they have edge highlights? Are they smeared? Some people refer to how lenses "render" images.

• Subject-background isolation refers to (subjectively) how well the subject stands out from the background. This can be achieved with depth of field and background blur, as well as appropriate lighting (such as rim lighting and creative use of "glow"). The common formula is to try to use narrow depth of field with high background blur. However, some types of bokeh can achieve good subject isolation with high depth of field and low background blur. For instance, Sonnar lenses create bokeh balls with an edge highlight toward the center of the frame, but a smear toward the edge of the frame. This tends to emphasize the sharpness of the subject toward the center, while also emphasizing the blurriness of the background toward the periphery.

Depth of Field and Background Blur tend to be inversely related. To minimize DOF and maximize background blur:

• Use a longer focal length.
• Use a larger aperture.
• Use a smaller camera-subject distance (or larger subject-background distance).

To illustrate DOF vs bokeh, consider images taken at F2.8 on four different lenses: 35/2.8 (x2), 35/1.4, and 35/1.7. They were taken handheld from the same standing position. DOF is approximately the same in all of the images, which you can see by examining the flower for sharpness. (Try to ignore the glow, which affects perceived sharpness.)

However, note that:

• They have different amounts of background blur (differently sized bokeh balls).
• One has a noticeably shorter focal length than the others.
• Three exhibit a "swirl" (oval shaped bokeh along the edge of the frame).
• One has a one-sided edge highlight.
• Two have medial edge highlights.
• One has a lateral "fade".
• One has a mild lateral "smear".
• One is very smooth.

Lenses: Focal/Cimko 35/2.8; Hansa 35/2.8; FujiFilm XF 35/1.4; Fujinon 35/1.7 (c-mount)

Here are the FujiFilm XF 35/1.4 and Fujinon 35/1.7 wide open:

Depth of Field (DOF), background blur, and bokeh are related, but different concepts. There is also subject-background isolation/separation.

• Depth of field is based on focal length, aperture, distance, and a predefined acceptable sharpness level. It is concerned with what parts of the image are expected to be sharp, not what parts of the image will be blurry, or how blurry unsharp portions of the image will be.

• Background blur – How blurry is the background? I think of it as something that can be quantified. How big are bokeh balls a given distance from the lens? Different lenses with the same focal lengths, apertures, and distances can create different, though similar, amounts of blur because of different amounts of distortion, aberration, and field curvature. (There's also foreground blur, but people tend to be less interested.)

• Bokeh is a qualitative description of the blur that is produced. Are the bokeh balls round? Do they vary in shape throughout the frame? Are they smooth? Do they have edge highlights? Are they smeared? Some people refer to how lenses "render" images.

• Subject-background isolation refers to (subjectively) how well the subject stands out from the background. This can be achieved with depth of field and background blur, as well as appropriate lighting (such as rim lighting and creative use of "glow"). The common formula is to try to use narrow depth of field with high background blur. However, some types of bokeh can achieve good subject isolation with high depth of field and low background blur. For instance, Sonnar lenses create bokeh balls with an edge highlight toward the center of the frame, but a smear toward the edge of the frame. This tends to emphasize the sharpness of the subject toward the center, while also emphasizing the blurriness of the background toward the periphery.

Depth of Field and Background Blur tend to be inversely related. To minimize DOF and maximize background blur:

• Use a longer focal length.
• Use a larger aperture.
• Use a smaller camera-subject distance (or larger subject-background distance).

To illustrate DOF vs bokeh, consider images taken at F2.8 on four different lenses: 35/2.8 (x2), 35/1.4, and 35/1.7. They were taken handheld from the same standing position. DOF is approximately the same in all of the images, which you can see by examining the flower for sharpness. (Try to ignore the glow, which affects perceived sharpness.)

However, note that:

• They have different amounts of background blur (differently sized bokeh balls).
• One has a noticeably shorter focal length than the others.
• Three exhibit a "swirl" (oval shaped bokeh along the edge of the frame).
• One has a one-sided edge highlight.
• Two have medial edge highlights.
• One has a lateral "fade".
• One has a mild lateral "smear".
• One is very smooth.

Lenses: Focal/Cimko 35/2.8; Hansa 35/2.8; FujiFilm XF 35/1.4; Fujian 35/1.7 (c-mount)

Here are the FujiFilm XF 35/1.4 and Fujian 35/1.7 wide open:

Depth of Field (DOF), background blur, and bokeh are related, but different concepts. There is also subject-background isolation/separation.

• Depth of field is based on focal length, aperture, distance, and a predefined acceptable sharpness level. It is concerned with what parts of the image are expected to be sharp, not what parts of the image will be blurry, or how blurry unsharp portions of the image will be.

• Background blur – How blurry is the background? I think of it as something that can be quantified. How big are bokeh balls a given distance from the lens? Different lenses with the same focal lengths, apertures, and distances can create different, though similar, amounts of blur because of different amounts of distortion, aberration, and field curvature. (There's also foreground blur, but people tend to be less interested.)

• Bokeh is a qualitative description of the blur that is produced. Are the bokeh balls round? Do they vary in shape throughout the frame? Are they smooth? Do they have edge highlights? Are they smeared? Etc.

• Subject-background isolation refers to (subjectively) how well the subject stands out from the background. This can be achieved with depth of field and background blur, as well as appropriate lighting (such as rim lighting and creative use of "glow"). The common formula is to try to use narrow depth of field with high background blur. However, some types of bokeh can achieve good subject isolation with high depth of field and low background blur. For instance, Sonnar lenses create bokeh balls with an edge highlight toward the center of the frame, but a smear toward the edge of the frame. This tends to emphasize the sharpness of the subject toward the center, while also emphasizing the blurriness of the background toward the periphery.

Depth of Field and Background Blur tend to be inversely related. To minimize DOF and maximize background blur:

• Use a longer focal length.
• Use a larger aperture.
• Use a smaller camera-subject distance (or larger subject-background distance).

To illustrate DOF vs bokeh, consider images taken at F2.8 on four different lenses: 35/2.8 (x2), 35/1.4, and 35/1.7. They were taken handheld from the same standing position. DOF is approximately the same in all of the images, which you can see by examining the flower for sharpness. (Try to ignore the glow, which affects perceived sharpness.)

However, note that:

• They have different amounts of background blur (differently sized bokeh balls).
• One has a noticeably shorter focal length than the others.
• Three exhibit a "swirl" (oval shaped bokeh along the edge of the frame).
• One has a one-sided edge highlight.
• Two have medial edge highlights.
• One has a lateral "fade".
• One has a mild lateral "smear".
• One is very smooth.

Lenses: Focal/Cimko 35/2.8; Hansa 35/2.8; FujiFilm XF 35/1.4; Fujinon 35/1.7 (c-mount)

Here are the FujiFilm XF 35/1.4 and Fujinon 35/1.7 wide open:

Depth of Field (DOF), background blur, and bokeh are related, but different concepts. There is also subject-background isolation/separation.

• Depth of field is based on focal length, aperture, distance, and a predefined acceptable sharpness level. It is concerned with what parts of the image are expected to be sharp, not what parts of the image will be blurry, or how blurry unsharp portions of the image will be.

• Background blur – How blurry is the background? I think of it as something that can be quantified. How big are bokeh balls a given distance from the lens? Different lenses with the same focal lengths, apertures, and distances can create different, though similar, amounts of blur because of different amounts of distortion, aberration, and field curvature. (There's also foreground blur, but people tend to be less interested.)

• Bokeh is a qualitative description of the blur that is produced. Are the bokeh balls round? Do they vary in shape throughout the frame? Are they smooth? Do they have edge highlights? Are they smeared? Some people refer to how lenses "render" images.

• Subject-background isolation refers to (subjectively) how well the subject stands out from the background. This can be achieved with depth of field and background blur, as well as appropriate lighting (such as rim lighting and creative use of "glow"). The common formula is to try to use narrow depth of field with high background blur. However, some types of bokeh can achieve good subject isolation with high depth of field and low background blur. For instance, Sonnar lenses create bokeh balls with an edge highlight toward the center of the frame, but a smear toward the edge of the frame. This tends to emphasize the sharpness of the subject toward the center, while also emphasizing the blurriness of the background toward the periphery.

Depth of Field and Background Blur tend to be inversely related. To minimize DOF and maximize background blur:

• Use a longer focal length.
• Use a larger aperture.
• Use a smaller camera-subject distance (or larger subject-background distance).

To illustrate DOF vs bokeh, consider images taken at F2.8 on four different lenses: 35/2.8 (x2), 35/1.4, and 35/1.7. They were taken handheld from the same standing position. DOF is approximately the same in all of the images, which you can see by examining the flower for sharpness. (Try to ignore the glow, which affects perceived sharpness.)

However, note that:

• They have different amounts of background blur (differently sized bokeh balls).
• One has a noticeably shorter focal length than the others.
• Three exhibit a "swirl" (oval shaped bokeh along the edge of the frame).
• One has a one-sided edge highlight.
• Two have medial edge highlights.
• One has a lateral "fade".
• One has a mild lateral "smear".
• One is very smooth.

Lenses: Focal/Cimko 35/2.8; Hansa 35/2.8; FujiFilm XF 35/1.4; Fujinon 35/1.7 (c-mount)

Here are the FujiFilm XF 35/1.4 and Fujinon 35/1.7 wide open: