Crop vs Full Frame - DoF

[outdoors]

Is there a significant difference in the DoF on a Full Frame vs a Crop?

 

[KmH]

Yes, there is a significant difference.

 

[jake337]

Google is your friend.

Photo Technique #007 @Digital Outback Photo

Depth of Field, Digital Photography and Crop Sensor Cameras - Bob Atkins Photography

Depth of field

I copied this from another forum.

• Using the same lens on a EOS 10D and a 35mm film body, the 10D image has 1.6x LESS depth of field than the 35mm image would have (but they would be different images of course since the field of view would be different)

• If you use the same lens on a EOS 10D and a 35mm film body and crop the 35mm image to give the same view as the digital image, the depth of field is IDENTICAL

• If you use the same lens on an EOS 10D and a 35mm film body, then shoot from different distances so that the view is the same, the 10D image will have 1.6x MORE DOF then the film image.

• Close to the hyperfocal distance, the EOS 10D has a much more than 1.6x the DOF of a 35mm film camera. The hyperfocal distance of the EOS 10D is 1.6x less than that of a 35mm film camera when used with a lens giving the same field of view."

 

[Derrel]

The articles that jake337 links to above are ones I myself have read and studied extensively. I think one additional fact from the Atkins article is worth bringing up here: when the focusing distance is close to the hyperfocal distance, with a lens of a focal length of 31.25mm, the above-mentioned 10D Canon or APS-C 1.6x sensor size camera will yield a depth of field that is not merely 1.6x more than a 35mm camera would, but 2.85x more.

As Atkins writes, "Note that as the focus distance approaches the hyperfocal distance, DOF increases rapidly. Since this happens for the a Canon APS-C crop sensor camera with a 31.25mm lens first (because the hyperfocal distance is least), the ratio of the DOF of the a Canon APS-C crop sensor camera to that of 35mm full frame becomes larger than the ~1.6x that you would get if the lens was focused at a distance much shorter than the hyperfocal distance. The plot below shows this graphically. Between about 0.2m and 3m the Canon APS-C crop sensor camera shows about 1.6-1.7x the DOF of 35mm full frame. At very close distances the ratio goes up, and as the distance approaches the hyperfocal distance for a 31.25mm lens at f8 on a Canon APS-C crop sensor camera (6.6m) the ratio rapidly rises - this is because the DOF behind the subject in the Canon APS-C crop sensor camera image is rapidly moving towards infinity."

What this means in PRACTICAL terms is that with short focal length lenses, on any APS-C camera, is that once the short focal length, wider-angle lenses are focused around 25 to 20 feet, the depth of field is so immense that it's almost impossible to make the background be unrecognizable. With shorter focal length lenses, and on farther-away subjects, when one uses an APS-C sized sensor, even areas that are outside of the band of acceptable sharpness, are often quite "recognizable"; even if say, a tree is not rendered in perfect crisp detail, it might very easily be "readable" by a human.

 

[outdoors]

Interested in the choice between full frame vs crop when it comes to DoF. For example, if you have both available do you always use the full frame if you want a narrow DoF and conversly always use the crop if you want a huge DoF? Put another way, if a friend was in the market for a new body and his main purpose was for portraits with narrow DoF would you suggest a full frame over crop?

 

[Derrel]

Interested in the choice between full frame vs crop when it comes to DoF. For example, if you have both available do you always use the full frame if you want a narrow DoF and conversly always use the crop if you want a huge DoF? Put another way, if a friend was in the market for a new body and his main purpose was for portraits with narrow DoF would you suggest a full frame over crop?

For portraiture and "people" work, FF is a better choice in many cases. Not all, but typically, FF allows one to use the "portrait lenses" like the 85,105,and 135 as they were intended to be used. I always give this example: 85mm lens, 1.6x Canon body, needs to be 34 feet away to properly frame a standing man and woman; with a FF 5D Canon, the same lens shoots the same picture height from 20 feet away, with shallower depth of field and MUCH MORE background separation than with the crop-body camera. With longer lenses, like 100,105,135,180,200, with the crop-sensor cameras, the photographer must be a looooong ways away from the people to do anything except tight headshots; at loooooong ranges, depth of field increases at a huge rate as the lens approaches hyperfocal distance.

With wide-angle work indoors, the crop-bodies lead to lots of too-close camera positioning, and very short focal lengths as well, due to the loss of field of view. For portraiture and people, the 24x36mm capture size has proven its worth over many decades; not so with APS-C, which was a stopgap measure.

 

[Robin Usagani]

Sigh.. This topic again. Basically if you shoot with with a full frame, using cropped sensor would give you the same thing except you crop some of the picture around it. As simple as that.

 

[djacobox372]

Technically speaking the dof is the same regardless of sensor size, only aperture, distance to subject, and focal length affect dof.

However, with a larger sensor you end up using longer focal lengths to achieve the same composition, the end result is a smaller dof due to the longer focal length or shorter distance to the subject.

 

[djacobox372]

Sigh.. This topic again. Basically if you shoot with with a full frame, using cropped sensor would give you the same thing except you crop some of the picture around it. As simple as that.

True, but if u "crop" the full frame optically (use a longer lens) the dof shrinks significantly. For example a 35mm 1.4 on a crop sensor has a similar fov as a 50mm 1.4 on ff, but the dof on the 50 at the same aperture and focus distance is much more narrow.

 

[Derrel]

Sigh.. This topic again. Basically if you shoot with with a full frame, using cropped sensor would give you the same thing except you crop some of the picture around it. As simple as that.

Yes, this topic again; you might note that the OP has 12 posts to his name...the queartioin comes up quite often...I've tried to give some real information about the FF vs APS-C DIFFERENCES without sighing over a repetitive post topic.

Your thought process in this post isn't clear to me Schwetty. Not sure what you mean "using cropped sensor would give you the same thing except you crop some of the picture around it. A simple as that." Uh, no, it's not as simple as that, and the images made with a crop-body and a FF body are often vastly different, and are nowhere near the same thing.

Try using a 135mm lens on a 1.6x Canon body indoors; then, actually ENJOY being able TO use the same 135mm lens, indoors. Sorry, but the much larger sensor area of 24x36, either film or digital, is quite a bit different than capturing on APS-C or 4/3 or other tiny sensors. Schwetty, I see you're shooting with full-frame digital; why not APS-C digital? How did you arrive at your current format of choice? Were you after the superior High-ISO performance of the full-frame cameras?

 

[Overread19]

I can't add much to what has been said already simply to add that as another example of where depth of field shifts between the fullframe and crop sensors is in macro work - at 1:1 between the same macro lens on a fullframe and crop sensor camera body (ie focal length, aperture and distances all the same) the crop sensor will have around one stop more depth of field compared to the fullframe.

In the macro world this is oft countered by the fact that you typically get one stop more to close down before diffraction softening kicks in with the fullframe bodies.

 

[djd3mo]

Sigh.. This topic again. Basically if you shoot with a full frame, using cropped sensor would give you the same thing except you crop some of the picture around it. As simple as that.

True. Depth of Field is strictly dependent upon the lens and the subject distance. NOT sensor size. DoF increases when:
- subject distance increases;
- focal length decreases (Field of View increases);
- aperture decreases (f-number increases);
- size of lens type decreases.

If the first three may be easy to grasp, the last one is a bit strange but let me go through with it. An FX 50mm lens produces a wider FoV than a DX 50mm lens. If the FoV is bigger but the focal length is the same then what changed ? Well, the size of the optical elements grew. The lens is thicker and another "side" effect of this growth is a shallower DoF. So an FX 50mm lens not only produces a wider FoV but also a shallower DoF than a DX 50mm lens. That's why you can never mimic all the aspects of a full frame photo with a cropped sensor photo. You may be able to get the same FoV as the FX 75mm lens using a DX 50mm lens but the DoF will be bigger. Or you can use the same FX 75mm lens to get the same DoF but then the sensor will only record a cropped FoV.

Hope it helped !

 

[Helen B]

There are four main factors that determine depth of field: distance to the object that is focused on, relative aperture (f-number), focal length of lens and maximum acceptable diameter of the circle of confusion (how much blur can be tolerated in the image on the film/sensor before it appears to be out of focus in the final, viewed, image - with the same CoC criterion being applied to both of the viewed images).

The latter comes into play when comparing different sensor sizes (and even sensors of the same size but different photosite sizes). To get the same size of viewed image, the image from a small sensor has to be enlarged more than the image from a large sensor, therefore it needs to be sharper to begin with - ie the maximum acceptable CoC is smaller. This partly offsets the advantage of using lenses of shorter focal length when at the same subject distance, but the focal length has more effect on the DoF (DoF is approximately inversely proportional to the square of the focal length) than the CoC diameter does (approx. simple proportionality). At the same subject distance, field-of-view and relative aperture the crop sensor will have more DoF than the larger sensor, ignoring diffraction, lens aberrations and sensor/film resolution.

This does mean that if you hold everything else constant (ie distance, focal length, aperture and size of final viewed image) the image from a cropped sensor will generally look less sharp than one from a full-frame (using the full frame of course). This situation is not the usual one for comparing DoF because the framing of the two images in terms of field-of-view is different.

Best,
Helen

 

[Robin Usagani]

I am getting confused reading all of this.

 

[Robin Usagani]

This is from Bob Atkin's website Jake posted.:
• If you use the same lens on a Canon APS-C crop sensor camera and a 35mm full frame body and crop the full frame 35mm image to give the same view as the APS-C crop image, the depth of field is IDENTICAL

I can't add much to what has been said already simply to add that as another example of where depth of field shifts between the fullframe and crop sensors is in macro work - at 1:1 between the same macro lens on a fullframe and crop sensor camera body (ie focal length, aperture and distances all the same) the crop sensor will have around one stop more depth of field compared to the fullframe.

In the macro world this is oft countered by the fact that you typically get one stop more to close down before diffraction softening kicks in with the fullframe bodies.