Can someone explain the difference in DoF based on FF vs Crop sensors?

I frequently see passing mention of the "better" DoF on FF cameras vs crop body cameras, but I'm afraid I don't really get how the sensor has an effect on that.

Can anyone here explain what the actual difference is and why the size of the sensor affects it?

Thanks in advance.

Snydremark wrote in post #9963744
I frequently see passing mention of the "better" DoF on FF cameras vs crop body cameras, but I'm afraid I don't really get how the sensor has an effect on that.

Can anyone here explain what the actual difference is and why the size of the sensor affects it?

Thanks in advance.

Sorry, but I can't explain the physics and optical background as to why, but what really matters to us photographers is "what depth of field will we have" when we fit "X" lens to "Y body with its specific sensor" and set the aperture to "Z".

You can obtain that information from a DOF table here.

What's more, you could read a few values for your own body plus an alternative, etc, and see exactly what the differences are. It's one thing being told, and quite another to discover a problem and get a solution yourself. I took no notice of what others were telling me until I realised how often I was falling foul of the limits.

Hope that helps.

Better DoF, or better bokeh? They're not quite the same.

Assuming the same camera position and framing, you'll be using a longer focal length lens on the FF body than on the crop. For example, a 50 mm lens on a 50D at f/5.6 and 10 ft. will give you DoF of about 2.6'; an 80 mm will give you the same angle of view on a FF body and at he same f/5.6 and 10 ft., your DoF is about 1.6' The formulas for calculating DoF vary as the inverse of the aperture but as the square of the focal length, so the longer lens you need on a FF body will always have a shallower DoF than will the shorter lens on a crop if all else remains constant.

Bokeh (the quality of the OOF areas) may appear better on FF cameras than on crops both because of the shallower DoF and because the long lenses are more likely to have both a circular (multi-segment) aperture opening and a less-complex optical design, both of which can favor better (smoother) bokeh.

This question gets asked at least 5 times a week and there have been lots of discussion about it.

Check out the "Similar Posts" below and see how some of those threads progressed.

Actually, if focal length and distance to subject is the same, the depth of field is the same. What it really means is that to get the same field of view on a full frame camera as a crop camera from the same distance, you would need a longer focal length on the full frame camera, thus creating a shallower depth of field.

I hope this helps explain it. So if distance to subject is 10 feet, you are at f/2.8, 55mm on a crop would equal the same field of view as 88mm on a full frame camera. You would have a dof of approximately 1 foot with the crop camera and .6 feet with the full frame.

The easiest way to see the differences is to use a depth of field calculator.

Changing the format (size of the film frame or digital sensor in a camera) of the camera changes a factor called the "circle of confusion". That will change the depth of field calculation along with changes in any of the focal length, aperture (f-stop), and/or distance from the film (sensor) plane to the sharply focused plane in the scene.

To do a realistic comparison between a so-called "full-frame" camera and an APS-C camera, you would want to input the so-called "35mm Equivalent Focal Length" value for all cameras. In other words, for comparison of a "full-frame" camera to an APS-C format camera, use 160mm for the "full-frame" camera and use 100mm for the APS-C format camera (or any other pair of focal lengths with a X1.6 difference such as my example). This will keep the framing of both images the same when both cameras are used in the same position.


It looks like we had an explosion of answers at roughly the same time...

SkipD wrote in post #9963864
The easiest way to see the differences is to use a depth of field calculator.


It looks like we had an explosion of answers at roughly the same time...

I never understand why some prefer not to take note of a very valuable resource (DOF Calculator), but instead want the complete answer to life in one posting and then have to ask again when it dawns on them that there is no single figure for DOF.

I'm kind of stupid and I read these complicated formulas for calculating DOF but it's not that easy to remember and use. So in plain and simple, you get 1,6 times shallower DOF with FF. And it equals to about one F-stop.

So if you have a 35mm lens on a crop-body at f/2.8:
Near limit: 6.96 m
Far limit: 17.8 m
Total: 10.8 m

It is almost equal to a 50mm at f/4 on a FF-body:
Near limit: 7.24 m
Far limit: 16.1 m
Total: 8.9 m

(Focusing distance at 10m)

WaltA wrote in post #9963850
This question gets asked at least 5 times a week and there have been lots of discussion about it.

Check out the "Similar Posts" below and see how some of those threads progressed.

Thanks, but none of those discussion quite hit on what I'm asking about here (at least, not in a way that I grasped).

Jon wrote in post #9963840
Better DoF, or better bokeh? They're not quite the same.

Assuming the same camera position and framing, you'll be using a longer focal length lens on the FF body than on the crop. For example, a 50 mm lens on a 50D at f/5.6 and 10 ft. will give you DoF of about 2.6'; an 80 mm will give you the same angle of view on a FF body and at he same f/5.6 and 10 ft., your DoF is about 1.6' The formulas for calculating DoF vary as the inverse of the aperture but as the square of the focal length, so the longer lens you need on a FF body will always have a shallower DoF than will the shorter lens on a crop if all else remains constant.

Yes, this is what I was asking about; thanks, Jon. So, DoF isn't actually "better" on FF bodies, you just need an "equivalent" lens to get the SAME DoF between the two (assuming same aperture and distance to subject). Which then winds up working better for some folks than others...

Snydremark wrote in post #9964022
Thanks, but none of those discussion quite hit on what I'm asking about here (at least, not in a way that I grasped).

Yes, this is what I was asking about; thanks, Jon. So, DoF isn't actually "better" on FF bodies, you just need an "equivalent" lens to get the SAME DoF between the two (assuming same aperture and distance to subject). Which then winds up working better for some folks than others...

I'm not sure what you mean by DOF being "better". In some shots you want shallow DOF and in some you want infinity.

The calculator Skip pointed to lets you see what the change in DOF is between say an XtI and a 5D.

Snydremark wrote in post #9964022
Thanks, but none of those discussion quite hit on what I'm asking about here (at least, not in a way that I grasped).

Yes, this is what I was asking about; thanks, Jon. So, DoF isn't actually "better" on FF bodies, you just need an "equivalent" lens to get the SAME DoF between the two (assuming same aperture and distance to subject). Which then winds up working better for some folks than others...

No - if you reread my example:
50D, 50 mm lens, f/5.6, 10' to subject, DoF 2.6'
5DII, 80 mm lens, f/5.6, 10' to subject, DoF 1.6'
80 mm on FF gives the same coverage as a 50 on the crop body. So the FF gives you shallower DoF (by, as Superboy said, about 1 stop's worth - you'd need to shoot f/4 on the 50D with the 50 mm lens to get about the same DoF you can on the 5D2/80 at f/5.6. Go to the calculator Skip linked to and plug in those numbers and you'll see the results I posted.

WaltA wrote in post #9964056
I'm not sure what you mean by DOF being "better".

The calculator Skip pointed to lets you see what the change in DOF is between say an XtI and a 5D.

That's why I was asking such a subjective question, really. The way I've seen it stated was that people wanted FF cameras because their DoF was 'better' than crop cameras. So I was trying to get a handle on whether there was something aside from the general 'crop factor' that was affecting DoF between the two. And it looks like there isn't, really.

Jon wrote in post #9964436
No - if you reread my example:
50D, 50 mm lens, f/5.6, 10' to subject, DoF 2.6'
5DII, 80 mm lens, f/5.6, 10' to subject, DoF 1.6'
80 mm on FF gives the same coverage as a 50 on the crop body. So the FF gives you shallower DoF (by, as Superboy said, about 1 stop's worth - you'd need to shoot f/4 on the 50D with the 50 mm lens to get about the same DoF you can on the 5D2/80 at f/5.6. Go to the calculator Skip linked to and plug in those numbers and you'll see the results I posted.

This is the best answer and example i have seen regarding dof crop vs FF. I moved up from 40D crop to 5D a year ago, and on my 40D I had a hard time getting shallow dof on f4 with my 24-105, but on the 5D I remember my first shot of some fruit with nice bokeh. After I bought my 5D I had trouble using my expensive fast glass on larger apertures, and I thought it as because of the FF. But As i found out a couple of days ago, The camera had a bad frontfocus issue. that probably didn't help my lowlight shooting.

I don't like pictures where face is in focus and ears not, so I try to learn a way to know which aperture gives me how much dof without looking at doftables. Check out my thread https://photography-on-the.net/forum/showthre​ad.php?t=855216 I may be all wrong...

Snydremark wrote in post #9964534
That's why I was asking such a subjective question, really. The way I've seen it stated was that people wanted FF cameras because their DoF was 'better' than crop cameras. So I was trying to get a handle on whether there was something aside from the general 'crop factor' that was affecting DoF between the two. And it looks like there isn't, really.

One way people put it is that they have more "control" over Depth of Field, in that for a given aperture they can get the shallower DOF when framing the image -- they have that option as well as the option to stop down some.

tonylong wrote in post #9965956
One way people put it is that they have more "control" over Depth of Field, in that for a given aperture they can get the shallower DOF when framing the image -- they have that option as well as the option to stop down some.

Thank you, that is what I was trying to get at.