Depth of Field & Sensor Sizes

Mark S Abeln said:

LensReflex said:

I was watching a video course on the foundations of Photography, and course material says that a smaller sensor camera is better suited to landscapes because it has a broader depth of field vs. a larger (i.e. Full Frame) sensor. Is this true?

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No, that’s not true, as you can usually stop lenses down to the point where depth of field is huge. Most of my full frame lenses can be stopped down to f/22, which gives me greater DoF than what I can get on my smartphone, which has an equivalent f/stop of f/11.

Mark S Abeln said:

It seems to me that full frame cameras are used quite a lot in landscape photography as well. Does it become difficult to get a broader depth of field (that is, no blurriness in the photo) with a full frame camera under certain conditions, or does this assertion have no basis in reality?

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As mentioned, depth of field isn’t an issue. However. In dim lighting, stopping down a lot either requires heightened ISO or the use of a tripod with a longer shutter time. Larger sensors typically are able to use higher ISOs than smaller, and the effects cancel each other, leading to equivalent photos. But if you do use a tripod, then the larger sensor typically wins.

Depth of field only has three factors: the lens diameter, the distance to the subject, and a subjective factor for how tolerant your eyes are to blur. Sensor size isn’t a part of it, though of course it can be included in the formula at the expense of greater complexity:

https://en.wikipedia.org/wiki/Depth_of_field

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Are you sure you do not omit to mention focal length ? I do not see how it can be true..

Bob A L said:

But to produce an image with the same field of view, the M43 will use a 50mm lens resulting in greater dof at the same f stop.

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Which is precisely what I said in my own post. Though even there, this is only true if the f-number is not also adjusted for the crop factor. So your statement is incomplete; I suggest you read my response to the OP.

The post I am responding to claimed that the depth of field would be the same (and then later claimed greater) if a lens of the same focal length is used with either sensor size. That is not true, as demonstrated.

Dave

Bob A L said:

If you stand in the same spot, use the same f stop, shutter speed and iso and use the appropriate lens to frame the same desired area, you will be using a lens with 1.5 times the focal length with the FF camera which will always result in a shallower. depth of field.

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Sorry, that's only true if you artificially freeze the f-number. Changing the f-number to equalize the depth of field is trivial. The real point here is that sensor size does not automatically bestow lesser or greater depth of field. It also depends on what is done with the other primary factors. That is the lesson that the OP needs to take away, not the simplistic and incorrect generalization that he came in with.

Bob A L said:

Look up any dof calculator and compare a 100mm lens at f5.6, at 100 feet and compare that with a 150mm lens at f5.6, at 100 feet and you will see the difference. And feel free to pick any f stop or focal length when you compare. Or if you want to go to the effort, go out and. photograph something with your FF with a 150mm lens at. any specific aperture, and then take the same photograph from the same distance with a 100mm lens from the same distance with the same f stop on a dx sensor and compare the results. That's how smart phones get almost infinite dof with a f1.8 lens as they require a much shorter focal length to achieve the same field of view due to their small sensor sizes.

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Dave

MarshallG said:

Bob A L said:

If you stand in the same spot, use the same f stop, shutter speed and iso and use the appropriate lens to frame the same desired area, you will be using a lens with 1.5 times the focal length with the FF camera which will always result in a shallower. depth of field. Look up any dof calculator and compare a 100mm lens at f5.6, at 100 feet and compare that with a 150mm lens at f5.6, at 100 feet and you will see the difference. And feel free to pick any f stop or focal length when you compare. Or if you want to go to the effort, go out and. photograph something with your FF with a 150mm lens at. any specific aperture, and then take the same photograph from the same distance with a 100mm lens from the same distance with the same f stop on a dx sensor and compare the results. That's how smart phones get almost infinite dof with a f1.8 lens as they require a much shorter focal length to achieve the same field of view due to their small sensor sizes.

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True, but only because you’ve added an unnecessary and unrealistic constraint, which is making the aperture the same.

If we do the math, it shows that we can reduce aperture on the FF camera and correspondingly increase the ISO… and we would obtain equivalent quality. But in reality, that is not what we would do. We would just close the aperture to what we want and use all the shutter speed in the world, because landscapes don’t move. Either use a tripod or rely on IBIS and you can have a long enough shutter speed.

There is not a case where the crop sensor camera delivers more depth of field with the same quality as the full frame, unless it’s an old full frame at high ISO. This doesn’t mean the full frame is perfect for everyone or that the added quality of full frame is necessary for everyone, but

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MarshallG said:

it does mean that the crop sensor camera is not superior to the full frame.

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Should then work both ways, right? FF vs MF (say Hasselblad/Fuji GFX). "Quality" wise ofcourse.

mujana said:

MarshallG said:

Bob A L said:

If you stand in the same spot, use the same f stop, shutter speed and iso and use the appropriate lens to frame the same desired area, you will be using a lens with 1.5 times the focal length with the FF camera which will always result in a shallower. depth of field. Look up any dof calculator and compare a 100mm lens at f5.6, at 100 feet and compare that with a 150mm lens at f5.6, at 100 feet and you will see the difference. And feel free to pick any f stop or focal length when you compare. Or if you want to go to the effort, go out and. photograph something with your FF with a 150mm lens at. any specific aperture, and then take the same photograph from the same distance with a 100mm lens from the same distance with the same f stop on a dx sensor and compare the results. That's how smart phones get almost infinite dof with a f1.8 lens as they require a much shorter focal length to achieve the same field of view due to their small sensor sizes.

Click to expand...

True, but only because you’ve added an unnecessary and unrealistic constraint, which is making the aperture the same.

If we do the math, it shows that we can reduce aperture on the FF camera and correspondingly increase the ISO… and we would obtain equivalent quality. But in reality, that is not what we would do. We would just close the aperture to what we want and use all the shutter speed in the world, because landscapes don’t move. Either use a tripod or rely on IBIS and you can have a long enough shutter speed.

There is not a case where the crop sensor camera delivers more depth of field with the same quality as the full frame, unless it’s an old full frame at high ISO. This doesn’t mean the full frame is perfect for everyone or that the added quality of full frame is necessary for everyone, but

it does mean that the crop sensor camera is not superior to the full frame.

Click to expand...

Should then work both ways, right? FF vs MF (say Hasselblad/Fuji GFX). "Quality" wise ofcourse.

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Yes, absolutely. And a lot more landscape photographers would shoot medium format, except for the high cost.

MarshallG said:

mujana said:

MarshallG said:

Bob A L said:

If you stand in the same spot, use the same f stop, shutter speed and iso and use the appropriate lens to frame the same desired area, you will be using a lens with 1.5 times the focal length with the FF camera which will always result in a shallower. depth of field. Look up any dof calculator and compare a 100mm lens at f5.6, at 100 feet and compare that with a 150mm lens at f5.6, at 100 feet and you will see the difference. And feel free to pick any f stop or focal length when you compare. Or if you want to go to the effort, go out and. photograph something with your FF with a 150mm lens at. any specific aperture, and then take the same photograph from the same distance with a 100mm lens from the same distance with the same f stop on a dx sensor and compare the results. That's how smart phones get almost infinite dof with a f1.8 lens as they require a much shorter focal length to achieve the same field of view due to their small sensor sizes.

Click to expand...

True, but only because you’ve added an unnecessary and unrealistic constraint, which is making the aperture the same.

If we do the math, it shows that we can reduce aperture on the FF camera and correspondingly increase the ISO… and we would obtain equivalent quality. But in reality, that is not what we would do. We would just close the aperture to what we want and use all the shutter speed in the world, because landscapes don’t move. Either use a tripod or rely on IBIS and you can have a long enough shutter speed.

There is not a case where the crop sensor camera delivers more depth of field with the same quality as the full frame, unless it’s an old full frame at high ISO. This doesn’t mean the full frame is perfect for everyone or that the added quality of full frame is necessary for everyone, but

it does mean that the crop sensor camera is not superior to the full frame.

Click to expand...

Should then work both ways, right? FF vs MF (say Hasselblad/Fuji GFX). "Quality" wise ofcourse.

Click to expand...

Yes, absolutely. And a lot more landscape photographers would shoot medium format, except for the high cost.

Click to expand...

I shoot portraits/landscape/architecture and travel. And yes, I do see differences.

LensReflex said:

I was watching a video course on the foundations of Photography, and course material says that a smaller sensor camera is better suited to landscapes because it has a broader depth of field vs. a larger (i.e. Full Frame) sensor. Is this true?

Click to expand...

No.

LensReflex said:

It seems to me that full frame cameras are used quite a lot in landscape photography as well. Does it become difficult to get a broader depth of field (that is, no blurriness in the photo) with a full frame camera under certain conditions, or does this assertion have no basis in reality?

Click to expand...

In reality FF and MF are often "slightly better" for landscape even when shot at the same DOF and the same shutter speed as smaller formats. That's because larger sensors typically have higher Mpx count which helps with the foliage.

I've wanted to try this for a while and finally got around to it today. It's very simple. I put the very same 50mm lens on two cameras (FF & APS-C) and took two photos at the same distance (~ 80 cm), and the same f-number (f/1.4). The results are predictable but perhaps enlightening to someone fresh to photography.

I used my old Lenscal focus calibrator with scale markings adjusted for a 45° angle, ie, the distance between each major hashmark measures 1.4 cm. So the "2" numerals on the scale are 2 cm in front or behind the target.

Full-frame camera (A7RV, 61 mp):


I'll say the DOF is about ± 2 cm. People with better eyes might say ± 1 cm or even less. Hover your mouse pointer over this photo for EXIF info.

APS-C camera (A6500, 24 mp):


Looking at the scale the DOF measures the same to me. Hover your mouse pointer over the photo for EXIF info.

So when someone says "APS-C cameras have more depth-of-field." what do they really mean? If we measure it with a scale, the DOF seems to be the same.

Finally, here's a photo of the Lenscal focus calibrator for those who have never seen one. These things were used in the DSLR days to drive DSLR owners crazy:


Spyder Lenscal.

Feel free to edit these three photos. Re-posting is restricted to DPReview.com only.

--
Lance H

You are right I suppose. The greater depth of field experienced with smaller sensors cameras isn't because of the sensor size, it's because a shorter focal length lens is required to capture the same field of view as with a FF sensor. So it's because of the lens focal length, not the sensor size. :-D

Same lens, same focal length, same f stop, same distance to subject =. same depth of field. Easy to prove. sensor size does not matter.

Just do as you have done and prove it. Thank you

I operated a process camera for years. They have vacuum back to hold the negative film. When set at the same focal length, with subject at same distance, I could use a 24" square piece of film or a 2" square piece of film and the images would be identical for the area recorded on both pieces of film. The larger. piece of film (sensor today) just recorded more area. Raised my family operating these cameras.

And if I for some crazy reason would want the small piece of film to record the same field of view that the large piece recorded I would have to reduce the focal length which with the same f stop would also increase the dof.

Just go take some photos and see the results.

Bob A L said:

Same lens, same focal length, same f stop, same distance to subject =. same depth of field. Easy to prove. sensor size does not matter.

Just do as you have done and prove it. Thank you

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Lehill's demonstration was not precise enough to reach any valid conclusion. But the standard methods of determining depth of field show unequivocally that an image made with the same focal length, subject distance, and f-number but different sensor sizes will have less depth of field with the smaller sensor. They cannot be the same, because one of the key physical factors is different: the degree of enlargement needed to produce a print of a given size. While the blur delivered by the lens to sensor surface is the same, the greater enlargement results in larger blur in the print. The larger blur is more readily perceived by the viewer, and thus the depth of field will be perceived as shallower.

This is easily verified using a depth of field calculator such as DOFMaster. Just use the same focal length, subject distance, and f-number, but choose cameras with different sensor sizes, and compare the Total depth of field of the result. I gave an example of that in an earlier reply:

https://www.dpreview.com/forums/post/67867608

Bob A L said:

I operated a process camera for years. They have vacuum back to hold the negative film. When set at the same focal length, with subject at same distance, I could use a 24" square piece of film or a 2" square piece of film and the images would be identical for the area recorded on both pieces of film. The larger. piece of film (sensor today) just recorded more area. Raised my family operating these cameras.

Click to expand...

Well of course you were focusing on a flat surface, so depth of field was irrelevant. Had you been recording a three-dimensional scene, and enlarged the negatives to the same print size, you would have gotten the result explained above.

And yes, enlargement from the recording medium to a standard print size is an essential element of depth of field. Without accounting for production of a viewable print, the concept of depth of field is meaningless.

Bob A L said:

And if I for some crazy reason would want the small piece of film to record the same field of view that the large piece recorded I would have to reduce the focal length which with the same f stop would also increase the dof.

Just go take some photos and see the results.

Click to expand...

Dave

--
http://www.pbase.com/dsjtecserv

Bob A L said:

You are right I suppose. The greater depth of field experienced with smaller sensors cameras isn't because of the sensor size, it's because a shorter focal length lens is required to capture the same field of view as with a FF sensor. So it's because of the lens focal length, not the sensor size. :-D

Click to expand...

It's because of all of the factors working together, and depends on how each is applied, not one determinative factor. Those factors are under the photographer's control. That is the lesson that the OP, other beginners, and experienced photographers alike should pick up and internalize.

Dave

lehill said:

I've wanted to try this for a while and finally got around to it today. It's very simple. I put the very same 50mm lens on two cameras (FF & APS-C) and took two photos at the same distance (~ 80 cm), and the same f-number (f/1.4). The results are predictable but perhaps enlightening to someone fresh to photography.

I used my old Lenscal focus calibrator with scale markings adjusted for a 45° angle, ie, the distance between each major hashmark measures 1.4 cm. So the "2" numerals on the scale are 2 cm in front or behind the target.

Full-frame camera (A7RV, 61 mp):


I'll say the DOF is about ± 2 cm. People with better eyes might say ± 1 cm or even less. Hover your mouse pointer over this photo for EXIF info.

APS-C camera (A6500, 24 mp):


Looking at the scale the DOF measures the same to me. Hover your mouse pointer over the photo for EXIF info.

So when someone says "APS-C cameras have more depth-of-field." what do they really mean? If we measure it with a scale, the DOF seems to be the same.

Click to expand...

Thank you for the test. Hovewer concept is not correct in my opinion.

I use or used FF, apsc and m4/3 cameras. My favourite lens is 35mm FF eq. prime. I don't really care what number is written on the lens, I want my favourite field of view - 35mm on FF, 24mm on apsc or 17mm on m4/3.

So, you should do the test with 33 or 35mm apsc lens to match the field of view of 50mm FF lens. So yes, apsc cameras in general offer more depth of field.

lehill said:

Finally, here's a photo of the Lenscal focus calibrator for those who have never seen one. These things were used in the DSLR days to drive DSLR owners crazy:


Spyder Lenscal.

Feel free to edit these three photos. Re-posting is restricted to DPReview.com only.

--
Lance H

Click to expand...

lehill said:

I've wanted to try this for a while and finally got around to it today. It's very simple. I put the very same 50mm lens on two cameras (FF & APS-C) and took two photos at the same distance (~ 80 cm), and the same f-number (f/1.4). The results are predictable but perhaps enlightening to someone fresh to photography.

I used my old Lenscal focus calibrator with scale markings adjusted for a 45° angle, ie, the distance between each major hashmark measures 1.4 cm. So the "2" numerals on the scale are 2 cm in front or behind the target.

Click to expand...

How did you view the images to decide what was in-focus and what was out-of-focus?

Wow, thank you all for all the responses. I've read them all and will probably reread a couple more times...

It is very difficult to accurately estimate the depth of field by visual inspection. The difference between APS-C and FF is too small to see easily by visual inspection.

However, a bigger difference makes it easy to see that the depth of field of a cropped image is smaller than the DoF of the full image:




Full image




Small crop of the image above

It is easy to see that both eyes are reasonably sharp in the full image, while only one eye is sharp in the cropped image.

I am sure we've been here before. Multiple times.

Bob A L said:

Same lens, same focal length, same f stop, same distance to subject =. same depth of field.

Click to expand...

No, it is not. The enlargement necessary to view the images needs to be taken into account.

Bob A L said:

Easy to prove. sensor size does not matter.

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Except that it does. Cropping a digital image always reduces DOF. You don't even need a second camera to demonstrate that. Take an image. Print it on A4. Now crop the middle part, say 1/4 of same image. Print it on A4.

Now, a 5-million dollar question: which print will show more blur around the subject when viewed from 12" away?

Bob A L said:

Just do as you have done and prove it. Thank you

I operated a process camera for years. They have vacuum back to hold the negative film. When set at the same focal length, with subject at same distance, I could use a 24" square piece of film or a 2" square piece of film and the images would be identical for the area recorded on both pieces of film. The larger. piece of film (sensor today) just recorded more area. Raised my family operating these cameras.

And if I for some crazy reason would want the small piece of film to record the same field of view that the large piece recorded I would have to reduce the focal length which with the same f stop would also increase the dof.

Just go take some photos and see the results.

Click to expand...

SEE is the key word here. Are you veweing both images displayed at the same size?

LensReflex said:

I was watching a video course on the foundations of Photography, and course material says that a smaller sensor camera is better suited to landscapes because it has a broader depth of field vs. a larger (i.e. Full Frame) sensor. Is this true?

Click to expand...

I think you should try a different course. Landscape photographers want sharp details. That’s why they use very expensive tripods, remote shutter releases, and sensors which can resolve the most detail. Back in the days of film, 4”x5” size negatives and larger were the preferred choice for landscape photographers.

Depth of field is one way of improving the acceptable sharpness when you have both foreground and background subject matter in the same shot. But using a tiny camera to achieve that defeats the primary directive of capturing fine details.

LensReflex said:

It seems to me that full frame cameras are used quite a lot in landscape photography as well. Does it become difficult to get a broader depth of field (that is, no blurriness in the photo) with a full frame camera under certain conditions, or does this assertion have no basis in reality?

Click to expand...

I’ve been on several landscape photography expeditions with professional photographers. Everyone shoots full frame. No one is concerned about not being able to deal with DOF.

Ansel Adams produced amazing high DOF photograph with very large film plates - much larger than 35mm “full frame”.

https://blogs.getty.edu/iris/what-ansel-adams-taught-me/

LensReflex said:

Wow, thank you all for all the responses. I've read them all and will probably reread a couple more times...

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I hope you understand that there are not two opinions on this subject. The facts are clear: There is definitely not a depth of field advantage to crop sensors.

LensReflex said:

I was watching a video course on the foundations of Photography, and course material says that a smaller sensor camera is better suited to landscapes because it has a broader depth of field vs. a larger (i.e. Full Frame) sensor. Is this true?

Click to expand...

False. You can stop down a larger format camera to get the same depth of field as a smaller-format camera. And at the same size, the extra diffraction effects and noise performance will be cancelled out exactly by the larger sensor.

So NO, small-format cameras have no large depth-of-field advantage.