Busting the FF vs Crop DoF Bokeh Myth

you might want to try this test outdoors... hopefully by then, you will see how creamy the bokeh will be with FF (same distance, Aperture and pls dont crop, )

also, i know by then, it's your test thats ganna be busted and not the myth, btw, its not a myth, its a fact backed by physics and math calculations.

pls, just try it outside, a park, on a table, bring a toy and watch the background blurs.

if you want , pls do 2 test.

1) same distance and aperture.
2) same framing and aperture - meaning diff distance)

good luck.
--
Canon Shooter:
5D Mark II, 1D Mark II and 1D Mark II N

15mm Fisheye, 16-35L2, TS-E 24L, 24-105L IS, 24-70L,
28-135 IS, 50L, 50 1.8, 85L2, TS-E 90, 135L, 75-300,
70-200L IS 2.8, 200L 2.0, 1.4X Tele, 2X Tele

580EX II (3x), RadioPoppers (3x), ST-E2, CP-E4,
White Lightning X1600, Vagabond II, V2s Wireless Trigger
Zeus 2500 w/ Z2500HS (2x), 47' Octabox, Calumet Strip Box
Sekonic L-758DR & Calibration Target

Manfrotto 058B & RC322, Manfrotto 055XBPro and Manfrotto Monopod.

Try explaining that to some. they say move the FF closer then the results will be real (Real skewed that is) or you have to use an 85mm and a 50mm so the comparison is the same (NOT). There is a large group here that go through life with their blinders on....

Just look a few lines up if you don't believe me....

chinch wrote:

the 1.6x crop is just that... A CROP so obviously it won't change DOF all it does is crop the outer portion of the image.

LOL not a revelation!

Now move on and see why this thread failed at the first post.

Cal Dawson wrote:

I did this years ago and all it brought was grief.... Nobody wants to see the truth they all want to change something distance, FOV etc then they say the test will be fair or unfair dependent upon whether your results are what they want....
--
Cal

Put a Canon to your head, You deserve it....

http://funshots.smugmug.com/

Cal Dawson wrote:

I did this years ago and all it brought was grief.... Nobody wants to see the truth they all want to change something distance, FOV etc then they say the test will be fair or unfair dependent upon whether your results are what they want....

No, the same field of view, not different fields of view, that is the whole point. These shots do not have the same field of view.

It isn’t a case of fairness or unfairness, it is a case of validity. All these shots disprove is a myth that didn’t exist, except perhaps by some misunderstanding.

Most people already understand ‘the truth’ in this case. The OP isn’t busting any myth other than his own misconception.

Brian A.

you've never brought your 50mm to the zoo, They don't let me go over the barrier and into the cage so I can frame the same as the other guy...

Sometimes it just doesn't work....Sometimes you have no choice but to shoot from the exact same vantage point. So the OP's point is valid. Now whether you ever need it that's up to you....

Cheburashka wrote:

therickman wrote:

Many people have argued that the DoF and bokeh using the same lens on a full frame and 1.6x crop camera at the same aperture and the same distance from the subject will yield different DoF and different bokeh... And they're flat out wrong!

When people say that the DOF is different on FF and 1.6x using the same focal length and the same f-ratio, they mean for the whole of the frame and displayed at the same dimensions. They don't mean to crop the FF image to the same framing as the 1.6x image. Why would they do that?

I mean, who, for example, uses a 50/1.4 at f/2 on FF and crops to the same framing as they would get with a 50/1.4 at f/2 on 1.6x? Now, in some cases, such as extreme telephoto, where the FF camera is focal length limited (due to availablity, expense, size, or weight) or extreme macro where more than 1:1 is needed, this may be common. But other than that, it's unheard of.

Canon_Lover wrote:

you might want to try this test outdoors... hopefully by then, you will see how creamy the bokeh will be with FF (same distance, Aperture and pls dont crop, )

also, i know by then, it's your test thats ganna be busted and not the myth, btw, its not a myth, its a fact backed by physics and math calculations.

pls, just try it outside, a park, on a table, bring a toy and watch the background blurs.

if you want , pls do 2 test.

1) same distance and aperture.
2) same framing and aperture - meaning diff distance)

good luck.
--
Canon Shooter:
5D Mark II, 1D Mark II and 1D Mark II N

15mm Fisheye, 16-35L2, TS-E 24L, 24-105L IS, 24-70L,
28-135 IS, 50L, 50 1.8, 85L2, TS-E 90, 135L, 75-300,
70-200L IS 2.8, 200L 2.0, 1.4X Tele, 2X Tele

580EX II (3x), RadioPoppers (3x), ST-E2, CP-E4,
White Lightning X1600, Vagabond II, V2s Wireless Trigger
Zeus 2500 w/ Z2500HS (2x), 47' Octabox, Calumet Strip Box
Sekonic L-758DR & Calibration Target

Manfrotto 058B & RC322, Manfrotto 055XBPro and Manfrotto Monopod.

Sorry, but you are wrong. Indoors or outdoors. Think of it this way. The same lens is projecting the same image circle at the plane of the sensor. The "crop" sensor is smaller, but in the same location as the FF sensor. The "crop" sensor is seeing the exact same image with the same DOF and bokeh, it is simply cropping the image compared to the FF sensor (that is why it is called a crop sensor). The ONLY thing confusing the results presented here is the pixel density. If we repeated the experiment with two cameras with identical pixel density, you'd see that the OP is correct. (I think a 30D and a 5DII should be very close to the same pixel density).

dherzstein wrote:

I don't think that the OP understands DOF.
--
-Dave
http://pixseal.com

I do. DoF is much different than FoV - which everybody here seems to be confusing.

Cal Dawson wrote:

I did this years ago and all it brought was grief.... Nobody wants to see the truth they all want to change something distance, FOV etc then they say the test will be fair or unfair dependent upon whether your results are what they want....

Cal Dawson continued:

Try explaining that to some. they say move the FF closer then the results will be real (Real skewed that is) or you have to use an 85mm and a 50mm so the comparison is the same (NOT). There is a large group here that go through life with their blinders on....

I'm afraid I'm missing your point(s). When comparing DOFs between systems, we need to spell out the conditions. In my opinion, the most natural conditions are the same perspective (subject-camera distance), same framing, and same display dimensions (this is what DOF calclulators presume). In this situation, FF needs to use 1.6x the focal length for the same framing and 1.6x the f-ratio for the same aperture. So, under these condtions, the images will have the same DOF. Do you disagree?

Another situation, that which the OP presented, is different. In this case, he used the same perspective (subject-camera distance) but different framing. This is an unusual way to compare the DOF between systems. However, what he demonstrated was that, under these conditions, if we use the same focal length and f-ratio (and thus same aperture), but then crop the more widely framed FF image to the same framing as the more tightly framed 1.6x image, and display the two at the same dimensions, then the resulting DOFs will also be the same.

However, as no one I know of has used a FF camera in that manner, except when focal length limited for extreme telephoto, or needed greater apparent magnification in macro, then this is an odd way to discuss the DOF between systems.

From http://www.josephjamesphotography.com/equivalence/#dof:

We can now make the following generalizations about the DOF of images on different formats for non-macro situations (when the subject distance is "large" compared to the focal length), keeping in mind that aperture = focal length / f-ratio:

1) For the same perspective, framing, f-ratio, and display size, larger sensor systems will yield a more shallow DOF than smaller sensors.

2) For the same perspective, framing, aperture, and display size, all systems have the same DOF.

3) For the same focal length, framing, aperture (same focal length and aperture also means same f-ratio), and display size, all systems have the same DOF (but different perspectives).

4) For the same perspective and focal length, larger sensor systems will have a wider framing. If the same f-ratio is used, then both systems will also have the same aperture. As a result, if the image from the larger sensor system is displayed at a larger size in proportion to the sensor sizes, or the image from the larger sensor system is cropped to the same framing as the image from the smaller sensor system and displayed at the same size, then the two images will have the same DOF.

Hugowolf wrote:

Cal Dawson wrote:

I did this years ago and all it brought was grief.... Nobody wants to see the truth they all want to change something distance, FOV etc then they say the test will be fair or unfair dependent upon whether your results are what they want....

No, the same field of view, not different fields of view, that is the whole point. These shots do not have the same field of view.

Exactly and the OP never stated different, but everyone wants to change the experiment to suit their ideas....

It isn’t a case of fairness or unfairness, it is a case of validity. All these shots disprove is a myth that didn’t exist, except perhaps by some misunderstanding.

Exactly and that misunderstanding is that given the same lens, distance and aperture the FF will have a narrower DOF (Not true) it does become true if you change any of the above....

Most people already understand ‘the truth’ in this case. The OP isn’t busting any myth other than his own misconception.

Look at the arguments above the truth is "In this instance" the DOF "IS" the same and his methodology is valid if for some reason you cannot move closer (Barriers etc...)

Brian A.

Cal Dawson wrote:

you've never brought your 50mm to the zoo, They don't let me go over the barrier and into the cage so I can frame the same as the other guy...

Sometimes it just doesn't work....Sometimes you have no choice but to shoot from the exact same vantage point. So the OP's point is valid. Now whether you ever need it that's up to you....

In fact, I have. But I didn't use it to shoot pics knowing that I'd later crop my pics after the fact to an 80mm AOV and then compare the DOF of my pics to those of a 1.6x DSLR.

Hugowolf wrote:

It isn’t a case of fairness or unfairness, it is a case of validity. All these shots disprove is a myth that didn’t exist, except perhaps by some misunderstanding.

Most people already understand ‘the truth’ in this case. The OP isn’t busting any myth other than his own misconception.

It's a myth that people here are still perpetuating. I never had a misconception about this.

coldbivy wrote:

Sorry, but you are wrong. Indoors or outdoors. Think of it this way. The same lens is projecting the same image circle at the plane of the sensor. The "crop" sensor is smaller, but in the same location as the FF sensor. The "crop" sensor is seeing the exact same image with the same DOF and bokeh, it is simply cropping the image compared to the FF sensor (that is why it is called a crop sensor). The ONLY thing confusing the results presented here is the pixel density. If we repeated the experiment with two cameras with identical pixel density, you'd see that the OP is correct. (I think a 30D and a 5DII should be very close to the same pixel density).

Pixel density has nothing to do with DOF:

http://www.josephjamesphotography.com/equivalence/#dof

It is important to note that the DOF depends neither on the number of pixels that make up the image nor the sharpness of the lens. This misconception comes from the fact that more pixels and/or sharper lenses usually resolve more detail. However, the resolved detail is independent of the DOF. A simple way to visualize the difference between DOF and resolved detail is to apply a Gaussian Blur to an image. While the blurred image will have less detail, the depth from the focal point that is considered to be in focus will be unaffected. So, while DOF, sharpness, and detail are all intertwined, they are independent quantities. A good way to understand this is to imagine an image taken of the same scene from the same position with the same framing and aperture using cameras with very different pixel counts. Now resample both images to the same dimensions so that they just fit on your computer monitor. The DOFs will be the same. It would be no different when printing the images, so long as they were printed with the same dimensions. So, just as detail cannot be changed with sharpening, DOF cannot be changed with more detail.

therickman wrote:

I do. DoF is much different than FoV - which everybody here seems to be confusing.

DOF is a function of the FoV, among other factors -- something which you seem to be ignoring.

I commend you on your endeavors, however they are in vain, you haven't solved anything here.

An outdoors test surely would have been appropriate here, I feel you have wastwed your time here, and I have wasted my own giving any rise what so ever to this un substantiated test

In the spirit of good review, can we please refrain from misleading people with information claimed to be fact, that is infact opinion

regards

Cheburashka wrote:

coldbivy wrote:

Sorry, but you are wrong. Indoors or outdoors. Think of it this way. The same lens is projecting the same image circle at the plane of the sensor. The "crop" sensor is smaller, but in the same location as the FF sensor. The "crop" sensor is seeing the exact same image with the same DOF and bokeh, it is simply cropping the image compared to the FF sensor (that is why it is called a crop sensor). The ONLY thing confusing the results presented here is the pixel density. If we repeated the experiment with two cameras with identical pixel density, you'd see that the OP is correct. (I think a 30D and a 5DII should be very close to the same pixel density).

Pixel density has nothing to do with DOF:

http://www.josephjamesphotography.com/equivalence/#dof

It is important to note that the DOF depends neither on the number of pixels that make up the image nor the sharpness of the lens. This misconception comes from the fact that more pixels and/or sharper lenses usually resolve more detail. However, the resolved detail is independent of the DOF. A simple way to visualize the difference between DOF and resolved detail is to apply a Gaussian Blur to an image. While the blurred image will have less detail, the depth from the focal point that is considered to be in focus will be unaffected. So, while DOF, sharpness, and detail are all intertwined, they are independent quantities. A good way to understand this is to imagine an image taken of the same scene from the same position with the same framing and aperture using cameras with very different pixel counts. Now resample both images to the same dimensions so that they just fit on your computer monitor. The DOFs will be the same. It would be no different when printing the images, so long as they were printed with the same dimensions. So, just as detail cannot be changed with sharpening, DOF cannot be changed with more detail.

I didn't quite say that pixel density does have anything to do with DOF. However, the size of the displayed image does have something to do with DOF, and if you have different pixel densities and choose to display a 100% magnified image, you have now based your display size on the pixel density.

coldbivy wrote:

I didn't quite say that pixel density does have anything to do with DOF. However, the size of the displayed image does have something to do with DOF, and if you have different pixel densities and choose to display a 100% magnified image, you have now based your display size on the pixel density.

Please accept my apologies, then, for the misinterpretation of what you wrote.

Yaamon wrote:

Thanks for your test but how about adjusting the distance with the crop body so that it matches the 5D to compare with your original photos?

I did.

Now, I'm going to explain this like I'm talking to a bunch of 5-year olds so you all understand. I'm incredibly tired of everyone here contorting my original post into something entirely different than what it was, and making me out to be some kind of imbicile. So here it goes...

The 50D has a 1.6x crop sensor, correct? Yayy!! Good job. Now time for some math. To get roughly the same field-of-view (or similar composition) as a full frame 5D at 5 feet from the subject, I moved the 50D 8 feet away from the subject.

5 X 1.6 = 8

Yayy!! You all get a smiley sticker for getting that correct. Below are two snapshots. One of the 5D with 85mm at f/2 at a distance of 5 feet, and one of the 50D with 85mm at f/2 at a distance of 8 feet. I attempted to frame the shots as identical as possible.

Obviously, the DoF of the 5D will be thinner than that of the 50D because of the closer distance, and this is evident in the photos.

(If I read someone post that these samples disprove my own observation, I'm seriously going to blow a stack. Please read my original post before you comment further. I never, I repeat NEVER claimed similar images from a 5D and 50D will have the same depth-of-field. I disproved the myth that depth-of-field will still be different using the same lens at the same distance from subject at the same aperture.)

Why do I get the feeling people are still going to completely ignore the evidence - and my original post - and still try to make me out to be a moron?

durack7 wrote:

I commend you on your endeavors, however they are in vain, you haven't solved anything here.

An outdoors test surely would have been appropriate here, I feel you have wastwed your time here, and I have wasted my own giving any rise what so ever to this un substantiated test

In the spirit of good review, can we please refrain from misleading people with information claimed to be fact, that is infact opinion

The tests were performed outdoors, on my deck, against my brick wall. I'm not really sure what you're saying here. My test was measured accurately to show the effects of DoF at the same distance from the subject. The books were spaced 1 foot and 2 feet behind the subject (Ansel Adams) book to demonstrate identical blur (bokeh) caused by OOF background objects. Using bushes, trees, telephone poles or buildings as a backdrop wouldn't change anything.