Calling all portrait photographers!

[Ysarex]

But, if I am using an FX sensor in DX mode, isn't that the same as using DX sensor (and thus changing the Circle of Confusion)?

Exactly. You're cropping the FX sensor down to DX in the camera. Cropping the FX image after you've taken it does exactly the same thing and produces the same result. The DOF for a DX sensor is the same as the DOF for a DX sensor. If you want to compare the difference in DOF between a DX and FX sensor you have to in fact use the FX sensor uncropped and take the same photo with both cameras.

Joe

 

[Destin]

But, if I am using an FX sensor in DX mode, isn't that the same as using DX sensor (and thus changing the Circle of Confusion)?

Exactly. You're cropping the FX sensor down to DX in the camera. Cropping the FX image after you've taken it does exactly the same thing and produces the same result. The DOF for a DX sensor is the same as the DOF for a DX sensor. If you want to compare the difference in DOF between a DX and FX sensor you have to in fact use the FX sensor uncropped and take the same photo with both cameras.

Joe

But in order to take the same photo with both cameras the image either has to be cropped or the full frame camera has to be moved closer. It’s impossible to take the same images without doing one or the other.

 

[snowbear]

But, if I am using an FX sensor in DX mode, isn't that the same as using DX sensor (and thus changing the Circle of Confusion)?

Exactly. You're cropping the FX sensor down to DX in the camera. Cropping the FX image after you've taken it does exactly the same thing and produces the same result. The DOF for a DX sensor is the same as the DOF for a DX sensor. If you want to compare the difference in DOF between a DX and FX sensor you have to in fact use the FX sensor uncropped and take the same photo with both cameras.

Joe

I'm just trying to understand, but you seem to be contradictory here.

I say shooting the a FX sensor in FX and DX modes will produce two images with different DoF (no cropping or enlarging in post - take a JPEG and post full size to the web, unaltered in the HTML). At first you agree ("Exactly You're cropping the FX down to DX . . ." but, then you say I need two different cameras (use FX sensor uncropped and take the same photo with both cameras"). I wish you'd make up your mind.

@alex_ethridge: I apologize for my part in hijacking your thread. My testing results will be done in my own thread.

 

[Ysarex]

Obviously when you *zoom* in on an image you get a better view of what was *actually* sharp in the first place.

At lower magnification levels you can’t make out the minor imperfections as well.

But that doesn’t mean the imperfections don’t exist. It just means you aren’t looking close enough to see them.

And that is how our discipline defines DOF: It's defined by what you can see in the final print/display, not by what you can't. Talk about DOF if you want to talk about DOF but don't change the subject and talk about something else. Learn how DOF is in fact defined. You're not in a position at this point to be taken seriously if you're trying to redefine it.

Joe

It’s the same reason that a sensor with higher megapixel count makes your focus accuracy more critical: the higher resolution makes the flaws that were *originally there* more apparent.

By your example, the depth of field would also have to become thinner with higher resolution sensors because you can better see which areas are in focus. But that isn’t the case; sensor resolution has no effect on depth of field in the same way that cropping to change the pixel size has no effect on depth of field.

You act like I actually care if anyone on an Internet forum takes me seriously.

I’ve researched this topic to exhaustion in the last hour; it seems that half of the true respected professional photographers agree with you and the other half with me.

There are textbooks that teach it one way, and textbooks that teach it another.

Like I said, we’re essentially saying the same thing and wording it differently. By cropping the image you may change the *effective* or *apparent* depth of field.

I'm only talking about DOF. There is no *effective* or *apparent* DOF. And again: DOF is defined ONLY in the final print/display image.

But the amount of the image that was physically sharp when you captured the image does not actually change, no matter how much it appears to have done so.

DOF is defined only in the final print/display image. There are no DOF calculations that exist to determine what is and isn't sharp on the sensor/film.

If you want to get technical about what existed when the photo was taken we should be comparing 1:1 crops of the original image; which again would be affected by sensor resolution.

I don't and never said I did -- I'm talking about DOF.

And yet sensor resolution is never taken into account in a DOF calculator.

And I never said it was. That's coming from you.

Even doing that, the results will end up being extremely subjective because we all define differently what we consider to be sharp.

While we’re applying your fluid definition of depth of field, it would also change based on the subjective nature of who is viewing it.

Please recall that my definition of DOF is the one shared by the major and accepted DOF calculators available for you to run simulations through. They agree with me. Please provide a link to a calculator or reference a set of equations that do not agree with me.

Allowed for by incorporating averages for human visual acuity.

Joe

And therefore you could never actually measure it because we’d all see different limits on where the sharpness of the in focus area ends.

 

[Destin]

Obviously when you *zoom* in on an image you get a better view of what was *actually* sharp in the first place.

At lower magnification levels you can’t make out the minor imperfections as well.

But that doesn’t mean the imperfections don’t exist. It just means you aren’t looking close enough to see them.

And that is how our discipline defines DOF: It's defined by what you can see in the final print/display, not by what you can't. Talk about DOF if you want to talk about DOF but don't change the subject and talk about something else. Learn how DOF is in fact defined. You're not in a position at this point to be taken seriously if you're trying to redefine it.

Joe

It’s the same reason that a sensor with higher megapixel count makes your focus accuracy more critical: the higher resolution makes the flaws that were *originally there* more apparent.

By your example, the depth of field would also have to become thinner with higher resolution sensors because you can better see which areas are in focus. But that isn’t the case; sensor resolution has no effect on depth of field in the same way that cropping to change the pixel size has no effect on depth of field.

You act like I actually care if anyone on an Internet forum takes me seriously.

I’ve researched this topic to exhaustion in the last hour; it seems that half of the true respected professional photographers agree with you and the other half with me.

There are textbooks that teach it one way, and textbooks that teach it another.

Like I said, we’re essentially saying the same thing and wording it differently. By cropping the image you may change the *effective* or *apparent* depth of field.

I'm only talking about DOF. There is no *effective* or *apparent* DOF. And again: DOF is defined ONLY in the final print/display image.

But the amount of the image that was physically sharp when you captured the image does not actually change, no matter how much it appears to have done so.

DOF is defined only in the final print/display image. There are no DOF calculations that exist to determine what is and isn't sharp on the sensor/film.

If you want to get technical about what existed when the photo was taken we should be comparing 1:1 crops of the original image; which again would be affected by sensor resolution.

I don't and never said I did -- I'm talking about DOF.

And yet sensor resolution is never taken into account in a DOF calculator.

And I never said it was. That's coming from you.

Even doing that, the results will end up being extremely subjective because we all define differently what we consider to be sharp.

While we’re applying your fluid definition of depth of field, it would also change based on the subjective nature of who is viewing it.

Please recall that my definition of DOF is the one shared by the major and accepted DOF calculators available for you to run simulations through. They agree with me. Please provide a link to a calculator or reference a set of equations that do not agree with me.

Allowed for by incorporating averages for human visual acuity.

Joe

And therefore you could never actually measure it because we’d all see different limits on where the sharpness of the in focus area ends.

Show me a DOF calculator that calculates how much cropping or enlarging a print will physically change the DOF.

 

[Ysarex]

But, if I am using an FX sensor in DX mode, isn't that the same as using DX sensor (and thus changing the Circle of Confusion)?

Exactly. You're cropping the FX sensor down to DX in the camera. Cropping the FX image after you've taken it does exactly the same thing and produces the same result. The DOF for a DX sensor is the same as the DOF for a DX sensor. If you want to compare the difference in DOF between a DX and FX sensor you have to in fact use the FX sensor uncropped and take the same photo with both cameras.

Joe

But in order to take the same photo with both cameras the image either has to be cropped or the full frame camera has to be moved closer. It’s impossible to take the same images without doing one or the other.

Not true -- you can change the lens focal length on one of the cameras. And in fact to do an appropriate same photograph comparison you'll have to do that. When you take the same photograph with two different sensor size cameras from the same place and at the same f/stop the DOF will be different between them. It will in part be due to the sensor size which will be accounted for in the calculations in the variable circle of confusion.

Joe

 

[Destin]

But, if I am using an FX sensor in DX mode, isn't that the same as using DX sensor (and thus changing the Circle of Confusion)?

Exactly. You're cropping the FX sensor down to DX in the camera. Cropping the FX image after you've taken it does exactly the same thing and produces the same result. The DOF for a DX sensor is the same as the DOF for a DX sensor. If you want to compare the difference in DOF between a DX and FX sensor you have to in fact use the FX sensor uncropped and take the same photo with both cameras.

Joe

But in order to take the same photo with both cameras the image either has to be cropped or the full frame camera has to be moved closer. It’s impossible to take the same images without doing one or the other.

Not true -- you can change the lens focal length on one of the cameras. And in fact to do an appropriate same photograph comparison you'll have to do that. When you take the same photograph with two different sensor size cameras from the same place and at the same f/stop the DOF will be different between them. It will in part be due to the sensor size which will be accounted for in the calculations in the variable circle of confusion.

Joe

But changing focal length to match the field of view will make the DOF thinner. In order for it to be a fair comparison you cannot change focal length.

 

[Ysarex]

Obviously when you *zoom* in on an image you get a better view of what was *actually* sharp in the first place.

At lower magnification levels you can’t make out the minor imperfections as well.

But that doesn’t mean the imperfections don’t exist. It just means you aren’t looking close enough to see them.

And that is how our discipline defines DOF: It's defined by what you can see in the final print/display, not by what you can't. Talk about DOF if you want to talk about DOF but don't change the subject and talk about something else. Learn how DOF is in fact defined. You're not in a position at this point to be taken seriously if you're trying to redefine it.

Joe

It’s the same reason that a sensor with higher megapixel count makes your focus accuracy more critical: the higher resolution makes the flaws that were *originally there* more apparent.

By your example, the depth of field would also have to become thinner with higher resolution sensors because you can better see which areas are in focus. But that isn’t the case; sensor resolution has no effect on depth of field in the same way that cropping to change the pixel size has no effect on depth of field.

You act like I actually care if anyone on an Internet forum takes me seriously.

I’ve researched this topic to exhaustion in the last hour; it seems that half of the true respected professional photographers agree with you and the other half with me.

There are textbooks that teach it one way, and textbooks that teach it another.

Like I said, we’re essentially saying the same thing and wording it differently. By cropping the image you may change the *effective* or *apparent* depth of field.

I'm only talking about DOF. There is no *effective* or *apparent* DOF. And again: DOF is defined ONLY in the final print/display image.

But the amount of the image that was physically sharp when you captured the image does not actually change, no matter how much it appears to have done so.

DOF is defined only in the final print/display image. There are no DOF calculations that exist to determine what is and isn't sharp on the sensor/film.

If you want to get technical about what existed when the photo was taken we should be comparing 1:1 crops of the original image; which again would be affected by sensor resolution.

I don't and never said I did -- I'm talking about DOF.

And yet sensor resolution is never taken into account in a DOF calculator.

And I never said it was. That's coming from you.

Even doing that, the results will end up being extremely subjective because we all define differently what we consider to be sharp.

While we’re applying your fluid definition of depth of field, it would also change based on the subjective nature of who is viewing it.

Please recall that my definition of DOF is the one shared by the major and accepted DOF calculators available for you to run simulations through. They agree with me. Please provide a link to a calculator or reference a set of equations that do not agree with me.

Allowed for by incorporating averages for human visual acuity.

Joe

And therefore you could never actually measure it because we’d all see different limits on where the sharpness of the in focus area ends.

Show me a DOF calculator that calculates how much cropping or enlarging a print will physically change the DOF.

Certainly.

Joe

 

[Destin]

But, if I am using an FX sensor in DX mode, isn't that the same as using DX sensor (and thus changing the Circle of Confusion)?

Exactly. You're cropping the FX sensor down to DX in the camera. Cropping the FX image after you've taken it does exactly the same thing and produces the same result. The DOF for a DX sensor is the same as the DOF for a DX sensor. If you want to compare the difference in DOF between a DX and FX sensor you have to in fact use the FX sensor uncropped and take the same photo with both cameras.

Joe

But in order to take the same photo with both cameras the image either has to be cropped or the full frame camera has to be moved closer. It’s impossible to take the same images without doing one or the other.

Not true -- you can change the lens focal length on one of the cameras. And in fact to do an appropriate same photograph comparison you'll have to do that. When you take the same photograph with two different sensor size cameras from the same place and at the same f/stop the DOF will be different between them. It will in part be due to the sensor size which will be accounted for in the calculations in the variable circle of confusion.

Joe

But changing focal length to match the field of view will make the DOF thinner. In order for it to be a fair comparison you cannot change focal length.

I’d like to add that *literally nobody here* is arguing that using a longer focal length, or moving a camera closer will not change DOF. Obviously it will.

We are arguing that if you keep all other values the exact same, and change *only the sensor size* the out of focus area of the image will retain the same appearance in both photos. By definition to run this experiment the only thing that can change is the sensor size. Period.

Anything else and you’ve destroyed the experiment.

 

[Ysarex]

But, if I am using an FX sensor in DX mode, isn't that the same as using DX sensor (and thus changing the Circle of Confusion)?

Exactly. You're cropping the FX sensor down to DX in the camera. Cropping the FX image after you've taken it does exactly the same thing and produces the same result. The DOF for a DX sensor is the same as the DOF for a DX sensor. If you want to compare the difference in DOF between a DX and FX sensor you have to in fact use the FX sensor uncropped and take the same photo with both cameras.

Joe

But in order to take the same photo with both cameras the image either has to be cropped or the full frame camera has to be moved closer. It’s impossible to take the same images without doing one or the other.

Not true -- you can change the lens focal length on one of the cameras. And in fact to do an appropriate same photograph comparison you'll have to do that. When you take the same photograph with two different sensor size cameras from the same place and at the same f/stop the DOF will be different between them. It will in part be due to the sensor size which will be accounted for in the calculations in the variable circle of confusion.

Joe

But changing focal length to match the field of view will make the DOF thinner. In order for it to be a fair comparison you cannot change focal length.

In order for it to be a fair comparison and so compare the effect of sensor size you have to take the same photograph. To do that with two different size sensor you must change focal length. And yes that focal length change will factor in but so does the sensor size. If you don't take the same photograph you have nothing to compare.

Joe

 

[Destin]

But, if I am using an FX sensor in DX mode, isn't that the same as using DX sensor (and thus changing the Circle of Confusion)?

Exactly. You're cropping the FX sensor down to DX in the camera. Cropping the FX image after you've taken it does exactly the same thing and produces the same result. The DOF for a DX sensor is the same as the DOF for a DX sensor. If you want to compare the difference in DOF between a DX and FX sensor you have to in fact use the FX sensor uncropped and take the same photo with both cameras.

Joe

But in order to take the same photo with both cameras the image either has to be cropped or the full frame camera has to be moved closer. It’s impossible to take the same images without doing one or the other.

Not true -- you can change the lens focal length on one of the cameras. And in fact to do an appropriate same photograph comparison you'll have to do that. When you take the same photograph with two different sensor size cameras from the same place and at the same f/stop the DOF will be different between them. It will in part be due to the sensor size which will be accounted for in the calculations in the variable circle of confusion.

Joe

But changing focal length to match the field of view will make the DOF thinner. In order for it to be a fair comparison you cannot change focal length.

In order for it to be a fair comparison and so compare the effect of sensor size you have to take the same photograph. To do that with two different size sensor you must change focal length. And yes that focal length change will factor in but so does the sensor size. If you don't take the same photograph you have nothing to compare.

Joe

Joe - by changing any of those other factors to take the same photograph you cannot isolate the factor that is changing the depth of field. That isn’t how scientific experiments work.

You can only have one variable that changes, otherwise you have no idea what is actually causing the change.

The *only way* to create the same photo as a DX camera using an FX camera is to crop the FX image down to match the DX image.

In doing so, both images will appear *identical*

Therefore the sensor size does not physically affect DOF, other than by forcing you to change other variables to make the field of view the same.

 

[Ysarex]

But, if I am using an FX sensor in DX mode, isn't that the same as using DX sensor (and thus changing the Circle of Confusion)?

Exactly. You're cropping the FX sensor down to DX in the camera. Cropping the FX image after you've taken it does exactly the same thing and produces the same result. The DOF for a DX sensor is the same as the DOF for a DX sensor. If you want to compare the difference in DOF between a DX and FX sensor you have to in fact use the FX sensor uncropped and take the same photo with both cameras.

Joe

But in order to take the same photo with both cameras the image either has to be cropped or the full frame camera has to be moved closer. It’s impossible to take the same images without doing one or the other.

Not true -- you can change the lens focal length on one of the cameras. And in fact to do an appropriate same photograph comparison you'll have to do that. When you take the same photograph with two different sensor size cameras from the same place and at the same f/stop the DOF will be different between them. It will in part be due to the sensor size which will be accounted for in the calculations in the variable circle of confusion.

Joe

But changing focal length to match the field of view will make the DOF thinner. In order for it to be a fair comparison you cannot change focal length.

I’d like to add that *literally nobody here* is arguing that using a longer focal length, or moving a camera closer will not change DOF. Obviously it will.

We are arguing that if you keep all other values the exact same, and change *only the sensor size* the out of focus area of the image will retain the same appearance in both photos. By definition to run this experiment the only thing that can change is the sensor size. Period.

No. I never claimed that and never would. In fact early on in the thread I cautioned that there was no point in making a comparison unless the two cameras/sensors were used to take the same photograph. I'm happy to also claim that if you do as you said and use the same lens from same place at same f/stop with different sensors the DOF is different as I fist demonstrated with the DOF Master illustration, but then it's not the same photo and you have to compare different images without cropping the FX image.

I posted early in the thread and said sensor size effects DOF. It does. Solarflare said that was wrong. He's wrong. You said the effect was indirect. It is not -- it is direct.

If you want to do a comparison that makes any sense then take the same photo with both. Otherwise go ahead and do you FX/DX same lens same place same f/stop but you then must accept the DOF from the full FX image. All the calculators say the DOF will be different. It's stupid to compare DX with FX cropped to DX -- that's the same thing.

Joe

Anything else and you’ve destroyed the experiment.

 

[Derrel]

Destin: I sincerely hope that you will be able to try to replicate my 20-foot FX and 34.5 foot DX, full-length portrait example; the definition of the words direct and indirect will become more clear once you see that you can NOT create the same image UNLESS the camera-to-subject distance is altered, materially. There is a direct link, as it relates to creating the same picture, while using same, exact lens, but when also using two, differing format sizes.

You've brought up a point abut depth of field in a final print; that if you do crop the images, you CAN get the same apparent DOF look from two different format cameras. But that is not the normal way to use a camera....there's no sense in shooting on a big, large, high-definition piece of film, and then tossing 40,50,60,70,90 percent of the image captured into the trash, in order to make an 8x10 inch print that approximates the look of a 110-film format capture.

I GET where you are coming from, and yet, and yet earlier, you seemed to indicate that you did not understand that CROPPING THE IMAGE changes the depth of field...so...kind of weird...you've got the concept half right...you have a point.

Anyway...making the SAME PICTURE: try my experiment, please. Do not crop an FX image, but instead, shoot the full-length shot at 34.5 feet on APS-C, then use a full-frame camera from 20 feet away. See whatcha' think!

And, as Ysarex said--it is indeed silly to compare a cropped FX image with a DX-shot image...please try the 20-foot FX versus 34.5 foot APS-C comparison with whatever single focal length lens you havbe at hand (50mm,85mm, or one end of a 70-00 zoom, etc,).

 

[snowbear]

In order for it to be a fair comparison and so compare the effect of sensor size you have to take the same photograph. To do that with two different size sensor you must change focal length. And yes that focal length change will factor in but so does the sensor size. If you don't take the same photograph you have nothing to compare.

Joe

So you are saying that all other things being equal, two different sized sensors will produce a digital image with the same Depth of Field. By "all other things" I am referring to focal length, distance to subject, aperture, and uncropped or unenlarged images displayed at the images' native resolution. Obviously the view angles and actual sizes (in pixels) will differ between the images.

I'm done with the hijacking of this thread. My observations from any testing will be posted elsewhere.

 

[Ysarex]

But, if I am using an FX sensor in DX mode, isn't that the same as using DX sensor (and thus changing the Circle of Confusion)?

Exactly. You're cropping the FX sensor down to DX in the camera. Cropping the FX image after you've taken it does exactly the same thing and produces the same result. The DOF for a DX sensor is the same as the DOF for a DX sensor. If you want to compare the difference in DOF between a DX and FX sensor you have to in fact use the FX sensor uncropped and take the same photo with both cameras.

Joe

But in order to take the same photo with both cameras the image either has to be cropped or the full frame camera has to be moved closer. It’s impossible to take the same images without doing one or the other.

Not true -- you can change the lens focal length on one of the cameras. And in fact to do an appropriate same photograph comparison you'll have to do that. When you take the same photograph with two different sensor size cameras from the same place and at the same f/stop the DOF will be different between them. It will in part be due to the sensor size which will be accounted for in the calculations in the variable circle of confusion.

Joe

But changing focal length to match the field of view will make the DOF thinner. In order for it to be a fair comparison you cannot change focal length.

In order for it to be a fair comparison and so compare the effect of sensor size you have to take the same photograph. To do that with two different size sensor you must change focal length. And yes that focal length change will factor in but so does the sensor size. If you don't take the same photograph you have nothing to compare.

Joe

Joe - by changing any of those other factors to take the same photograph you cannot isolate the factor that is changing the depth of field. That isn’t how scientific experiments work.

You can only have one variable that changes, otherwise you have no idea what is actually causing the change.

Then the thing you must hold constant is the same photograph at the same f/stop. Both the lens fl change and the sensor size change will have an effect. That's why we've incorporated a variable in the math to account for the sensor size change. Can I repeat that: We've incorporated a variable in the math to account for the sensor size change. We've done this by the way. Before you were born we did this quite exhaustively and worked it all out. I first worked through the math using an old Leica manual from the 1930s. Nothings changed by the way and it was already old stuff back when the book was written.

The *only way* to create the same photo as a DX camera using an FX camera is to crop the FX image down to match the DX image.

In doing so, both images will appear *identical*

Therefore the sensor size does not physically affect DOF, other than by forcing you to change other variables to make the field of view the same.

No. Sorry it's a bit more complex than that, but let me repeat again We've incorporated a variable in the math to account for the sensor size change. Decades before you were born that wouldn't have been done if it hadn't been necessary. OK. Let's try this: Give me a link to any DOF calculator or a reference to any set of equations that calculate DOF and do not incorporate a value for the size of the film/sensor.

Joe