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RX1R II - Cropping

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Mike Fewster said:
Robgo2 said:
0lf said:
Crop does impact DOF. You change the circle of confusion diameter.
Click to expand...
This is true, if the entire image is projected onto the crop area, as happens with a cropped sensor, but not if only a portion of the image is, as happens with a crop on a FF sensor.

Rob
Click to expand...
I may be misunderstanding you, but I don't think this is correct. There is no such thing as a "cropped sensor" it is simply a smaller sensor. The "cropping' refers to the image created by the lens and whether or not the lens is creating an image larger than the sensor. The image is exactly the same if you use a FF lens on a small sensor where some of the image formed is outside the sensor or whether you crop the image formed by the same lens on a FF sensor so that you are now looking at an area of the same size as the smaller sensor. My point in my previous post (and no one has commented on it yet) was that if you take a shot knowing that you intend cropping it later, you might change the point of focus for the shot to allow for this.
Click to expand...
 
The DOF is a function of the spacial relationships between the objects being photographed.

Changing the position from which the image is taken changes the spacial relationship between the objects. Although the objects in the image have not moved the ratio of the distance from the camera to the objects has changed, changing the DOF.
 
Robgo2 said:
Mike Fewster said:
Robgo2 said:
0lf said:
Crop does impact DOF. You change the circle of confusion diameter.
Click to expand...
This is true, if the entire image is projected onto the crop area, as happens with a cropped sensor, but not if only a portion of the image is, as happens with a crop on a FF sensor.

Rob
Click to expand...
I may be misunderstanding you, but I don't think this is correct. There is no such thing as a "cropped sensor" it is simply a smaller sensor. The "cropping' refers to the image created by the lens and whether or not the lens is creating an image larger than the sensor. The image is exactly the same if you use a FF lens on a small sensor where some of the image formed is outside the sensor or whether you crop the image formed by the same lens on a FF sensor so that you are now looking at an area of the same size as the smaller sensor. My point in my previous post (and no one has commented on it yet) was that if you take a shot knowing that you intend cropping it later, you might change the point of focus for the shot to allow for this.
Click to expand...
Click to expand...
 
Jerry R said:
An image taken with a FF sensor and a cropped sensor with the same lens and f stop, taken from the same place will have the same DOF. Cropping an image has no effect on the DOF of the image.

--
Sony R1, NEX C3 & 5R + Zeiss 24mm, 16-70, & FE 70-200 Lenses, Nikon V1 + 10-30 & 30-110 lenses.
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I disagree

The images will have the same DOF when viewed at their native sensor size ( because of same lens, same apperture, same distance...). But when printed at the same size, the DOF will be different because you apply different magnification ratio from their respective native sensor size to the final print size. Magnification (and so, crop) impact DOF by changing CoC.

DOF is generated both by the camera and the viewing conditions :
  • the camera (lens, subject distance) generate the focus plane and focus transition
  • the viewing conditions (viewer's eyes, print size, distance from print to viewer) generate the CoC on print.
 
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You have to separate DOF of the optical image from image display. They are two different concepts. One can do a lot with PP including blurring both background and foreground to simulate a shallower DOF.
 
IMO, optical image DOF = 0. There is only a focus plane and how quickly the amount of blur increase in out of focus area (what I called "focus transition" previously)
 
0lf said:
IMO, optical image DOF = 0. There is only a focus plane and how quickly the amount of blur increase in out of focus area (what I called "focus transition" previously)
Click to expand...
Well yes but that is a bit purist in image creation terms albeit theoretically correct. For practical purposes the DoF is the area of acceptable focus on either side of the plane of focus. All these apps to enable calculation of the DoF and hyperfocal distance are entirely misleading in the degree of precission they suggest for the inner and outer limits of the DoF.
 
Highland grey beard said:
0lf said:
IMO, optical image DOF = 0. There is only a focus plane and how quickly the amount of blur increase in out of focus area (what I called "focus transition" previously)
Click to expand...
Well yes but that is a bit purist in image creation terms albeit theoretically correct. For practical purposes the DoF is the area of acceptable focus on either side of the plane of focus. All these apps to enable calculation of the DoF and hyperfocal distance are entirely misleading in the degree of precission they suggest for the inner and outer limits of the DoF.

--
Andy

Jerry R wrote:

All though you are technically correct, DOF, in photography, refers to the range the image is perceived to be in focus, hyperfocal distance.

--
Sony R1, NEX C3 & 5R + Zeiss 24mm, 16-70, & FE 70-200 Lenses, Nikon V1 + 10-30 & 30-110 lenses.
Click to expand...
as I previously said, the area of acceptable focus is function of viewing conditions, so is impacted by the size of the printed picture : the more you magnify, the more you can see focus default, the less DOF you have. And a crop is just that : you magnify a portion of your image.
 
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Jerry R said:
The DOF is a function of the spacial relationships between the objects being photographed.

Changing the position from which the image is taken changes the spacial relationship between the objects. Although the objects in the image have not moved the ratio of the distance from the camera to the objects has changed, changing the DOF.
Click to expand...
 
Trijicon123 said:
Jerry R said:
The DOF is a function of the spacial relationships between the objects being photographed.

Changing the position from which the image is taken changes the spacial relationship between the objects. Although the objects in the image have not moved the ratio of the distance from the camera to the objects has changed, changing the DOF.
Click to expand...
Click to expand...
 
0lf said:
Highland grey beard said:
0lf said:
IMO, optical image DOF = 0. There is only a focus plane and how quickly the amount of blur increase in out of focus area (what I called "focus transition" previously)
Click to expand...
Well yes but that is a bit purist in image creation terms albeit theoretically correct. For practical purposes the DoF is the area of acceptable focus on either side of the plane of focus. All these apps to enable calculation of the DoF and hyperfocal distance are entirely misleading in the degree of precission they suggest for the inner and outer limits of the DoF.
Click to expand...
Click to expand...
 
Trijicon123 said:
0lf said:
Highland grey beard said:
0lf said:
IMO, optical image DOF = 0. There is only a focus plane and how quickly the amount of blur increase in out of focus area (what I called "focus transition" previously)
Click to expand...
Well yes but that is a bit purist in image creation terms albeit theoretically correct. For practical purposes the DoF is the area of acceptable focus on either side of the plane of focus. All these apps to enable calculation of the DoF and hyperfocal distance are entirely misleading in the degree of precission they suggest for the inner and outer limits of the DoF.
Click to expand...
Click to expand...
Click to expand...
 
Last edited:
Jerry R said:
Explain, and please try to understand we are discussing the acquisition of an image and not the display.

--
Sony R1, NEX C3 & 5R + Zeiss 24mm, 16-70, & FE 70-200 Lenses, Nikon V1 + 10-30 & 30-110 lenses.
Click to expand...
I already explained it. DOF is only relevant about the displayed images.
 
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Mike Fewster said:
Robgo2 said:
Mike Fewster said:
Robgo2 said:
0lf said:
Crop does impact DOF. You change the circle of confusion diameter.
Click to expand...
This is true, if the entire image is projected onto the crop area, as happens with a cropped sensor, but not if only a portion of the image is, as happens with a crop on a FF sensor.

Rob
Click to expand...
I may be misunderstanding you, but I don't think this is correct. There is no such thing as a "cropped sensor" it is simply a smaller sensor. The "cropping' refers to the image created by the lens and whether or not the lens is creating an image larger than the sensor. The image is exactly the same if you use a FF lens on a small sensor where some of the image formed is outside the sensor or whether you crop the image formed by the same lens on a FF sensor so that you are now looking at an area of the same size as the smaller sensor. My point in my previous post (and no one has commented on it yet) was that if you take a shot knowing that you intend cropping it later, you might change the point of focus for the shot to allow for this.
Click to expand...
Click to expand...
Click to expand...
 
Stephen McDonald said:
Mike Fewster said:
Robgo2 said:
Mike Fewster said:
Robgo2 said:
0lf said:
Crop does impact DOF. You change the circle of confusion diameter.
Click to expand...
This is true, if the entire image is projected onto the crop area, as happens with a cropped sensor, but not if only a portion of the image is, as happens with a crop on a FF sensor.

Rob
Click to expand...
I may be misunderstanding you, but I don't think this is correct. There is no such thing as a "cropped sensor" it is simply a smaller sensor. The "cropping' refers to the image created by the lens and whether or not the lens is creating an image larger than the sensor. The image is exactly the same if you use a FF lens on a small sensor where some of the image formed is outside the sensor or whether you crop the image formed by the same lens on a FF sensor so that you are now looking at an area of the same size as the smaller sensor. My point in my previous post (and no one has commented on it yet) was that if you take a shot knowing that you intend cropping it later, you might change the point of focus for the shot to allow for this.
Click to expand...
Click to expand...
Click to expand...
Click to expand...
 
Stephen McDonald said:
Mike Fewster said:
Robgo2 said:
Mike Fewster said:
Robgo2 said:
0lf said:
Crop does impact DOF. You change the circle of confusion diameter.
Click to expand...
This is true, if the entire image is projected onto the crop area, as happens with a cropped sensor, but not if only a portion of the image is, as happens with a crop on a FF sensor.

Rob
Click to expand...
I may be misunderstanding you, but I don't think this is correct. There is no such thing as a "cropped sensor" it is simply a smaller sensor. The "cropping' refers to the image created by the lens and whether or not the lens is creating an image larger than the sensor. The image is exactly the same if you use a FF lens on a small sensor where some of the image formed is outside the sensor or whether you crop the image formed by the same lens on a FF sensor so that you are now looking at an area of the same size as the smaller sensor. My point in my previous post (and no one has commented on it yet) was that if you take a shot knowing that you intend cropping it later, you might change the point of focus for the shot to allow for this.

--
Mike Fewster
Adelaide Australia
Click to expand...
Mike,

Let's take the case of using either an APS-C lens or a FF lens on a camera with an APS-C sensor In both cases, the actual focal length is multiplied by a factor of 1.5 to produce a longer effective focal length (FF equivalent), but the DOF remains unchanged. The only difference is that with the APS-C lens, most of the image circle is projected onto the sensor, while with the FF lens, only part of it is. In the same fashion, if you crop an image, either in camera or on the monitor, DOF should remain the same, as the lens has not changed. If I am missing something here, please enlighten me.

Rob
Click to expand...
I don't think the focal length is multiplied at all when we crop or just use a smaller sensor. It appears to be multiplied and that is not the same thing. Apparent multiplication factor would be a better term. When you crop an image and blow it up you seem to have moved closer as though using a longer focal length lens. The dof will remain the same also. But. Consider the following. You are taking a shot and the readings at F2. You focus on something in the foreground. Depending on how close the object you are focussing on is, there will be a narrow DOF. Now supposing you start cropping in on that image Depending on wher you crop you may well get a shot that is largely out of focus. I am exaggerating the situation a little here to make clearer what I am saying. If however when you took the shot you took it knowing that you were going to crop, you might take care with the AF to make sure that you were focussing further back into the scene to ensure you got the dof where you wanted it in the cropped image.

--
Mike Fewster
Adelaide Australia
Click to expand...
This is one reason why using what was previously called, "Smart Zoom" by Sony, has an advantage. The crop is done before the shot is taken, so you can see just what you're getting in the area to be kept for the photo. Also, the metering and focusing is done only for the smaller, selected zone. You can use these modes with smaller frame-sizes, to better include or exclude items near the margins and the photos don't have to be re-processed one extra time, after cropping.

--
Steve McDonald
http://www.ipernity.com/home/305883
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Click to expand...
The problem with Sony (at least on the camera I have) implementation of the feature is the focus box, which is extended to nearly the whole frame, so I am not sure it is an improvement in term of focus precision.

And yes, it is jpeg only.
 
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