RX1R II - Cropping

adam10 · Oct 18, 2015

Can I please have your advice.

We know that the 42 mp sensor will yield great detail.

If I crop to the equivalent of 50mm and 70mm focal lengths what amount of mp will the 50mm crop and 70mm crop yield.

I say this as this new camera could effectively become your versatile 35, 50, 70 mm equivalent.

Thanks,

Adam.

Raist3d · Oct 18, 2015

adam10 said:
Can I please have your advice.

We know that the 42 mp sensor will yield great detail.

If I crop to the equivalent of 50mm and 70mm focal lengths what amount of mp will the 50mm crop and 70mm crop yield.

I say this as this new camera could effectively become your versatile 35, 50, 70 mm equivalent.

Thanks,

That's exactly how I am trying to see it. My estimate is: 24 MP @ 50mm, 10 MP @ 70 mm. What I am hoping is that Sony allows us to compose in live view with those crops while shooting in RAW mode.

adam10 said:
Adam.

--
Raist3d/Ricardo (Photographer, software dev.)- I photograph black cats in coal mines at night...
“The further a society drifts from truth the more it will hate those who speak it.” - George Orwell

edoriel · Oct 18, 2015

Yeah, to work out the MP for a given focal length equivalent you divide the 'zoom' you want to work out by the actual lens length you are using. So in the RX1Rii's case to figure out the res for 50mm you divide 50mm by 35mm. That gives you 1.43. You then take the full MP count (42MP) and divide it by 1.43 twice. So for 50mm you will get 24.4 MP. For 70mm you get 10.5MP (42/2/2), for 85mm you get 7.1MP (42/2.43/2.43) etc. At least I think that's how it works... but I'm hopeless at maths...

As 7MP is still high enough res to still get a decent size enlargement, apart from depth of field effects, I see the 42MP of the new RX1 as a real advantage as it all but gives you a 35-85mm lens.

Davidgilmour · Oct 19, 2015

edoriel said:
Yeah, to work out the MP for a given focal length equivalent you divide the 'zoom' you want to work out by the actual lens length you are using. So in the RX1Rii's case to figure out the res for 50mm you divide 50mm by 35mm. That gives you 1.43. You then take the full MP count (42MP) and divide it by 1.43 twice. So for 50mm you will get 24.4 MP. For 70mm you get 10.5MP (42/2/2), for 85mm you get 7.1MP (42/2.43/2.43) etc. At least I think that's how it works... but I'm hopeless at maths...

As 7MP is still high enough res to still get a decent size enlargement, apart from depth of field effects, I see the 42MP of the new RX1 as a real advantage as it all but gives you a 35-85mm lens.

What kind DoF does cropping give? Is the IQ of a cropped to 50mm 24MP the same IQ as a full frame 50mm 24MP f2.0 camera?

Robgo2 · Oct 19, 2015

Davidgilmour said:
edoriel said:

Yeah, to work out the MP for a given focal length equivalent you divide the 'zoom' you want to work out by the actual lens length you are using. So in the RX1Rii's case to figure out the res for 50mm you divide 50mm by 35mm. That gives you 1.43. You then take the full MP count (42MP) and divide it by 1.43 twice. So for 50mm you will get 24.4 MP. For 70mm you get 10.5MP (42/2/2), for 85mm you get 7.1MP (42/2.43/2.43) etc. At least I think that's how it works... but I'm hopeless at maths...

As 7MP is still high enough res to still get a decent size enlargement, apart from depth of field effects, I see the 42MP of the new RX1 as a real advantage as it all but gives you a 35-85mm lens.

Click to expand...

What kind DoF does cropping give? Is the IQ of a cropped to 50mm 24MP the same IQ as a full frame 50mm 24MP f2.0 camera?

I think not, as it is still a 35mm lens.

Rob

SonyRX1 · Oct 19, 2015

Davidgilmour said:
edoriel said:

Yeah, to work out the MP for a given focal length equivalent you divide the 'zoom' you want to work out by the actual lens length you are using. So in the RX1Rii's case to figure out the res for 50mm you divide 50mm by 35mm. That gives you 1.43. You then take the full MP count (42MP) and divide it by 1.43 twice. So for 50mm you will get 24.4 MP. For 70mm you get 10.5MP (42/2/2), for 85mm you get 7.1MP (42/2.43/2.43) etc. At least I think that's how it works... but I'm hopeless at maths...

As 7MP is still high enough res to still get a decent size enlargement, apart from depth of field effects, I see the 42MP of the new RX1 as a real advantage as it all but gives you a 35-85mm lens.

Click to expand...

What kind DoF does cropping give? Is the IQ of a cropped to 50mm 24MP the same IQ as a full frame 50mm 24MP f2.0 camera?

52.5mm = f3.0

70mm = f4.0

Think of it as a 35-70mm f2-f4 zoom in terms of DoF. It stills gathers a f2 equivalent amount of light throughout that zoom range.

Highland grey beard · Oct 20, 2015

SonyRX1 said:
Davidgilmour said:

edoriel said:

Yeah, to work out the MP for a given focal length equivalent you divide the 'zoom' you want to work out by the actual lens length you are using. So in the RX1Rii's case to figure out the res for 50mm you divide 50mm by 35mm. That gives you 1.43. You then take the full MP count (42MP) and divide it by 1.43 twice. So for 50mm you will get 24.4 MP. For 70mm you get 10.5MP (42/2/2), for 85mm you get 7.1MP (42/2.43/2.43) etc. At least I think that's how it works... but I'm hopeless at maths...

As 7MP is still high enough res to still get a decent size enlargement, apart from depth of field effects, I see the 42MP of the new RX1 as a real advantage as it all but gives you a 35-85mm lens.

Click to expand...

What kind DoF does cropping give? Is the IQ of a cropped to 50mm 24MP the same IQ as a full frame 50mm 24MP f2.0 camera?

Click to expand...

52.5mm = f3.0

70mm = f4.0

Think of it as a 35-70mm f2-f4 zoom in terms of DoF. It stills gathers a f2 equivalent amount of light throughout that zoom range.

That simply cannot be right. It is a 35mmm lens on a FF sensor. You get the DoF appropriate to the aperture being used. Assuming the OP meant PP cropping all that is doing is selecting a smaller part of the same image. The IQ and DoF of the actual image are unchanged because the image itself is unchanged except for the selection of a smaller part of it. So the MP you are left with affects only the size of image to be gained before loss of detail occurs.

Trijicon123 · Oct 20, 2015

Highland grey beard said:
SonyRX1 said:

Davidgilmour said:

edoriel said:

Yeah, to work out the MP for a given focal length equivalent you divide the 'zoom' you want to work out by the actual lens length you are using. So in the RX1Rii's case to figure out the res for 50mm you divide 50mm by 35mm. That gives you 1.43. You then take the full MP count (42MP) and divide it by 1.43 twice. So for 50mm you will get 24.4 MP. For 70mm you get 10.5MP (42/2/2), for 85mm you get 7.1MP (42/2.43/2.43) etc. At least I think that's how it works... but I'm hopeless at maths...

As 7MP is still high enough res to still get a decent size enlargement, apart from depth of field effects, I see the 42MP of the new RX1 as a real advantage as it all but gives you a 35-85mm lens.

Click to expand...

What kind DoF does cropping give? Is the IQ of a cropped to 50mm 24MP the same IQ as a full frame 50mm 24MP f2.0 camera?

Click to expand...

52.5mm = f3.0

70mm = f4.0

Think of it as a 35-70mm f2-f4 zoom in terms of DoF. It stills gathers a f2 equivalent amount of light throughout that zoom range.

Click to expand...

That simply cannot be right. It is a 35mmm lens on a FF sensor. You get the DoF appropriate to the aperture being used. Assuming the OP meant PP cropping all that is doing is selecting a smaller part of the same image. The IQ and DoF of the actual image are unchanged because the image itself is unchanged except for the selection of a smaller part of it. So the MP you are left with affects only the size of image to be gained before loss of detail occurs.

0lf · Oct 20, 2015

Crop does impact DOF. You change the circle of confusion diameter.

Mike Fewster · Oct 20, 2015

0lf said:
Crop does impact DOF. You change the circle of confusion diameter.

Doesn't this depend on where you focus? If you take a shot knowing that you intend cropping later, generally you will have adjusted focus to further back in the scene?

Highland grey beard · Oct 20, 2015

0lf said:
Crop does impact DOF. You change the circle of confusion diameter.

You are going to have to explain since I am by no means clear on how this happens since my rudimentary understanding of CoC is that it is a function of the light passing through the lens onto the sensor and this defines the DoF being the area of acceptable focus either side of the plane of focus. Having taken the image and in PP crop a part of it how does the DoF then change if the cropped and uncropped images are both viewed on screen at 100%? I can see that the IQ will be different if the cropped and uncropped images are enlarged to the same physical size but how does that affect perceived DoF?

0lf · Oct 20, 2015

Highland grey beard said:
0lf said:

Crop does impact DOF. You change the circle of confusion diameter.

Click to expand...

You are going to have to explain since I am by no means clear on how this happens since my rudimentary understanding of CoC is that it is a function of the light passing through the lens onto the sensor and this defines the DoF being the area of acceptable focus either side of the plane of focus.

IMO, the relevant CoC for perceived DOF is what your eyes can resolve on a printed picture (on screen or on paper). It is not define by lens and sensor. Then, you convert the CoC on print into CoC on sensor for calculations.

Highland grey beard said:
Having taken the image and in PP crop a part of it how does the DoF then change if the cropped and uncropped images are both viewed on screen at 100%? I can see that the IQ will be different if the cropped and uncropped images are enlarged to the same physical size but how does that affect perceived DoF?

--
Andy

A crop is like a magnification, and can reveal out of focus where you were into area of acceptable focus before crop. So, DOF is also print's size dependant, and when you compare a croped and uncroped picture at 100%, you are comparing two different print sizes.

Robgo2 · Oct 20, 2015

0lf said:
Crop does impact DOF. You change the circle of confusion diameter.

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

0lf · Oct 20, 2015

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

I disagree.

Given that you view the croped (x2 for example) and uncroped pictures on a same sized print (full screen on a 15" computer for example), and from the same distance, then, the CoC on the prints will have the same size in both cases (depending on what your eyes can resolve).

Then, resize both images to the size they had on the sensor. Since the size ratio is different (15" to 24x36mm in one case, 15" to 12x18 in the other case), the CoC on sensor is different.

Mike Fewster · Oct 20, 2015

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

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.

Jerry R · Oct 20, 2015

The focal length of the lens and aperture define the optical characteristic of the image not the sensor, digital or film.

Mike Fewster · Oct 20, 2015

Jerry R said:
The focal length of the lens and aperture define the optical characteristic of the image not the sensor, digital or film.

Robgo2 · Oct 20, 2015

0lf 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 disagree.

Given that you view the croped (x2 for example) and uncroped pictures on a same sized print (full screen on a 15" computer for example), and from the same distance, then, the CoC on the prints will have the same size in both cases (depending on what your eyes can resolve).

Then, resize both images to the size they had on the sensor. Since the size ratio is different (15" to 24x36mm in one case, 15" to 12x18 in the other case), the CoC on sensor is different.

I agree with your first paragraph, and that is what I was alluding to in my comment. The question is whether the cropping affects DOF.

Rob

Jerry R · Oct 20, 2015

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. If the same FOV is used (the FF sensor closer to the subject) the DOF will be different. Cropping an image has no effect on the DOF of the image.

Mike Fewster · Oct 20, 2015

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. If the same FOV is used (the FF sensor closer to the subject) the DOF will be different. Cropping an image has no effect on the DOF of the image.

RX1R II - Cropping

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