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Zoom reach on crop sensors
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Jan 13, 2019 16:05:03   #
Longshadow (a regular here)
 
PHRubin wrote:
It is worse than that, the image is cropped both in length and width.
A Canon APS-C sensor is 329mm² while a FF is 864mm². 24*(329/864) = 9.14 MP.
For Nikon it is almost as bad: 24*(380/864)=10.56 MP


I'm lost, do these numbers have any usefulness?

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Jan 13, 2019 16:58:04   #
PHRubin
 
Longshadow wrote:
I'm lost, do these numbers have any usefulness?


Only to realize that cropping an image from a FF camera to equal the reach of a crop sensor loses a great amount of resolution. You lose more than 1/2 the pixels.

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Jan 13, 2019 17:02:41   #
Longshadow (a regular here)
 
PHRubin wrote:
Only to realize that cropping an image from a FF camera to equal the reach of a crop sensor loses a great amount of resolution. You lose more than 1/2 the pixels.

As would cropping an image from a camera using 50mm lens to make it look like a 150mm lens?

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Jan 13, 2019 17:05:44   #
PHRubin
 
Longshadow wrote:
As would cropping an image from a camera using 50mm lens to make it look like a 150mm lens?


True, but you are taking this thread into a different direction. I was simply correcting some misinformation.

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Jan 13, 2019 17:08:33   #
Longshadow (a regular here)
 
PHRubin wrote:
True, but you are taking this thread into a different direction. I was simply correcting some misinformation.

Just trying to clarify your statement in my mind so I understand correctly, not trying to re-direct.

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Jan 13, 2019 19:51:43   #
nadelewitz (a regular here)
 
Longshadow wrote:
Okay. So there is no real or apparent zooming with a crop sensor?
I've been calling these variable-field-of-view lenses by the wrong name?

That's not what is being discussed here.
What is then?


What does zooming have to do with crop sensor? Zooming is what you do with a variable-focal-length lens. Yes, changing focal length changes field of view.
The field of view of the LENS does not change with what type of body you put it on. What changes is HOW MUCH of the lens's field of view (whatever it is depending on the focal length) the sensor captures.

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Jan 13, 2019 19:56:13   #
Longshadow (a regular here)
 
nadelewitz wrote:
What does zooming have to do with crop sensor? Zooming is what you do with a variable-focal-length lens. Yes, changing focal length changes field of view.
The field of view of the LENS does not change with what type of body you put it on. What changes is HOW MUCH of the lens's field of view (whatever it is depending on the focal length) the sensor captures.


Okay.

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Jan 13, 2019 21:25:20   #
JLM
 
If you have two cameras one with a full frame sensor and the other with an APS-c sensor and both sensors are exactly the same except for size (same kind and number of pixels per square MM etc.), if you crop the image from the full frame sensor to exactly the same size as the image from the APS-c sensor the cropped image from the full frame sensor will be identical to the image from the APS-c sensor (same number of pixels, same resolution, etc). If you blow the two images up they will look the same at all magnifications.

Your software displays full frame and aps-c images the same size because it enlarges the image from c sensors.

A lens of a given focal length that can be used on both types of camera simply shows more of the subject area when used on a full frame camera.

If you want the best quality image and you want the 'reach' of an aps-c sensor the best way to do it is usually to use a full frame camera and crop the image because full frame cameras usually have higher quality sensors. All pixels are not created equal. There are many valid reasons for choosing an aps-c sensor camera over a full frame camera (cost, size, weight, etc.) but extended reach of the lens is not one of them.

Another way of looking at it is that if you shot a subject with an aps-c camera and backed off with a full frame camera so you shot the same subject subject at the same 'magnification' with the full frame camera and both camera sensors were identical except for size the full frame image would have more pixels than the aps-c image so it could be enlarged to a greater size. One advantage of a full frame camera over and aps camera if that you can always crop unwanted information out of a full frame image a lot easier than you can add information to a 'cropped' image.

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Jan 14, 2019 11:43:03   #
nadelewitz (a regular here)
 
JLM wrote:


A lens of a given focal length that can be used on both types of camera simply shows more of the subject area when used on a full frame camera.

If you want the best quality image and you want the 'reach' of an aps-c sensor the best way to do it is usually to use a full frame camera and crop the image because full frame cameras usually have higher quality sensors. All pixels are not created equal. There are many valid reasons for choosing an aps-c sensor camera over a full frame camera (cost, size, weight, etc.) but extended reach of the lens is not one of them.

br br A lens of a given focal length that can be... (show quote)


1. The lens does not show more or less of the subject. The lens sees and transmits the SAME THING (field of view) regardless of what body you put it on.
The difference is what part of the transmitted field DIFFERENT SIZE SENSORS CAPTURE.

2. An APS-C sensor is not "reaching" further at all. It is CROPPING. Please stop using the term "extended reach of the lens". This only confuses people who are trying to understand this subject.

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