GH13 GH13 Crop question
- Thread starter mojo43
- Start date
I don't know how the Nikon achieves it's video image, but the GH1 uses an oversize sensor which expands the image horizontally in 16:9 recordings, rather than cropping a 4:3 or 3:2 sensor. I think this might be the reason for so much confusion over the difference between the FOV on the Canon APS and GHxx cams. As far as I'm aware, the Canons crop the image, when in filming mode, to achieve 16:9. The GH doesn't really change, it just covers a different area on the sensor.
mojo43
Well-known member
Sorry, but I am not sure I am following...
The GH cameras don't crop the sensor to achieve 16:9 when filming. Therefore, it's possible that your GH13 has a horizontally wider field of view, with a similar effective focal length lens to the NIkon, which I presume does crop the sensor when filming. There is an explanation of the oversize sensor at http://fourthirds-user.com/2009/04/the_biggest_four_thirds_sensor_yet.php
This might not be the cause of the difference, but I suspect it might.
stoneinapond
Veteran
I've talked to some knowledgable people and here is what I'm told.
Take a 50mm from Nikon, a 50mm from Canon and a 50mm from Leica for example. You'd think they would all have the same angle of view on the same camera (forget cropping for now). However, the 50mm is a designation that may or may not be totally accurate. There is a 50mm Leica lens that is designated 50mm, but in their own technical specifications they say that the true focal length is 51.x (can't remember the exact fraction). It's not called a 51.x lens, it is rounded out to 50mm, but compared to a lens that is absolutely a 50mm, you would notice a very slight difference.
The other point that Adrian was stating is that possibly the 2x crop on the GH1 is also not absolute. I remember discussions about the GH2 having a 1.9 crop when filming in a 16x9 ratio due to the way the sensor is designed. So perhaps both of those factors are responsible for what you are observing.
Take a 50mm from Nikon, a 50mm from Canon and a 50mm from Leica for example. You'd think they would all have the same angle of view on the same camera (forget cropping for now). However, the 50mm is a designation that may or may not be totally accurate. There is a 50mm Leica lens that is designated 50mm, but in their own technical specifications they say that the true focal length is 51.x (can't remember the exact fraction). It's not called a 51.x lens, it is rounded out to 50mm, but compared to a lens that is absolutely a 50mm, you would notice a very slight difference.
The other point that Adrian was stating is that possibly the 2x crop on the GH1 is also not absolute. I remember discussions about the GH2 having a 1.9 crop when filming in a 16x9 ratio due to the way the sensor is designed. So perhaps both of those factors are responsible for what you are observing.
Ian-T
Veteran
People keep saying 2x when they try to stress this is better than that etc. But it's never accurate. The fact is the GH-Xs have this strange oversized sensor compared to other m4/3 cameras (even the AF100). Doesn't necessarily make it better....just different. The Canons (7D, 60D, T2i etc) are 1.6x crop. So in reality the difference is not a great deal (which is what a lot of folks have been trying to say for many moons).
In addition to this however what folks mentioned up above about video mode is true. The Canons might have a bigger sensor which benefits it in stills mode...but in video mode it's a whole other story. It's sensor is a square 4:3 sensor where the GH-Xs are rectangle. They both end up with a rectangle 16:9 image in video mode but the GH-Xs use the whole sensor to achieve it while the Canons crop off the top and bottom (which takes away from the benefit of having a bigger sensor). So in the end....it almost evens out. Which is why I say the crop factor between these cameras is negligable. At least that's how I interpret it.
In addition to this however what folks mentioned up above about video mode is true. The Canons might have a bigger sensor which benefits it in stills mode...but in video mode it's a whole other story. It's sensor is a square 4:3 sensor where the GH-Xs are rectangle. They both end up with a rectangle 16:9 image in video mode but the GH-Xs use the whole sensor to achieve it while the Canons crop off the top and bottom (which takes away from the benefit of having a bigger sensor). So in the end....it almost evens out. Which is why I say the crop factor between these cameras is negligable. At least that's how I interpret it.
Ian-T
Veteran
When it comes to your initial post....of course. You said:
Those are two different sized lenses. The 14mm on the GH-x will be a good deal wider than the 18mm already. Now take into account the information about crop size that I mentioned above I can assume that it will still be a little wider or even close to one another. I'm just speculating here though. But ...if you say it is...then all those factors (IMO) are contributing to it.
Just forget about your initial thought of a 2x crop.
Those are two different sized lenses. The 14mm on the GH-x will be a good deal wider than the 18mm already. Now take into account the information about crop size that I mentioned above I can assume that it will still be a little wider or even close to one another. I'm just speculating here though. But ...if you say it is...then all those factors (IMO) are contributing to it.
Just forget about your initial thought of a 2x crop.
Actually, I believe it is simple math. 14mm is nearly 30% wider than 18mm.
himynameisnathan
Active member
The sensor in the GH series is slightly bigger than the 4/3rd standard (which has an aspect ratio of 4:3). This mean's when you crop to different aspect ratio's (3:2, 16:9) the crop factor (which is measured diagonally) is always the same (x2), whereas non GH series camera's which use a non-oversized sensor, literally cut the top and bottom of the frame off, giving them a larger crop (x2.1?) in video mode due to the sensor making a 4:3 image into a 16:9 one.
Canon/nikon camera's use a 3:2 sensor (x1.6/1.5 crop), which is slightly wider than it is tall compared to the 4/3rd standard (which is more square in shape) When you use video, which is 16:9 on Canon/nikon camera's it does the same thing that 4/3rds do on non GH cameras, and simply cuts the top and bottom of the frame off, meaning the crop shrinks slightly, probably about x1.6 for nikon and x1.7 for canon. The image sensing area is still bigger than the GH series, however, due to the sensor "expanding in width" on the GH cameras, you do get a slightly wider field of view, while at the same time, the vertical Field of view is cropped due to 16:9 being wider then 4:3, so while the crop is still x2 in diagonal terms, you actually get about x1.85 horizontal fov which is contrasted by a loss of vertical fov (bringing it up to about x2.15?)
In simplest terms, there is a gap between the two in video, but not enough to be noticeable, almost like the difference between canon and nikons APS-C sensor's; ie, negligible.
Hope that makes sense, alot of brackets and numbers in there
Canon/nikon camera's use a 3:2 sensor (x1.6/1.5 crop), which is slightly wider than it is tall compared to the 4/3rd standard (which is more square in shape) When you use video, which is 16:9 on Canon/nikon camera's it does the same thing that 4/3rds do on non GH cameras, and simply cuts the top and bottom of the frame off, meaning the crop shrinks slightly, probably about x1.6 for nikon and x1.7 for canon. The image sensing area is still bigger than the GH series, however, due to the sensor "expanding in width" on the GH cameras, you do get a slightly wider field of view, while at the same time, the vertical Field of view is cropped due to 16:9 being wider then 4:3, so while the crop is still x2 in diagonal terms, you actually get about x1.85 horizontal fov which is contrasted by a loss of vertical fov (bringing it up to about x2.15?)
In simplest terms, there is a gap between the two in video, but not enough to be noticeable, almost like the difference between canon and nikons APS-C sensor's; ie, negligible.
Hope that makes sense, alot of brackets and numbers in there
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This got me curious. If you punch in the numbers on a FOV calculator, then you end with a similar FOV between the 2 camera lens combinations. If you increase the crop ratio on the Nikon, to either 1.6 or 1.7 then the GH 14 combo comes out slightly wider. Add in, that all lenses aren't created equal, as others have pointed out there is some variations in lens focal length from different manufacturers.
Mix it all together and it makes a perfect recipe for the rectangle of confusion
Mix it all together and it makes a perfect recipe for the rectangle of confusion
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