How JVC could nail it

You guys are just getting confused with terminology like "magnification factor." You should probably be talking about "cropping factor."

Either way, focal length is focal length, regardless of the sensor size. It is the FIELD OF VIEW that changes depending on sensor size.

So what you really want to know is the difference in size between 35mm, 16mm and 1/3".

You can easily figure out any factor based on these dimensions:

35mm still photography = 36mm x 24mm

Digital SLR still photography (Canon Digital Rebel) = 22.5mm x 15mm

35mm motion picture film = 22mm x 18.59mm (1.33:1)

16mm motion picture film = 9.65mm x 7.26mm (1.33:1)

2/3" CCD = 8.8mm x 6.6mm (1.33:1)

1/3" CCD = 4.8mm x 3.6mm (1.33:1)

ADDED: HD100 1/3" HD CCD: 4.864mm x 2.739mm (16x9, 1.78:1)


So based on these dimensions, if you wanted to figure out 1/3" FOV based on 16mm FOV, then divide 9.65 by 4.8 = 2.01

1/3" compared to 35mm SLR still photography, 36/4.8 = 7.5

1/3" compared to 35mm motion picture film, 22/4.8 = 4.58

1/3" compared to 2/3" CCD, 8.8/4.8 = 1.83

and so on...
 
dashwood,

You are so right. The concept of relating the focal length of video camera lenses to the focal length of the SLR lens (or 35mm Cine or any other format) to the focal length of the lens that gives an equivalent field of view on the video format causes seemingly endless confusion.

The one small point is that the size of the typical 1/3 " 16x9 sensor is approx 2.95 mm high x 5.22 mm wide meaning that a given lens will be a bit wider horizontally on the 16x9 camera than on a 4x3. (the corner to corner or diagonal field of view remains the same as the diagonal of both formats in a 1/3" inch sensor is the same (approx 6 mm)

Everyone needs to keep in mind (as you clearly say :

"focal length is focal length, regardless of sensor size. It is the FIELD OF VIEW that changes depending on the sensor size. "

For instance, when you attach a 5Omm SLR lens to a Canon XL1/2 , H1 , or the JVC 100 the FIELD OF VIEW is the same as the camera's zoom lens set to 50mm.

But I have seen this confusion in one form or another for 30 years, so I dont think it will go away anytime soon inspite of the best efforts to explain it.

Bill Turner
Schneider Optics, Inc
Century Division
 
Bill__Turner said:
The one small point is that the size of the typical 1/3 " 16x9 sensor is approx 2.95 mm high x 5.22 mm wide meaning that a given lens will be a bit wider horizontally on the 16x9 camera than on a 4x3. (the corner to corner or diagonal field of view remains the same as the diagonal of both formats in a 1/3" inch sensor is the same (approx 6 mm)
Click to expand...

Bill,

This is interesting. I've tried to find specs on 16x9 1/3" CCDs, but everyone seems to do it a little differently. For example, the Canon XL2 just uses a 4x3 1/3" chip, but crops the top and bottom to achieve its 16x9, then crops the left and right of that to achieve its 4x3. http://dvinfo.net/canonxl2/articles/article06.php

Curiously, in my FOV comparison tests with HD100 and the DVX100, I noted that 5.5mm focal length on the HD100 is actually wider than the 4.5mm focal length on the DVX100.
This lead me to believe that the CCD on the HD100 was wider than standard 1/3" as you suggested. I think Fuji may have screwed up a little though, because there is obvious vignetting when the lens is wide, so it feels like there isn't enough coverage on the CCD block.
 
Dashwood:

Based on what I know, I believe that the 1/3" sensors in the Sony, Panasonic, JVC, and Canon HD/HDV cameras are approx the size I stated- in terms of the active area being used for 16:9 format images. The actual size and shape of the whole sensor is unknown to me.

Bill Turner
 
mmm said:
A 20mm SLR lens is very wide angle, even fish-eye. A 9.5mm lens focusing on a 1/3" CCD is not very wide at all. For example a DVX lens goes to 4.5mm, which still doesn't give a very wide angle of view, I am guessing similar to a 40-50mm SLR lens...?
Click to expand...

Thanks Tim, the above should really read:

"A 20mm lens on a 35mm SLR is very wide angle, even fish-eye. A 9.5mm lens focusing onto a 1/3" CCD does not give nearly such a wide angle of view. For example a DVX lens goes to 4.5mm, which still doesn't give as wider angle of view as the 20mm lens would on a 35mm SLR. I am guessing it is similar to the field of view of a 40-50mm lens when used on an 35mm SLR...?"

Sorry, sloppy writing on my part:embarasse . Of course an DVX lens is "exclusive" and fixed to that camera, and so has a set field of view (excluding the zoom range!:lipsrseal ) So in effect you can say "a DVX lens has a viewing angle of X." You can't do that with an interchangeable lens which will be used on different sized imagers.
 
I've been pondering an idea for awhile now. I'm no lens expert, mind you, but what if you could adapt a lens from an old 8mm film camera to work with one of these cameras (XL series and the JVC). Isn't the image size of the sensors closer to an 8mm frame than a 16mm frame?

I've seen various 8mm cameras with zooms and 3 lens wheels on them. A little tinkering and I would think that you could accomplish this.

I'm sure I'm grasping at straws and there will be those who think I'm nuts, but It seems to me that this could be possible. Well...let the firing squad commence:laugh:
 
There are some tests on the XL2 lens here. Looks pretty good to me. Apparently it is noticably worse than the XLH1 lens though.
 
nateweaver said:
The lens on any 8mm camera I can think of would not really be up the task of resolving enough for 1/3" HD.
Click to expand...

This is off topis slightly but, I was thinking that it could be a viable option for an XL series camera. The specific lens I had in mind would be the one on the end of the Chinon 12 SMR 8mm film camera. Probably one of the bigger 8mm lenses I have ever seen. I used to have one (too bad I sold it years ago) but I recall it having a lens aperture of f1.8. The lens itself was at the very least 58mm... possibly 72mm.

http://www.mondofoto.com/cameras/Chinon_Pacific-12SMR_a.jpg

Wait, I found the lens specs...
6-72mm f/1.8 Macro Zoom lens. Filter size is 72mm
 
Bill__Turner said:
dThe one small point is that the size of the typical 1/3 " 16x9 sensor is approx 2.95 mm high x 5.22 mm wide meaning that a given lens will be a bit wider horizontally on the 16x9 camera than on a 4x3. (the corner to corner or diagonal field of view remains the same as the diagonal of both formats in a 1/3" inch sensor is the same (approx 6 mm)
Click to expand...


Bill, Stephen found a chart that confirms the actual size of the HD100 CCD is 4.864mm x 2.739mm.

Here's the document. http://pro.jvc.com/pro/attributes/HDTV/manual/HD100_shooting_angle.pdf
 
Dashwood,

Thankyou, that is a very interesting table. It would appear that JVC is using a bit less than the full 1/3" CCD, but I suspect others maybe as well. The numbers I quoted would be for a full 6 mm diagonal.

Bill Turner
 
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