HVX and 35MM adapter Calculations

[morisato]

I posted this in the 35mm adapter section, but it doesnt seem like many people hang out there and since this does involve the HVX, I feel it is appropriate to be posting this here.

Here's what I posted in the other thread:

I have a 35mm adapter and some lenses. I was wondering if there's a mathmatical equation to find out what the HVX+lens equivalent field of view is on a 35mm camera. I know that the field of view is dependent on the ratio between the lens and chip, so that a 50mm lens on a HVX is not equivalent to a 50mm lens on a 35mm camera, right?

I know that the the HVX is 1/3" which is about 8.4mm and a 35mm camera is... well... 35mm. What I dont know is how to figure out what lens I would need to put on my HVX to match the same field of view as a 50mm on a 35mm camera. If the ratio were to stay the same, that would mean I would need a 12mm lens on my HVX... that doesnt sound right. Please help!

[Matty_g]

Because you are using the ground glass relay with a 35mm adapter a 35mm lens should have the same dof and fov as on regular 35mm.

[morisato]

oh... ok... I guess that makes sense.

Edit:

But wait... there's room to zoom in past the edges on the 35mm adapter, so would that field of view be equivalent to setting the HVX to see the entire projection from corner to corner?

[Ryan Patrick O'Hara]

Since the image is "projected" from the SLR lens to the ground glass, the HVX and CCD does not influence field of view....

With that being said, what does influence field of view is how zoomed in you are on the ground glass.

So as the image projected on the ground glass is technically the same as a 35mm still camera, the HVX does zoom in on that image to get past the motor and side edges of the M2.

To find out for yourself, set up your M2 and HVX. Find the maximum distance you can zoom out with the HVX while not getting the motor, sides, or vinetting.

After that, remove the lens and attatch to a still photography camera. Take picture and compare.

Try to have the image plane (film plane) and the ground glass parallel when taking photos to compare.

The next question you will probably as, which I do not know the answer, is "Since the HVX is 16:9 (1.78:1) and 35mm still photography is 3:2 (1.5:1), how does that effect the feild of view?"

I don't know. I suppose the HVX has so zoom in on the image to fill the edges of its frame with the less wide 35mm aspect ratio.

Thoughts?

[Barry_Green]

I know that the the HVX is 1/3" which is about 8.4mm and a 35mm camera is... well... 35mm.
1/3" in CCD or CMOS sensor sizes is NOT 1/3". No sensor measures anywhere near what its "type" of size would indicate. 1/3" CCD camcorders are more like about 5.3 x 3mm.


What I dont know is how to figure out what lens I would need to put on my HVX to match the same field of view as a 50mm on a 35mm camera.
On a still camera? Multiply the HVX lens mm by about 7.8. So zoom to about 6.5mm and the field of view should about approximate a 35mm still camera.

If you're using a 35mm lens adapter, the numbers change; now you have to approximate 35mm movie camera focal lengths against 35mm still camera focal lengths. The ratio is more like 2:1, but it's far more complicated depending on what type of frame your adapter is using. 35mm adapters are *supposed* to use a 24x18 frame, but many of them use a much larger frame to get extremely shallow DOF.

[morisato]

1/3" in CCD or CMOS sensor sizes is NOT 1/3". No sensor measures anywhere near what its "type" of size would indicate. 1/3" CCD camcorders are more like about 5.3 x 3mm.


On a still camera? Multiply the HVX lens mm by about 7.8. So zoom to about 6.5mm and the field of view should about approximate a 35mm still camera.

If you're using a 35mm lens adapter, the numbers change; now you have to approximate 35mm movie camera focal lengths against 35mm still camera focal lengths. The ratio is more like 2:1, but it's far more complicated depending on what type of frame your adapter is using. 35mm adapters are *supposed* to use a 24x18 frame, but many of them use a much larger frame to get extremely shallow DOF.

I think you're comparing HVX stock lens vs SLR lens vs Film Lens. What I was talking about was the HVX+SLR Lens vs Film lens on a 35mm format camera and finding the equation to translate the field of view of one to the other.

[Barry_Green]

I know, that's what I was answering in the third paragraph.

If you're using a standardized adapter like the mini35, the calculation is easy and repeatable. If you're using one of the low-cost adapters, precise calculations are going to be nearly impossible because those adapters use different frame sizes. And even then you have to also answer if you're talking about 35mm movie film or 35mm still-camera film, because they're not the same frame size. Movie film uses the space between the sprockets as its width, still film uses that space as its height, so still film uses a frame size that's 2x as big as the movie frame size.

[filmstox]

Dennis Wood, maker of the Brevis posted this image over at the Cinevate website, it should help with your calculations. I don't know how it compares to the M2 but I should think they will be similar.


http://www.edgecentric.com/hvx200/frame.jpg

I found a great primer on frame sizes put out by the EBU here (http://www.edgecentric.com/hvx200/tec_text_r86-2000_tcm6-4781.pdf) .

[Ryan Patrick O'Hara]

Dennis Wood, maker of the Brevis posted this image over at the Cinevate website, it should help with your calculations. I don't know how it compares to the M2 but I should think they will be similar.


http://www.edgecentric.com/hvx200/frame.jpg

I found a great primer on frame sizes put out by the EBU here (http://www.edgecentric.com/hvx200/tec_text_r86-2000_tcm6-4781.pdf) .

Hmmmm... so the Brevis shows more angle of view than the lens would on a 35mm camera? Is this black box representative of the camera zoomed past all vignetting?

[filmstox]

As far as I can tell, it represents the available image area on the diffuser excluding the edge area that would be rendered unusable by the vibration of the diffuser. So it represents the maximum potential useful imaging area. vignetting will vary by lens and by focal length so the portion of the diffuser you can use will vary accordingly.