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35mm still lenses for 16mm


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#1 Melissa North

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Posted 26 June 2006 - 02:22 AM

Hi,

If using a still 35mm lens with a focal length of say 50mm, on a 16mm camera (obviously with a lens mount converter); is the 'field of view' / perspective / frame size, going to be that of: a standard 50mm focal length on a 35mm camera, or standard 50mm focal length for 16mm camera or is it something completely different?

Im sure I have read some where that it stays the same as the 35mm format focal length. Im just a little confused as I know that the 'normal' focal length in 35mm is around 50mm, and 'normal' in 16mm is around 25mm.

Also, if using 35mm still lenses on a 16mm camera, which DOF charts and focal lengths do I refer to to calculate my Depth of Field?

Appreciate your help,

Thanks,
Mel.
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#2 Robert Hughes

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Posted 26 June 2006 - 07:16 AM

Check the back threads for several posts on this topic. In short; 50mm is 50mm for any format; with a smaller format such as 16mm you have a smaller image area so the result is that 50mm is a telephoto lens, akin to 100mm in 35mm motion picture format.
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#3 Charles MacDonald

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Posted 26 June 2006 - 10:18 PM

Check the back threads for several posts on this topic. In short; 50mm is 50mm for any format; with a smaller format such as 16mm you have a smaller image area so the result is that 50mm is a telephoto lens

Unfortunatly some digital camera makers have started marking lenses as "equivelent focal lenght" just ot confuse folks.

A 50MM lens will be 50mm (slight telephoto) on a 16mm camera.
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#4 Matt Pacini

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Posted 28 June 2006 - 06:08 PM

50mm is 50mm is 50mm, but it will LOOK more telephoto on a smaller format.

Also, I keep having to repeat this:
50mm on a 35mm motion picture camera IS NOT NORMAL.
50mm is condidered normal for 35mm still cameras, which have a MUCH larger frame size than 35mm motion picture film. 8 perfs horizontal.
This keeps getting repeated over and over, and it's just wrong.
It's more like 28mm-ish if I remember right, but it sure as hell isn't 50mm.

MP

Edited by Matt Pacini, 28 June 2006 - 06:08 PM.

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#5 Charles MacDonald

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Posted 28 June 2006 - 08:38 PM

50mm is 50mm is 50mm, but it will LOOK more telephoto on a smaller format.

Also, I keep having to repeat this:
50mm on a 35mm motion picture camera IS NOT NORMAL.
50mm is condidered normal for 35mm still cameras, which have a MUCH larger frame size than 35mm motion picture film. 8 perfs horizontal.
This keeps getting repeated over and over, and it's just wrong.
It's more like 28mm-ish if I remember right, but it sure as hell isn't 50mm.
MP

My understanding from a way back is that for every given format you take the diaginal of the frame,and thet should be the the focal lenth of a "normal lens..

35MM still camera 24*36 MM == Sqroor ot 24^2 +36^2 == SQr 1872.0 == 43.26 mm so 40 to 50 is Normal.

Just to put a fly in the porage, many 16mm movie camera came with a 25mm Lens as "normal". 8mm Cameras came with a 13.
so these slight telephoto lens came to be considered "normal" A 25mm lens would be "normal" for a 1 inch Vidicon.

A 25 Mm is actually close to normal for 35mm Movies. which would make the 13 good for 16mm and an 8 mm about right for Regular 8.
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#6 Chris Keth

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Posted 29 June 2006 - 12:04 AM

The lenses will work just fine. Ju8st as these guys have stated, DoF, field of view, everything will be the same as any other lens of similar focal length at whatever given stop. The nice thing is that they are much cheaper then cine lenses.

The downfalls of doing that are:

1.)a lot of still lenses are not as fast as lenses meant for film production and
2.) still lenses breath like a sonofabitch and that are not geared for use with follow focus units or any of that good stuff. One picture at a time doesn't deal with focus change so the lens designers didn't worry about it. On the vast, vast majority of still lenses, don't even think about focus pulls. It will just look like a little zoom and generally look like poop. I suppose you might do this if you're trying to evoks b-movie or something, but it generally sucks the rest of the time.

Those are the pros and cons I've found.
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#7 Leo Anthony Vale

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Posted 29 June 2006 - 01:30 PM

Just to put a fly in the porage, many 16mm movie camera came with a 25mm Lens as "normal". 8mm Cameras came with a 13.
so these slight telephoto lens came to be considered "normal" A 25mm lens would be "normal" for a 1 inch Vidicon.


---The 1" vidicon refers to the diameter of the tube, not the target area.
That would be 16mm.
11mm on a 2/3".
22mm on a 1 & 1/4".

---El Pedante
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#8 Charles MacDonald

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Posted 29 June 2006 - 08:19 PM

---The 1" vidicon refers to the diameter of the tube, not the target area.
That would be 16mm.
11mm on a 2/3".
22mm on a 1 & 1/4".

I was going by looking at the front of an RCA 7735A. The mask goes almost to the edge of the tube, but I did not measure it. The useable image area WOULD be slightly less than 1 Inch diagonal. I will have to dig out the tube and my calipers and get a better figure. (reminding myselfthat I bought a GBC camera with an Hitachi 7735A to play with and I have not got it running yet)

Most of the small Vidicon TV camaera I ghave seen also come with a 1 or even a 2 inch lens. Unfortunatly these lenes often won't fit a film camera as the TV camera had no need of a shutter, and so the lens designer concentrated on getting an image on th etarget of the tube.

Bottom line is most movie cameras are .equiped by default with what would be a slight telephoto in the still camera world. This get worse when you have something like the Russian K-3 witha still camera lens mount, al except for the original lens you are dealing with Still lenes that are intended for a much bigger format.
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#9 Leo Anthony Vale

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Posted 30 June 2006 - 01:12 PM

I was going by looking at the front of an RCA 7735A. The mask goes almost to the edge of the tube, but I did not measure it. The useable image area WOULD be slightly less than 1 Inch diagonal. I will have to dig out the tube and my calipers and get a better figure. (reminding myselfthat I bought a GBC camera with an Hitachi 7735A to play with and I have not got it running yet)

The target area has a 16mm diagonal.

Is it actually marked off on the tube?
If not, how can you measure it?

This gives the dimensions of CCTV areas:

http://www.rapitron.it/guidaobE.htm

The focal lenngth of a nrmal cine lens has always been longer than anormal still lens.

A still camera normal lens is the diagonal of the format because one is expected to view a photo print from a distance that is the diagonal othe print so the viewer's perspective matchs the prints perspective.

films are viewed under a different condition.

---LV
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