Focal lengths:  dvx100 vs SLR vs film camera

B

Bill_Hooper

Active member
Okay,

So I'm trying to understand this. How do SLR focal length, film camera's focal lengths and the DVX100 focal lengths compare?

Correct me if I'm wrong. SLR 35mm focal length is different from dvx100 and film cameras? For example 85mm on SLR looks different than 85mm on a film camera?

In the manual it says the DVX 100's focal length is 4.5 to 45 mm, and 35mm equivalent is 32.5. to 325mm. Again, 32.5 to 325mm is the SLR equivalent?

I've been talking to the camera operator on Malcolm in the Middle (I work on the show), and he says they use primarily 8mm, 12mm and 16mm. So if I zoom in a little bit with my DVX that should give me about 8mm, right?

Thanks for any enlightenment.
Bill
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

32.5 to 325 is the SLR equivalent, yes.

When you're talking about Malcolm in the Middle using 8mm, 12mm and 16mm, the question is, on what format? The focal length stays the same, but the field of view changes based on what format you're using. If they're shooting 35mm movie film, 8mm would be insanely wide, but 8mm is a common wide-angle length for a 16mm movie camera (a bit wider than the DVX's 4.5mm wide-angle).

If they're using a 2/3" video camera, that has roughly the same field of view as a 16mm movie camera, so a 16mm lens on a 2/3" camera would deliver about the same field of view as 8mm on a DVX. Roughly.
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

SInce Barry already answered, I had another question:

From my early 35mm SLR days, I remember that 'normal' lens is considered one that has same focal length as the diagonal of the frame, which should be about 43.25mm. Despite that, everyone thinks 'normal' for SLR as 50mm lens.

In the world of film (especially 35mm), you can have different frame sizes (standard 35, super35, cinemascope, etc.). How is 'normal' defined in these circumstances?

For 1/3" CCD, is 1/3" the diagonal or the horizontal dimension? If the former, 8mm would be roughly a 'normal' lens, corresponding with about 40mm lens on a 35mm SLR.

Barry, can you comment?
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

Thanks Barry! Very helpful.

Malcolm shoots on 16mm movie cameras. So you're saying the 4.5mm focal length on the DVX does NOT have the same field of view as a 16mm movie camera with a 4.5mm focal length. Hmm. I see.

Is there any way BESIDES putting both cameras side by side to get the same field of view at a fixed focus depth (e.g. subject 5 feet away)? In other words, is there any calculation I could do to match a 16mm movie camera's field of view with an 8mm focal length to my DVX?

Thanks again
Bill
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

You can in terms of field of view (i.e., angle), but not depth of field. The smaller the frame (or CCD), the shorter focal length you must use for the same angle, and the deeper your depth of field will be.

For field of view calculations only, you can use basic geometry (isomorphic triangles? - I am sorry if it's not the correct term. I know my math but in another language).

I was looking for an example on the web I could refer to, but I didn't find anything useful. So I am going to try to explain it without pictures.

If you think of your eye as the optical centre of the lens, and your computer screen as the film frame (CCD chip), the distance from your eye is similar to the focal length. The field of view the computer screen takes increases as you get closer to it, and gets smaller as you get farther away. Try it!

Now take an object that is smaller than your computer screen - index card, or a sticky note. Put it between your eye and the screen so that it covers the screen as precisely as possible. See how it's much closer to your eye than the computer screen? That's the smaller frame/shorter focal length analogy.

Now with a little bit of math... There is a directly proportional relationship between the two to give you the same field of view:

f1/d1 = f2/d2

where f1, f2 are the two focal lengths, and d1, d2 dimensions of the picture (usually diagonal, I suppose). So, if you want to find what focal length you should use on the DVX to match the field of view of a 16mm film, it also depends what cameras you compare. For example, the gate dimensions on a super 16mm Arri camera is 12.35x7.5mm, which gives you the frame diagonal about 14.45mm (d1).

If you put 8mm (f1) lens in front of it, you need to know the diagonal of the 1/3" CCD, which is approximately 6mm (d2).

From the equation above,

f2 = f1*(d2/d1) which is 8mm*(6mm/14.45mm) = 3.32mm

As you can see, that's too wide to match on the DVX!

Conversely, you can find what's the shortest lens you can use for Arri Super16 if you were to match its field view with the DVX's widest zoom setting (Z00=4.5mm=f2):

f1 = f2*(d1/d2) = 4.5mm*(14.45mm/6mm) = 10.8mm

I got these numbers from Panavision website (http://www.panavision.co.nz/main/kbase/reference/tbleframelist.asp), but I suspect the 1/3" CCD dimensions are a bit higher than that (6mm is less than 1/4"). In any case, the calculations would be the same, with different numbers.

See, it's simple!
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

[quote author=Jerry XCheck link=board=Events;num=1102623605;start=0#2 date=12/09/04 at 14:53:08]For 1/3" CCD, is 1/3" the diagonal or the horizontal dimension? If the former, 8mm would be roughly a 'normal' lens, corresponding with about 40mm lens on a 35mm SLR.

Barry, can you comment?[/quote]
Well, the problem is that "1/3" is a lie, when talking about CCD sizes. The actual effective area is rarely as large as the advertised area. So if you're talking about what focal length would deliver the same field of view as a 40mm SLR lens, on the DVX it's about 6mm, not 8mm.
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

[quote author=Bill_Hooper link=board=Events;num=1102623605;start=0#3 date=12/09/04 at 16:17:46]So you're saying the 4.5mm focal length on the DVX does NOT have the same field of view as a 16mm movie camera with a 4.5mm focal length.  Hmm.  I see.  [/quote]
That's correct.  The 16mm camera will have a much wider field of view.  Just like 4.5mm is "equivalent" to 32.5mm on an SLR, it's also equivalent to about 10mm on a 16mm camera.

Is there any way BESIDES putting both cameras side by side to get the same field of view at a fixed focus depth (e.g. subject 5 feet away)?  In other words, is there any calculation I could do to match a 16mm movie camera's field of view with an 8mm focal length to my DVX?
Click to expand...
Do you want exact, or ballpark?  Exact would take some math (as Jerry demonstrates) but for ballpark, a DVX needs a little under half the focal length to deliver the same field of view as a 16mm camera.  So 4.5-45mm on the DVX equates (approximately) to about 10-100mm on a 16mm camera.

If you want to calculate exact, there's a spreadsheet that seems accurate here:
http://www.edward.grabczewski.btinternet.co.uk/Cine_Charts.htm
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

Hi Bill,
 
This chart was from an equivalent from 35 mm movie lense Pan.
 
Here is a chart for relatives focals between formats:
 
Angle   35 mm phot  35 mm ciné   16mm ciné     video 2/3
Frontal 36x24mm     24x18.6 mm   10.16x7.62mm    8.8x6.6 mm
 
77.0°   18.0 mm 15.0 mm   5.9 mm     5.9 mm
61.0°   24.0   19.0     7.6       6.6
54.0°   30.0   25.0     10.0     8.7
44.0°   40.0   30.0     12.5   10.8
35.0°   50.0   40.0     16.0   14.0
23.0°   80.0   60.0     25.0   22.0
12.0°   160.0     125.0     50.0   43.0
07.8°   235.0     190.0     75.0   65.0
05.8°   320.0     250.0     100.0       87.0
03.8°   470.0     380.0     150.0     130.0
02.8°   640.0     500.0     200.0     175.0
01.9°   950.0     750.0     300.0     280.0
01.2°  1575.0   1250.0     500.0     430.0
00.7°  2500.0   2000.0     800.0     700.0
00.6°  3150.0   2500.0   1000.0     865.0
 
Sorry if the chart is not well align.  Hope it help you.
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

Thanks everyone! This has been very helpful. I'm always amazed how much you guys know.

I'll find out exactly what kind of 16mm movie camera Malcolm uses, get the dimensions and do a more accurate calculation.

Okay, let me try this. Say I want to match the field of view of a super 16mm movie camera, using a 16mm focal length. I'll use Jerry's f1/d1 = f2/d2 equation. "Super 16mm's movie camera has a frame diagonal of about 14.45mm (d1)" DVX frame diagonal is 6mm (d2). So if f1=16mm, then f2 = 6.64mm.

Here's some math to get DVX zoom #'s. I'm just guessing. F=4.5 to 45mm. So range is 45mm - 4.5mm = 40.5mm. [(Zoom number / 100) x 40.5] + 4.5 = DVX focal length. Example, zoom of 0 would be (0/100 x 40.5) + 4.5 = 4.5. Or zoom of 100 would be (100/100 x 40.5) + 4.5 = 45mm

So if DVX focal length is 6.6mm, then: (Zoom number / 100 X 40.5mm) + 4.5mm = 6.64mm

And (Zoom number / 100) X 40.5mm = 2.14mm
And (Zoom number / 100) = 0.053

So zoom number would be 5.

Does this look right?

Thanks
Bill
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

I have no idea what you just said.  Might be accurate, but I'd say just look at Ed's excel chart.  Print it out and bring it with you.

According to the chart, a S16 camera with a 16mm lens would be equivalent to a DVX at about 6mm lens.  A regular-16 camera with a 16mm lens on it is about equivalent to a DVX at about 7.5mm.

For lens focal length equivalents on the DVX, you have to refer back to the Z00-Z99 - to - mm chart, which is:

Z        DVX        35mm still photography equivalent
----------------------------
00       4.5       32.5
05       4.8       34
10       5.2       37
15       5.8       41
20       6.4       46
25       7.0       50
30       7.6       55
35       8.2       59
40       8.8       64
45       9.5       69
50      10.3       74
55      11.3       81
60      12.5       90
65      14.1       101
70      16.1       116
75      18.7       135
80      22.1       159
85      26.4       190
90      31.8       230
95      38.5       278
99      45.0       325


So: to match a super16 camera's angle of view when the S16 camera is using a 16mm lens, set the DVX to Z07.

To match a regular 16 camera's angle of view when the R16 camera is using a 16mm lens, set the DVX to Z29.
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

Barry,

"I have no idea what you just said."

Whoops! Sorry. I guess I got a little carried away.

Anyways, your answer was great. I totally get it now.

I got your book and DVD. Love the DVD. Looking forward to reading the book.
Thanks
Bill
 
Re: Focal lengths:  dvx100 vs SLR vs film cam

Re: Focal lengths:  dvx100 vs SLR vs film cam

Barry,
Did you mention about the focal lenght in your book?
 
Re: Focal lengths:  dvx100 vs SLR vs film camera

Re: Focal lengths:  dvx100 vs SLR vs film camera

That chart is in the book, yes.
 
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