crop factor for smaller sensors

http://en.wikipedia.org/wiki/Crop_factor

I think you take the diagonal of the sensor size:

44mm = 35mm
22mm = 4/3rd
So, it's 2x
just do the math...

Leslie's more or less right. If the two sensors have the same aspect ratio, you can use width, height, or the diagonal, but if you want to calculate crop factor between sensors that don't have the same aspect ratio, the diagonal is the best way to do it. You can calculate the diagonal by the Pythagorean theorem.

Using the numbers in Curtis' post, Super 16 has a diagonal of 14.55mm, and 16mm has a diagonal of 12.7mm. The crop factor of 16mm is roughly 1.15 compared to Super 16.

Craig, how did you get that diagonal number for super 16? is there a mathematical equation? and how do I determine the crop factor in comparison to a 35mm film SLR.

All I want to know is this, If I have a 12mm wide angle lens designed for a super 16mm piece of film what is my multiplier? 1.6? 2.0? etc!

can some one tell me the equation to find this out?

A squared + B squared = C squared

• A = length
• B = width
• C = diagonal

By tradition, the "normal" lens for any format is one with a focal length that about equals the diagonal measure of the frame. Often this value, when calculated is weird so opticians tend to round this value up. As an example, the full frame 35mm format measure 24 by 36mm; the diagonal measure of this rectangle is 43.27mm. The convention is to round this value to
50mm.

Now if a lens is fitted that exactly matches the diagonal measure of the frame, the angle of view as measured diagonally is always 53°. This is the angle of view that is most often published by the lens maker, however knowing this seems dubious as to value. Something like TV sizes are stated based on the diagonal measure of the image rectangle. More importantly, if so fitted, the horizontal angle of view will be approximately 45⁰ and is said to be the "human experience".

OK, the 16mm format is 7.49 x 10.26 thus the diagonal measure is 12.55mm. The Super 16 format is 7.41 x 12.55 thus the diagonal measure is 14.55mm. The difference is 12.55 ÷ 14.55 = 0.8625 or the inverse 14.55 ÷ 12.55 = 1.16

OK, what the hell does this all mean?
The 16mm frame is 86.25% of the super 16 frame. In others words it's smaller.
The super 16 frame is 116% larger than the 16mm frame.

If a 25mm lens is mounted on a 16mm camera, you must mount a 25 x 1.16 = 29mm on the super 16 to duplicate this same perspective.

If a 25mm is mounted on a super 16, to duplicate the same perspective you should mount a 25 x 0.8625 = 21.5mm to duplicate the same perspective.

Allow me to add that perspective is actually intertwined with subject to camera distance and focal length. Thus, this is a difficult subject to get across. Additionally, all lenses have a limited covering power. If a too small lens is fitted, a vignette is likely. Special designs increase the covering power, however this adds to cost. In addition, the human experience as to perspective is the basis for the rule-of-thumb to fit a "normal" lens based on the diagonal measure.

The 'normal' lens for a 16mm camera was/is always a 1" or 25mm or 25.4 if you double the diagonal which I found interesting. That the normal 16mm lens was roughly equal to a 90mm on 35mm still camera.
If you do the diagonal measurement for 35mm still film you arrive at 40mm whereas everybody knows the 'normal' is 2" or say 50mm.
The normal lens for a 35mm film camera was 2" yet it has a half sized gate ... curiouser and curiouser as somebody famous once said.
I base my point on ownership of both 16mm and 35mm motion picture cameras in the past.

the difference between FX and DX according to math (43.3 / 25.9 = 1.67)

so the exact crop factor between FX and DX is 1.67 then? So a 200mm lens on a DX sensor is like (200x1.67=334) 334mm on a full frame sensor... but then some one said 43.3 gets rounded to 50, which doesnt make any sense.

Anyway, so lets get this straight! the difference between Super 16 and 35mm still film is 2.98 (43.3 / 14.5 = 2.98)

So if I have a 12mm wide angle lens for a super 16 camera, I would multiply that by 2.98 to find out what the equivalent would be on a 35mm SLR film camera. Is this making sense to everyone? So 12mm x 2.98 = 36. So 12mm in super 16 is the same as 36mm in full frame SLR?

This is what i'm trying to do. These lenses here are made for Super 16mm motion picture cameras.

http://www.visualproducts.com/storeProductDetail03.asp?productID=1029&Cat=8&Cat2=18&Cat3=25

I want to know what each of those correspond to in Full Frame 35mm SLR's. This way I can go to a set, take photos in 35mm film with the exact same field of view.