Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Aug 14, 2007, 9:10 PM   #1
Junior Member
 
Join Date: Oct 2006
Posts: 13
Default

I'm using a 1/3 ccd would a lens thats made for 1/2 ccd give the same magnification/field of view as a lens made for 1/3 ccd.?
kam213 is offline   Reply With Quote
Sponsored Links
Old Aug 15, 2007, 4:28 AM   #2
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,571
Default

kam213 wrote:
Quote:
I'm using a 1/3 ccd would a lens thats made for 1/2 ccd give the same magnification/field of view as a lens made for 1/3 ccd.?
Unfortunately, the terms you use are not precise enough for me to be able to tell you what the difference would be.

Different lenses of the same focal length will provide different fields of view on different size image sensors.

The same lens will provide different fields of view on different size image sensors.

It is possible to get the exact same field of view on different size image sensors by using lenses of different focal lengths.

What are you after?
TCav is offline   Reply With Quote
Old Aug 15, 2007, 9:00 AM   #3
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default


The smaller the film or sensor size, the narrower your angle of view (more apparent magnification) for any given focal length. The larger the film or sensor size, the wider your angle of view for any given focal length (less apparent magnification).

Lenses (designed for digital or not) are usually marked by their actual focal lengths.

What changes is the angle of view (apparent magnification), depending on the sensor or film size a lens is being used on.

With non-removable lens models (as models using tiny sensors like you're describing would be), the manufacturers usually give a "35mm equivalent" focal range, too. For example, you may see a compact Ultra Zoom digital camera with a "35mm equivalent" rating shown in the marketing specs as something like 36-420mm, when the actual focal length of the lens is really 6-72mm.

That just lets users know how the lens compares to the same focal length lens on a 35mm camera from an angle of view (apparent magnification) perspective. If 35mm cameras were not so popular, we wouldn't really need that.

If you really want to know the formula, here it is:
  • Angle of View = 2 * ArcTan(Film Dimension / (2 * Focal Length * (1 + Magnification)))[/*]
Here is a handy angle of view calculator. Just enter a focal length and the sensor or film dimensions to get angle of view:

http://www.mat.uc.pt/~rps/photos/angles.html

Note that you'll need the exact sensor dimensions in mm for weight and height. You can't go by what the manufacturers call the sensor size. That's just a type designator based on an old standard for a tube diameter..

The actual sensor size is smaller than these type designations. For example, a typical 1/3" sensor with a 4:3 aspect ratio (ratio of width to height) usually has these dimensions:

Width: 4.8mm
Height: 3.6mm
Diagonal: 6.0mm

But, again, digital camera models using sensor sizes that small don't have removable lenses anyway. They are carefully designed to work with a given sensor size and camera's electronics for controlling the zoom mechanism, focus mechanism, aperture iris and more. You also couldn't use a lens designed for a smaller film or sensor size on a camera with a larger film or sensor size (otherwise, the image circle would be too small and you'd get vignetting).

Now, it is common to use lenses designed for 35mm cameras on DSLR models with smaller sensors (for example, APS-C size sensors), provided you have a lens mount that supports them. In that case, the above applies (you'll have a narrower angle of view for any given focal length on the DSLR using a smaller sensor, compared to using the same focal length lens on a 35mm camera).

You see the same thing using a lens designed for 645 format on a 35mm camera (you can find adapters that let you do that). You'll have a narrower angle of view using one on a 35mm camera, compared to using the same focal length lens on a medium format model with a larger film or sensor size.

Here is another calculator you may find handy. It's a Depth of Field calculator. But, it also gives you field of view calculations for many camera models:

http://stegmann.dk/mikkel/barnack/

JimC is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 6:34 PM.