35mm Focal equivalent for metrogon cameras

[s_f_c]

<p>I am totally new to the camera/film world, so please bare with me. I am currently attempting to process some old aerial photography and the software I am using is asking for the 35mm Focal Equivalent. I know that this typically applies to digital photography, so my first question is whether this even applies to the old analog imagery or not. If it does, can someone help me with calculating the Focal Equivalent? The images I am using were taken with a metrogon Fairchild camera. The lens's calibrated focal length is 153.86mm and the film size is 9x9 inches (or ~229mm x 229mm). The f/stop (or aperture) is f/8 and the shutter speed is 1/300.<br>

<br />-Cheers!</p>

[Norman 202]

from wikipedia

<p>

<i>According to CIPA guidelines[2] 35 mm equivalent focal length are to be calculated like this: “Converted focal length

into 35mm camera” = Diagonal distance of image area in the 35mm camera (43.27mm) / Diagonal distance of image area

on the image sensor of the DSC × focal length of the lens of the DSC.</i>

<p>

so the crop factor of your camera is 43.27/(229xsqrt(2)) = 43.27/323.85 = 0.1336

<p>

which gives a 35mm equiv focal length of approximately 20mm (153.86 x 0.1336)

[Norman 202]

in answer to your first question, you can talk about 35mm equivalent focal lengths in the film world but people rarely, if

ever, did

[GerrySiegel]

A question Sarah. What are you trying to do? I mean it would help if you described what is the output product with, I am assuming, old roll film negative aerial roll film-(?). I was thinking of some kind of flatbed scanner maybe in lieu of a contact printer? Or like what? Someone I am sure will be able to offer a more precise answer. I mean I never recall needing to know what you are asking, have to say in a Navy lab. On second thought, -an idea-you might indeed approach the Navy photo archivist staff at their museum, government funded. Where they likely have worked or work with such film stock.

Here is what I got for search starters,hope it is useful.

 

 

http://www.history.navy.mil/research/archives.html

 

(nhhcphotoarchives@navy.mil)

[glen_h]

<blockquote>

<p> you can talk about 35mm equivalent focal lengths in the film world but people rarely, if ever, did<br>

</p>

</blockquote>

<p>More rare than for digital cameras today, but not completely unknown. Sometimes for medium format, when someone was more used to using a 35mm camera. I suppose it would be much less usual for large format. </p>

[James G. Dainis]

Back in the good old, old days of film most cameras came with a "normal" lens - <P>

 

50mm lens for 35mm film, <BR>

80mm lens for medium format (MF) <BR>

150mm lens for large format (4x5 inch film)<P>

 

You knew what you were going to see in the viewfinder/ focusing screen/ground glass, a ~45° view of the same scene just smaller in the viewfinder than on the ground glass or focusing screen. Zoom lenses for 35mm changed all that. The concept of a "normal" lens disappeared for most people. The "crop factor equivalent" came into being. Instead of an APS-C digital camera coming with a simple 30mm "normal" lens that would show the same view as 50mm lens on 35mm camera, 80mm lens on MF camera, etc. the digital camera came with zoom lenses and one needed the crop factor to understand the focal lengths in 35mm terms.<P>

 

For people who use MF film, 35mm film has a crop factor of 1.6, so to find the equivalent focal length of a 50mm lens multiply by 1.6 to get 80mm equivalent for MF. But, that just seems silly. People who use MF know what they are doing and what a lens will deliver for MF.

[john_robison4]

<p>Back in the old film days (and now in the current film days) us folks who shot 'half frame' sure talked about 'equivalent focal length, generally a 1.4X factor or with best crop of the 24X36 negative a 1.33X factor on the enlarger. Of course a 50mm lens stuck on my Pen F with an adapter is still 50mm but the angle of view/field size at a given distance is less than full frame.</p>