# An elementary question on overlap

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• 12-19-2009, 09:49 AM
YvesG
Re: An elementary question on overlap
In fact as far as I understood the crop factor is the ration between 36mm and the horizontal dimension of the sensor.
I guess I can make the sensor dimension to be visible and possible to be documented, so that the focal length written will not have to be recalculated.
• 12-19-2009, 09:55 AM
YvesG
Re: An elementary question on overlap
I just have verified the formulas and it possible to make the modification in the file to fit any camera.
I will just add the horizontal and vertical sensor size input and remove the comment on focal length.
That means, after documenting the sensor size, you will just have to tell what focal length you use, without any crop factor.

I am going to do that immediately and post the new file.
• 12-19-2009, 10:02 AM
John Houghton
Re: An elementary question on overlap
Quote:

Originally Posted by YvesG
In fact as far as I understood the crop factor is the ration between 36mm and the horizontal dimension of the sensor.

The crop factor is usually taken to be the ratio of the diagonal sizes.

John
• 12-19-2009, 10:45 AM
YvesG
Re: An elementary question on overlap
No problem.
In fact with the formulas I use, I just need the sensor size now.
I have modified the file, so that you can document it freely and it is now on line.

Panorama calculator for all

I hope it will work correctly.
:biggrin:
• 12-19-2009, 04:01 PM
YvesG
Re: An elementary question on overlap
Quote:

Originally Posted by John Houghton
The crop factor is usually taken to be the ratio of the diagonal sizes.

John

I have read my book again about photographic mathematics and I confirm that :
the crop factor is the ratio between 36mm (argentic) and the larger size (width) of the sensor, not the diagonal.
• 12-19-2009, 04:29 PM
YvesG
Re: An elementary question on overlap
And here is what I found that puts me back to the beginning of the way to calculate crop factor :

Some camera companies use the diagonal field of view measurement method. That is, if they describe a camera as having a particular 35mm equivalent focal length, it means the camera produces the same field of view along the diagonal as a 35mm camera with a lens having the stated focal length.

Other companies use the horizontal field of view rather than the diagonal field of view. This produces a slightly different result from using the diagonal because the aspect ratio of the digital image (usually 4:3) is different from the aspect ratio of 35mm film images (exactly 3:2). When a digital camera produces the same horizontal field of view as a 35mm camera with a lens having a particular focal length it actually has a larger diagonal field of view.

At the end, it is not an issue as formulas are based on sensor size and not the crop factor.
But I am still questionning myself on what is the official definition (not wikipedia).
• 12-19-2009, 06:39 PM
nick fan
Re: An elementary question on overlap
Quote:

Originally Posted by YvesG
No problem.
In fact with the formulas I use, I just need the sensor size now.
I have modified the file, so that you can document it freely and it is now on line.

Panorama calculator for all

I hope it will work correctly.
:biggrin:

great thanks.

Nick
• 12-20-2009, 03:11 AM
YvesG
Re: An elementary question on overlap
Concerning crop factor :

For a sensor that has the same format ratio than 24x36, you can use either the diagonal or the width of the sensor to calculate this ratio. It is giving the same result.
For other formats, you have to consider the width and not the diagonal.

So, as a general rule, to calculate the crop ratio, you should apply : Crop ratio = 36 / Sensor width(mm)
• 12-20-2009, 09:08 AM
YvesG
Re: An elementary question on overlap
I have just reworked the results presentation area in order to simplify the reading.
I hope it will bring something and that you will like it.

http://idata.over-blog.com/2/52/89/1...o-calc-low.jpg
• 12-20-2009, 09:27 AM
nick fan
Re: An elementary question on overlap
Quote:

Originally Posted by YvesG
I have just reworked the results presentation area in order to simplify the reading.
I hope it will bring something and that you will like it.

http://idata.over-blog.com/2/52/89/1...o-calc-low.jpg

That is a nice tweak!
THx

Nick
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