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Author Topic: 35 mm film equivalent lenses meaning  (Read 810 times)

jadephilo

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35 mm film equivalent lenses meaning
« on: May 08, 2017, 08:52:19 PM »
The photoscan mannual says: "Avoid ultra-wide angle and fisheye lenses. The best choice is 50 mm focal length (35 mm film equivalent) lenses. It is recommended to use focal length from 20 to 80 mm interval in 35mm equivalent."
I have a Nikon D7200 with a 20mm lens, and thinking about changing it. But I'm confused at which lens I should buy, since D7200 has (23.5 x 15.6 mm) sensor, does it mean that I should buy a 35mm to achieve least distortion?
« Last Edit: May 08, 2017, 09:53:06 PM by jadephilo »

3DPLUS

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Re: 35 mm film equivalent lenses meaning
« Reply #1 on: September 07, 2017, 10:25:36 AM »
Hi, 35mm equivalent means:  35mm focal length with fullframe camera.
With CROP camera ( like your) the, Crop ratio is about 1,6x , so. If you have 20mm lens, it will multiply 1,6 times ~36mm.
Its looked good. But, the low focus length affect the image ( objects are defromed too much than normal )
I've opened 3D scan service with Agisoft, I use Canon 60D and 40mm pancake lens.
I hope everything works well!
My website, scan 3D: https://blogin3d.com/dich-vu-scan-3d-quet-mau-3d-tp-hcm
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Yoann Courtois

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Re: 35 mm film equivalent lenses meaning
« Reply #2 on: September 08, 2017, 09:58:46 AM »
Hi !

3Dplus explanation is right. But then, do be so strict about your lens choice.
Obviously, it depend on your objectives. But during my project I was able to get sub-pixel accuracy (0,4 mm accuracy in Z axis with a GSD of 1 mm) by using consumer UAV (Phantom 4 pro) or even micro-sensor like GoPro.

Frame sensor and 50 mm focal length (35 mm equivalent) should achieve better results. But as I said, depending on your objectives you may not need such materials :)
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           Yoann COURTOIS
Engineer in Geodesy, Cartography & Surveying ( graduated from INSA Strasbourg, FRANCE )
Topographic engineer in ALTEA Experts, special. in Photogrammetric survey methods ( Lyon, FRANCE )
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khouji

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Re: 35 mm film equivalent lenses meaning
« Reply #3 on: November 06, 2017, 04:58:06 AM »
Your suggestion is good. Worth a try.


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« Last Edit: November 07, 2017, 12:08:16 PM by khouji »