Focal length

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Coling
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Focal length

Post by Coling » 25 Apr 2018, 11:00

Hi all
Can anyone tell me which of the lens will be closer to the sensor of an e700 camera 12 mm or 16 mm cheers

phoenix
BRUCE ALMIGHTY
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Re: Focal length

Post by phoenix » 25 Apr 2018, 12:33

I'm not sure there would be any difference in the distance from the back of either lens to the sensor.
It's the curvature of the glass in the lens that sets the focal length, not the physical distance from the back of the lens assembly to the surface of the sensor

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Bruce
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Coling
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Re: Focal length

Post by Coling » 25 Apr 2018, 13:45

Hi Bruce
The reason I ask is sure sell two types of camera housing for the E700 one is a 12mm and the other is a 16mm that’s just the housing not the full assembly cheers

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some bloke
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Re: Focal length

Post by some bloke » 25 Apr 2018, 14:28

If you are planning a spotter build the 12mm metal camera case has a shorter neck that will allow a C mount lens to get close enough to the sensor. The lens that comes in the camera would be removed for a spotter.
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Coling
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Re: Focal length

Post by Coling » 25 Apr 2018, 16:29

Cheers Dave
That’s exactly what I wanted to know :thumbup:

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some bloke
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Re: Focal length

Post by some bloke » 25 Apr 2018, 16:45

Be advised that 'C' mount lenses need to get the rear flange within 17.526 mm of the sensor (not the glass that protects the sensor) I say within because most lenses we use for spotters have their barrels move in or out quite a bit to focus between near and infinity.

We don't generally need to get close enough for face portraits so closer is better than further away if there has to be a mounting adaptor compromise: If the back focal distance is longer you will not acheive infinty. If you get it closer it simply means you will get infinity before the focus meets the end of its travel which is not an issue for us.

CS mount lenses have to get about 5mm closer than a 'C' mount lens.
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Coling
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Re: Focal length

Post by Coling » 25 Apr 2018, 20:36

Hi Dave thanks for that appreciate it

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