Measuring flange depth?

[andrewbuchanan]

How does one check the flange depth? Is this this space from the rear of the mount to the back of the lens in a straight line? I am asking because I have read that some lenses will not clear the mirror on my partciluar camera (a BNCR 2C). I would like to know how to measure this because sometimes I see excellent BNCR lenses for good prices... but don't know if they will clear the mirror. I would really hate to smash my mirror too. Thanks for any advice.

[Kevin Zanit]

You use a flange focal depth gage. It could be a little tricky to test the clearance with this (as the way the gage's I have worked with are a little clumsy). Honestly, you could just mount the lens and slowly and carefully inch the camera while looking (and listening) carefully. If the mirror hits, you would know it without doing any damage.

 

 

Kevin Zanit

[LimHKim]

hi andrew,

 

Of course by using the flange focal depth gadge will determine whether that particular lens is cleared from your shutter mirror. That's the safest and the easiest way. If you do not have, make your own with a white perspect. I'm not sure if you can buy one specifically for BNCR 2C camera. If you want some advice on making one, do email me. :)

[GWilliamPatrickB]

How does one check the flange depth?  Is this this space from the rear of the mount to the back of the lens in a straight line?  I am asking because I have read that some lenses will not clear the mirror on my partciluar camera (a BNCR 2C).  I would like to know how to measure this because sometimes I see excellent BNCR lenses for good prices... but don't know if they will clear the mirror.  I would really hate to smash my mirror too.  Thanks for any advice.

<{POST_SNAPBACK}>

 

Flange depth is not there for checking lens clearence, it is there for focal plane precision. It lets you know that with a properly mounted lens, the place where the film plane is, will be exactly where the lens is focusing the image so the picture is sharp and crisp. If we have done our jobs and set up the shot properly it will be in focus. Now, it just so happens that as a sideline, sometimes, if we measure a lens at the rear (from the mount point to its own end point) we can tell it will have a problem with length. Why sometimes ? Easy, because not all lenses we mount will have the plane of focus properly set and centered on the focal plane even though they clear the mirror.

 

GWPB