Camera lens to CCD sensor distance?

[Domis]

Hi guys,I'm trying to adapt some Canon Ef lenses for use with the SPC900 webcam, Is there a way to calculate the distance the rear lens of the camera lens needs to be from the CCD sensor to be able to focus at infinity? The lens is 67mm dia. and 100 -400mm telefoto at f/4.5-6.7, or is trial and error the only way?

[yesyes]

See this thread

The EOS EF lens registration seems to be 44mm. It is my understanding that this is where the CCD should be.

[focaldepth]

Hi I asked (vaguely) similar question in the thread

http://stargazerslounge.com/equipment-help/145314-help-ccd-flattener-spacings.html

Anyway 44mm from lens mounting plate on the camera to sensor.

[Photosbykev]

44mm is the offical distance but as long as you can get inside that distance then infinity is achievable.

I made up some adaptors for the Canon EF lens myself using a rear dust cap bonded into an ally block which takes normal nose pieces. Details on my website if you are interested.

[Domis]

This forum is incredible! It hasn't been a half an hour and you guys have offered up the info.Thank you very much. OK, so at the moment I'm at aprox. 40mm from the lens shoulder to the sensor. Is there a reason to shim the remaining 4mm or as Photosbykev has suggested any distance inside the 44mm mark should be OK?

Photosbykev;those are some awesome pics you have on your website! I take it that photography is more than a hobby for you. I could not find your "adapter build" on there though.What heading is it under? I would be most interested in taking a look at what you have done. I'm using would at the moment as a prototype until I get it all worked out,than I'll probably fashion something using aluminum. BTW, I hit on the dust cap approach as well,I couldn't find just a standard mounting ring anywhere.

[Photosbykev]

This forum is incredible! It hasn't been a half an hour and you guys have offered up the info.Thank you very much. OK, so at the moment I'm at aprox. 40mm from the lens shoulder to the sensor. Is there a reason to shim the remaining 4mm or as Photosbykev has suggested any distance inside the 44mm mark should be OK?

Photosbykev;those are some awesome pics you have on your website! I take it that photography is more than a hobby for you. I could not find your "adapter build" on there though.What heading is it under? I would be most interested in taking a look at what you have done. I'm using would at the moment as a prototype until I get it all worked out,than I'll probably fashion something using aluminum. BTW, I hit on the dust cap approach as well,I couldn't find just a standard mounting ring anywhere.

Photography is my passion rather than a profession The link you want is here SPC880 webcam and the moon

I would try to get close to 44mm, but don't go above it, or if you are using a standard nosepiece then there should be plenty of outward adjustment using that.

[Domis]

photosbykev; very well then, I'll try to stay very close to the 44mm mark. I took a look at your adapter,nice work,thats very similar to what I had in mind. Once I'm sure I can get these lens to work reasonably well I'll turn out something similar.Thanks for all the help everyone.

[gbealnz]

Get it close the arbitrary 44mm and then fine tune it while imaging.

Gary