Attaching webcam to camera lens

[blinky]

OK I have got hold of a Cosina 135MM lens. I thought I was in luck as the lens screwed in to the wencam to EP adapter. Problem is I cannot seem to get it to focus It was at night so I could not really try it outside, but I did point it down the road and the wierd thing is it seemed to nearly reach focus on the neighbours outside light but when I looked at the lens it was set to it's minimum focus i.e. 2.8metres. The house was about 25metres away.

I am wondering if I need to have the CCD chip the same distance away from the lens as the original camera film would be?

I know CC has done this before as I have had a look at his website so have you or anybody else any tips?

[blinky]

Just had a thought (and wanted to tell everybody as it does not ahppen often ) but does the lens need to be the same distance from the CCD as the CCD is from the Secondry mirror? If so I suppose I could measure that distance and see what I can d.

[Kaptain Klevtsov]

First one. The lens reaches focus behind the screw fitting or bayonet where it attaches to the front of the camera. You need to get the CCD where the film would be in a camera. Sounds like you need more distance between the lens and the webcam.

On the 135mm lens I butchered modified I undid some tiny screws which allowed me to change the end stop positions for focusing. I could then turn it far enough to get the lens to focus. You will need about another 10mm of distance if it's the same as mine.

Captain Chaos

[GordonCopestake]

A simple way to extend focus is to stick the webcam in a barlow without the barlow lens attached. Gives you another inch or 2 depending on your barlow tube

[blinky]

Broken it now

I undid the screw and twisted it a bit further, unfortunatly a bit too much further and the thing fell appart

Ach well it was free anyways! I have tried to put it back together and while the aperature ring is gubbed (who cares i want it fully open anyway) I can still sort of twist the lens in and out and managed to sort of catch a glimpse of a street light. This was only really to test the principal as I have not got my webcam modded yet and when I do I will search around ebay for a larger lens. Incidently what is the lens fitting I am looking for that fits on the end of the webcams?

[blinky]

Would this lens conect up OK?

http://cgi.ebay.co.uk/camera-lens-with-black-case_W0QQitemZ120083885996QQihZ002QQcategoryZ30077QQrdZ1QQcmdZViewItem

[Kaptain Klevtsov]

I'm still confused as to how you screwed it in in the first place Blinky. Is it just a standard webcam nosepiece or something else that you screwed the lens into?

The E-Bay lens doesn't even say what fitting it's for so I couldn't possibly comment.

Captain Chaos

[Jamie]

The only way that i know to connect an SLR camera lens to a webcam is using a webcam to m42 adapter.

Something like this

Or this

The lens you use must be a screw fit with the m42 thread on it.

See here http://www.trutek-uk.com/toucam/toucam_pro.html

[blinky]

thats what I have Jamie, the top one. So i am looking for an M42 lens. Will keep my eyes open. TBH it was only to test as I need to get the webcam modded before I could use any lens.

[Jamie]

You might also need an extension tube of sorts to bring the lens to focus.

[blinky]

OK I have managed to get this: http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=017&sspagename=STRK%3AMEWN%3AIT&viewitem=&item=270087955245&rd=1&rd=1

For the pricely sum of £6.49 including postage

All I need to do now is modify my webcam and figure out how to mount the lens!

On another note, I will try again this afternoon and see if I can get the lens that fell appart to focus. I did put it all back together but the aperature is gubbed. The strange thing was that it seemed to focus last night but not at infinity. It appeared to reach focus when the focus ring was around 7metres Is this because I need an extension ring of some sort? I did try it in my variable projection adapter but it seemed to be too far 'out' for it to reach focus at all so I am not sure if an extension tube would be needed?

[Kaptain Klevtsov]

Blinky, I use the AC646 found low down on this page http://www.sherwoods-photo.com/meade_scopes/digital_mounts_fs.htm as it seems to give enough spacing off and I can just manage to fit a filter inside with the little thumbscrew. Another gizmo that I can use is a filter wheel with T threads as that gives some spacing as well. Don't be worried if the focus isn't at the marked infinity setting, that doesn't matter at all.

Captain Chaos

[blinky]

Finally got it working, thanks for the advice folks

Just have to work out 1st how to mount to the scope for some widefield shots ans 2nd how to support the lens on the small webcam adapter, it's a lot of weight and it will get worse when the 200mm lens arrives.

I was also thinking of getting one of the lens multiplier thingies a times 3 on a 200mm lens would give 600mm almost as much as a scope

[Kaptain Klevtsov]

Blinky, you will have to fix the lens and let the webcam hang off that, not the other way around. Lots of telephoto lenses have a tripod fitting so it's fairly easily done.

Captain Chaos