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hacking a lens to fit a C mount

gmoe

New member
Wow that's just what I was asking folks here about in terms of how to get lenses to fit better in the c-mount adapter. Is there anything you need to be aware about when you grind that edge? I have a Dremel with a grinder you think that will do it to smooth it out. I also don't want to ruin my tv lens granted it wasn't that expensive.

Thanks for that post and info.!
 

slosync

Member
Thanks for that picture and your excellent description on your blog for modifying the Comutar Lens. I have the similar issue with a 25mm 1.4 Cosmicar, but perhaps a little more filing may be necessary.

As soon as I receive my Hawk C adapter, I will make the modification. I have the little C Pentax 25mm 1.4, I'm hoping the Cosmicar lens may a little sharper. Here's a picture of my Grandaughter using the Pentax.

Pentax TV C lens 25mm f/1.4 at 1.4 - Grandaughter

Cheers,
Don

Hi

I did a hack on a Computar lens to get it to fit an adaptor.

http://cjeastwd.blogspot.com/2009/06/adapting-lens-to-fit-mount.html





:)
 
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pellicle

New member
Hi

Wow that's just what I was asking folks here about in
thanks, a bit of positive feedback goes miles :)

terms of how to get lenses to fit better in the c-mount adapter. Is there anything you need to be aware about when you grind that edge? I have a Dremel with a grinder you think that will do it to smooth it out.
actually a Dremel (well controled) would be prefect .. I found myself wishing for mine (which is back in Australia). I understand there is quite an amount on there to shave off, but I just took it carefully and slowly trying it from time to time.

I also turned the lens around and screwed it in from the back to see how much I should be expecting to come through too.

HTH
 

kweide

New member
One pass on a turning lathe......just some seconds work...
Less than 5 Minutes with a Dremel
 

pellicle

New member
Hi

some examples from today:





The lens seems to have quite some curvature of filed as the distance around the edges happened to be in focus when the foreground center was.
 

Godfrey

Well-known member
thank you! I've ordered one of Hawk's adapters ... eh? you can't take it with you ... ;-) ... as it looks like I can hack the Cosmicar 12.5mm similarly. Might as well have some fun with it.
 

monza

Active member
Actually they were machined to fit the Hawk but should work on any c-mount adapter. I added shims (in the form of metallic tape) to fine tune infinity...
 

m3photo

New member
Taken with a Carl Zeiss DDR Tevidon 25/1.4

G1 - 16:9 format 1/25th f5.6 800 ISO hand-held (elbows firmly on the table).
 
R

Ranger 9

Guest
Godfrey - looks good, although there seems to be a surprising lack of DOF for f/4... the bubbles in the espresso are sharp, but the spoon and truffles look to be OOF a bit.

Also, the vignetting along the edges of your shot looks quite straight-edged; I've got the 12.5/1.9 Cosmicar (the older, skinnier one) and its edge-falloff pattern is noticeably round.

-- Is the f/1.4 version "squarer"?

-- Or did you vignette the edges in post to blend in with the natural falloff in the corners? If so -- good trick! I'll have to try that myself.
 
P

patbon23

Guest
I am Italian and not speak English very well,
how can I solve the problem of focus to infinity with a tevidon 25mm?
thanks
 

m3photo

New member
Re: Focus to infinity with a tevidon 25mm

I am Italian and not speak English very well,
how can I solve the problem of focus to infinity with a tevidon 25mm?
thanks
Hello,
On this page go to message number 8 - in the picture you will see 4 lenses, yours is the smallest one. If you don't have a lathe, print the picture and take it with you together with the lens and the adapter to a machine shop and explain that you need this part grinding down so it fits better in the adapter - this is why you aren't able to get infinity focus with the lens as it is.

I don't speak Italian, maybe you can understand some Spanish:

Hola,
En esta página sube hasta el mensaje número 8 - en la foto verás 4 objetivos, el tuyo es el más pequeño. Si no tienes torno, imprime la foto y llévatela junto con el objetivo y el adaptador a un tornero y explícale que necesitas rebajar esta parte para que encaje mejor en el adaptador - esta es la razón por la cual no consigues enfocar al infinito con el objetivo como está.
 
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