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Zeiss Biotar 58mm f2 M42 on EOS focusing to infinity issue
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PostPosted: Fri Nov 17, 2017 11:27 am    Post subject: Zeiss Biotar 58mm f2 M42 on EOS focusing to infinity issue Reply with quote

I all
I have a biotar 58mm f2 pre-set version n.3538762 (see picture) which I want to use with my eos 100D. To do that I bought an adapter EMF confirmation chip M42 to EOS.
I tried the adapter with a HELIOS 58mm f2 (see picture) and it works fine focusing to infinity too. On Biotar the same adapter does not fit perfectly, in fact
I cannot screw it in thoroughly (missing 2 mm) to get inifity focus. How is it possible? both lenses m42 mount seams to be similar. Have you any suggestion?
Thanks in advance
Giorgio

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PostPosted: Fri Nov 17, 2017 3:07 pm    Post subject: Re: Zeiss Biotar 58mm f2 M42 on EOS focusing to infinity iss Reply with quote

gi0rgi0ba wrote:
I all
I have a biotar 58mm f2 pre-set version n.3538762 (see picture) which I want to use with my eos 100D. To do that I bought an adapter EMF confirmation chip M42 to EOS.
I tried the adapter with a HELIOS 58mm f2 (see picture) and it works fine focusing to infinity too. On Biotar the same adapter does not fit perfectly, in fact
I cannot screw it in thoroughly (missing 2 mm) to get inifity focus. How is it possible? both lenses m42 mount seams to be similar. Have you any suggestion?
Thanks in advance
Giorgio

#1


#2


#3


#4


Welcome gi0rgi0ba

Photos showing now. Smile

Others will also answer -- I think maybe changed the thread from M42 to T-mount -- same diameter, different threads per inch.


PostPosted: Fri Nov 17, 2017 3:52 pm    Post subject: Reply with quote

Buy another adapter...


PostPosted: Fri Nov 17, 2017 4:08 pm    Post subject: Reply with quote

calvin83 wrote:
Buy another adapter...


I do not know the T mount , I read in a post (http://vintage-camera-lenses.com/carl-zeiss-jena-biotar-258/) that the biotar was manufactured in these mounts

M42 / Pentax mount
EXA / Exakta mount
Praktina mount

what is the difference between M42 and T mount, just the number of threads / inch?
thanks
G.


PostPosted: Fri Nov 17, 2017 5:16 pm    Post subject: Reply with quote

One is 42x1mm other is 42x0.75mm


PostPosted: Fri Nov 17, 2017 5:20 pm    Post subject: Reply with quote

Oh! If adapter has flange to press in the M42 aperture pin, the pin on biotar could be preventing full twist-on. Need flangeless adapter?


PostPosted: Fri Nov 17, 2017 5:36 pm    Post subject: Reply with quote

if it were a t mount then a classic m42 with 1mm pitch should not screw up on it due to the different pitch. Is it correct? I have to investigate on it.
G.


PostPosted: Sat Nov 18, 2017 12:18 am    Post subject: Reply with quote

visualopsins wrote:
Oh! If adapter has flange to press in the M42 aperture pin, the pin on biotar could be preventing full twist-on. Need flangeless adapter?

I think so. The flange prevents the lens fully screw in.


PostPosted: Sat Nov 18, 2017 9:29 am    Post subject: Reply with quote

calvin83 wrote:
visualopsins wrote:
Oh! If adapter has flange to press in the M42 aperture pin, the pin on biotar could be preventing full twist-on. Need flangeless adapter?

I think so. The flange prevents the lens fully screw in.


Yes, correct. I resolved the problem removing / brushing few millimeters of the internal flange. Now it screw in perfectly and it can focus to infinity. Very sharp lens at F5.6 / F8.
Thaks all of you for helping me.
Cheers
G.


PostPosted: Sat Nov 18, 2017 8:04 pm    Post subject: Reply with quote

Congrats Whoo Turtle Welcome Turtle


PostPosted: Sun Nov 19, 2017 2:59 pm    Post subject: Reply with quote

The adapter probably doesnt "sit" tight enough on the lens - the screwing job is not 100% finished to its end. That sort of problem often occures on Canon, especially with Flektogons, or possibly any other screw mount wide lens very sensitive on the matter of register distance change.