RangeFinders @ Infinity : Query

[pareshpandit]

Hi


I recently read an article on FED2 at a website [Through APUG Forums ]where, the author concluded that the RF was out of alignment based on the observation that the RF didnot align to infinity...

I have recently acquired a Contax II...
I have noticed that it's RF also doesnot align at infinity...
However, it doesnot seem off!
I have put through 2-3 rolls and all seem fine and alignments upto its before-infinity limit (and beyond as well) are very perfect...
For example, you could follow the link below:
http://photos1.blogger.com/img/27/1667/640/amravati04_KhadiBhndr_Port0.jpg
The shot shown here is taken at f1.5 and under low light; yet, I could focus and the focus seems right-on...

Is it that alignment at infinity should be proper!?
My RF is great and doesnot seem a least bit misaligned!

Kindly Help...
Awaiting your replies...


Regards

Paresh Pandit
Mumbai, IN
Sept 12, 2004


P.S.: The FED 2 article can be found here : http://open.hr/~dpleic/photo/fed2.html

 

[Denis P.]

Since you're referring to my FED2 "essay", I guess I could provide an answer.
The text of the essay was intended as a humorous report, not a detailed technical advice.
Anyway, the RF on my example *WAS* off - when the images concided when I aimed at my friend about 1,5 meters away, the engraved scale said something quite different - obviousl the RF was off.
Then I aimed at a far object, and focused on it (in the RF window) - the distance scale was again off - or it wouldn't align the RF patch at all, I don't really remember.
In short, I fixed it, taking several test shots, using a ground glass & a loupe, etc..

If you're satisfied with yours, there's no reason to mess with it.

Regards,

Denis

 

[pareshpandit]

Dear Sir


Thanks for the quick clarification ...

I think I somehow knew that mine was OK; still, just wanted to know whether it is normal for not getting alignment at infinity (I suppose it should be :-? ...) in a perfectly normal RF...
Besides, it is said that the Contax II RF is built in such a way (full prism, no mirror - i think) that it would virtually never fall out of alignment...
I was just scared at the thought of spending on an exception ...

BTW, loved your afore-mentioned article...
I wanted to get a FED; but, my vendor (and good friend) advices me against...
Maybe one of the reasons is that we have less (stock) to choose from in the Indian market; so the chances of finding a working/workable one are slimmer ...


Thanks
Regards

Paresh Pandit
Mumbai, IN
Sept 13, 2004

 

[John Koehrer]

Paresh:
To confirm the accuracy of the RF. Open/remove the back of the camera, open lens to widest aperture, lock shutter open on bulb, use a small piece of ground glass held against film guide/rail & check focus. Then check focus again at a known closer distance.
There is probably a greater tolerance for error at infinity than at closer distances.

 

[rjr]

Paresh,

I´m not quite sure wether I understood your problem. ;-)

As you wrote, there isn´t much in a Kiev/Contax-Rangefinder that can get knocked out.... usually the glass block will break upon impact and thats it... but it can happen.

To check infinity alignment you need to peak on a _very_ distant object - when adjusting my FEDs and Zorkiis I tried it with a tower in 800m distance... too close, it left a bit to desire.

Karen Nakamura has given a discription how to align the rangefinder by yourself.

http://www.photoethnography.com/ClassicCameras/Kiev4a.html

Shaggy, Denis,

I heavily vote against using a groundglass for checking alignment on 35mm cameras - the tolerances are too tight, the quality of the groundglass has too much influence as does your loupe and your eye sight have.

Better to use a DIY collimator approach.

Thomas Boeder has made a visual discription, I use a slightly different method.

http://www.leica-camera.com/discus/messages/22/25880.html?1077094599

Mine as follows:

place a long hair in place of the film plane, mount the camera with lens (set on infinity) on a tripod, with the open back facing towards the sky. Open the shutter set at B.

Take a SLR with a lens longer that 50mm and set it to infinity. Look through the Kiev lens with the SLR - if the hair is straight, undisturbed by the microprims on the SLRs groundglass the flange to film plane distance is OK. If not you need to adjust the distance with shims under the helicoids.

I have successfully used that method with a few cameras, it´s my standard test on 6x9-folder cameras with front lens focussing that rarely are properly adjusted.

Good luck with the camera!

 

[John Koehrer]

rjr
Have used GG @ film plane for years in repair shop as have other techs.
(owner too cheap to buy collimater) With over 60 yrs combined experience at the business & no problems it's hard to accept the argument that using GG at film plane isn't accurate enough. Theory and practice I guess.

 

[rjr]

Shaggy,

in my opinion too many things can go wrong when checking infinity with a ground glass - for amateur use. You as a professional repairman know what your are doing and thus you act - but the now and then repair hobbyist (as I am one ;-) would leard the hard way... and I did, I couldn´t trust my Moskva5, my Adox Start, my Agfa Billy 6,3 until I aligned them with the fathom collimator method.

What can go wrong?

- too coarse grain in the GG
- wrong size, wrong position, wrong side up front
- judging the sharopness is highly subjective - it depends on your eyesight and a personal jugdment ("It´s sharp... NOW!").

With the collimator method you´ll see a straight line for a moment and this is the position to stop - the microprims/indicators on the SLRs ground glass make that easy to judge. With a very low margin of errors.

 

[elekm]

This works for ensuring the lens focuses at infinity, but it does not address a rangefinder that it out of calibration. To correct that, you need to remove the top of the camera.