Dioptre adjustment

Hi all,

 

There is a chap who, everywhere on PN that he can, has posted that you must

adjust the dioptre on the Contax 645 AF every time you change the lens. I am

curious as to the reasoning for this. The dioptre only affects between the

groundglass and the eyepiece - it has no bearing at all on the distance between

the mount and the film plane nor on the autofocus mechanism. In other words it

only affects the image in the viewfinder and once set correctly should never be

changed. And even if you have it set wrongly, the body will still autofocus

correctly (I have tested this). So what on Earth did he mean?

 

Thanks!

I also don't know what he meant. Your argument about the viewfinder optical system and the unchanging nature of it makes complete sense to me.

 

As an aside, with a rangefinder camera, it is not quite the same. You are still looking at the subject, not ground glass at a fixed distance, and if your eyes have very little accomodation (i.e. you are old) the clarity of the subject in the viewfinder depends a little on its distance, even with the optimal diopter fitted. And of course, changing the taking lens makes no difference here either.

I can't find that posting, though I do remember reading it.

 

It's entirely untrue. You just need to adjust the dioptre once to suit your own eyes.

 

Of course, if you wear lenses (glasses) when using the camera, then you will have to change the setting each time your glass lenses are revised or removed!

It's <a href="http://www.photo.net/equipment/contax/645">here</a>, <a href="http://www.photo.net/equipment/contax/645-lenses">here</a>, <a href="http://www.photo.net/ezshop/product?product_id=1983">here</a> and <a href="http://www.photo.net/ezshop/product?product_id=1988">here</a>, at least those are the ones I've seen there are probably more. The dude is like totally obsessed with fiddling with his dioptre. He's gone through PN and posted this odd bit of advice on every Contax article. One need only to look at the camera to realize that if what he says were true, you would also need to adjust the distance between the lens mount and the film plane every time you changed a lens as well...

Colin : I find taking off my eye glas's is far better than trying to view with them at all::

The only reason I can think of to change the setting would be in the event that one's vision should vary slightly through the course of the day. I don't imagine it varies much, though--probably not enough to bother with it. It doesn't occur to me to change mine, unless I feel it's out of adjustment for whatever reason.

Lauren, I only wear glasses for reading and don't use/need them when photographing.

 

Rob, Though untested by me,(?) I don't think there is enough dioptre adjustment in the Contax, to account for blurred vision brought on by heavy drinking late into the evening!! This is the only cause of significant eye deteriation that I can imagine occuring throughout the day. LOL