Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
Quote:
Originally Posted by
Darin Boville
I saw mention of this thread elsewhere here and realized that I'd never done a focus check on my Chamonix 4x5. Here's a Polaroid with a 150 5.6 with the focus point right on the five-inch line. It looks good to me. Perhaps the focus issue is not widespread?
http://www.boville.net/Focus_Test.jpg
--Darin
Did you intend to post a shot with the 5" line?! I presume the 5" line was spot on focus?
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
You just quoted Darin as saying "Here's a Polaroid with a 150 5.6 with the focus point right on the five-inch line. It looks good to me."
:D
Ian
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
Easy fresnel fix for Chamonix 45-N1, see photos for details.
1. Bend and cut to length paperclip holders. I used a pair of needle-nose pliers.
2. Install fresnel with the grooves toward the ground glass.
3. Insert paperclip holders under ground glass holding washers.
4. Re-attach ground glass holding washers. (Be careful with those tiny screws you could very easily strip the hole in the wood out)
5. Enjoy a brighter screen again! That is in focus!!!
Two paperclips on the diagonal are plenty to hold the fresnel in place, although you could use four if you wanted to. The protector plate attaches just a little more snug, but works just fine.
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
Wow!! I have just stumbled across this old post after thinking it ended after one page! Four pages later!! Since my earlier post, I have just been using the plain GG (which Hugo sent me when I first noted the problem) and haven't had any issues with focus, apart from the fact that of course I would like it to be brighter now. Am thinking of also getting a Maxwell screen and was just wondering if I can send him the back that I had the original issue with (Groundglass/fresnel screen combo) or if I should really send him the back that I have been using, that has had good focus (without the fresnel). Have Chamonix accounted for the fresnel in determining where the groundglass is positioned? Or have they neglected this fact and this is the reason why people are having focus issues? Also, what is the best way of taking the fresnel out? Is it just glued in or something like that? Is it easy to put the groundglass back without affecting focus accuracy? Ok, Thanks for the responses. Best Regards Josh
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
You don't need a new ground glass or focusing screen. The original Chamonix fresnel is not glued in. All you need to do is carefully remove the four screws that secure the ground glass and fresnel in place. Remove the fresnel from underneath the ground glass. Then replace the ground glass. After that you can follow my instructions above. Screen is about the same brightness as before. The plastic screen will scratch more easily so be careful using a loop on it.
I never had noticeable problems with 135mm and longer lenses although I imagine there was a measurable error. I have had significant problems with my 75mm. Not anymore!
I wish we could get some type of actual solution from Chamonix. This is a pretty big screw-up on their part.
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
Just curious, but what do you mean "actual solution"? Several people have mentioned something similar but they never state what it is they actually want Chamonix to do.
Chamonix posted recommended fixes on their website. According to the information posted, the back is made correctly for a standard GG just like most every other currently available view camera, they just improperly stuck a fresnel in front of it.
Cheers, Steve
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
Quote:
Originally Posted by
Steve Hamley
Just curious, but what do you mean "actual solution"? Several people have mentioned something similar but they never state what it is they actually want Chamonix to do.
Chamonix posted recommended fixes on their website. According to the information posted, the back is made correctly for a standard GG just like most every other currently available view camera, they just improperly stuck a fresnel in front of it.
Chamonix needs to modify all existing cameras so that they focus properly with the fresnel installed correctly. It's a matter of shaving a precise amount off the edge-seat on which the inner fresnel rests. The cameras came with fresnels and they should work properly with fresnels. Posting customer fixes is okay but it should be as an "option" at the discretion of the customer. If they don't support their product, as in a "recall" with free two-way shipping, they lose much credibility, IMHO. In fact, I'm not buying a Chamonix product until I see what they do about this. I'm thinking Shen-Hao at the moment but I'm still on the fence as I do like the Chamonix design better. I'll bet Canham wouldn't leave the fix up to the customer.....
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
Mike,
Quote:
Originally Posted by
Mike1234
It's a matter of shaving a precise amount off the edge-seat on which the inner fresnel rests.
O.K., that I might argue with; it isn't consistent with how I understand an "unfrosted" fresnel to work. You'd still have a Nth power lens in the optical path and the image-forming surface behind it would be in the same place. So that wouldn't work, right?
Quote:
Originally Posted by
Mike1234
The cameras came with fresnels and they should work properly with fresnels.
Amen.
Quote:
Originally Posted by
Mike1234
Posting customer fixes is okay but it should be as an "option" at the discretion of the customer.
Yep, and if I were Chamonix, I wouldn't really want the customer fixing the problem unless they were completely comfortable doing so.
But Chamonix's response I think has broader implications. How many people would buy a used one knowing that it needs fixing - in other words, what does it do to resale value? If the resale value is significantly reduced, can first line sales be far off?
Cheers, Steve
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
That's another reason the chamonix is so cheap compared to other cameras..... No support from the factory. It's a big cock up from their end and they have no plans to fix it. Only to merely tell you how to work around it.
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
Quote:
Originally Posted by
Steve Hamley
O.K., that I might argue with; it isn't consistent with how I understand an "unfrosted" fresnel to work. You'd still have a Nth power lens in the optical path and the image-forming surface behind it would be in the same place. So that wouldn't work, right?
Hi Steve,
It's not the frosted/unfrosted fresnel that's the issue. It's the extra spacing caused by the fresnel when it's installed between the GG and the body. If correct focus occurs with it removed and the GG is move forward the thickness of the fresnel then the factory failed to account for the thickness of the fresnel when they machined the body. Or am I missing something? :)
