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sully75
11-Apr-2012, 14:15
I just got a Chamonix 45n-2 and really love the camera. Exactly what I was looking for and couldn't be more pleased with it.

EXCEPT

Not sure I'm into the fresnel. I've never really used one before. It feels like the image never gets really sharp for focusing, even with the loupe. I don't have a proper view camera loupe, I bought the cheap Peak 5x that someone here recomended, so it could be that the loupe is not properly focused on the ground glass.

Anyway, from reading a bit about the Chamonix and the Fresnels, it seems like it can only be replaced by the factory? Do I have that right? If I took off the Fresnel myself, would I be able to use the camera with just the groundglass? Would I be able to replace the Fresnel myself?

Thanks
Paul

Carterofmars
11-Apr-2012, 20:53
Get a good loupe first before anything else.

genotypewriter
11-Apr-2012, 21:26
It feels like the image never gets really sharp for focusing, even with the loupe.

That's correct, for off-center with wider-angle lenses. The center has no issues.

If your loupe has a removable base, take it off and hold it close to the groundglass to get perfect focus (on the loupe).

With that said, I quite like the fresnel+gg... done a lot of shots with it without even using a loupe and gotten them sharp:

Nikkor 65mm f/4 SW wide open:
http://www.flickr.com/photos/genotypewriter/6834544293

Xenotar 150mm f/2.8 wide open:
http://www.flickr.com/photos/genotypewriter/6806479707

(Anyone who's not familiar with flickr, right click on the images and select 'original' to see approximately 12MP images.)

Doremus Scudder
12-Apr-2012, 01:38
Simply turn you loupe around, using the base as a sort of eyepiece and then move your head and loupe (as a unit) closer and farther from the ground glass until it is in focus. Yes, you have to find the right spot and hold it there without resting anything on the ground glass, but this works really well with Fresnel screens.

For shorter lenses that are often more of a focusing problem with Fresnel screens you can now change the angle of the loupe to the ground glass to find the sweet spot, i.e., somewhere not exactly perpendicular to the ground glass. The correct angle is always in line with the lens, easy to find.

If you focus on the frosted/ground side of the ground glass, you should have a sharp image this way. I've been focusing for years like this and would never go back; it's just more convenient for me.

FWIW, I have cameras with both Fresnel and plain ground glass and have no problems with either. The advantage to the Fresnel is that I can often dispense with the dark cloth. That's never the case with plain ground glass.

There have been a few discussions here and on APUG about focusing lately. A quick search should turn them up.

Best,

Doremus

chuck94022
12-Apr-2012, 01:58
That's correct, for off-center with wider-angle lenses. The center has no issues.



This was correct for the 045-N1 but according to Hugo has been corrected with the 045-N2, so off center and wider-angle lenses should no longer cause focus issues. The fresnel on the -N2 has been mounted on the outside of the gg, not the inside (and a protective glass is placed outside the fresnel, so it is now a sandwich).

Michael Graves
12-Apr-2012, 05:41
I own th 45N-1 and was having similar issues with focus when using a Toyo loupe. It did not have diopter correction and apparently recent eye surgery had affected my vision to the point that it was no longer a good match for my eyes. I purchased a Peak 7x with the ability to adjust for diopter correction and have been happier than a pig in s...I have not had any issues since.

genotypewriter
12-Apr-2012, 08:18
This was correct for the 045-N1 but according to Hugo has been corrected with the 045-N2, so off center and wider-angle lenses should no longer cause focus issues. The fresnel on the -N2 has been mounted on the outside of the gg, not the inside (and a protective glass is placed outside the fresnel, so it is now a sandwich).

There are no focus issues in the sense where the gg/fresnel is placed at a wrong distance. I think this was the problem with the first version. Please correct me if I'm wrong.

Ari
12-Apr-2012, 22:52
The loupe of which you speak was probably my recommendation; I've used it for years without problems.
I have a Linhof with a Yanke GG/fresnel and a Wista with the same type of screen, and both work very well with the Peak 5x loupe.

I'm not familiar with Chamonix accessories, but I used to wrestle with separate GGs and fresnels, now I much prefer when they are one piece; brightness is much more even, as well.

rknewcomb
13-Apr-2012, 09:23
A somewhat related question...
1) Does a Yanke GG/fresnel change the point of focus such that it creates an error between the focus on the glass and what you get on the film?
2) If most any groundglass is used with a fresnel on the OUTside, does it keep the focus point the same so the image is focused properly on the film?
thanks!
Robert

Ari
13-Apr-2012, 11:28
A somewhat related question...
1) Does a Yanke GG/fresnel change the point of focus such that it creates an error between the focus on the glass and what you get on the film?
Robert

No; it is one piece, with a plain acrylic overlay.
Pretty hard to screw up, much like the superior Wista screen.

Ari
13-Apr-2012, 11:30
A somewhat related question...
2) If most any groundglass is used with a fresnel on the OUTside, does it keep the focus point the same so the image is focused properly on the film?
thanks!
Robert

Manufacturers vary in their use of the fresnel in front of, or behind, the GG.
If you're in doubt, best to contact the manufacturer to see what's what, or post the question here for your specific camera make and model.

So switching the fresnel to the front when it should be behind might cause focusing errors.

Old-N-Feeble
13-Apr-2012, 11:39
1) Does a Yanke GG/fresnel change the point of focus such that it creates an error between the focus on the glass and what you get on the film?
2) If most any groundglass is used with a fresnel on the OUTside, does it keep the focus point the same so the image is focused properly on the film?


No; it is one piece, with a plain acrylic overlay.
Pretty hard to screw up, much like the superior Wista screen.

And similar to the Canham Fresnel but the Canham uses a glass protective cover.

sully75
13-Apr-2012, 14:36
I own th 45N-1 and was having similar issues with focus when using a Toyo loupe. It did not have diopter correction and apparently recent eye surgery had affected my vision to the point that it was no longer a good match for my eyes. I purchased a Peak 7x with the ability to adjust for diopter correction and have been happier than a pig in s...I have not had any issues since.

http://www.bhphotovideo.com/c/product/40694-REG/Peak_1301975_7x_Scale_Loupe.html

this one Michael?

Damn expensive stupid hobby!!

rknewcomb
14-Apr-2012, 07:46
What I was wondering about was...
I have an older plain and dim ground glass. If I replace the old groundglass and put in a Yanke screen, will my focus then be off.

Old-N-Feeble
14-Apr-2012, 09:28
What I was wondering about was...
I have an older plain and dim ground glass. If I replace the old groundglass and put in a Yanke screen, will my focus then be off.

That depends on the construction of your original GG. If the actual focus plane (frosted plane) of your screen is the front-most part then it'll be fine. If the fresnel is at the front then your focal plane will be off the thickness of the Fresnel.

Doremus Scudder
14-Apr-2012, 10:10
rknewcomb,

To elaborate a bit on Old-N-Feeble: Since you have just a ground glass screen and no Fresnel at this point, you need a Fresnel-ground-glass sandwich in which the Fresnel is mounted behind the ground glass, i.e, where the frosted surface of the ground glass is closest to the lens and the Fresnel part of the sandwich is closest to you when you are viewing the image.

Yanke makes several products: a thin Fresnel screen (0.85mm) that placed in front of the ground glass (you don't want this one), a thicker Fresnel screen that can be placed in either position (which would work for you, but you need to keep your original ground glass), or a Fresnel-ground-glass sandwich (which would also be fine for your application and would replace your ground glass).

Some sandwiches have the opposite configuration, and they will cause a focusing error if you use them. You should, however, be fine with a Yanke screen if you get the one of the proper ones.

Best,

Doremus

rknewcomb
16-Apr-2012, 12:08
Thanks Doremus for explaining that. It is most helpful!
Robert

lbenac
1-Jun-2012, 21:13
Well I just changed my 45N2's gg/fresnel for a Hopf GG. First impression is very good. Waiting the week-end to try it out in the field.

Cheers,

Luc