New Chamonix 45n-2

[Krist]

Hi everyone,
I'm pretty new to this, actually just got my first LF today. Looking at the ground glass i noticed this "dot", "spot". Can someone explain what it is?
I got the camera brand new and it was like this out the box. I suspect it is because of the tensions between the fresnel and the glass but im not sure. Looks like it is not supposed to be there.

Sorry for asking what might be a stupid question, but i dont know anywhere else to ask.

Kristian

 

[Nicholas Lindan]

They are called "Newton's Rings" and are caused by very close contact between the smooth back sides of the GG and the fresnel.

The rings should be invisible when you are using the camera.

Loosening the screws holding the fresnel in place should remove them. If not then a few paper shims between the GG and the fresnel should space the two apart.

 

[grat]

Contact Hugo Zhang via email at hugoz_2000 at yahoo com if that doesn't work. He's the North American rep for Chamonix.

 

[Krist]

Thanks alot for the fast replies!
Will try and loosening the screw. Then contact Hugo if it dosen't work.

 

[grat]

Enjoy the camera. I have the 45N-1 "Classic", and it's a genuine pleasure to use.

 

[Alan Edward Klein]

I'd contact Hugo first.

 

[Kodachromeguy]

I'd contact Hugo first.

Why? Why should he not loosen the screws a tiny bit and see if the Newton rings change?

 

[MattKing]

Why? Why should he not loosen the screws a tiny bit and see if the Newton rings change?

For a brand new camera, I think I'd like to receive that advice from the manufacturer's representative first before I made that adjustment.

 

[Greg Kriss]

The rings should be invisible when you are using the camera.

My 4x5 Chamonix had the same Newton Rings (albeit in a different place on the GG) when I acquired the camera. I just ignored them since they essentially disappeared when I was actually using the camera. For the heck of it, I just checked the back of my Chamonix and they are still there... I just haven't noticed their presence in years since they had zero effect when I was using the camera.

 

[Alan Edward Klein]

Why? Why should he not loosen the screws a tiny bit and see if the Newton rings change?

It might change the focusing process if it shifts the GG or fresnel away from each other. The screws may keep them tight together. Maybe something else. His call. It's his camera.

 

[Bob S]

If the Fresnel is closest to his eye it’s repositioning won’t effect the image placement. The image is formed on the frosted side of the gg.

 

[Alan Edward Klein]

If the Fresnel is closest to his eye it’s repositioning won’t effect the image placement. The image is formed on the frosted side of the gg.

Wouldn't the loupe's focusing point be different?

 

[Bob S]

Wouldn't the loupe's focusing point be different?

You focus the loupe on the ground side of the gg, not on the Fresnel screen,

 

[Alan Edward Klein]

You focus the loupe on the ground side of the gg, not on the Fresnel screen,

So when I have my loupe against the Fresnel lens, even though it's away from the focus point, I still am focusing on the GG? My eye adjusts automatically?

 

[Bob S]

So when I have my loupe against the Fresnel lens, even though it's away from the focus point, I still am focusing on the GG? My eye adjusts automatically?

No, you should be using a loupe with a focusing eyepiece that you have focused onto the grain of the gg. Otherwise you are not focusing on the image itself and are always slightly out of focus.

 

[Alan Edward Klein]

No, you should be using a loupe with a focusing eyepiece that you have focused onto the grain of the gg. Otherwise you are not focusing on the image itself and are always slightly out of focus.

But my loupe doesn't have an adjustable lens. Do you need one like that?

 

[Bob S]

But my loupe doesn't have an adjustable lens. Do you need one like that?

If you want critical focus. Otherwise you are focusing on the plane your loupe is resting on.

 

[ic-racer]

The amount of light that bounces back and forth between, or goes through, the reflective surfaces is based on probability for every photon. One way to explain it is using vector addition and subtraction to represent probabilities.

 

[Alan Edward Klein]

If you want critical focus. Otherwise you are focusing on the plane your loupe is resting on.

So why does anyone use a loupe? I'd be better off focusing by eye. No?

 

[Bob S]

So why does anyone use a loupe? I'd be better off focusing by eye. No?

No

 

[PonySoldier1887]

Alan, the use of a loupe is helpful (due to the magnification) but you do need to be able to focus on the ground-glass. The best way is to bring the loupe into contact with the rear-most surface and, with no lens installed, adjust the focus of the loupe so that the "grain" of the ground-glass is in sharp focus. With no lens installed you are not distracted by any image and are indeed viewing the magnified image plane. There are some who prefer higher magnification but common practice is to use a loupe having a magnification of about 4 - 6 times. Wista makes a convenient loupe but there are others as well - just make sure that you have the ability to focus the loupe because this enables you to bring the loupe to the same distance by resting on the surface. Needless to say, if you subsequently add any aid (such as a fresnel) to the back side, you must refocus the loupe because you will have changed the distance.
Joel

 

[Alan Edward Klein]

Alan, the use of a loupe is helpful (due to the magnification) but you do need to be able to focus on the ground-glass. The best way is to bring the loupe into contact with the rear-most surface and, with no lens installed, adjust the focus of the loupe so that the "grain" of the ground-glass is in sharp focus. With no lens installed you are not distracted by any image and are indeed viewing the magnified image plane. There are some who prefer higher magnification but common practice is to use a loupe having a magnification of about 4 - 6 times. Wista makes a convenient loupe but there are others as well - just make sure that you have the ability to focus the loupe because this enables you to bring the loupe to the same distance by resting on the surface. Needless to say, if you subsequently add any aid (such as a fresnel) to the back side, you must refocus the loupe because you will have changed the distance.
Joel

My 8x loupe can;t be focused other than by moving it closer or further from the plane. Someone said it would still work. How?

 

[PonySoldier1887]

Alan, it will function but you cannot be certain that you are focusing at the image plane. It equates to the old Fred Picker "one-foot-on-a-rock" lament - you need one fixed point of reference! The lack of a fixed point of reference means you may, or may not, be looking at the same focal plane. If you do vary the distance until the image of the grain is sharp, you will indeed accomplish sharp focus but you have to bear in mind that the image and the grain are somewhat "busy" and it is difficult to determine the convergence of image at the focal plane. If you have someone nearby who has a loupe which is capable of being focused, adjust for sharp focus (no lens installed), attach a lens and focus using the loupe resting on the ground-glass. I think you will be surprised at how much better the process flows. The short answer is "yes" but not as quickly, as easily and with the same degree of certainty that you "nailed it."
Joel

 

[Alan Edward Klein]

Alan, it will function but you cannot be certain that you are focusing at the image plane. It equates to the old Fred Picker "one-foot-on-a-rock" lament - you need one fixed point of reference! The lack of a fixed point of reference means you may, or may not, be looking at the same focal plane. If you do vary the distance until the image of the grain is sharp, you will indeed accomplish sharp focus but you have to bear in mind that the image and the grain are somewhat "busy" and it is difficult to determine the convergence of image at the focal plane. If you have someone nearby who has a loupe which is capable of being focused, adjust for sharp focus (no lens installed), attach a lens and focus using the loupe resting on the ground-glass. I think you will be surprised at how much better the process flows. The short answer is "yes" but not as quickly, as easily and with the same degree of certainty that you "nailed it."
Joel

So you suggest I remove the lens and then try to see if I'm focusing on the ground glass by seeing the "grain" in the GG?

 

[PonySoldier1887]

Yes, that is one way of seeing whether you are actually looking at the true focal plane. You can then note the distance of your loupe from the ground-glass. Again Alan, you can do it your way but it is more a "hit or miss" situation whereas with a focusing loupe you are certain that you are at the same reference each time.
Joel