I'll make a test at about 5 to 7 yards. I expect the effect to be the larger the greater the distance is. May be up to 3 yards it doesn't make a difference and about infinity it doesn't matter any more. May concern is with the distances in between.
Ulrich
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
I realize this topic was beat to death...
But I've read through the posts and for the life of me I don't understand why it's a Chamonix specific problem.
Surely it makes sense that at some point, the Fresnel lens will interfere with the ability of the user to adjust the image-focus plane as seen through the ground glass to match the exact film plane.
IE: If the Fresnel lens is placed in front of the GG .
Granted, the benefit is to protect the brightening Fresnel lens element if you do...
This is how my camera was constructed when I purchased the used 045N a few months ago.
Note: It's a whole different ball game if we are talking about custom screens like Maxwell, etc,...
IMHO, Nothing is for free.
Shadowleaves explained that quite clearly, see the post # 54.Originally Posted by rugenius
GPS: I get the post #54...
My point is,..
If the Fresnel is on the lens side between the GG...
You are ALWAYS making a compromise... however thin the Fresnel...
Especially in combination with short focal length wide angle optics.
The GG is supposed to define the film plane...
Any other position of the GG while involving a screen intensifier is a compromise.
Compensating for Fresnel thickness/effects require moving the GG position respective of the Camera back/ rear standard.
Chamonix doesn't tell us that we have to use the Fresnel, it's a viewing aid and has limitations like any.
Of course the compensating requires the GG position change, we all know it, that's the whole point. Chamonix didn't make that repositioning - the whole thread is about that.
And the Fresnell is on the camera in question - you have to use it unless you throw it away. What's so difficult to understand here?
Having re-read both threads, I still don't get it. I've read about focus error in wide angle architectural shots, infinity shots, people are checking for less than infinity, but longer than 5 yards, and there seems to be a good dose of misunderstanding about what a view camera just plain does as a function of tilt and shift and starting at the GG when T/S variables haven't been eliminated is just a bad idea. A simple look at some DOF tables has stopped me from doing any further testing. I pulled out the 75 f6.8 Rodenstock and a Schneider/Sinar SA, 90mm, f5.6 to play with today, but once I confirmed what I should expect from DOF, I said why bother. At just five feet you've got over a foot of DOF and at 15 you have almost 23 feet with the Rodenstock, I don't need a ruler to evaluate focus error, it would be very obvious in the years worth of photos I've taken.
A fresnel screen increases brightness, that is its sole point and it is another lens inserted in the light path, but with any normal aperture (even wide open) found on any typical LF lens, DOF should minimize it ever affecting your photos. If you're shooting a larger than f4 aperture on the Chamonix, you don't need a fresnel and should understand it might cause you problems. That's on any field camera. If someone has a specific test I should do and will list the focal length (got 47mm to 600mm) and the distance the test should be carried out at, I'll have at it, but otherwise, this whole continued dialogue seems like user error or something else.
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
GPS: We're both responding but don't seem to hear each other?
The whole thread started as a problem solving issue. Correct?
To that end,... I thought the gross erorr reported had more to do with the user than the Chamonix screen intensifier...
My concern was why people think Chamonix is to blame for a physics related phenomena related to the use of a Fresnel lens.
The "point of the thread" in your mind is the lack of positioning...
IMHO, articulating/moving the GG to compensate for an apparent focus through the Fresnel is bad optics engineering and invites more problems/ headaches if the non-expert users are allowed to play with it. The 1/3rd thickness rule is generalized at this point.
If Chamonix committed to resolving your problem via that method for all the variety of WA lenses,... it would invite more problems than it resolved.
A fixed GG plane is the correct method.
Assuming screen intensification is necessary,... imaging can be accomplished via ultra thin Fresnel to reduce the said effects, else place the intensifier between the person and the GG.... Else there are other brightening methods too.
There are other people in the forum that pointed out to simply remove the Fresnel, or use another screen intensifier, etc,...
Again,... While you can try to convince me the right thing to do is blame Chamonix for not providing a degree of freedom so that the user can move the optics to compensate for the Fresnel/ Fresnel thickness...I claim that's a bad engineering band aid and it will never satisfy the whole audience anyway.
So,... that's my point,... and I can definitely see the point of complaining to Chamonix that the setup is not optimized... but IMHO the solution is not as you proposed.
I appreciate the dialogue...
Cheers!
Indeed, somehow we don't understand each other.
Nobody wants Chamonix to "allow to play with it". Chamonix didn't do what any other manufacturer did - put the Fresnell combo to the right position right away. In that way the consumer has nothing to do.
I don't think somebody wanted to force Chamonix to allow customers themselves to do so on their cameras. You're still misunderstanding the thread, I'm afraid.
GPS, my apologies for not taking the time understand all the details...
I purchased the camera second hand and thought the screen intensifier was an accessory/add-on for the Chamonix camera GG.
However, it was sold as part of the camera, integral to it and all specification.... and to this end I guess the Chamonix factory has admitted that the Fresnel location is a "design defect" and that it cannot be fixed,... emphasizing the whole point concerning the engineering shortcomings of placing the Fresnel between the GG and lens on ANY view camera.
http://www.chamonixviewcamera.com/Announcement.html
Hello. I'm here to dig up this thread.
I have a 045-f1. I do enjoy using it. However I have found focusing issues that I think are related to the Fresnel screen.
I have used in the past both a toyo field and sinar view camera as well as a tachi 8x10 without this issue.
Seems when I push my loupe against the protective screen, the image is in focus through the loupe, when I remove my loupe, the image on the GG does not appear in focus. Critical focusing is very frustrating and at shots where it matters, it seems that more often than not after development my negatives are out of focus, particularly with my 90mm lens (even when using smaller apertures)
This is on the F1 model, not N1 or N2.
I understand people are saying that the F1 saw this issue rectified, but I feel as if mine is still having a problem.
My main question here is, if I remove the Fresnel and just replace the plastic protective screen, will this affect my focusing? Or will it be true as the normal GG in the Chamonix? Or would it be best to leave the GG completely bare?
Anyone else with a F1 model have the problem?
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