Bosscreens different for different cameras?

[David Karp]

Hi all,

I have a question for you. Can a Bosscreen for one camera be used on another? Another way of putting it is whether the only difference between Bosscreens for different cameras is the length and width dimensions required to allow them to fit in the GG frame.

Somehow I seem to remember that there might be differences in thickness, which might make a difference in the plane of focus. Is this correct (or am I nuts)? OK, I am nuts, but is this correct?

Thanks.

[Glenn Thoreson]

I've never seen one, but if it's actually a viewing screen, like ground glass, the only thing that matters is that the matte (?) surface faces the lens. If it is a stand alone screen, the thickness plays no part in the focus, just the fit. If it's like a fresnel lens, it does matter. On the other hand, you can place a fresnel on top of the ground glass, not in front of it. In that position, thickness plays no part.

[David Karp]

The rub with the Bosscreen is that it they are two pieces of glass with a layer of wax in between. I think that the image is actually formed on the wax, as opposed to the glass. So, if there is a difference in glass thickness between different versions, then the image may be formed in the wrong plane.

[Bob Salomon]

The rub with the Bosscreen is that it they are two pieces of glass with a layer of wax in between. I think that the image is actually formed on the wax, as opposed to the glass. So, if there is a difference in glass thickness between different versions, then the image may be formed in the wrong plane.

That is correct.

[David Karp]

Bob, are you saying that there is a difference in glass thickness among Bosscreens for different cameras? Or are you agreeing that if there is a difference, then this will result in the image being formed in the wrong plane?

[Bob Salomon]

Bob, are you saying that there is a difference in glass thickness among Bosscreens for different cameras? Or are you agreeing that if there is a difference, then this will result in the image being formed in the wrong plane?

David,

It depends on the camera and where the screen actually fits into the camera. Speaking for Linhof the gg sits on top of 4 adjustable shims. The Boss screen has to be made in such a way that to use it on a Linhof the bottom piece of glass has to be cut away in the corners where the shims are so that the paraffin wax layer lies on the proper image plane. If the corners were not cut away the paraffin layer would be too far back to focus correctly. The shims do not have enough travel to adjust for a Boss screen with an improperly placed wax layer.

We originally looked at the original Boss screen before it was a view camera focusing screen. It was presented to us by the Dutch inventors around 1981 as an aerial image screen surface to copy slides and home movie films to video. As such it was about 8 x 11" and came in a styrofoam package with a slot that held the screen upright.

We suggested to them that the screen would make an interesting view camera focusing screen and they started to test that concept and found that since a gg lies directly on the image plane in a camera that the bottom layer of glass would have to be off set or be of varying thicknesses depending on the camera it was made for. Thus virtually every screen had to be customized for the camera system it was made for.

Then we discovered what happens to the screen when it gets very cold or very hot or goes from one extreme to the other. That is when we decided not to get involved with it. We had one in the trunk of the car in winter and ended up with a reticulated and cracked wax pattern after it came in from the cold one day.

The last problem was that the wax surface has no "grain" as a ground glass does. Thus under many lighting conditions, and especially with very wide angle lenses it became very difficult to focus critically compared to gg and fresnel technology from the camera manufacturers in the early 80s.

[David Karp]

Bob,

Thanks for the detailed response. I really appreciate it.

I understand that some have had problems with these. I have one that I used on my old Cambo monorail. I really liked it a lot. Used it in Yosemite in winter, and in S. Calif. in the summer with no problems. I never left it in the trunk or in the car though.

Well, it won't be going on my next camera, based on your response, and I am glad I did not just drop it in and try to use it.

Thanks again.

[Brian Ellis]

I don't know for sure but I've bought four diffferent BosScreens for four different cameras and each time I was asked for the make and model of the camera so I assume the company thinks it's relevant. I never used any of mine in cold weather but I did use them extensively in very hot weather (Florida summers, 95 degree temperature, 90 degree humidity) and never had a problem. I think Maxwells are the best viewing screen presently made and BosScreens are the next best.

[Ted Harris]

Like Brian, I've never had trouble with them in very hot weather but I lost one to -20°F while shooting in the Winter in NH. Screen developed a severe case of the reticulation Bob described.

[Photobackpacker]

I have been using the bossscreen on my linhof MT for 8 years without problem - even in the Minnesota cold.

I had the beginnings of reticulation after using it in -20 degree weather but this was fixed easily by allowing the screen to reach room temp and then heating it slightly with a hair dryer.

The brightness and critical focusing is the best I have experienced.

[David Karp]

Thanks all for the responses.

If not for the question of the proper focusing plane, I would not hesitate to use the Bosscreen on another camera. I really liked using it, even though I had concerns about excess heat or cold in the back of my mind. Maybe I will make some tests, but I hate to waste my limited time for photography making tests.

[Colin Myers]

This does raise a very interesting point about the plane of sharp focus of the Boss Screen. Would images taken with the lens stopped well down, appear sharper than those taken with a bigger aperture?
None of my cameras have the facility to effectively recess the screen further into the ground glass frame. How do others cope with this?
Colin Myers

[Photobackpacker]

None of my cameras have the facility to effectively recess the screen further into the ground glass frame. How do others cope with this?
Colin Myers

With the Boss screen - the wax is sandwitched between 2 pieces of glass. The piece of glass that is closest to the camera lens is clipped on the edges and/or corners so it does not come in contact with the camera's mounting system. In this way, the plane of the wax core is positioned identically to where a conventional gg would be.

I have not found it necessary to adjust the position of the gg when using a Boss screen.