Fresnel lenses and ground glass focusing screens your worries answered

[Bob Salomon]

I think the Fresnel introduces a bit of unsharpness on the ground glass. On either side, faced any way. I bought extras because they were only $2.50 each. I was using one as a magnifying glass and I noticed that the page I was looking at was clearer without the Fresnel gglens. The Fresnel lens is a bunch of triangles... not a nice perfectly smooth magnifying glass. So in my opinion, a Fresnel is not a good choice for highly detailed focusing.

Assuming your gg is properly positioned then by placing a fresnel behind the gg can not effect the image since the image has already been focused on the ground side of the gg.

[Pere Casals]

... Perhaps it may also depend on the graininess of the GG, perhaps that effect can be seen a bit more in very good GGs with bad fresnels.

[Bob Salomon]

... Perhaps it may also depend on the graininess of the GG, perhaps that effect can be seen a bit more in very good GGs with bad fresnels.

There are no bad fresnel. There are incorrect fresnel and correct ones. Fresnels are lenses and all of them have a focal length. Large format camera manufacturers usually offer fresnel lenses for their cameras that have the proper focal lengths for the commonly used lenses for that format. Some companies, Wista for one, also offer other focal lengths for different lenses. In Wista’s case they offer one for long lenses.
If you remember Nikon they also offered a range of fresnels in their K screen series for 35mm cameras.
The cheap fresnels sold for reading are usually not the correct focal length to perform optimally with large format lenses.
Try an actual modern camera fresnel and compare the difference!

[Pere Casals]

...

Thanks for the info.

Yes... most SLR Nikon focusing screens were fresnel type, I just reviewed it for my F5... https://mir.com.my/rb/photography/ha...ml/screens.htm

[pepeguitarra]

I purchased a Super Speed Graphic from the son of a man who bought it in 1961. Apparently the man used it very carefully. I shot several frames with it and was pleased. After reading about fresnel, I went inside and noticed that there was a fresnel lens placed between the lens and the gg. The rough side of the gg was in contact with the rough side of the fresnel. I took it away and moved it to the outside, placed it between the smooth side of the gg and my eyes. The rough side of the fresnel touching the smooth side of the gg. I noticed a big difference, a lot more light coming out and I can see everything more clearly. However, Most of my last 8 shots have been out of focus. Does this mean that the Super Speed Graphic came with a fresnel originally? I will put it back where I found it. Does any one have knowledge of the Super Speed Graphic on this regard? I appreciate it. Maybe Bob Salomon knows. Thanks, Pepe.

=================
UPDATE:

Never mind, I found a manual of repair of the Super Graphic and the Super Speed Graphic with all the parts displayed. The camera came originally with the fresnel. The rough side of the gg is in contact with the rough side of the fresnel. So, I screwed up my original set up and need to correct it.

[pepeguitarra]

Just to take advantage of the knowledge here. I purchased on the auction site a 4x5 fresnel for my Calumet CC400, which originally did not come with a fresnel. This time, I placed it rough side of the fresnel on top of the smooth side of the gg, basically, I am looking at the fresnel. The increase in light was incredible, it was too much light. However, It is hard for me to focus because I do not see sharp lines anywhere, not even with the loupe. Is this typical case? The fresnel was made by and for WISTA 4x5 cameras, and it has a circle in the middle about 3/4 of an inch that is smooth. So, in order to take the picture, I had to remove the fresnel. BTW, I was using the Schneider SA 90/8 lens.

[Bob Salomon]

I purchased a Super Speed Graphic from the son of a man who bought it in 1961. Apparently the man used it very carefully. I shot several frames with it and was pleased. After reading about fresnel, I went inside and noticed that there was a fresnel lens placed between the lens and the gg. The rough side of the gg was in contact with the rough side of the fresnel. I took it away and moved it to the outside, placed it between the smooth side of the gg and my eyes. The rough side of the fresnel touching the smooth side of the gg. I noticed a big difference, a lot more light coming out and I can see everything more clearly. However, Most of my last 8 shots have been out of focus. Does this mean that the Super Speed Graphic came with a fresnel originally? I will put it back where I found it. Does any one have knowledge of the Super Speed Graphic on this regard? I appreciate it. Maybe Bob Salomon knows. Thanks, Pepe.

=================
UPDATE:

Never mind, I found a manual of repair of the Super Graphic and the Super Speed Graphic with all the parts displayed. The camera came originally with the fresnel. The rough side of the gg is in contact with the rough side of the fresnel. So, I screwed up my original set up and need to correct it.

Your gg just has to be positioned by a technician.

[consummate_fritterer]

I knew there was a focus problem with a used Chamonix 45N-1 before I bought it. After paying for the camera I had the seller mail it directly to the technician Maxwell recommends for installation/alignment and Maxwell sent a screen to the same person. After installation the camera was forwarded to me, along with the original GG/Fresnel.

[Doremus Scudder]

Just to take advantage of the knowledge here. I purchased on the auction site a 4x5 fresnel for my Calumet CC400, which originally did not come with a fresnel. This time, I placed it rough side of the fresnel on top of the smooth side of the gg, basically, I am looking at the fresnel. The increase in light was incredible, it was too much light. However, It is hard for me to focus because I do not see sharp lines anywhere, not even with the loupe. Is this typical case? The fresnel was made by and for WISTA 4x5 cameras, and it has a circle in the middle about 3/4 of an inch that is smooth. So, in order to take the picture, I had to remove the fresnel. BTW, I was using the Schneider SA 90/8 lens.

The Wista Fresnel/ground glass is more than just a Fresnel lens. Every Wista Fresnel screen I know of is a sandwich of ground glass (acrylic, actually), frosted on one side with a Fresnel lens affixed to the viewing side. It is meant to replace the ground glass, not be added to an existing one. If your Calumet came with just a plain ground glass, and the Wista screen is the right size, you should just remove the original one and replace it with the Wista screen, frosted side facing the lens. Then you should be able to focus without a problem.

Best,

Doremus

[Bob Salomon]

The Wista Fresnel/ground glass is more than just a Fresnel lens. Every Wista Fresnel screen I know of is a sandwich of ground glass (acrylic, actually), frosted on one side with a Fresnel lens affixed to the viewing side. It is meant to replace the ground glass, not be added to an existing one. If your Calumet came with just a plain ground glass, and the Wista screen is the right size, you should just remove the original one and replace it with the Wista screen, frosted side facing the lens. Then you should be able to focus without a problem.

Best,

Doremus

Wista makes and offers more gg and fresnel then you are familiar with.