Ground glass and fresnel lens issues...greenspun.com : LUSENET : Large format photography : One Thread
I have been following ground glass and fresnel lens thread posted recently. I have a question related to the same issue. I have a Busch pressman 4x5 camera. Focusing on this camera without cloth over your head is almost impossible. Recently i added fresnel lens in front of the ground glass i.e. the fresnel lens is on my side with lens smooth side is facing me and, the grain side is in contact with ground glass. The image quality has improved drastically. I have not exposed any film after this addition. I want to know if this will alter focusing accuracy in any way. Thanks
-- Reddy (email@example.com), April 29, 1999
Hi Reddy, i have similar set-up on my 4X5, and it works fine. Often I use a magnifying glass if i want a bigger picture yet. for general purpose composition, i think this works fine, but for tricky selective focus and purposeful soft focus, i find it is difficult to use a loup with the fresnel, and then i wonder why i ever put the fresnel on there in the first place.
-- david clark (firstname.lastname@example.org), April 29, 1999.
A fresnel installed on the eye side of the ground glass won't affect your plane of focus.
On the lens side, it's a different story. Some compensation must be made.
-- Mike Long (email@example.com), April 29, 1999.
I also find the information posted at this site most valuable and informative. In particular, this subject about GG alignment is about the most critical as far as I am concerned. I wanted to share some info I found on the Toyoview Board regarding this issue. I found it interesting that Mamiya/Toyoview recomended NOT repositioning the GG once is the fresnel lens is installed in FRONT of the GG. Here is the question and answer:
Q: When using my Toyo M 8x10 with a wide angle lens, the corners of the ground glass get rather dark. I would like to add a Fresnel lens. There seems to be a ridge in the frame forward from the groundglass (looking at the bellows) which could be meant for placing a Fresnel. Toyo does not sell any such article. I also own a Tachihara 8x10 which has a Fresnel lens placed in front of the groundglass. Are these Fresnel lenses of standard size and can I place the Tachihara lens in front of the Toyo groundglass without infringing on the focusing ability of the camera? What do the Mamyia and other large format experts have to say about this?
A: Toyo does not offer an 8x10 fresnel. You may want to try Beattie in Cleveland , Tenn. If you try the Tachihara, make sure not to move the ground glass from its original position.
-- Jim Billups (firstname.lastname@example.org), May 01, 1999.