fresnel screen with wide angle lensesgreenspun.com : LUSENET : Large format photography : One Thread
I have a Linhof Technikardan 45S with 58, 110, 135, 180 and 360mm lenses. While on a recent trip I was using the standard ground-glass and found that it was hard to see the whole image due to light fall off. Longer focal lengths are better and short ones worse.
It was suggested that I used a fresnel screen. I have a few questions though:
1. My understanding is that the fresnel screen mounts behind the ground glass somehow and that both are then used. Is this just a matter of releasing some tabs already on the camera, or do I need additional hardware?
2. Without a fresnel, the 58mm is just a host spot in the middle; it's impossible to see the entire image without moving ones head. Will the fresnel make this situation better or worse? I'm hearing that since it's such a wide angle that it will be worse. Also, I plan on getting the new Super Symmar XL 80/f4.5. Will it work OK with that lens?
Thanks for any help, Lloyd
-- Lloyd Chambers (firstname.lastname@example.org), October 05, 2000
I can't speak directly ot the 58mm on 4X5, but I do use a 121mm on 8X10 frequently. As these are roughly equivalent wide angles for the formats I can say that the fresnel doesnot make the viewing any easier and in fact the corners suffer from the fresnel becoming blurred. I have found with these wides the only real solution is to do the "dark cloth bounce" and move your head around.
The lenses from the 110 up should all benefit from the fresnel; as you noted the longer the lens the better the viewing. teh wicer the lens the less benfit I have gained, I presume having used a 90mm on 4X5 a good bit that the 80mm will react alot like the 58 does.
-- Marv (email@example.com), October 05, 2000.
1. there should be a clip on either end of the groundglass attached to the middle, longer screw. these are the fresnel clips and are meant to hold the fresnel behind (eye side) the groundglass.
2. wide angles require special fresnels. linhof sells them, as do others. make sure the one you get is sized for the tk. a good person to speak to is bill maxwell. you can find his info under the focussing screens thread at the bottom of this page. he can answer all your questions and most likely solve your screen problems.
-- adam friedberg (firstname.lastname@example.org), October 05, 2000.
I have a Wide Angle screen made by Bill Maxwell. The screen is optimised for 75mm focal length, as I recall. I use Schneider 72XL and it works well with the screen with no noticeable light falloff. The new SS XL 80mm should be compatible with this screen.
Because I don't want to get bothered with having two screens, one for wide and the other for normal, I just use the wide angle screen for my other lens Fuji A 180mm. It works fine with the screen but a little hard to focus under insufficient light, due to light bending effects.
-- Masayoshi Hayashi (email@example.com), October 06, 2000.
If you get the right fresnel, then it will make using the 58 mm a joy to work with. I use the 58 mm on 6 cm x 9 cm and have a custom built fresnel from Bill Maxwell. He'll explain the whole thing to you, that fresnels have focal lengths and that to get optimal performance you would want a separate fresnel for each lens. Of course, no one is that nuts, but it really helps to have a separate fresnel for your very wide lenses and another fresnel for your other lenses.
I haven't spoken to Bill in over a year, but last time I talked to him he was at: (404) 244-0095/ Maxwell Precision Optics; P.O. Box 33146; Decatur, GA 30033-0146.
I researched it pretty thoroughly and found that Bill was able to explain the problems and solutinos better than anyone else and was very reasonably priced. He also received rave reviews, mostly from medium format shooters. Bill actually makes the fresnels for at least one very well known large format manufacturer (I can't say who). He was also consulted extensively by Alpa when they released their recent medium format wide angle camer
-- Howard Slavitt (firstname.lastname@example.org), October 06, 2000.
Lloyd, If you can get hold of one I recommend the wide angle fresnel from Ebony which will fit most 4x5 cameras. It is excellent in proving even illumination right to the coners of the ground glass. I use it with lenses from the 35 Apo-Grandagon to the 135 Sironar-N. Mount it between the ground glass and protective glass. It cost about #50(approx.$70 plus shipping) from Robert White(UK). Regards,
-- Trevor Crone (email@example.com), October 06, 2000.
I have an older TK45 with a Linhof Super Screen. I don't know how well it compares to Maxwell's fresnel screens, but it works well for my lenses, the widest of which is 90 mm. That's a long ways from 58 mm, I know. But perhaps you should try a compromise screen like the Super Screen, considering that you have a 360 mm lens in addition to your 58.
My Super Screen is mounted between the clear glass and the film plane.
Let us know of your solution and how it works out!
-- Bruce M. Herman (firstname.lastname@example.org), October 07, 2000.
Thanks everyone for the info. It's very helpful.
There's nothing like seeing it for oneself. So I obtained a Lihof fresnel (about $100) and mounted it in a few seconds (once I figured it out). I just moved the metal tabs back, laid the fresnel on top of the ground glass and moved the tabs back (with the scored towards the lens)
Results: I briefly tried the 58/5.6 XL, the 110/5.6XL and the 135/5.6 Sironar S with the fresnel in dim lighting conditions. All were improved I think. Even the 58mm worked well--I could see the whole image (although I did have to stay centered to see it). Without the fresnel, the 58mm is a "move the head around a lot" lens.
I did not do any critical focusing to see if there was any issue with that, but coarse focusing seemed fine. Nor did I remove the fresnel for each focal length and compare the difference. Nor did I check the 180 and/or 360. I'll do all that when I have time. Maybe I'll find an issue in which case it sounds like Bill Maxwell is a good resource.
-- Lloyd Chambers (email@example.com), October 09, 2000.