Best Mounting Position for Center Filtersgreenspun.com : LUSENET : Large format photography : One Thread
I have a Nikor 90mm SW and I'm about to purchase a center filter. I was curious, where is the best place to mount a center filter. I would think the rear. That way, you could leave it and "forget" about it. Do center filters work rear mounted or do they always need to be front mounted? Another question relating to all these filters. While using a center filter, there may be times where I might need a polarizing filter and a warming filter or a polarizing filter and a color filter. This would mean 3 filters on one lense. How much would this degrade the image. I use exclusively B&W filters. Would it me better to mount the center filter in the rear and the other two in front? This might alleviate some of the problems?
Any help or suggestions would be greatly appreciated.
I will be getting a Wisner Pocket Edition 4x5 shortly.
Thanks in advance,
-- Thomas W Earle (email@example.com), February 27, 2000
Thomas, one of the first thought that comes to my mind when speaking of center filters is the oversize of these filters. They are huge compared to standard filters. For a f8 lens with 67mm mount, the outer diameter is 88mm and for a f5,6 of 82mm it reaches 107 mm or even 112 for an XL, I doubt it would fit into your Wisner hole. If you mount it from the back, you would have difficulties achieving movements without touching the bellows. Secondly, center filters make you loose 1 1/2 f stops. Focussing a 90mm f8 with the center filter mounted on is unpractical. Nikkor SW and Super Angulons have no rear mounting threads, so this could not be considered anyway. I also have heard of an optical factor that makes the use of a rear filters inadequate in some situations. Using a polarizer on a 90mm is OK. You would be well advised to get a polarizer specially designed for wide angles . They are oversized and the mount is thinner than on conventional models, making them less prone to vignetting. This is specially important for wide angles with limited image circle such as the 65 and 75 mm. More, as normally, you would use the polarizer on top of the center filter, choose one for the larger center filter thread and use a step-up ring if you do not use the center filter. The combination of the two filters will darken considerably your image, (up to 3 1/2 stops) but should be OK if you use first class filters such as the B&W, at least on the 90 mm. A wider lens might suffer some vignetting and loss of sharpness in the corners, so a 90 mm with much movement. Adding a third filter will probably degrade a little more your image quality. However, a center filter on a 90 mm for 4x5 is not always necessary but can be useful in some situations, especially if you use movement or shoot indoors. I have one for my Super Angulon 5,6/ 90 mm, but rarely use it outside.
-- Paul Schilliger (firstname.lastname@example.org), February 27, 2000.
1: Center filters always are mounted in front. 2: Center filters MUST be used without a step up ring 3: Center filters must be screwed directly into the lens. ZNot into another filter 4: Any pther filters used should be wide angletypes 5: Heliopan and some others make warmtone polarizers which are a combination warming filter and polarizer. This keeps the number of filters down. Warm polarizers are not made in wide angle tyoes so a step up ring must be used. Fortunatly Heliopan brass black anodized step up rings are very thin to minimize vignetting and to keep the filters as close to the front of the lens as possible to minimize problems with the filter coming into a position that effects resolution.
-- Bob Salomon (email@example.com), February 27, 2000.
Do you have any knowledge about the Hoya brand of center filters? I have a Nikkor-SW 120mm lens, with a 77mm filter thread. I cannot find a center filter from either Schneider or Rodenstock to fit a 77mm thread.
The Hoya line offers a 77mm HMC neutral density filter, still priced at $235...
-- Bruce Gavin (firstname.lastname@example.org), June 04, 2000.
Bruce ; alternatively, you could consider the centre filter Fuji makes for the 90mm & 105mm lenses for the GX617. That's a 77mm thread, and I just leave it in my G617 all the time. I also have a Nikkor SW120, but on 4x5 I'd be surprised if you needed a centre filter. On 8x10, maybe.
-- fw (email@example.com), June 04, 2000.
Heliopan makes 77mm center filters
-- Bob Salomon (firstname.lastname@example.org), June 04, 2000.